MDT Mini Fracture Technique

How to directly measure stresses downhole

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Outline

Stress measurements: why and how Wireline stress measurements

Method Tool Procedure

Examples of advanced applications Conclusions

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Applications of Stress Measurements

Prediction of wellbore stability Prediction of sand production Planning of stimulation treatments Completion design Management of reservoirs

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Possible Methods for Measuring Stresses

Extended leak-off tests Log interpretation methods (sonic based) Image analysis (breakouts, fault slip, drilling induced

fractures Hydraulic fracturing calibration test Core relaxation techniques Tests on pre-existing fractures Mini-hydraulic fracturing technique (MDT)

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Why MDT Mini Frac?

Cheaper and Faster Than LOTs High Resolution, Focusable Measurement Can Be Combined With Other Wireline Logging Tools

(save more more time) Can Be Run In Cased Hole

Recent Example: Tight Formation, Where No Pressure Had Been Possible Mini Frac In Cased Hole => Gave The Reservoir Pressure

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Usual Micro-Hydraulic Fracturing Technique for Stress Testing

A 2 wing fracture grows perpendicular to the far-field minimum stress.

Wellbore subparallel to principal stress

Fracture has to grow away from wellbore dominated region

PackerFracture

Fluid Injection

PressureGauge

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A Wireline ConveyedStress Tool

Downhole pump

Software controlled in real time

Very stiff hydraulic system

=> crisp pressure records

PumpoutPumpoutPumpoutPumpout modulemodulemodulemodule

PackerPackerPackerPacker

WirelineWirelineWirelineWireline

PackerPackerPackerPacker

Pressure gagePressure gagePressure gagePressure gage

Flow controlFlow controlFlow controlFlow controlModuleModuleModuleModule

SlidingSlidingSlidingSlidingcouplingcouplingcouplingcoupling

P

P

Inflate sealInflate sealInflate sealInflate sealvalvevalvevalvevalve

Interval sealInterval sealInterval sealInterval sealvalvevalvevalvevalve 1m1m1m1m

SampleSampleSampleSamplechamberchamberchamberchamber

P

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Test Procedure

Packer inflation Leak-off cycles Hydraulic fracturing cycle Hydraulic reopening cycle Packer deflation Analysis of each cycle

separately for stress indicators

InjectionInjectionInjectionInjection raterateraterate

Interval pressureInterval pressureInterval pressureInterval pressure

PackerPackerPackerPackerinflationinflationinflationinflation

Packer pressurePacker pressurePacker pressurePacker pressure

LeakLeakLeakLeakoffoffoffoff

Hydraulic Hydraulic Hydraulic Hydraulic fracturingfracturingfracturingfracturing

HFHFHFHF Packer Packer Packer Packer DeflationDeflationDeflationDeflation

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Example of Reopening Analysis

Linear fitLinear fitLinear fitLinear fit

Fracture reopensFracture reopensFracture reopensFracture reopens

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Example of Shut-in Analysis

Fracture closesFracture closesFracture closesFracture closes

Linear fitLinear fitLinear fitLinear fit

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Example of Rebound Analysis

Start rebound Start rebound Start rebound Start rebound

StartStartStartStart flowbackflowbackflowbackflowback

Interval Interval Interval Interval pressure pressure pressure pressure

Packer Packer Packer Packer pressure pressure pressure pressure

Rebound pressureRebound pressureRebound pressureRebound pressure

(Impermeable Formation Prebound 3)

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Breakdown pressureBreakdown pressureBreakdown pressureBreakdown pressure

Propagation pressurePropagation pressurePropagation pressurePropagation pressure

ISIPISIPISIPISIP

Closure pressureClosure pressureClosure pressureClosure pressure Reopening pressureReopening pressureReopening pressureReopening pressure

Selected closure stressSelected closure stressSelected closure stressSelected closure stress

Example of Reconciliation PlotTrend Stabilises => Frac Has Propagated Beyond NWB

Looking for trends in the data to select the closure stress

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Imaging the Created Fracture

AfterBefore

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Stress Measurements Unleashed

Wireline stress testing classically limited to low permeability formations

Application typically limited to design of hydraulic fracturing stimulation

With more and more complex well paths, knowledge of stress is a key input to better field development

To get the full value of the measurement, one needs to extend its applicability: wider range of formation permeability portability of results, horizontal stress contrast

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Stress Testing Impermeable Formations

Applications

Stress contrast for HF containment

Stress in cap rock for storage of hydrocarbons

Problem rock for drilling

Challenges

Proper fracture initiation

Fracture does not close naturally

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Example 1: Stress Testing a Cap Rock

Purpose: Measuring the minimum stress acting on the cap rock

of a gas storage reservoir.

Existing well: perform test cased hole (1.5 ft, 45o phasing, 12 spf)

Procedure Flowback/rebound test

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Results

Four measurements in the cap rock (confidence) Safe operating pressure confirmed for the storage

ShutShutShutShut----InInInInStartStartStartStart flowbackflowbackflowbackflowback

Max. rebound pressure Max. rebound pressure Max. rebound pressure Max. rebound pressure

Start reboundStart reboundStart reboundStart rebound

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Determination of Maximum Horizontal Stress: H

Based on packer reopening of an already tested fracture by Sleeve Fracturing

preopening = 3 h - H + pfrac Where Pfrac is fluid Pressure in frac

pfrac = pmud column if filter cakepfrac = preservoir without filter cake

Valid only if wellbore subvertical (

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Example 2: Stress Testing a Tight Gas Reservoir

Purpose: Measuring the horizontal stresses to decide on the

development of the field: hydraulic fracturing vs. short radius drainage holes. Question: What is Stress Anisotropy?

New well: open hole test.Procedure: combination of hydraulic fracturing and packer

fracturing

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Results: Low Horizontal Stress Contrast

Confirmed with DSCA on cores No preferred drilling direction for wellbore stability

Parabolic fit Parabolic fit Parabolic fit Parabolic fit Fracture reopens Fracture reopens Fracture reopens Fracture reopens

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Job Histories From Tight Carbonate Fields

Venezuela Tests = 3, Depth = 4800 m,Formation = limestone, BS =

8.5 in gauge Verify That Low Permeability Formation Can Withstand

Mud Weight of 16.5 lb/ft Answer: Yes Allowed Petrobras to drill ahead without

setting casing Oman

Tight Formation, depths were 2600 to 2825 metres. Objective: Determine Frac Gradients Result: Sleeve Fracturing => Frac Gradient = 1.25 psi/ft

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Job From Recent Abu Dhabi WellPump Sequence at 8870ft

3000

4000

5000

6000

7000

8000

9000

7600 8600 9600 10600 11600 12600 13600 14600 15600

time seconds

pres

sure

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

pum

pout

mot

or s

peed

Interva Quartz GaugeCorrected Packer PressurePOMS

Packer Failed Apparently

Packer Inflate

Filtration Tests

Attempt PO More

Reinflate

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Interpretation Of Data Packer Pressurevs Pumpout Volume

Implies A Probable Sleeve FractureLast Major Pumpup

5600

6100

6600

7100

7600

8100

1505000 1510000 1515000 1520000 1525000 1530000 1535000 1540000 1545000 1550000

POPV CC

Corr

ecte

d Pa

cker

Pre

ssur

e

Correct_Packer_pressure

Probable Sleeve Fracture

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Typical Sleeve Fracture Response

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Packer Interval Pressures Indicated Fracturing Reached Packer Interval

1st Major Pressure Up @8870ft

4500

5000

5500

6000

6500

7000

7500

11890 11910 11930 11950 11970 11990 12010 12030 12050 12070 12090

time seconds

pres

sure

0

1000

2000

3000

4000

5000

6000

7000

8000

pum

pout

mot

or s

peed

Interva Quartz GaugePASGCorrected Packer PressurePOMS

Sleeve Frac?

Sleeve Fracture Reaches Packer Interval

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Conclusions New developments of a wireline tool for stress

measurements provide measurements of stress magnitudes in a wide range of formations.

The information can be combined with images for determination of stress direction.

Such data provides critical input to applications at the scale of the field: field development, completion strategy or enhanced recovery.

Building a calibrated stress model ensures portability of the results.