fault and their potential
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8122019 Fault and Their Potential
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Faults and their potential influence on fluid flow
Nicol A1 Seebeck H1 Hemmings-Sykes S12 Ilg B3 Childs C4Walsh J4
1 GNS Science Lower Hutt New Zealand2 Victoria University of Wellington Wellington New Zealand3 New Zealand Petroleum amp Minerals Wellington New Zealand4 Fault Analysis Group School of Geological Sciences University College Dublin Dublin 4Ireland
Email anicolgnscrinz
AbstractFaults have the potential to be both barriers to lateral flow and conduits for vertical
movement of fluids We examine where and why faults locally enhance the flow of fluids
using mainly outcrops tunnel excavations and seismic reflection lines Outcrop studies of
normal faults within the Mount Messenger Formation reveal that the thickness of fault zones
(containing clay-rich fault rock and fractures) generally increases with displacement and
varies by several orders of magnitude on individual faults Elevated densities of small-scale
faults and the greatest fault zone widths typically occur at irregularities on fault surfaces
(eg relays bends and fault intersections) Data from ground water flow in tunnels and gas
chimneys imaged in seismic reflection lines show that for low permeability rocks (eg seals)
fluid flow is primarily achieved via fault zones that flow rates are greatest on larger faults
and that migration of f luids is locally enhanced along fault irregularities (ie the sites where
the highest densities of small-scale faults occur) Geomechanical analysis of faults does notappear to be a reliable predictor of gas chimney locations and migration pathways on
individual faults perhaps because stress conditions near faults can depart significantly from
the regional stress field used in these analyses
Keywords fault zones fluid flow gas chimneys geomechanical modelling
IntroductionIn many sedimentary basins it has long been postulated that clay-rich fault rock and
associated small-faultsfractures strongly influence the sub-surface migration and
accumulation of hydrocarbons (eg Wade 1913 Illing 1942 Neglia 1979 Faulkner et al2010) Individual faults can be both barriers to lateral flow and conduits for vertical movement
of fluids The potential for faults to impede lateral flow of fluids within reservoir units has been
extensively studied (eg Yielding et al 1997 Manzocchi et al 1999 2010) Faults can also
act as conduits to fluid migration enhancing their up-sequence flow and influencing the ability
of traps to retain oil or gas columns over geological timescales Up-sequence fluid flow along
faults is thought to occur in the Taranaki Basin where petroleum generated from Late
Cretaceous to Eocene source rocks have the ability to migrate through a thick (1-3 km)
Oligocene to Miocene mudstone-rich sequence which has implications for the locations of oil
and gas fields It is therefore important to determine where and under what circumstances
faults (and fractures) enhance the movement of petroleum fluids
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In this paper we utilise outcrop tunnel and seismic reflection data (2D amp 3D) from the
Taranaki Basin and the North Island of New Zealand to describe the structure of normal fault
zones examine where and why fluid flow is focused within these fault zones and test the
predictive power of geomechanical techniques for identifying faults or parts of a fault that
may locally enhance up-sequence flow Our analysis supports the view that channelized flow
of gas and water often occurs within fault zones Geomechanical techniques (ie SlipTendency Dilation Tendency and Fracture Stability) proved an unreliable means of
predicting the locations of channelized flow Qualitative analysis of the data suggest that in
many cases fluid flow is observed close to geometric complexities on fault surfaces (eg
fault relays bends and intersections) where the densities of small-scale faults is likely to be
highest
Fault Zone StructureFaults typically comprise zones that accommodate heterogeneous shear strains (eg Caine
et al 1996 Childs et al 2009 Faulkner et al 2010) The highest shear displacements are
focused within (or bounding) fault rock that typically contains fine-grained fault gouge and
breccia (products of crushing and intense fracturing) Fault rock in the Mount Messenger
Formation varies in content and dimensions depending on the host rock fault-zone structure
and total displacement (Childs et al 2007 2009 Nicol et al 2013)(Fig1a) Fault rock is
generally (but not always) accompanied by fracturing and small-scale faulting and
collectively these structures form the fault zone (Fig 1a) Fault zones typically comprise an
anastomosing system of intersecting fault segments which bound lenses of variably
fractured host rock The thickness of fault zones shows a broad positive relationship with
displacement however there is significant heterogeneity of fault zone thickness for a given
displacement The thicknesses of both fault zones and fault rock can change on individual
structures by an order of magnitude or more over distances of metres (eg Childs et al2009 Nicol et al 2013) For example a recently studied normal fault with ~6-8 m of
displacement displayed a factor of five change in fault-zone thickness over 5 m horizontal
distance (10 cm to 50 cm) and a factor of 25 change over 40 m (10 cm to 25 m) These
changes indicate that the spread in fault-zone thickness for a given displacement on all
sampled faults may be approximately replicated by the variability on individual faults (Fig
1b) The 1-25 orders of magnitude range of fault zone thickness for a given displacement on
all faults in Fig 1b reflects the fact that fault zones comprise a combination of single planar
fault surfaces and multiple slip surfaces with variable amounts of associated secondary
fracturing The widest fault zones are generally associated with fault complexities including
segmentation and segment boundaries (eg relays) fault bending fault intersections andfault terminations (Childs et al 2009 Nicol et al 2013) In many cases these zones of fault
complexity are sites with increased numbers of fractures and are considered by many to be
zones of likely elevated fault-zone permeability (eg Gartrell et al 2004 Ilg et al 2012)
The role of these zones of fracturing on fluid flow and petroleum fluid migration are
discussed in the following sections
Fluid Flow along FaultsMany quantitative and qualitative models have been proposed to explain where and why
fluid flow occurs along faults Historically one of the most significant impediments to testing
these models has been a lack of empirical data on fluid flow in areas where faulting is wellunderstood Here we present the results of three studies in which data are available for both
8122019 Fault and Their Potential
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983137 983138
faults and fluid flow (Hemmings-Sykes 2012 Ilg et al 2012 Seebeck et al 2014) These
studies confirm that fluid flow (water or gas) occurs within fault zones and is highly
channelized and heterogeneous They also permit testing of geomechanical methods for
predicting the locations of elevated fluid flow on fault surfaces
Fig 1 a) Schematic diagram showing a fault with definitions of fault rock (also referred to as fault
core) and fault zone illustrated (from Childs et al 2009) b) Plot of fault zone width versus
displacement for normal faults in the Mount Messenger Formation on the north Taranaki coast
Vertical bars show variations in fault zone thickness for individual faults
Water flow into tunnels through fault zones has been analysed to determine the relationships
between faulting and fluid flow (locations and rates) (Seebeck et al 2014) The datasetincludes information on fault geometries and their spatial relationships to water flowing into
tunnels located along the margins of the Taupo Rift New Zealand (Fig 2) Faults and water
flow data from engineering geological logs and reports have been used to examine the
factors influencing the rates and localisation of groundwater flows in relation to fault zone
architecture and connectivity of the fault-fracture network As faults locally promote fluid
migration through seal and reservoir rocks our analysis may have implications for the
exploration and production of petroleum fluids (Manzocchi et al 2010 Ilg et al 2012) In
the tunnels localised ground water inflows occur almost exclusively (ge~90) within and
immediately adjacent to fault zones Fault zones in contrasting lithologies comprise fault
rock small-scale faults and fractures with thicknesses of 001 to ~110 m approximating
power-law distributions and bulk permeabilities of 10-9-10-12 m2 (Fig 2a) Variability in fault-
zone structure results in highly heterogeneous flow rates and channelised flow Within
basement rocks ~80 of the flow rate occurs from fault zones ge10 m wide with ~30 of the
total localised flow rate originating from a single fault zone (ie consistent with the golden
fracture concept) (Fig 2a) No simple relationships are found between flow rates and either
fault strike or hydraulic head (Fig 2b) with le50 of fault zones in any given orientation
flowing A general positive relationship does however exist between fault zone thickness and
maximum flow rate Higher flow rates from larger fault zones may arise because these
structures have greater dimensions and are more likely (than smaller faults) to be connected
to other faults in the system and the ground surface These results suggest that faults
passing through the reservoir and seal in hydrocarbon systems are most likely to promote oil
andor gas migration through the seal However it is clear that not all faults or all parts of
8122019 Fault and Their Potential
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faults connecting the reservoir to strata above the seal will compromise petroleum traps
(see next section for further discussion)
Fig 2 Fluid flow and fault data from tunnels in the Taupo Rift (Seebeck et al 2014) a) Proportion of
localised flow carried by basement fault zones Illustrates ~80 of total cumulative flow rate occur on
lt3 of basement faults which typically have zones gt10 m wide Note one fault accounts for ~30 of
total flow rate entering basement tunnels b) 983106983137983155983141983149983141983150983156 983142983137983157983148983156 983162983151983150983141983155 ge983089 983149 983159983145983140983141 983159983145983156983144 983137983150983140 983159983145983156983144983151983157983156 983159983137983156983141983154
983142983148983151983159983086 983124983144983141 983142983148983151983159 983137983150983140 983150983151 983142983148983151983159 983142983137983157983148983156 983152983151983152983157983148983137983156983145983151983150983155 983144983137983158983141 983155983145983149983145983148983137983154 983137983162983145983149983157983156983144 983140983145983155983156983154983145983138983157983156983145983151983150983155 983155983157983143983143983141983155983156983145983150983143 983156983144983137983156 983142983137983157983148983156
983155983156983154983145983147983141 983149983137983161 983150983151983156 983138983141 983137 983155983156983154983151983150983143 983140983141983156983141983154983149983145983150983137983150983156 983142983151983154 983159983144983145983139983144 983142983137983157983148983156983155 983159983145983148983148 983137983139983139983151983149983149983151983140983137983156983141 983159983137983156983141983154 983142983148983151983159983086 983111983154983141983161 983152983151983148983161983143983151983150
983155983144983151983159983155 983156983144983141 983137983152983152983154983151983160983145983149983137983156983141 983151983152983156983145983149983137983148 983142983137983157983148983156 983137983162983145983149983157983156983144 983142983151983154 983142983148983151983159 983140983141983156983141983154983149983145983150983141983140 983142983154983151983149 983143983141983151983149983141983139983144983137983150983145983139983137983148 983156983141983139983144983150983145983153983157983141983155
983142983151983154 983137 983149983137983160983145983149983157983149 983144983151983154983145983162983151983150983156983137983148 983155983144983151983154983156983141983150983145983150983143 983156983154983141983150983140983145983150983143 983137983156 983166983088983094983088ordm 983080983154983141983140 983148983145983150983141983081983086
The role of normal faults in up-sequence flow of fluid has also been examined using 2D and
3D seismic-reflection data from the southern Taranaki Basin New Zealand (Hemmings-Sykes 2012 Ilg et al 2012) The spatial distributions of late-stage normal faults gas
chimneys thickness of the Oligocene mudstone-rich seal (Otaraoa Formation) and modelled
petroleum expulsion volumes have been compared in our studies Gas chimneys are most
common above Cretaceous source rocks modelled to have expelled hydrocarbons Most
(~70) of the observed gas chimneys follow andor are rooted in late-stage normal faults
These faults are the primary seal bypass mechanism for hydrocarbons where they displace
the seal (or intersect faults that displace the seal) and the seal is thick (eg gt~340 m) Gas
flow up along faults in low permeability mudstones (lt1 mD) is channelized with steep
chimneys often occurring close to fault tips and relay ramps In these cases gas flow may be
focused by the presence of high densities of open fractures (as is observed in outcrop)locally elevating up-sequence bulk permeabilities in the seal
Gas chimneys and normal faults imaged in a 3D seismic reflection volume provide a means
of testing the ability of geomechanical models to predict the locations of up-fault hydrocarbon
migration The use of geomechanical methods for predicting leakage risk is only applicable
as a first-order estimate of which fault sets present the highest risk of up-dip migration
(Hemmings-Sykes 2012) Slip Tendency and Dilation Tendency were able to differentiate
fault orientations in the Kupe Area most at risk of leakage and both indicated higher risk of
leakage for the fault set striking parallel to the maximum horizontal stress (approximately
northeast-southwest) In contrast Fracture Stability was not able to differentiate fault setsmost at risk of leakage in the Kupe Area The ability of geomechanical modelling methods to
983120983154983151983152983151983154983156983145983151983150 983156983151983156983137983148 983142983148983151983159
983110 983137 983157 983148 983156 983162 983151 983150 983141 983159 983145 983140 983156 983144
983149
983110 983154 983141 983153 983157 983141 983150 983139 983161
983138983137
983105983162983145983149983157983156983144
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locate zones on fault surfaces with a high risk of up-sequence gas flow appears to be
limited There was no statistical difference in leakage risk between chimney and non-
chimney locations on fault surfaces when applying Slip Tendency Dilation Tendency and
Fracture Stability (Fig 3)
Fig 3 Oblique view of fault surfaces from the Kupe region with colours showing contours of slip
tendency on the fault surfaces (Hemmings-Sykes 2012) White line polygons indicate the outline of
gas chimneys mapped on the fault surfaces The chimneys are of limited extent and their locations do
not seem to be related to zones of higher Slip Tendency Refer to Hemmings-Sykes (2012) for further
details
The inability of geomechanical analyses to predict the locations of chimneys might arise
because i) these techniques do not include small-scale information on the local stress
tensor andor on the locations of open interconnected fractures and ii) they do not takeaccount of whether individual faults breach the seal and are likely to intersect a petroleum
source The poor relationship between fault orientation and fluid flow rates in the tunnel
dataset supports the view that in some cases geomechanical methods may not provide a
robust means of assigning risk of up-fault fluid flow for fault sets with widely varying strike
(Seebeck et al 2014) In our experience geomechanical modelling should be used with
caution and does not seem to be a reliable predictor of fluid flow in the New Zealand
examples studied
Conclusions
Analysis of outcrop and seismic-reflection studies of normal faults and fluid flow in NewZealand support a number of conclusions These are
1) The thickness of fault zones (containing clay-rich fault rock and fractures) generally
increases with displacement and varies by several orders of magnitude on individual
faults Elevated densities of small-scale faults (and greatest fault zone widths) typically
occur at irregularities on fault surfaces (eg relays bends and fault intersections)
2) Ground water flow in tunnels and gas chimneys imaged on seismic reflection lines show
that in low permeability rocks (eg seals) fluid flow is primarily achieved via fault zones
and that flow rates are greatest on larger faults
3) Geomechanical analysis does not appear to be a reliable predictor of where channelized
flow will occur on individual faults
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4) Up-fault migration is locally enhanced at fault irregularities (ie the sites where the
highest densities of small-scale faults occur)
References
Caine JS Evans JP Forster CB 1996 Fault zone architecture and permeability
structure Geology 24(11) 1025-1028Childs C Walsh J J Manzocchi T Strand J Nicol A Tomasso M Schopfer M
Aplin A 2007 Definition of a fault permeability predictor from outcrop studies of a
faulted turbidite sequence Taranaki New Zealand In Structurally Complex
Reservoirs Geological Society of London Special Publication 292 235-258
Childs C Walsh JJ Manzocchi T Bonson C Nicol A Schoumlpfer MPJ 2009 A
geometric model of fault zone and fault rock thickness variations Journal of
Structural Geology 31 117-127
Faulkner DR Jackson CAL Lunn RJ Schlische RW Shipton ZK Wibberley
CAJ Withjack MO 2010 A review of recent developments concerning the
structure mechanics and fluid flow properties of fault zones Journal of StructuralGeology 32 1557-1575
Hemmings-Sykes S 2012 The influence of faulting on hydrocarbon migration in the Kupe
area south Taranaki Basin New Zealand Unpublished MSc Victoria University of
Wellington p 224
Gartrell A Zhang Y Lisk M Dewhurst D 2004 Fault intersections as crictical
hydrocarbon leakage zones integrated field study and numerical modelling of an
example from the Timor Sea Australia Marine amp Petroleum Geology 23 1165-1179
Ilg BR Hemmings-Sykes S Nicol A Baur J Fohrmann M Funnell R Milner M
2012 Normal faults and gas migration in an active plate boundary southern Taranaki
Basin offshore New Zealand Amercian Association of Petroleum Geology Bulletin 96(9) 1733-1756
Illing VC 1942 Geology applied to petroleum Proceedings of the Geologists Association
53(3-4) 156-187
Manzocchi T Walsh JJ Nell P Yielding G 1999 Fault transmissibility multipliers for
flow simulation models Petroleum Geoscience 5(1) 53-63
Manzocchi T Childs C Walsh JJ 2010 Faults and fault properties in hydrocarbon flow
models Geofluids 10(1-2) 94-113
Nicol A Childs C Walsh J Schafer K 2013 A geometric model for the formation of
deformation bands Journal of Structural Geology 55 21-33
Neglia S 1979 Migration of f luids in sedimentary basins American Association ofPetroleum Geology Bulletin 63(4) 573-597
Seebeck H Nicol A Walsh JJ Childs C Beetham RD Pettinga J 2014 Fluid flow
in fault zones from an active rift Journal of Structural Geology 62 52-64
Wade A 1913 The natural history of petroleum Proceedings of the Geologistsrsquo
Association 24(1) 1-13 IN1-IN3
Yielding G Freeman B Needham DT 1997 Quantitative fault seal prediction American
Association of Petroleum Geology Bulletin 81(6) 897-917
8122019 Fault and Their Potential
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In this paper we utilise outcrop tunnel and seismic reflection data (2D amp 3D) from the
Taranaki Basin and the North Island of New Zealand to describe the structure of normal fault
zones examine where and why fluid flow is focused within these fault zones and test the
predictive power of geomechanical techniques for identifying faults or parts of a fault that
may locally enhance up-sequence flow Our analysis supports the view that channelized flow
of gas and water often occurs within fault zones Geomechanical techniques (ie SlipTendency Dilation Tendency and Fracture Stability) proved an unreliable means of
predicting the locations of channelized flow Qualitative analysis of the data suggest that in
many cases fluid flow is observed close to geometric complexities on fault surfaces (eg
fault relays bends and intersections) where the densities of small-scale faults is likely to be
highest
Fault Zone StructureFaults typically comprise zones that accommodate heterogeneous shear strains (eg Caine
et al 1996 Childs et al 2009 Faulkner et al 2010) The highest shear displacements are
focused within (or bounding) fault rock that typically contains fine-grained fault gouge and
breccia (products of crushing and intense fracturing) Fault rock in the Mount Messenger
Formation varies in content and dimensions depending on the host rock fault-zone structure
and total displacement (Childs et al 2007 2009 Nicol et al 2013)(Fig1a) Fault rock is
generally (but not always) accompanied by fracturing and small-scale faulting and
collectively these structures form the fault zone (Fig 1a) Fault zones typically comprise an
anastomosing system of intersecting fault segments which bound lenses of variably
fractured host rock The thickness of fault zones shows a broad positive relationship with
displacement however there is significant heterogeneity of fault zone thickness for a given
displacement The thicknesses of both fault zones and fault rock can change on individual
structures by an order of magnitude or more over distances of metres (eg Childs et al2009 Nicol et al 2013) For example a recently studied normal fault with ~6-8 m of
displacement displayed a factor of five change in fault-zone thickness over 5 m horizontal
distance (10 cm to 50 cm) and a factor of 25 change over 40 m (10 cm to 25 m) These
changes indicate that the spread in fault-zone thickness for a given displacement on all
sampled faults may be approximately replicated by the variability on individual faults (Fig
1b) The 1-25 orders of magnitude range of fault zone thickness for a given displacement on
all faults in Fig 1b reflects the fact that fault zones comprise a combination of single planar
fault surfaces and multiple slip surfaces with variable amounts of associated secondary
fracturing The widest fault zones are generally associated with fault complexities including
segmentation and segment boundaries (eg relays) fault bending fault intersections andfault terminations (Childs et al 2009 Nicol et al 2013) In many cases these zones of fault
complexity are sites with increased numbers of fractures and are considered by many to be
zones of likely elevated fault-zone permeability (eg Gartrell et al 2004 Ilg et al 2012)
The role of these zones of fracturing on fluid flow and petroleum fluid migration are
discussed in the following sections
Fluid Flow along FaultsMany quantitative and qualitative models have been proposed to explain where and why
fluid flow occurs along faults Historically one of the most significant impediments to testing
these models has been a lack of empirical data on fluid flow in areas where faulting is wellunderstood Here we present the results of three studies in which data are available for both
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 36
983137 983138
faults and fluid flow (Hemmings-Sykes 2012 Ilg et al 2012 Seebeck et al 2014) These
studies confirm that fluid flow (water or gas) occurs within fault zones and is highly
channelized and heterogeneous They also permit testing of geomechanical methods for
predicting the locations of elevated fluid flow on fault surfaces
Fig 1 a) Schematic diagram showing a fault with definitions of fault rock (also referred to as fault
core) and fault zone illustrated (from Childs et al 2009) b) Plot of fault zone width versus
displacement for normal faults in the Mount Messenger Formation on the north Taranaki coast
Vertical bars show variations in fault zone thickness for individual faults
Water flow into tunnels through fault zones has been analysed to determine the relationships
between faulting and fluid flow (locations and rates) (Seebeck et al 2014) The datasetincludes information on fault geometries and their spatial relationships to water flowing into
tunnels located along the margins of the Taupo Rift New Zealand (Fig 2) Faults and water
flow data from engineering geological logs and reports have been used to examine the
factors influencing the rates and localisation of groundwater flows in relation to fault zone
architecture and connectivity of the fault-fracture network As faults locally promote fluid
migration through seal and reservoir rocks our analysis may have implications for the
exploration and production of petroleum fluids (Manzocchi et al 2010 Ilg et al 2012) In
the tunnels localised ground water inflows occur almost exclusively (ge~90) within and
immediately adjacent to fault zones Fault zones in contrasting lithologies comprise fault
rock small-scale faults and fractures with thicknesses of 001 to ~110 m approximating
power-law distributions and bulk permeabilities of 10-9-10-12 m2 (Fig 2a) Variability in fault-
zone structure results in highly heterogeneous flow rates and channelised flow Within
basement rocks ~80 of the flow rate occurs from fault zones ge10 m wide with ~30 of the
total localised flow rate originating from a single fault zone (ie consistent with the golden
fracture concept) (Fig 2a) No simple relationships are found between flow rates and either
fault strike or hydraulic head (Fig 2b) with le50 of fault zones in any given orientation
flowing A general positive relationship does however exist between fault zone thickness and
maximum flow rate Higher flow rates from larger fault zones may arise because these
structures have greater dimensions and are more likely (than smaller faults) to be connected
to other faults in the system and the ground surface These results suggest that faults
passing through the reservoir and seal in hydrocarbon systems are most likely to promote oil
andor gas migration through the seal However it is clear that not all faults or all parts of
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 46
faults connecting the reservoir to strata above the seal will compromise petroleum traps
(see next section for further discussion)
Fig 2 Fluid flow and fault data from tunnels in the Taupo Rift (Seebeck et al 2014) a) Proportion of
localised flow carried by basement fault zones Illustrates ~80 of total cumulative flow rate occur on
lt3 of basement faults which typically have zones gt10 m wide Note one fault accounts for ~30 of
total flow rate entering basement tunnels b) 983106983137983155983141983149983141983150983156 983142983137983157983148983156 983162983151983150983141983155 ge983089 983149 983159983145983140983141 983159983145983156983144 983137983150983140 983159983145983156983144983151983157983156 983159983137983156983141983154
983142983148983151983159983086 983124983144983141 983142983148983151983159 983137983150983140 983150983151 983142983148983151983159 983142983137983157983148983156 983152983151983152983157983148983137983156983145983151983150983155 983144983137983158983141 983155983145983149983145983148983137983154 983137983162983145983149983157983156983144 983140983145983155983156983154983145983138983157983156983145983151983150983155 983155983157983143983143983141983155983156983145983150983143 983156983144983137983156 983142983137983157983148983156
983155983156983154983145983147983141 983149983137983161 983150983151983156 983138983141 983137 983155983156983154983151983150983143 983140983141983156983141983154983149983145983150983137983150983156 983142983151983154 983159983144983145983139983144 983142983137983157983148983156983155 983159983145983148983148 983137983139983139983151983149983149983151983140983137983156983141 983159983137983156983141983154 983142983148983151983159983086 983111983154983141983161 983152983151983148983161983143983151983150
983155983144983151983159983155 983156983144983141 983137983152983152983154983151983160983145983149983137983156983141 983151983152983156983145983149983137983148 983142983137983157983148983156 983137983162983145983149983157983156983144 983142983151983154 983142983148983151983159 983140983141983156983141983154983149983145983150983141983140 983142983154983151983149 983143983141983151983149983141983139983144983137983150983145983139983137983148 983156983141983139983144983150983145983153983157983141983155
983142983151983154 983137 983149983137983160983145983149983157983149 983144983151983154983145983162983151983150983156983137983148 983155983144983151983154983156983141983150983145983150983143 983156983154983141983150983140983145983150983143 983137983156 983166983088983094983088ordm 983080983154983141983140 983148983145983150983141983081983086
The role of normal faults in up-sequence flow of fluid has also been examined using 2D and
3D seismic-reflection data from the southern Taranaki Basin New Zealand (Hemmings-Sykes 2012 Ilg et al 2012) The spatial distributions of late-stage normal faults gas
chimneys thickness of the Oligocene mudstone-rich seal (Otaraoa Formation) and modelled
petroleum expulsion volumes have been compared in our studies Gas chimneys are most
common above Cretaceous source rocks modelled to have expelled hydrocarbons Most
(~70) of the observed gas chimneys follow andor are rooted in late-stage normal faults
These faults are the primary seal bypass mechanism for hydrocarbons where they displace
the seal (or intersect faults that displace the seal) and the seal is thick (eg gt~340 m) Gas
flow up along faults in low permeability mudstones (lt1 mD) is channelized with steep
chimneys often occurring close to fault tips and relay ramps In these cases gas flow may be
focused by the presence of high densities of open fractures (as is observed in outcrop)locally elevating up-sequence bulk permeabilities in the seal
Gas chimneys and normal faults imaged in a 3D seismic reflection volume provide a means
of testing the ability of geomechanical models to predict the locations of up-fault hydrocarbon
migration The use of geomechanical methods for predicting leakage risk is only applicable
as a first-order estimate of which fault sets present the highest risk of up-dip migration
(Hemmings-Sykes 2012) Slip Tendency and Dilation Tendency were able to differentiate
fault orientations in the Kupe Area most at risk of leakage and both indicated higher risk of
leakage for the fault set striking parallel to the maximum horizontal stress (approximately
northeast-southwest) In contrast Fracture Stability was not able to differentiate fault setsmost at risk of leakage in the Kupe Area The ability of geomechanical modelling methods to
983120983154983151983152983151983154983156983145983151983150 983156983151983156983137983148 983142983148983151983159
983110 983137 983157 983148 983156 983162 983151 983150 983141 983159 983145 983140 983156 983144
983149
983110 983154 983141 983153 983157 983141 983150 983139 983161
983138983137
983105983162983145983149983157983156983144
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 56
locate zones on fault surfaces with a high risk of up-sequence gas flow appears to be
limited There was no statistical difference in leakage risk between chimney and non-
chimney locations on fault surfaces when applying Slip Tendency Dilation Tendency and
Fracture Stability (Fig 3)
Fig 3 Oblique view of fault surfaces from the Kupe region with colours showing contours of slip
tendency on the fault surfaces (Hemmings-Sykes 2012) White line polygons indicate the outline of
gas chimneys mapped on the fault surfaces The chimneys are of limited extent and their locations do
not seem to be related to zones of higher Slip Tendency Refer to Hemmings-Sykes (2012) for further
details
The inability of geomechanical analyses to predict the locations of chimneys might arise
because i) these techniques do not include small-scale information on the local stress
tensor andor on the locations of open interconnected fractures and ii) they do not takeaccount of whether individual faults breach the seal and are likely to intersect a petroleum
source The poor relationship between fault orientation and fluid flow rates in the tunnel
dataset supports the view that in some cases geomechanical methods may not provide a
robust means of assigning risk of up-fault fluid flow for fault sets with widely varying strike
(Seebeck et al 2014) In our experience geomechanical modelling should be used with
caution and does not seem to be a reliable predictor of fluid flow in the New Zealand
examples studied
Conclusions
Analysis of outcrop and seismic-reflection studies of normal faults and fluid flow in NewZealand support a number of conclusions These are
1) The thickness of fault zones (containing clay-rich fault rock and fractures) generally
increases with displacement and varies by several orders of magnitude on individual
faults Elevated densities of small-scale faults (and greatest fault zone widths) typically
occur at irregularities on fault surfaces (eg relays bends and fault intersections)
2) Ground water flow in tunnels and gas chimneys imaged on seismic reflection lines show
that in low permeability rocks (eg seals) fluid flow is primarily achieved via fault zones
and that flow rates are greatest on larger faults
3) Geomechanical analysis does not appear to be a reliable predictor of where channelized
flow will occur on individual faults
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 66
4) Up-fault migration is locally enhanced at fault irregularities (ie the sites where the
highest densities of small-scale faults occur)
References
Caine JS Evans JP Forster CB 1996 Fault zone architecture and permeability
structure Geology 24(11) 1025-1028Childs C Walsh J J Manzocchi T Strand J Nicol A Tomasso M Schopfer M
Aplin A 2007 Definition of a fault permeability predictor from outcrop studies of a
faulted turbidite sequence Taranaki New Zealand In Structurally Complex
Reservoirs Geological Society of London Special Publication 292 235-258
Childs C Walsh JJ Manzocchi T Bonson C Nicol A Schoumlpfer MPJ 2009 A
geometric model of fault zone and fault rock thickness variations Journal of
Structural Geology 31 117-127
Faulkner DR Jackson CAL Lunn RJ Schlische RW Shipton ZK Wibberley
CAJ Withjack MO 2010 A review of recent developments concerning the
structure mechanics and fluid flow properties of fault zones Journal of StructuralGeology 32 1557-1575
Hemmings-Sykes S 2012 The influence of faulting on hydrocarbon migration in the Kupe
area south Taranaki Basin New Zealand Unpublished MSc Victoria University of
Wellington p 224
Gartrell A Zhang Y Lisk M Dewhurst D 2004 Fault intersections as crictical
hydrocarbon leakage zones integrated field study and numerical modelling of an
example from the Timor Sea Australia Marine amp Petroleum Geology 23 1165-1179
Ilg BR Hemmings-Sykes S Nicol A Baur J Fohrmann M Funnell R Milner M
2012 Normal faults and gas migration in an active plate boundary southern Taranaki
Basin offshore New Zealand Amercian Association of Petroleum Geology Bulletin 96(9) 1733-1756
Illing VC 1942 Geology applied to petroleum Proceedings of the Geologists Association
53(3-4) 156-187
Manzocchi T Walsh JJ Nell P Yielding G 1999 Fault transmissibility multipliers for
flow simulation models Petroleum Geoscience 5(1) 53-63
Manzocchi T Childs C Walsh JJ 2010 Faults and fault properties in hydrocarbon flow
models Geofluids 10(1-2) 94-113
Nicol A Childs C Walsh J Schafer K 2013 A geometric model for the formation of
deformation bands Journal of Structural Geology 55 21-33
Neglia S 1979 Migration of f luids in sedimentary basins American Association ofPetroleum Geology Bulletin 63(4) 573-597
Seebeck H Nicol A Walsh JJ Childs C Beetham RD Pettinga J 2014 Fluid flow
in fault zones from an active rift Journal of Structural Geology 62 52-64
Wade A 1913 The natural history of petroleum Proceedings of the Geologistsrsquo
Association 24(1) 1-13 IN1-IN3
Yielding G Freeman B Needham DT 1997 Quantitative fault seal prediction American
Association of Petroleum Geology Bulletin 81(6) 897-917
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 36
983137 983138
faults and fluid flow (Hemmings-Sykes 2012 Ilg et al 2012 Seebeck et al 2014) These
studies confirm that fluid flow (water or gas) occurs within fault zones and is highly
channelized and heterogeneous They also permit testing of geomechanical methods for
predicting the locations of elevated fluid flow on fault surfaces
Fig 1 a) Schematic diagram showing a fault with definitions of fault rock (also referred to as fault
core) and fault zone illustrated (from Childs et al 2009) b) Plot of fault zone width versus
displacement for normal faults in the Mount Messenger Formation on the north Taranaki coast
Vertical bars show variations in fault zone thickness for individual faults
Water flow into tunnels through fault zones has been analysed to determine the relationships
between faulting and fluid flow (locations and rates) (Seebeck et al 2014) The datasetincludes information on fault geometries and their spatial relationships to water flowing into
tunnels located along the margins of the Taupo Rift New Zealand (Fig 2) Faults and water
flow data from engineering geological logs and reports have been used to examine the
factors influencing the rates and localisation of groundwater flows in relation to fault zone
architecture and connectivity of the fault-fracture network As faults locally promote fluid
migration through seal and reservoir rocks our analysis may have implications for the
exploration and production of petroleum fluids (Manzocchi et al 2010 Ilg et al 2012) In
the tunnels localised ground water inflows occur almost exclusively (ge~90) within and
immediately adjacent to fault zones Fault zones in contrasting lithologies comprise fault
rock small-scale faults and fractures with thicknesses of 001 to ~110 m approximating
power-law distributions and bulk permeabilities of 10-9-10-12 m2 (Fig 2a) Variability in fault-
zone structure results in highly heterogeneous flow rates and channelised flow Within
basement rocks ~80 of the flow rate occurs from fault zones ge10 m wide with ~30 of the
total localised flow rate originating from a single fault zone (ie consistent with the golden
fracture concept) (Fig 2a) No simple relationships are found between flow rates and either
fault strike or hydraulic head (Fig 2b) with le50 of fault zones in any given orientation
flowing A general positive relationship does however exist between fault zone thickness and
maximum flow rate Higher flow rates from larger fault zones may arise because these
structures have greater dimensions and are more likely (than smaller faults) to be connected
to other faults in the system and the ground surface These results suggest that faults
passing through the reservoir and seal in hydrocarbon systems are most likely to promote oil
andor gas migration through the seal However it is clear that not all faults or all parts of
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 46
faults connecting the reservoir to strata above the seal will compromise petroleum traps
(see next section for further discussion)
Fig 2 Fluid flow and fault data from tunnels in the Taupo Rift (Seebeck et al 2014) a) Proportion of
localised flow carried by basement fault zones Illustrates ~80 of total cumulative flow rate occur on
lt3 of basement faults which typically have zones gt10 m wide Note one fault accounts for ~30 of
total flow rate entering basement tunnels b) 983106983137983155983141983149983141983150983156 983142983137983157983148983156 983162983151983150983141983155 ge983089 983149 983159983145983140983141 983159983145983156983144 983137983150983140 983159983145983156983144983151983157983156 983159983137983156983141983154
983142983148983151983159983086 983124983144983141 983142983148983151983159 983137983150983140 983150983151 983142983148983151983159 983142983137983157983148983156 983152983151983152983157983148983137983156983145983151983150983155 983144983137983158983141 983155983145983149983145983148983137983154 983137983162983145983149983157983156983144 983140983145983155983156983154983145983138983157983156983145983151983150983155 983155983157983143983143983141983155983156983145983150983143 983156983144983137983156 983142983137983157983148983156
983155983156983154983145983147983141 983149983137983161 983150983151983156 983138983141 983137 983155983156983154983151983150983143 983140983141983156983141983154983149983145983150983137983150983156 983142983151983154 983159983144983145983139983144 983142983137983157983148983156983155 983159983145983148983148 983137983139983139983151983149983149983151983140983137983156983141 983159983137983156983141983154 983142983148983151983159983086 983111983154983141983161 983152983151983148983161983143983151983150
983155983144983151983159983155 983156983144983141 983137983152983152983154983151983160983145983149983137983156983141 983151983152983156983145983149983137983148 983142983137983157983148983156 983137983162983145983149983157983156983144 983142983151983154 983142983148983151983159 983140983141983156983141983154983149983145983150983141983140 983142983154983151983149 983143983141983151983149983141983139983144983137983150983145983139983137983148 983156983141983139983144983150983145983153983157983141983155
983142983151983154 983137 983149983137983160983145983149983157983149 983144983151983154983145983162983151983150983156983137983148 983155983144983151983154983156983141983150983145983150983143 983156983154983141983150983140983145983150983143 983137983156 983166983088983094983088ordm 983080983154983141983140 983148983145983150983141983081983086
The role of normal faults in up-sequence flow of fluid has also been examined using 2D and
3D seismic-reflection data from the southern Taranaki Basin New Zealand (Hemmings-Sykes 2012 Ilg et al 2012) The spatial distributions of late-stage normal faults gas
chimneys thickness of the Oligocene mudstone-rich seal (Otaraoa Formation) and modelled
petroleum expulsion volumes have been compared in our studies Gas chimneys are most
common above Cretaceous source rocks modelled to have expelled hydrocarbons Most
(~70) of the observed gas chimneys follow andor are rooted in late-stage normal faults
These faults are the primary seal bypass mechanism for hydrocarbons where they displace
the seal (or intersect faults that displace the seal) and the seal is thick (eg gt~340 m) Gas
flow up along faults in low permeability mudstones (lt1 mD) is channelized with steep
chimneys often occurring close to fault tips and relay ramps In these cases gas flow may be
focused by the presence of high densities of open fractures (as is observed in outcrop)locally elevating up-sequence bulk permeabilities in the seal
Gas chimneys and normal faults imaged in a 3D seismic reflection volume provide a means
of testing the ability of geomechanical models to predict the locations of up-fault hydrocarbon
migration The use of geomechanical methods for predicting leakage risk is only applicable
as a first-order estimate of which fault sets present the highest risk of up-dip migration
(Hemmings-Sykes 2012) Slip Tendency and Dilation Tendency were able to differentiate
fault orientations in the Kupe Area most at risk of leakage and both indicated higher risk of
leakage for the fault set striking parallel to the maximum horizontal stress (approximately
northeast-southwest) In contrast Fracture Stability was not able to differentiate fault setsmost at risk of leakage in the Kupe Area The ability of geomechanical modelling methods to
983120983154983151983152983151983154983156983145983151983150 983156983151983156983137983148 983142983148983151983159
983110 983137 983157 983148 983156 983162 983151 983150 983141 983159 983145 983140 983156 983144
983149
983110 983154 983141 983153 983157 983141 983150 983139 983161
983138983137
983105983162983145983149983157983156983144
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 56
locate zones on fault surfaces with a high risk of up-sequence gas flow appears to be
limited There was no statistical difference in leakage risk between chimney and non-
chimney locations on fault surfaces when applying Slip Tendency Dilation Tendency and
Fracture Stability (Fig 3)
Fig 3 Oblique view of fault surfaces from the Kupe region with colours showing contours of slip
tendency on the fault surfaces (Hemmings-Sykes 2012) White line polygons indicate the outline of
gas chimneys mapped on the fault surfaces The chimneys are of limited extent and their locations do
not seem to be related to zones of higher Slip Tendency Refer to Hemmings-Sykes (2012) for further
details
The inability of geomechanical analyses to predict the locations of chimneys might arise
because i) these techniques do not include small-scale information on the local stress
tensor andor on the locations of open interconnected fractures and ii) they do not takeaccount of whether individual faults breach the seal and are likely to intersect a petroleum
source The poor relationship between fault orientation and fluid flow rates in the tunnel
dataset supports the view that in some cases geomechanical methods may not provide a
robust means of assigning risk of up-fault fluid flow for fault sets with widely varying strike
(Seebeck et al 2014) In our experience geomechanical modelling should be used with
caution and does not seem to be a reliable predictor of fluid flow in the New Zealand
examples studied
Conclusions
Analysis of outcrop and seismic-reflection studies of normal faults and fluid flow in NewZealand support a number of conclusions These are
1) The thickness of fault zones (containing clay-rich fault rock and fractures) generally
increases with displacement and varies by several orders of magnitude on individual
faults Elevated densities of small-scale faults (and greatest fault zone widths) typically
occur at irregularities on fault surfaces (eg relays bends and fault intersections)
2) Ground water flow in tunnels and gas chimneys imaged on seismic reflection lines show
that in low permeability rocks (eg seals) fluid flow is primarily achieved via fault zones
and that flow rates are greatest on larger faults
3) Geomechanical analysis does not appear to be a reliable predictor of where channelized
flow will occur on individual faults
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 66
4) Up-fault migration is locally enhanced at fault irregularities (ie the sites where the
highest densities of small-scale faults occur)
References
Caine JS Evans JP Forster CB 1996 Fault zone architecture and permeability
structure Geology 24(11) 1025-1028Childs C Walsh J J Manzocchi T Strand J Nicol A Tomasso M Schopfer M
Aplin A 2007 Definition of a fault permeability predictor from outcrop studies of a
faulted turbidite sequence Taranaki New Zealand In Structurally Complex
Reservoirs Geological Society of London Special Publication 292 235-258
Childs C Walsh JJ Manzocchi T Bonson C Nicol A Schoumlpfer MPJ 2009 A
geometric model of fault zone and fault rock thickness variations Journal of
Structural Geology 31 117-127
Faulkner DR Jackson CAL Lunn RJ Schlische RW Shipton ZK Wibberley
CAJ Withjack MO 2010 A review of recent developments concerning the
structure mechanics and fluid flow properties of fault zones Journal of StructuralGeology 32 1557-1575
Hemmings-Sykes S 2012 The influence of faulting on hydrocarbon migration in the Kupe
area south Taranaki Basin New Zealand Unpublished MSc Victoria University of
Wellington p 224
Gartrell A Zhang Y Lisk M Dewhurst D 2004 Fault intersections as crictical
hydrocarbon leakage zones integrated field study and numerical modelling of an
example from the Timor Sea Australia Marine amp Petroleum Geology 23 1165-1179
Ilg BR Hemmings-Sykes S Nicol A Baur J Fohrmann M Funnell R Milner M
2012 Normal faults and gas migration in an active plate boundary southern Taranaki
Basin offshore New Zealand Amercian Association of Petroleum Geology Bulletin 96(9) 1733-1756
Illing VC 1942 Geology applied to petroleum Proceedings of the Geologists Association
53(3-4) 156-187
Manzocchi T Walsh JJ Nell P Yielding G 1999 Fault transmissibility multipliers for
flow simulation models Petroleum Geoscience 5(1) 53-63
Manzocchi T Childs C Walsh JJ 2010 Faults and fault properties in hydrocarbon flow
models Geofluids 10(1-2) 94-113
Nicol A Childs C Walsh J Schafer K 2013 A geometric model for the formation of
deformation bands Journal of Structural Geology 55 21-33
Neglia S 1979 Migration of f luids in sedimentary basins American Association ofPetroleum Geology Bulletin 63(4) 573-597
Seebeck H Nicol A Walsh JJ Childs C Beetham RD Pettinga J 2014 Fluid flow
in fault zones from an active rift Journal of Structural Geology 62 52-64
Wade A 1913 The natural history of petroleum Proceedings of the Geologistsrsquo
Association 24(1) 1-13 IN1-IN3
Yielding G Freeman B Needham DT 1997 Quantitative fault seal prediction American
Association of Petroleum Geology Bulletin 81(6) 897-917
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 46
faults connecting the reservoir to strata above the seal will compromise petroleum traps
(see next section for further discussion)
Fig 2 Fluid flow and fault data from tunnels in the Taupo Rift (Seebeck et al 2014) a) Proportion of
localised flow carried by basement fault zones Illustrates ~80 of total cumulative flow rate occur on
lt3 of basement faults which typically have zones gt10 m wide Note one fault accounts for ~30 of
total flow rate entering basement tunnels b) 983106983137983155983141983149983141983150983156 983142983137983157983148983156 983162983151983150983141983155 ge983089 983149 983159983145983140983141 983159983145983156983144 983137983150983140 983159983145983156983144983151983157983156 983159983137983156983141983154
983142983148983151983159983086 983124983144983141 983142983148983151983159 983137983150983140 983150983151 983142983148983151983159 983142983137983157983148983156 983152983151983152983157983148983137983156983145983151983150983155 983144983137983158983141 983155983145983149983145983148983137983154 983137983162983145983149983157983156983144 983140983145983155983156983154983145983138983157983156983145983151983150983155 983155983157983143983143983141983155983156983145983150983143 983156983144983137983156 983142983137983157983148983156
983155983156983154983145983147983141 983149983137983161 983150983151983156 983138983141 983137 983155983156983154983151983150983143 983140983141983156983141983154983149983145983150983137983150983156 983142983151983154 983159983144983145983139983144 983142983137983157983148983156983155 983159983145983148983148 983137983139983139983151983149983149983151983140983137983156983141 983159983137983156983141983154 983142983148983151983159983086 983111983154983141983161 983152983151983148983161983143983151983150
983155983144983151983159983155 983156983144983141 983137983152983152983154983151983160983145983149983137983156983141 983151983152983156983145983149983137983148 983142983137983157983148983156 983137983162983145983149983157983156983144 983142983151983154 983142983148983151983159 983140983141983156983141983154983149983145983150983141983140 983142983154983151983149 983143983141983151983149983141983139983144983137983150983145983139983137983148 983156983141983139983144983150983145983153983157983141983155
983142983151983154 983137 983149983137983160983145983149983157983149 983144983151983154983145983162983151983150983156983137983148 983155983144983151983154983156983141983150983145983150983143 983156983154983141983150983140983145983150983143 983137983156 983166983088983094983088ordm 983080983154983141983140 983148983145983150983141983081983086
The role of normal faults in up-sequence flow of fluid has also been examined using 2D and
3D seismic-reflection data from the southern Taranaki Basin New Zealand (Hemmings-Sykes 2012 Ilg et al 2012) The spatial distributions of late-stage normal faults gas
chimneys thickness of the Oligocene mudstone-rich seal (Otaraoa Formation) and modelled
petroleum expulsion volumes have been compared in our studies Gas chimneys are most
common above Cretaceous source rocks modelled to have expelled hydrocarbons Most
(~70) of the observed gas chimneys follow andor are rooted in late-stage normal faults
These faults are the primary seal bypass mechanism for hydrocarbons where they displace
the seal (or intersect faults that displace the seal) and the seal is thick (eg gt~340 m) Gas
flow up along faults in low permeability mudstones (lt1 mD) is channelized with steep
chimneys often occurring close to fault tips and relay ramps In these cases gas flow may be
focused by the presence of high densities of open fractures (as is observed in outcrop)locally elevating up-sequence bulk permeabilities in the seal
Gas chimneys and normal faults imaged in a 3D seismic reflection volume provide a means
of testing the ability of geomechanical models to predict the locations of up-fault hydrocarbon
migration The use of geomechanical methods for predicting leakage risk is only applicable
as a first-order estimate of which fault sets present the highest risk of up-dip migration
(Hemmings-Sykes 2012) Slip Tendency and Dilation Tendency were able to differentiate
fault orientations in the Kupe Area most at risk of leakage and both indicated higher risk of
leakage for the fault set striking parallel to the maximum horizontal stress (approximately
northeast-southwest) In contrast Fracture Stability was not able to differentiate fault setsmost at risk of leakage in the Kupe Area The ability of geomechanical modelling methods to
983120983154983151983152983151983154983156983145983151983150 983156983151983156983137983148 983142983148983151983159
983110 983137 983157 983148 983156 983162 983151 983150 983141 983159 983145 983140 983156 983144
983149
983110 983154 983141 983153 983157 983141 983150 983139 983161
983138983137
983105983162983145983149983157983156983144
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 56
locate zones on fault surfaces with a high risk of up-sequence gas flow appears to be
limited There was no statistical difference in leakage risk between chimney and non-
chimney locations on fault surfaces when applying Slip Tendency Dilation Tendency and
Fracture Stability (Fig 3)
Fig 3 Oblique view of fault surfaces from the Kupe region with colours showing contours of slip
tendency on the fault surfaces (Hemmings-Sykes 2012) White line polygons indicate the outline of
gas chimneys mapped on the fault surfaces The chimneys are of limited extent and their locations do
not seem to be related to zones of higher Slip Tendency Refer to Hemmings-Sykes (2012) for further
details
The inability of geomechanical analyses to predict the locations of chimneys might arise
because i) these techniques do not include small-scale information on the local stress
tensor andor on the locations of open interconnected fractures and ii) they do not takeaccount of whether individual faults breach the seal and are likely to intersect a petroleum
source The poor relationship between fault orientation and fluid flow rates in the tunnel
dataset supports the view that in some cases geomechanical methods may not provide a
robust means of assigning risk of up-fault fluid flow for fault sets with widely varying strike
(Seebeck et al 2014) In our experience geomechanical modelling should be used with
caution and does not seem to be a reliable predictor of fluid flow in the New Zealand
examples studied
Conclusions
Analysis of outcrop and seismic-reflection studies of normal faults and fluid flow in NewZealand support a number of conclusions These are
1) The thickness of fault zones (containing clay-rich fault rock and fractures) generally
increases with displacement and varies by several orders of magnitude on individual
faults Elevated densities of small-scale faults (and greatest fault zone widths) typically
occur at irregularities on fault surfaces (eg relays bends and fault intersections)
2) Ground water flow in tunnels and gas chimneys imaged on seismic reflection lines show
that in low permeability rocks (eg seals) fluid flow is primarily achieved via fault zones
and that flow rates are greatest on larger faults
3) Geomechanical analysis does not appear to be a reliable predictor of where channelized
flow will occur on individual faults
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 66
4) Up-fault migration is locally enhanced at fault irregularities (ie the sites where the
highest densities of small-scale faults occur)
References
Caine JS Evans JP Forster CB 1996 Fault zone architecture and permeability
structure Geology 24(11) 1025-1028Childs C Walsh J J Manzocchi T Strand J Nicol A Tomasso M Schopfer M
Aplin A 2007 Definition of a fault permeability predictor from outcrop studies of a
faulted turbidite sequence Taranaki New Zealand In Structurally Complex
Reservoirs Geological Society of London Special Publication 292 235-258
Childs C Walsh JJ Manzocchi T Bonson C Nicol A Schoumlpfer MPJ 2009 A
geometric model of fault zone and fault rock thickness variations Journal of
Structural Geology 31 117-127
Faulkner DR Jackson CAL Lunn RJ Schlische RW Shipton ZK Wibberley
CAJ Withjack MO 2010 A review of recent developments concerning the
structure mechanics and fluid flow properties of fault zones Journal of StructuralGeology 32 1557-1575
Hemmings-Sykes S 2012 The influence of faulting on hydrocarbon migration in the Kupe
area south Taranaki Basin New Zealand Unpublished MSc Victoria University of
Wellington p 224
Gartrell A Zhang Y Lisk M Dewhurst D 2004 Fault intersections as crictical
hydrocarbon leakage zones integrated field study and numerical modelling of an
example from the Timor Sea Australia Marine amp Petroleum Geology 23 1165-1179
Ilg BR Hemmings-Sykes S Nicol A Baur J Fohrmann M Funnell R Milner M
2012 Normal faults and gas migration in an active plate boundary southern Taranaki
Basin offshore New Zealand Amercian Association of Petroleum Geology Bulletin 96(9) 1733-1756
Illing VC 1942 Geology applied to petroleum Proceedings of the Geologists Association
53(3-4) 156-187
Manzocchi T Walsh JJ Nell P Yielding G 1999 Fault transmissibility multipliers for
flow simulation models Petroleum Geoscience 5(1) 53-63
Manzocchi T Childs C Walsh JJ 2010 Faults and fault properties in hydrocarbon flow
models Geofluids 10(1-2) 94-113
Nicol A Childs C Walsh J Schafer K 2013 A geometric model for the formation of
deformation bands Journal of Structural Geology 55 21-33
Neglia S 1979 Migration of f luids in sedimentary basins American Association ofPetroleum Geology Bulletin 63(4) 573-597
Seebeck H Nicol A Walsh JJ Childs C Beetham RD Pettinga J 2014 Fluid flow
in fault zones from an active rift Journal of Structural Geology 62 52-64
Wade A 1913 The natural history of petroleum Proceedings of the Geologistsrsquo
Association 24(1) 1-13 IN1-IN3
Yielding G Freeman B Needham DT 1997 Quantitative fault seal prediction American
Association of Petroleum Geology Bulletin 81(6) 897-917
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 56
locate zones on fault surfaces with a high risk of up-sequence gas flow appears to be
limited There was no statistical difference in leakage risk between chimney and non-
chimney locations on fault surfaces when applying Slip Tendency Dilation Tendency and
Fracture Stability (Fig 3)
Fig 3 Oblique view of fault surfaces from the Kupe region with colours showing contours of slip
tendency on the fault surfaces (Hemmings-Sykes 2012) White line polygons indicate the outline of
gas chimneys mapped on the fault surfaces The chimneys are of limited extent and their locations do
not seem to be related to zones of higher Slip Tendency Refer to Hemmings-Sykes (2012) for further
details
The inability of geomechanical analyses to predict the locations of chimneys might arise
because i) these techniques do not include small-scale information on the local stress
tensor andor on the locations of open interconnected fractures and ii) they do not takeaccount of whether individual faults breach the seal and are likely to intersect a petroleum
source The poor relationship between fault orientation and fluid flow rates in the tunnel
dataset supports the view that in some cases geomechanical methods may not provide a
robust means of assigning risk of up-fault fluid flow for fault sets with widely varying strike
(Seebeck et al 2014) In our experience geomechanical modelling should be used with
caution and does not seem to be a reliable predictor of fluid flow in the New Zealand
examples studied
Conclusions
Analysis of outcrop and seismic-reflection studies of normal faults and fluid flow in NewZealand support a number of conclusions These are
1) The thickness of fault zones (containing clay-rich fault rock and fractures) generally
increases with displacement and varies by several orders of magnitude on individual
faults Elevated densities of small-scale faults (and greatest fault zone widths) typically
occur at irregularities on fault surfaces (eg relays bends and fault intersections)
2) Ground water flow in tunnels and gas chimneys imaged on seismic reflection lines show
that in low permeability rocks (eg seals) fluid flow is primarily achieved via fault zones
and that flow rates are greatest on larger faults
3) Geomechanical analysis does not appear to be a reliable predictor of where channelized
flow will occur on individual faults
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 66
4) Up-fault migration is locally enhanced at fault irregularities (ie the sites where the
highest densities of small-scale faults occur)
References
Caine JS Evans JP Forster CB 1996 Fault zone architecture and permeability
structure Geology 24(11) 1025-1028Childs C Walsh J J Manzocchi T Strand J Nicol A Tomasso M Schopfer M
Aplin A 2007 Definition of a fault permeability predictor from outcrop studies of a
faulted turbidite sequence Taranaki New Zealand In Structurally Complex
Reservoirs Geological Society of London Special Publication 292 235-258
Childs C Walsh JJ Manzocchi T Bonson C Nicol A Schoumlpfer MPJ 2009 A
geometric model of fault zone and fault rock thickness variations Journal of
Structural Geology 31 117-127
Faulkner DR Jackson CAL Lunn RJ Schlische RW Shipton ZK Wibberley
CAJ Withjack MO 2010 A review of recent developments concerning the
structure mechanics and fluid flow properties of fault zones Journal of StructuralGeology 32 1557-1575
Hemmings-Sykes S 2012 The influence of faulting on hydrocarbon migration in the Kupe
area south Taranaki Basin New Zealand Unpublished MSc Victoria University of
Wellington p 224
Gartrell A Zhang Y Lisk M Dewhurst D 2004 Fault intersections as crictical
hydrocarbon leakage zones integrated field study and numerical modelling of an
example from the Timor Sea Australia Marine amp Petroleum Geology 23 1165-1179
Ilg BR Hemmings-Sykes S Nicol A Baur J Fohrmann M Funnell R Milner M
2012 Normal faults and gas migration in an active plate boundary southern Taranaki
Basin offshore New Zealand Amercian Association of Petroleum Geology Bulletin 96(9) 1733-1756
Illing VC 1942 Geology applied to petroleum Proceedings of the Geologists Association
53(3-4) 156-187
Manzocchi T Walsh JJ Nell P Yielding G 1999 Fault transmissibility multipliers for
flow simulation models Petroleum Geoscience 5(1) 53-63
Manzocchi T Childs C Walsh JJ 2010 Faults and fault properties in hydrocarbon flow
models Geofluids 10(1-2) 94-113
Nicol A Childs C Walsh J Schafer K 2013 A geometric model for the formation of
deformation bands Journal of Structural Geology 55 21-33
Neglia S 1979 Migration of f luids in sedimentary basins American Association ofPetroleum Geology Bulletin 63(4) 573-597
Seebeck H Nicol A Walsh JJ Childs C Beetham RD Pettinga J 2014 Fluid flow
in fault zones from an active rift Journal of Structural Geology 62 52-64
Wade A 1913 The natural history of petroleum Proceedings of the Geologistsrsquo
Association 24(1) 1-13 IN1-IN3
Yielding G Freeman B Needham DT 1997 Quantitative fault seal prediction American
Association of Petroleum Geology Bulletin 81(6) 897-917
8122019 Fault and Their Potential
httpslidepdfcomreaderfullfault-and-their-potential 66
4) Up-fault migration is locally enhanced at fault irregularities (ie the sites where the
highest densities of small-scale faults occur)
References
Caine JS Evans JP Forster CB 1996 Fault zone architecture and permeability
structure Geology 24(11) 1025-1028Childs C Walsh J J Manzocchi T Strand J Nicol A Tomasso M Schopfer M
Aplin A 2007 Definition of a fault permeability predictor from outcrop studies of a
faulted turbidite sequence Taranaki New Zealand In Structurally Complex
Reservoirs Geological Society of London Special Publication 292 235-258
Childs C Walsh JJ Manzocchi T Bonson C Nicol A Schoumlpfer MPJ 2009 A
geometric model of fault zone and fault rock thickness variations Journal of
Structural Geology 31 117-127
Faulkner DR Jackson CAL Lunn RJ Schlische RW Shipton ZK Wibberley
CAJ Withjack MO 2010 A review of recent developments concerning the
structure mechanics and fluid flow properties of fault zones Journal of StructuralGeology 32 1557-1575
Hemmings-Sykes S 2012 The influence of faulting on hydrocarbon migration in the Kupe
area south Taranaki Basin New Zealand Unpublished MSc Victoria University of
Wellington p 224
Gartrell A Zhang Y Lisk M Dewhurst D 2004 Fault intersections as crictical
hydrocarbon leakage zones integrated field study and numerical modelling of an
example from the Timor Sea Australia Marine amp Petroleum Geology 23 1165-1179
Ilg BR Hemmings-Sykes S Nicol A Baur J Fohrmann M Funnell R Milner M
2012 Normal faults and gas migration in an active plate boundary southern Taranaki
Basin offshore New Zealand Amercian Association of Petroleum Geology Bulletin 96(9) 1733-1756
Illing VC 1942 Geology applied to petroleum Proceedings of the Geologists Association
53(3-4) 156-187
Manzocchi T Walsh JJ Nell P Yielding G 1999 Fault transmissibility multipliers for
flow simulation models Petroleum Geoscience 5(1) 53-63
Manzocchi T Childs C Walsh JJ 2010 Faults and fault properties in hydrocarbon flow
models Geofluids 10(1-2) 94-113
Nicol A Childs C Walsh J Schafer K 2013 A geometric model for the formation of
deformation bands Journal of Structural Geology 55 21-33
Neglia S 1979 Migration of f luids in sedimentary basins American Association ofPetroleum Geology Bulletin 63(4) 573-597
Seebeck H Nicol A Walsh JJ Childs C Beetham RD Pettinga J 2014 Fluid flow
in fault zones from an active rift Journal of Structural Geology 62 52-64
Wade A 1913 The natural history of petroleum Proceedings of the Geologistsrsquo
Association 24(1) 1-13 IN1-IN3
Yielding G Freeman B Needham DT 1997 Quantitative fault seal prediction American
Association of Petroleum Geology Bulletin 81(6) 897-917
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