doing more with less - unconventional

17
DOING MORE WITH LESS - UNCONVENTIONAL Russell Gray - Total E&P UK Ltd. Tushar Patil - BHGE

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Page 1: DOING MORE WITH LESS - UNCONVENTIONAL

DOING MORE WITH LESS -

UNCONVENTIONAL

Russell Gray - Total E&P UK Ltd.

Tushar Patil - BHGE

Page 2: DOING MORE WITH LESS - UNCONVENTIONAL

THE CHALLENGE

● Determining pressures in tight formations above and below reservoir

intervals is critical information to define the pore pressure gradient

● Defines the drilling window

● Defines the well architecture

● Pore pressure estimated by models often lack definition of over

pressure ramps with limited tie in points (LOT, FIT)

● Requirement to define the pore pressure in the Cretaceous to

Kimmeridge Formations in very low porosity and permeability matrix

to constrain drilling windows.

Page 3: DOING MORE WITH LESS - UNCONVENTIONAL

CHALLENGES OF PRESSURE TESTING IN VERY

LOW MOBILITY FORMATIONS

● Issues with supercharging - Low volume

extraction

● High drawdown – Pre test rate &

volume dependency

● Slow build-up times - Tool storage/ Poor

stability / Poor repeatability

● Accurate Mobility calculation

Pre

ssure

Distance Away from

Wellbore

Flushed Virgin

Pres

PSC

Page 4: DOING MORE WITH LESS - UNCONVENTIONAL

RATE DEPENDENCY

PR

ES

SU

RE

TIME

Flo

wli

ne

de

co

mp

ressio

n

Pretest duration

Longer storage

dominated early

time build-up

Late time formation

response

Low Mobility Pretest

PR

ES

SU

RE

TIME

Flo

wli

ne

de

co

mp

res

sio

n

Pretest duration

Steady State Flow

(formation flow =

drawdown rate)

Storage

dominated

early time

build-upLate time formation

response

High Mobility Pretest

Fluid Flow Rate =

Drawdown Rate Rate

Fluid Flow Rate < Drawdown

RateRate

TIMETIME

Page 5: DOING MORE WITH LESS - UNCONVENTIONAL

PRESSURE TESTERS – THE OPTIONS

• Straddle packer tools

Long time to obtain a test and even longer for sampling.

Swabbing potential.

Limited life span – some reinforced straddle packers are good for ~6 tests.

High stuck in hole potential.

• Recent developments of large face probes available for formation testers

Increase surface area for testing.

Reduce time for pre tests.

More tests per run and significantly lower risk of stuck tools.

• FTeX new generation formation tester

Small internal tool volume.

Very precise and capable of very low rate drawdown.

Smart drawdown control.

Page 6: DOING MORE WITH LESS - UNCONVENTIONAL

PRESSURE TESTERS – TOOL AND PROBE SELECTION

FTeX:

0.1 psi/min RCX with XXR:

0.91 psi/min

FTeX vs XXR Overlay at Same Depth - FTeX Faster PBU at 0.008mD/cP

FTeX & XXR Overlay

FRA mobility: 0.008 mD/cP

- FTeX

- XXR

Efficiency – more data in less time (reduced rig time)

More confidence in data

TIME

PR

ES

SU

RE

Page 7: DOING MORE WITH LESS - UNCONVENTIONAL

FTEX: LARGER TEST AREA – FURTHER IMPROVEMENT

IN EFFICIENCY

Stability 1.8 psi/min

TIME TAKEN FOR TEST IS HALVED

BY INCREASING PROBE AREA.

Stability 0.91 psi/min

Stability 1.8 psi/min

Mobility = 0.003 mD/cP

37 tests (30 dry) in

13 hours with the

Standard packer

34 tests (18 dry) in

18 hours with the

Elongated packer

Straddle packer 4 tests (3 uncertain) 25 hours

XXR probe 16 tests in 18 hours

TIME

PR

ES

SU

RE

Volu

me

Page 8: DOING MORE WITH LESS - UNCONVENTIONAL

VALIDATION

8

Drawdown

pump

Isolation Valve

Quartz Gauge

Probe

Time since end of drawdown (s)

Theoretical Flow Regimes + Build Up Derivative Analysis

Spherical Radial

0.01

0.1

1

10

100

0.01 0.1 1 10 100 1000 10000

Radial

Spherical

Tool Storage

Slope = 1

Pre

ss

ure

dif

fere

nc

e a

nd

Deri

va

tive

(p

sia

)

Log-log plot

Skin effect

Probe type tools do not develop a

real radial flow, since pressure

transient lines propagate around the

wellbore. During a pressure test ,

only a few cc is drawn from

formation.

Page 9: DOING MORE WITH LESS - UNCONVENTIONAL

• Real time during the test evaluation and post job

• Using both linear and derivative plots.

• Mobility from Flow Rate Analysis –FRA (Area under methods tend to over estimate mobility – particularly in lower mobilities)

VALIDATION OF DATA

Page 10: DOING MORE WITH LESS - UNCONVENTIONAL

AREA UNDER METHOD FOR MOBILITY (SPE115825)

Shape factor is a function of

the tool geometry.

An error in the determination of

pretest volume will transform

linearly to an error in mobility

Page 11: DOING MORE WITH LESS - UNCONVENTIONAL

Time

Pre

ssu

re

Fluid Flow Rate

Pre

ssu

re

Slope

FORMATION RATE ANALYSIS (FRA)

Page 12: DOING MORE WITH LESS - UNCONVENTIONAL

DRAWDOWN MOBILITY MEDIUM/HIGH PERMEABILITY

CASEP

RE

SS

UR

E

Fluid Flow Rate =

Drawdown Rate

Page 13: DOING MORE WITH LESS - UNCONVENTIONAL

MAX RATE – DRAWDOWN MOBILITY

LOW PERMEABILITY

● Stable Pressure

● Drawdown Mobility Equation

k/μ = C * rate

● Rate

- Piston Rate (DDR)

- Fluid Flow Rate (FR)

DDR

FR

(Pf – Pmin)

Fluid Flow Rate vs Piston Rate

C = Constant, depends on probe

DD Rate Mobility 2.9 mD/cP vs Fluid Flow Rate Mobility 1.8 mD/cP

Page 14: DOING MORE WITH LESS - UNCONVENTIONAL

PRESSURE TEST – LOW PERMEABILITY

Pre

ssu

re

Dra

w D

ow

n R

ate

1st DD 2nd DD 3rd DD

Very precise control of drawdown rate allows

tool to monitor formation fluid flow = faster tests

Page 15: DOING MORE WITH LESS - UNCONVENTIONAL

INVERSE - RATE & VOLUME TO PRESSURE: SMART

TOOL

Page 16: DOING MORE WITH LESS - UNCONVENTIONAL

LOW MOBILITY TEST

Time

Formation flow rate

Pre

ssure

P

ressure

Efficiency factors:

• Pre job planning (tool selection /

probe selection)

• Real time job monitoring

• Minimum two draw downs

• Real time validation and QC –

ensure seeing formation response

not tool storage / static filtration

• Team work

• Experience

Page 17: DOING MORE WITH LESS - UNCONVENTIONAL

DOING MORE WITH LESS - CONCLUSION

• More pressure tests in less time and with considerably lower risk (probe

over packer tools)

• Valid pressures in very low mobility formations where no previous data

was possible

• Significant reduction in uncertainty in pore pressure prediction

• More accurate mobility calculations