“encouraging low salinity waterflood eor in the...
TRANSCRIPT
“Encouraging Low Salinity
Waterflood EOR in the North Sea”
Jonathan Thomas
UK Department of Energy & Climate Change
DEVEX, Aberdeen, 9th May 2012
Introduction & Context
PILOT Workgroup: Increased Recovery from
Existing Fields - Enhanced Oil Recovery
• One of the areas identified where cross industry
collaboration and sharing of best practice is needed to
maximise recovery
• Conducting screening exercise to assess the size of the
potential prize for EOR in the UKCS.
• Assess how and where EOR could apply to UKCS resources
-3000.0
-2500.0
-2000.0
-1500.0
-1000.0
-500.0
0.0
500.0
1000.0
1500.0
2000.0
Oil Remaining Resources at planned COP
Oil Possible Reserves
Oil 2P Reserrves
Oil Production to end 2010
Remaining Oil Resources at planned COP: fifty largest UKCS fields (excluding Clair field)
Oil Production to end 2010
Oil 2P Reserves
Oil Possible Reserves
Oil Remaining Resource at planned COP
21.8 billion bbls
1.4 billion bbls
4.3 billion bbls
36.4 billion bbls
Remaining Oil Resources at planned COP: CNS, NNS and WoS Fields
Oil Production to end 2010
Oil 2P Reserves
Oil Possible Reserves
IOR/EOR Aspiration (>51% RF)
Oil Remaining Resource at planned COP
21.8 billion bbls
c.31.3 billion bbls
4.3 billion bbls
1.4 billion bbls 5.1 billion bbls
Remaining Oil Resources at planned COP: Can we take more out than we leave behind ?
Low Salinity EOR
• Low Salinity EOR is a recognised technique with examples
of successful field applications around the world.
• Anticipated to be attractive for the North Sea where there is
long history of conventional waterflood.
• However Low Salinity EOR is still poorly understood by many
operators & there is a lack of confidence
• A Survey of North Sea EOR 1975 to 2005 – Awan et al.
(2008) - Doesn’t mention low salinity EOR
Aims and Objectives
• Desire to increase interest & build confidence in Low Salinity
EOR implementation.
• Aim to identify promising Low Salinity EOR candidates.
• Aim to identify clusters of fields which would benefit from
cooperative solutions (e.g. lab work, simulation work, field
pilot studies, offshore desalination plant).
Clair Ridge – A Huge Project
The Low Salinity Questionnaire
• Developed by Senergy with feedback from major
operators and leading academics.
• Was disseminated to UKCS Operators who use
secondary waterflood.
• DECC/Senergy have analysed the responses and
identified candidate fields.
Questionnaire Design
• Questionnaire relates to petrophysics, facilities &
fluid properties
• Users ranked each answer according to level of
certainty (high, medium, low)
• Overall score is based on weighting of each factor,
along with benefit, costs, rate of recovery & delay
in implementation
Questionnaire Layout
Petrophysics Considerations
• Candidate formation needs to be sandstone to be
suitable (not Aeolian)
• Clay content needs to be substantial (>10%)
• Kaolinite content should be significant and
distributed uniformly
• Core samples should be available for future
laboratory analysis
• Wettability should be mixed / intermediate
Detailed Petrophysics Questions
Facilities Considerations
• There needs to be a fresh water source available
– OR
• There needs to be available space on the
platform for installing a plant for generating low
salinity water
• Is there an area of the reservoir “ready made” to
act as a pilot test area?
• Is it possible to use or lay a pipeline for fresh
water supply ?
Detailed Facilities Questions
Fluid Properties Considerations
• The hydrocarbon needs to be have polar
compounds, so normal crude oils are suitable
(volatile oils & gas condensates will be
disqualified)
• Recent research(1) indicates that formation water
composition is important – presence of divalent
ions (especially Ca2+) is desirable
(1) SPE 129767 Austad T., Doust A.R. & Puntervold T.
Detailed Fluid Properties
Questions
Screening Tool Trial
Low Potential Low Cost
Low Salinity Water Flooding Screening Tool
Field Name ; Low Potential Low Cost
Field location ; **************
Field rating
Potential for incremental oil and higher rates 31.18
Cost and delay in implementing the Low salinity waterflooding 28.46
FACTORS answers certainty Flag
PETROPHYSICAL 0
formation type Aeolian sandstone high 0
clay content of formation <3% high 0
kaolinite distribution in the reservoir ? localized (<40 % reservoir volume) high 1
wettability strongly water wet high 0
residual oil <20% high 1
permeability low (<10md) high 1
vertical heterogeneity highly heterogeneous high
porosity low (<20%) high 1
are there natural fractures ?? yes high
are valid core samples available ? plenty of good quality from relevant zone high 2
FACILITIES
is there a fresh water source? onshore (or access to onshore facilites) high 2is there available space and weight capacity for a membrane
plant? no high 0
is it possible to lay / adapt existing pipeline for fresh water delivery?yes high 2
is a pilot area available ? yes high 2
are modifications to WI system necessary in order to
implement Low Sal to specific wells for pilot? no high
has waterflood been implemented ?? initiated in late field life high
FLUID PROPERTIES
oil type crude oil high 2
oil viscosity low high 2
reservoir temperature low high 2
connate water composition low salinity high 2
Low Potential Low Cost
0
50
100
0 50 100
Cost and delay in implementing the Low salinity waterflooding
Po
ten
tia
l fo
r i
nc
re
me
nta
l o
il a
nd
hig
he
r
ra
tes
high potential , low cost
low potential , low cost
high potential , high cost
low potential , high cost
Screening Tool Trial
High Potential High Cost
Low Salinity Water Flooding Screening Tool
Field Name ; High Potential High Cost
Field location ; **************
Field rating
Potential for incremental oil and higher rates 78.06
Cost and delay in implementing the Low salinity waterflooding 94.08
FACTORS answers certainty Flag
PETROPHYSICAL 0
formation type sandstone high 2
clay content of formation >15% high 2
kaolinite distribution in the reservoir ? widespread (>70% reservoir volume) high 2
wettability intermediate or mixed high 2
residual oil >20% high 2
permeability high (>1D) high 2
vertical heterogeneity mainly homogeneous high
porosity high (>20%) high 2
are there natural fractures ?? no high
are valid core samples available ? no high 0
FACILITIES
is there a fresh water source? none of the above possible high 0is there available space and weight capacity for a membrane
plant? no high 0
is it possible to lay / adapt existing pipeline for fresh water delivery? no high 0
is a pilot area available ? yes high 2
are modifications to WI system necessary in order to
implement Low Sal to specific wells for pilot? yes high
has waterflood been implemented ?? not at all high
FLUID PROPERTIES
oil type crude oil high 2
oil viscosity low high 2
reservoir temperature low high 2
connate water composition low salinity high 2
High Potential High Cost
0
50
100
0 50 100
Cost and delay in implementing the Low salinity waterflooding
Po
ten
tia
l fo
r in
cre
me
nta
l o
il a
nd
hig
he
r
rate
s
high potential , low cost
low potential , low cost
high potential , high cost
low potential , high cost
Analysis of Responses
• Questionnaires sent to Operators of UKCS offshore waterflood fields.
• Response rate is good (~65% eligible fields – very rough estimate).
• Questionnaire includes a scoring system – Potential score and cost score
– Certainty factor (low/medium/high) plays a role in the scoring
• Potential score normalised so that top ranked field scores 100%.
• Recognition that scoring system is very subjective.
List of Candidate Fields
• Arbitrary cut-off of 55% normalised potential score used to identify potential candidates
• Potential geographical cluster of fields identified in NNS
• HEALTH WARNING – importance is not relative placing of fields relative to each other
but identification of this overall sub-set of fields.
Secondary List of Candidates
Field Name Normalised Normalised Negatives Positives
Potential Cost
************* 54 45 Kaolinite not widespread. Drilling planned
************* 53 63 Kaolinite uncertain Drilling planned
************* 47 61 Wettability uncertain drilling now
************* 46 59 Wettability uncertain
************* 46 51 Wettability uncertain Drilling 2012
************* 44 42 Uncertain kaolinite Plenty of old core.
************* 42 45 Wettability uncertain good core; main clay is Kaolinite
************* 36 69 WI only on Alwyn Drilling planned; main clay is Kaolinite
• These fields have lower potential than those on previous slide.
• Good core coverage or with drilling planned with opportunity to acquire core.
• It is felt worthwhile carrying out corefloods on all or some of these fields.
Reasons for Failure
• In no particular order
– Aquifer drive (no water injection)
– Low clay content
– Unsuitable wettability
– No space for facilities upgrade
• In practice often a combination of factors
• Certainty factor (low/medium/high) can
have a significant part to play
Conclusions
• General literature survey and industry
discussions indicate significant potential for low
salinity waterflood EOR in the UKCS even for
mature fields.
• Requirement to identify the most promising
candidates in the UKCS.
• A screening tool has been developed which
includes focus on rock/fluid properties and
facility issues.
• A list of candidate fields has been identified
Next Steps
PILOT EOR Workgroup plans to engage with
identified Operators:
•review outcome of EOR Screening Exercise
•seek commitment on cross industry collaboration
and sharing of best practice (e.g. lab work,
simulation work)
Acknowledgement
• Thanks are due to Senergy for developing the
DECC Low Salinity Questionnaire
Senergy Ltd
15/16/17 Bon Accord Crescent
Aberdeen
AB11 6DE
UK
T: +44 1224 213440
Contact Details
Jonathan M Thomas
Senior Reservoir Engineer – EOR & Carbon Storage
Oil & Gas Team, Energy Development Unit
UK Department of Energy & Climate Change
Tel: +44 (0)0300 068 6065
Email: [email protected]