7/25/2019 SPE-177193-MS en Ingles

1/17

SPE-177193-MS

First Run Of A Lwd Micro-Resistivity Im!es "oo# $ontri%utes "o &'dte

"(e Loc# )eomec(nic# Mode# In "(e "'i Fie#d* Ecudor

O. Corozo, and G. E. Camacho, Petroamazonas;

M. S. Guerrero, H. A. Osorio, D. Medina, R. E. Ruiz, D. F. Di!a, and F. ". Ae!!an, #eather$ord

Co%&ri'ht ()*+, Societ& o$ Petro!eum En'ineers

his %a%er -as %re%ared $or %resentation at the SPE atin American and Cari//ean Petro!eum En'ineerin' Con$erence he!d in 0uito, Ecuador, *1 2() 3oem/er()*+.

his %a%er -as se!ected $or %resentation /& an SPE %ro'ram committee $o!!o-in' reie- o$ in$ormation contained in an a/stract su/mitted /& the author4s5.Contents o$ the %a%er hae not /een reie-ed /& the Societ& o$ Petro!eum En'ineers and are su/6ect to correction /& the author4s5. he materia! does not

necessari!& re$!ect an& %osition o$ the Societ& o$ Petro!eum En'ineers, its o$$icers, or mem/ers. E!ectronic re%roduction, distri/ution, or stora'e o$ an& %art o$ this%a%er -ithout the -ritten consent o$ the Societ& o$ Petro!eum En'ineers is %rohi/ited. Permission to re%roduce in %rint is restricted to an a/stract o$ not more than7)) -ords; i!!ustrations ma& not /e co%ied. he a/stract must contain cons%icuous ac8no-!ed'ment o$ SPE co%&ri'ht.

A%strct

During the drilling campaign in the Tapi field, Ecuador, events of total losses and directional unexpected

behaviors were observed. These issues represent a high risk in the operations and required a betterunderstanding of the geological structures. The use of a new Logging While Drilling LWD! "icro#

$esistivit% technolog% was used for the first time in Tapi field, Ecuador to stud% the geological and

geomechanical characteristics of this field in detail.

The tool string was run as a penta#combo with a rotar% steerable s%stem with the purpose of getting ahole in gauge and consequentl% a better image qualit%. The LWD micro#resistivit% images tool providedimages of the borehole. The interpretation of the "icro#$esistivit% &mage started showing an averagestructural dip trend towards 'E, identif%ing a main structural trend of the field.

Two post#drill geomechanical models based on wellbore stabilit% were made in the Tapi & and Tapi &&wells. (sing the LWD micro#resistivit% images technolog% the current geomechanical model was

confirmed. )ased on the geological information acquired through the image interpretation natural

fractures orientation, breakouts, faults, structural and stratigraphic dips!, the geomechanical modeluncertainties were minimi*ed.

Introduction

The Tapi field is located in the +riente basin in Ecuador ig. -!. The basin forms a ub#/ndean s%stem

and foreland basin deformed b% compressive stress ''E#W. "ain structures correspond to positive

flower structures developed along three tectonic s%stems. The Tapi ield was developed in the center ofthe basin, this structural domain is the result of the inversion of gravens which emerged, actuall% forming

part of an important uplift in the *one modified from )ab% et al., -0001 $ivadeneira % )ab%, -000!.

The Tapi field is a complex *one due to high tectonic influence, causing significant wellbore stabilit%

issues. &n addition, geological features, such as structural trends, fractures and faults1 can cause trapped over#

pressure. urthermore, the a*imuth and inclination of the planned wells and the bedding dips, pore pressure

gradients, in#situ stresses magnitudes and directions can cause additional problems to the wellbore stabilit%.

ields with this kind of complex geolog% and stabilit% issues require the use of Logging

7/25/2019 SPE-177193-MS en Ingles

2/17

( SPE9*::*79MS

Fi!ure 1+Structur# m' nd #oction of t(e Oriente ,sin* w(ere t(e t(ree tectonic domins re s(own modified from ,%y et #.*

1999/ Rivdeneir nd ,%y* 19990* nd #oction of t(e "'i I nd II we##s

While Drilling LWD! "icro#$esistivit% &mages technolog% to update the geomechanical model,improve the drilling efficienc%, and manage the risks.

The well studied was developed to obtain the best information possible and enhance the geological

understanding of the field. /s expected, the vertical resolution from the LWD micro#resistivit% images

was the indicated to detect the stratigraph% and tectonic events1 in general2 bedding, natural fractures,

induced fractures and faults were identified and interpreted. +verall, the information obtained on thisstud% was ver% useful and allowed a better drilling operation thus contributing to the successful

culmination of the pro3ect.

A ew L2 "ec(no#o!y4 ,ore(o#e Im!in!

Toda%, LWD tools have the abilit% to generate images of the borehole walls while drilling. Themagnetometers and inclinometers allow the oriented tools to set to magnetic north for vertical wells andhigh side of the hole for directional and hori*ontal wells. Tools oriented b% accelerometers and

magnetometers use surve%s a*imuth and inclination! as a reference to measure intercepted planes inside

the well.

The sinusoids are generated when the c%lindrical surface of the well is intersected b% non#perpendicular

planar events or events parallel to the axis of the tool. The amplitude of these sinusoids increases depending in

the si*e of the angle formed between these levels and the tool axis. The apparent dip a*imuth of the events, is

given b% the orientation of the line of maximum slope of the plane represented b% the sinusoids formed b% the

cut of the c%lindrical borehole wall, which is the orientation of the line that 3oinsSPE9*::*79MS 7

7/25/2019 SPE-177193-MS en Ingles

3/17

the highest part with the lowest of the sinusoids. When the hole is vertical, the amplitude of the sinusoidsis directl% proportional to the angle of inclination ig. 4!.

Fi!ure 5+Pers'ective of sinusoids ccordin! to t(e we##%ore tr6ectory

L2 micro-resistivity im!es "oo#

The Weatherford LWD micro#resistivit% images tool provides high resolution of the borehole imageswith a vertical resolution of 5.4 inch, while drilling in a wide range of water#based mud conditions.igure 6shows the LWD micro#resistivit% images tool technical specifications.

Fi!ure 3+L2 Micro-Resistiviy Im!e too# tec(nic# s'ecifictions

7/25/2019 SPE-177193-MS en Ingles

4/17

< SPE9*::*79MS

These images can reveal natural and induced fractures, faults, vugs, and fine#scale bedding features toprovide detailed structural and stratigraphic geological information.

/s the tool rotates, 7 and 8 axis magnetometers follow the orientation of the detector blade. The data

count rates are recorded each 49 milliseconds and sorted into a*imuthal bins. These a*imuthal curves are

interpolated verticall% and circumferentiall% to produce a 6:5 degrees borehole image ig. ;!.

Fi!ure +A8imut(# dt cuisition two first !r'(s on t(e #eft0. Inter'o#ted 1: %ins ; re# time midd#e0 nd inter'o#ted 15< %ins

; memory ri!(t0

/dvantages and applications of the LWD micro#resistivit% images tool include a full 6:5 degrees

borehole coverage rapid acquisition data into -4< bins recorded and real#time images into -: = 64 bins!,

proactive geosteering, earl% formation evaluation, stratigraphic dip, facies characteri*ation, evaluation of

secondar% porosit% and geomechanical and wellbore#stabilit% information. igure 9 shows a sample

image of natural fractures.SPE9*::*79MS +

7/25/2019 SPE-177193-MS en Ingles

5/17

Fi!ure =+An im!e 15< %ins0 e>m'#e of ntur# frctures s(owin! #r!e c#uster of conductive frctures

The micro#electric images use a color range to indicate the resistivit% of the materials, lighter tones

represent high resistivit% low conductivities! and, darker colors represent, low resistivit% high conduc#

tivities!. >igh conductivities can be caused b% conductive minerals, some t%pes of cla%s, like p%rite, thepresence of mud filtrate, non#resistive in fractures, dissolution cavities or in an% t%pe of porous space

ig.:!.

Fi!ure : +Im!in! code of co#ors - (i!( resistivity #ow conductivities0

This paper shows the interpreted results of the high resolution images used to update the geologicalfeatures and local geomechanical model.

7/25/2019 SPE-177193-MS en Ingles

6/17

= SPE9*::*79MS

Im!e Inter'rettion Resu#ts

+nce the field operations were completed and the memor% image data recovered, the information wasprocessed and interpreted1 showing the following results2

The geological features interpreted from the LWD micro#resistivit% images included a structural dip,

faults, natural fractures and breakouts. The structural dip was interpreted from features assumed to mark

paleo#hori*ontal surfaces, such as laminated shales and other low energ% sediments. The LWD resistivit%

image from the Tapi && well shows a low structural dip angle and a predominant a*imuth trend to the East

ig. ?!.

Fi!ure 7+Im!e inter'rettion of "'i II we## - Structur# di'

&nduced fractures were observed in the image from Tapi && well with main strike direction of W'W

= EE ig.

propagate an% significant distance awa% from the wellbore. &mage logs are essentiall% the onl% wa% to

know if drilling induced tensile fractures are present in a well @oback, 45-5!. The minimum stress

direction is normall% perpendicular to the maximum stress direction1 these stresses are related to

breakouts, which were interpreted also in the image ig.

7/25/2019 SPE-177193-MS en Ingles

7/17

Fi!ure < +Inter'reted im!e on "'i II we##* s(owin! induced frctures #eft0 nd %re?outs ri!(t0 directions* corro%ortin! t(e #oc#

stresses of t(e fie#d

The stress direction identified on the interpreted image matches with the regional maximum hori*ontalstress direction of the outh /merica /ndes $idge ig. 0!.

Fi!ure 9 +Orienttion of t(e m>imum (ori8ont# stress direction in Ecudor fter* 2or#d Stress M'0

The LWD micro#resistivit% images tool allowed the interpretation of several geological features such

7/25/2019 SPE-177193-MS en Ingles

8/17

as2

7/25/2019 SPE-177193-MS en Ingles

9/17

1 SPE9*::*79MS

Conductive natural fractures2 recogni*ed in the image for showing continuous and low resistive

sinusoid cutting the beds or structures. igure -5shows an example of conductive fracture interpreted at

the Tapi && well1 the stereonet shows the main strike direction for these fractures.

Fi!ure 1@ +Inter'retted ntur# frctures wit( stri?e direction 22-ESE* in t(e "'i II we##

Resistive natural fractures:recogni*ed in the LWD micro#resistive image for continuous and highresistive sinusoid cutting the beds or structures. igure --/ shows an example of resistive fractures

interpreted in the Tapi && well.SPE9*::*79MS

7/25/2019 SPE-177193-MS en Ingles

10/17

Fi!ure 11+$onductive miner#s nd resistive ntur# frctures

Conductive minerals: observed in some intervals of the image, showed on figure --). Theseconductive responses could be due to the metallic composition of the minerals1 the dark spots of theimage represent them.

/ micro-fault:interpreted on the image of this well can be seen on figure -4, where the resistivit%contrast is clearl% visible.

Fi!ure 15+Possi%#e inter'reted micro-fu#t in "'i II we##

7/25/2019 SPE-177193-MS en Ingles

11/17

*) SPE9*::*79MS

The interpreted geological features from the LWD micro#resistive images, including breakouts,

induced fractures directions, faults and structural dip, served to confirm the local geomechanical model in

the Tapi field, Ecuador.

$ontri%ution to t(e Loc# )eomec(nic# Mode# of t(e "'i Fie#d

Two post#drill geomechanical studies for the Tapi & and Tapi && wells were used to create a -D

Aeomechanical "odel based on wellbore stabilit% in the reservoir. &n the geomechanics stud% workflow,

the following information have been incorporated2 electrical logs, well designs, mud weights, &Ts, dail%

drilling reports, formation pressure test, and the new geological data acquired from LWD micro#

resistivit% images in the Tapi && well.

The geomechanical models were used to understand and predict instabilit% mechanisms for the local

forecast of the next Tapi well and minimi*e the non#productive time. The information of the LWD micro#

resistivit% images served to obtain better understanding of geopressures, in#situ stresses, and rock

mechanical properties calculations, to estimate the optimal operative mud#window in order to avoid more

costl% wells related to the borehole deterioration.

igure -6 shows the hori*ontal in#situ stress directions2 > 'W#E! and h 'E#W!. Data acquiredfrom "icro#$esistive &mages of LWD in Tapi && well.

Fi!ure 13+ori8ont# in-situ stress directions of "'i II we##

igure -; shows electrical logs from the LWD data2 lithological column, pore pressure, shear failure

gradient, fracture gradient, maximum hori*ontal stress gradient, and overburden gradient in the Tapi &

well Bost#Drill!.SPE9*::*79MS **

7/25/2019 SPE-177193-MS en Ingles

12/17

Fi!ure 1 +"'i I we##* from #eft to ri!(t* t(e first five trc?s s(ow t(e e#ectric #o!s* :t( trc? indictes t(e #it(o#o!ic# co#umn* 7t(

trc? defines t(e !eomec(nics mode# 'ore 'ressure !rdient* s(er fi#ure !rdient* frcture !rdient* over%urden !rdient nd

m>imum (ori8ont# stress !rdient0* nd

7/25/2019 SPE-177193-MS en Ingles

13/17

*( SPE9*::*79MS

Fi!ure 1=+"'i II we##* from #eft to ri!(t* t(e first five trc?s s(ow t(e e#ectric #o!s* :t( trc? indictes t(e #it(o#o!ic# co#umn* 7t(

trc? defines t(e !eomec(nics mode# 'ore 'ressure !rdient* s(er fi#ure !rdient* frcture !rdient* over%urden !rdient nd

m>imum (ori8ont# stress !rdient0* nd

7/25/2019 SPE-177193-MS en Ingles

14/17

Fi!ure 1: +"'i I we##* t(e trc?s in t(eir order from t(e #eft to t(e ri!(t s(ow/ )mm Ry* Lit(o#o!y $o#umn* &nconfined $om'ressive

Stren!t( &$S0 of t(e roc?s* PoissonBs Rtio 0* Sttic Coun!Bs Modu#us Cms0* $o(esive Stren!t( $s0 nd Friction An!#e FA0

igure -? shows rock mechanical properties of the Tapi && well, Tapi field Bost#Drill! obtained fromLWD information.

7/25/2019 SPE-177193-MS en Ingles

15/17

*< SPE9*::*79MS

Fi!ure 17+"'i II we##* t(e trc?s in t(eir order from t(e #eft to t(e ri!(t s(ow/ )mm Ry* Lit(o#o!y $o#umn* &nconfined $om'ressive

Stren!t( &$S0 of t(e roc?s* PoissonBs Rtio 0* Sttic Coun!Bs Modu#us Cms0* $o(esive Stren!t( $s0 nd Friction An!#e FA0

igure -< shows stereograms at two different depths of the reservoir in the Tapi & well, and suggeststhat wells with less than 4

7/25/2019 SPE-177193-MS en Ingles

16/17

igure -0 shows the attack angle in two units of reservoir formation in the Tapi & well.

Fi!ure 19 +"'i I we## ttc? n!#e in different units of reservoir formtions

/ccording to the attack angle plot shown in figure -0, the different units of reservoir formation weredrilled in an up#dip direction that offered better wellbore stabilit% in the reservoir of Tapi & well.

$onc#usion

The first run of the LWD "icro $esistivit% &mage tool in the Tapi ield in Ecuador produced high qualit%images, that allowed the interpretation of geological features and geological events that cannot bedetected with conventional LWD tools.

The geologic structures interpreted using the LWD micro#resistivit% images were structural dip,conductive minerals, faults, natural fractures, induced fractures and breakouts. This geological informa#tion was an important input for the reservoir geomechanical stud% performed on the Tapi & and Tapi &&wells.

The &nduced fractures and breakouts observed in the LWD micro#resistivit% images from the Tapi && well

corroborated the local in#situ hori*ontal stresses. The identified stress direction on the interpreted image,

matches with the regional maximum hori*ontal stress direction of the outh /merica /ndes $idge.

The geomechanical stud% in this field indicated that for deviated wells above 4orsrud, B.,Estimating Mechanical Properties of Shale from Empirical Correlations,BE 9:5-?.Weatherford Drilling ervices1 Technical Specification Sheets,>ouston, Texas, 45-6.

/squith, A., and Fr%gowski, D.1 )asic Well Log /nal%sisAAP Metho!s in E"ploration Series,'o.-:. Tulsa, +klahoma, 455;.