Formation Testing for Producibility...

Formation Testing for Producibility

FORMATION TESTING CORE

LEARNING OBJECTIVES

By the end of this lesson, you will be able to:

Learning Objectives

Identify the options available to formation testers to assess formation producibility

Explain the differences between pretest drawdown mobility and formation permeability

Understand how to use drawdown mobility profiles State the function of a mini-DST, its role in estimating

formation producibility, and its differences from a conventional drill stem test

Identify the uses of vertical interference tests (VIT) and understand which data it is meant to interpret

Distinguish the capabilities and limitations of formation testing for use in permeability and producibility testing compared to conventional well testing

═════════════════════════════════════════════════════════════════════════Formation Testing Core

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FORMATION TESTING FOR PRODUCIBILITY

Formation testing for producibility involves: setting formation testers at

selected depths performing flow and

pressure buildup sequences to assess the overall fluid flow capability, and possibly the productivity of the formation interval flowing to the surface.

Formation testing specializes in probing the permeability level of formation rocks and their ability to flow to the well surface, under the condition of downhole pumping operations and wellbore-mud invasion dynamics.

The investigation of the probing is designed to focus on formation intervals, not the far lateral

extent of the formation interval at the reservoir level.

FORMATION TESTING FOR PRODUCIBILITY

Comparing Forms of Well Testing

Formation Testing• Near‐wellbore interval• Downhole pump• Small volume

Well Testing• Well‐layer flow performance• Radial flow• Initial production

Reservoir Testing• Reservoir size• Pseudo‐steady state• In‐place volume

Formation Testing Core ═════════════════════════════════════════════════════════════════════════

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GR, CAL

RES DEN-NEU PORO SW PERM

FORMATION TESTING FOR WELL / FORMATION PRODUCIBILITY

A Formation Testing Event

Sealed Formation Interval

Upper packer

Lowerpacker

Wellbore

Sealing or open fault?

Perched water?Aquifer or water leg?

H

Wellbore

Packer

Packer

Formation Interval



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FORMATION TESTING FOR WELL PRODUCIBILITY

Major Test Practice Formation Testing

Pretest Drawdown Mobility

• Primarily qualitative characterization of formation rock permeability under mud-invasion

• Possibly correlable with NMR & core permeability• Drawdown mobility can be built in well cross section panels

Extended Flow with Probes

• Also known as micro-DST• Downhole pump operated flow and pressure builds• Thin intervals required to help pressure transient data

interpretation• Preferably integrated with fluid sampling

Mini‐DST

• Widely practiced with dual packer wireline tools• Conceivably comparable with a conventional DST tool

configuration but highly reliance on downhole pump• Flowing pressure data interpreted

Vertical Interference Test

• Also known as VIT• Multiple options with two or more basic wireline tester probes,

or probe-dual packer configuration• Integrated data interpretation for both the monitor probe

pressures and the flowing probe or dual packer pressures• Vertical permeability or barrier

FORMATION TESTING FOR WELL PRODUCIBILITY

Formation Testing does NOT…

…directly answer questions such as a well’s productivity index or a gas well’s AOF.

…address reservoir boundary or extent of oil‐in‐place volumes or the minimum drainable volumes which are usually answered from extended well testing or surveillance data.

…estimate the formation damage or skin level, which requires a large fluid volume evacuation from the reservoir.


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FORMATION TESTING PRETEST

Drawdown mobility is computed from the small volume pretest

during its quick flow event

A conventional plot of delta pressures and their derivatives

can be generated for both drawdown and buildup periods




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FORMATION TESTING PRETEST DRAWDOWN MOBILITY PROFILE

Pretest Drawdown Mobility Profile8800

8900

9000

9100

9200

9300

9400

9500

9600

97000.01 0.10 1.00 10.00 100.00

Drawdown Mobility (md/cp)

TV

D, f

t

Upper Sand

Middle Sand

Lower Sand

better quality sand

fair quality sand

fair quality sand

poor quality sandDrawdown Mobility Threshold?


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GEOSTEERING OF LWD TESTING WITH DRAWDOWN MOBILITY

Tar Mat

GEOSTEERING OF LWD TESTING WITH DRAWDOWN MOBILITY

Tar Mat



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PROBE-BASED EXTENDED FLOW AND PRESSURE BUILDUP

Early practiced by Norsk-Hydro in North Sea to acquire formation permeability as alternative to well testing (SPE 48962, 1998)

Operation sequence similar to a typical well flow and subsequent shut-in for pressure buildup; downhole pump required in order to generate large flow volumes

Data treated with conventional pressure transient analysis (PTA); radial flow regime identification required for kh/μ and skin estimates

Commonly found useful in thin layers which have confined interval thickness, H

Questions of invaded zone effect in short flows Long term fluid sampling events improve

multiphase mobility transition during clean-up

flowing


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flowing


Frimann-Dahl et al (1998) SPE 48962



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Cosan Ayan et al. (2001) Oilfield Review



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MINI-DST TEST

MINI-DST TEST



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MINI-DST TEST BENEFITS

Ramaswami et al (2012) SPE 139837Harmawan et al (2012) SPE 145764

MINI-DST TEST APPLICATIONS

Harmawan et al (2012) SPE 145764


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MINI-DST TEST APPLICATION

Courtesy SPE 158383 (Aguilera et al, 2012)

MINI-DST TEST INTERPRETATIONS

0. 1. 2. 3. 4. 5. 6.

-5.

5.10

.20

.

T ime (hours)

ST

B/D

0. 1. 2. 3. 4. 5. 6.

500

.1

000.

150

0.20

00.

250

0.

PS

I

2010/08/10-0000 : OIL

10-4 10-3 10-2 10-1 100

10-1

100

101

102

Delta-T (hr)

DP

& D

ER

IVA

TIV

E (

PS

I/S

TB

/D)

0. 1. 2. 3. 4.

800.

1000

.12

00.

1400

.16

00.

1800

.20

00.

T ime (hours)

pre

ssur

es (

PS

I)

2010/08/10-0252 : OIL

P ti l P t ti W ll

DeconvolvedDerivatives



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VERTICAL INTERFERENCE TEST VIT

flowing

flowing

monitormonitor

Probe M

odule

Probe M

odule

Probe M

odule

Probe M

odule



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VERTICAL INTERFERENCE TEST WITH PROBE AND PACKERS

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

0 10000 20000 30000

Pre

ssu

re (

psi

a)

Elapsed time (s)

0

10

20

30

40

50

Oil

Rat

e (

cm3

/s)

Pre-Test Straddle Packer

Initial Build-up

Final Build-up in progress

Observation Prob

6.5 feet

3.28 feet

Straddle Packer

Inflatable Elements


23025

23030

23035

23040

23045

23050

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Elapsed Time (sec)

Pre

ssu

res

at T

wo

Mo

nit

or

Pro

bes

(kP

aa)

0

5000

10000

15000

20000

25000

30000

35000

Pre

ssu

res

at F

low

ing

Pro

be

(kP

aa)

BSG1

BSG3

BSG2

sampling



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tAkz

qtp v

hpv

1

4)(

tBkkr

qtp h

vhw

h 1

8)(

2pt

v

zC

kA

2wt

h

rC

kB

1v 5117.0h

Zimmerman et al (1990) OSEA 90105


Sp

ecia

lP

rob

eP

rob

e M

od

ule

Sample Chamber Induced VIT TestOpenhole Size = 222 mm


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0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

11.00

12.00

0 200 400 600 800 1000 1200

Elapsed Time (sec)

De

lta

Pre

ss

ure

s (

kP

a)

Actual

0.73 m

2.39 m

4.57 m

9.14 m

12.19 m

Kh=57 md, Kv=21 md, viscosity=0.6 cp

Delta Pressures (psi)

Elapsed Time (sec)



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LEARNING OBJECTIVES


Learning Objectives


Identify the options available to formation testers to assess formation producibility

Explain the differences between pretest drawdown mobility and formation permeability

Understand how to use drawdown mobility profiles State the function of a mini-DST, its role in estimating

formation producibility, and its differences from a conventional drill stem test

Identify the uses of vertical interference tests (VIT) and understand which data it is meant to interpret

Distinguish the capabilities and limitations of formation testing for use in permeability and producibility testing compared to conventional well testing

You have now learned to:

SUMMARY

Formation testing offers specialized pressure transient data at targeted formation intervals for qualitative and quantitative permeability estimates and producibility assessment

Extended probe-based flow and mini-DST tests are operated and interpreted with conventional pressure transient analysis approachesExtended flow and mini-DST work best in thinner intervals with easier interval thickness quality control and radial flow regime justificationsVertical interference tests VIT provide an option for thick homogeneous formations for data with additional quality control

Both mini-DST and VIT can investigate tens of metres deep into the formation

Drawdown mobility from wireline and LWD pretests offer quick formation permeability profiling


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Formation Testing for Producibility...

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