(Formation Evaluation and the Analysis of Reservoir Performance)

Module for:

Analysis of Reservoir Performance

Pressure Transient Testing T.A. Blasingame, Texas A&M U. Department of Petroleum Engineering Texas A&M University College Station, TX 77843-3116 (979) 845-2292 — [email protected] (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing

Slide — 1

Pressure Transient Testing Orientation — This module focuses on familiarization with deliverability tests and the analysis and interpretation pressure transient test data. The following issues must be clear: test design, data acquisition/data quality control, and test execution are critical activities. Deliverability Testing: "4-point" tests are appropriate (analyze as well tests). Isochronal/modified isochronal testing is difficult.

Pressure Transient Test Analysis/Interpretation: Conventional analysis — specialized plots. Model identification — type curves, simulation, etc. Test design — simplicity is the key. (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing

Slide — 2

Deliverability Testing — Basics

a. "Standard" 4-point test deliverability test — note that the rates increase (to protect the reservoir).

c. Modified "Isochronal" test sequence — note that each "buildup" is not required to achieve pi.

b. "Isochronal" test sequence — note that each "buildup" is required to achieve pi.

d. Governing equations for "deliverability" test analysis/interpretation.

(04 December 2002)

PETE 689 (02C) — Pressure Transient Testing

Slide — 3

Deliverability Testing — Orientation

a. Basic "pressure-squared" relation that is presumed to describe gas flow — analogous form can be derived from steady-state flow theory (Darcy's law).

c.Traditional "deliverability" plot — probably derived from empirical plotting of data.

b."Rate-squared" (or velocity-squared) formulation — analogous form can be derived from steady-state flow theory (Forchheimer Eq.).

d. Modified "deliverability" plot — note that bqsc2 must be known (... need alternative approach).

(04 December 2002)

PETE 689 (02C) — Pressure Transient Testing

Slide — 4

Deliverability Testing — 4-Point Tests

b. "Standard" 4-point test deliverability test — note that the rates increase (to protect the reservoir).

Discussion: The value "value" of deliverability tests is in the process — the data can be be more effectively analyzed as "well test data" than as deliverability data. However, deliverability analysis can serve as a quality control (data checking). a.Basic deliverability test analysis — note the difference in the simplified and "LIT" cases.

(04 December 2002)

PETE 689 (02C) — Pressure Transient Testing

Slide — 5

Deliverability Testing — Isochronal Tests Isochronal Test Analysis — Note the multiple trends.

(04 December 2002)

PETE 689 (02C) — Pressure Transient Testing

Slide — 6

Well Test Analysis — Multirate Testing

a. Multirate (4-point) rate sequence (note pressure match (solid trend through the data).

c. Results summary — note that non-Darcy flow, changing wellbore storage, and an infiniteacting reservoir system were considered in this analysis. b. Log-log "summary plot" — note good agreement in comparison of data and model.

(04 December 2002)

PETE 689 (02C) — Pressure Transient Testing

Slide — 7

Well Test Analysis — "Well Interference"

a. "Well Interference" plot — note the linear trend through the data functions (confirms interference) .

c. Horner semilog plot — note the two semilog trends confirm the radial composite model.

Discussion:

b. Log-log "summary plot" — note the corrected and uncorrected data (well interference).

(04 December 2002)

"Well interference" is much more common than previously thought — and we must recognize the characteristic behavior on each plot: – Log-log plot (b) – Semilog plot (c) – Specialized plot (a)

PETE 689 (02C) — Pressure Transient Testing

Slide — 8

Well Test Analysis — Basic Plots

a. Log-log "preliminary analysis" plot — wellbore storage and radial flow (Cs, k).

c. Semilog "middle-time" plot — used to analyze radial flow behavior (k, s).

e. Cartesian "Arps" plot — used to estimate average reservoir pressure.

b. Cartesian "early-time" plot — used to analyze wellbore storage (p0, Cs).

d. Horner "middle-time" plot — used to analyze radial flow behavior (k, s, p*).

f. Log-log "summary" plot — summary of all analysis (Cs, k, s, A, etc).

(04 December 2002)

PETE 689 (02C) — Pressure Transient Testing

Slide — 9

Well Test Analysis — Basic Plots (1)

Example: "Preliminary Analysis" (log-log). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 10

Well Test Analysis — Basic Plots (2)

Example: "Horner Semilog Analysis" (semilog). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 11

Well Test Analysis — Basic Plots (3)

Example: "Analysis Summary Plot" (log-log). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 12

Well Test Analysis — Work Relations

Given data — Lee text (1st edition), Example 2.2.

(04 December 2002)

Working relations — Lee text (1st edition), Example 2.2).

PETE 689 (02C) — Pressure Transient Testing Slide — 13

Well Test Analysis — WBS Type Curves

a. Type Curve: Radial flow with wellbore storage and skin effects (pD, pDd).

b. Type Curve: Radial flow with wellbore storage and skin effects (pD, pDd, pDr1).

c. Type Curve: Radial flow with wellbore storage and skin effects (pD, pDdd).

d. Type Curve: Radial flow with wellbore storage and skin effects (pDi, pDid).

e. Type Curve: Radial flow with wellbore storage and skin effects (pDi, pDid, pDir1).

f. Type Curve: Radial flow with wellbore storage and skin effects (pDi, pDir2).

(04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 14

Well Test Analysis — WBS Type Curves (1)

Type Curve: "Gringarten-Bourdet" (pD, pDd). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 15

Well Test Analysis — WBS Type Curves (2)

Type Curve: "Second Derivative) (pD, pDdd). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 16

Well Test Analysis — WBS Type Curves (3)

Type Curve: "Integral Functions" (pDi, pDid). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 17

Well Test Analysis — Bounded Reservoir

a. Type Curve for sealing faults (pDd).

c. Type Curve for pressure buildup test in a closed rectangular reservoir (pDd).

(04 December 2002)

b. Type Curve for conductive (leaky) faults (pDd).

d. Type Curve for pressure buildup test in a closed rectangular reservoir (pDid).

PETE 689 (02C) — Pressure Transient Testing Slide — 18

Well Test Analysis — Bounded Reservoir (1)

Type Curve: "Sealing Faults" (pDd). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 19

Well Test Analysis — Bounded Reservoir (2)

Type Curve: "Closed Reservoir" (Buildup Only) (pDd). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 20

Well Test Analysis — Composite Systems

a. Composite Reservoir (ηr=1x10-3).

b. Composite Reservoir (ηr=1x10-2).

d. Composite Reservoir (ηr=1x100).

(04 December 2002)

c. Composite Reservoir (ηr=1x10-1).

e. Composite Reservoir (all ηr cases).

PETE 689 (02C) — Pressure Transient Testing Slide — 21

Well Test Analysis — Composite Systems (1)

Type Curve: all ηr cases (Tang-Brigham). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 22

Well Test Analysis — Fractured Wells

a. Type Curve: CfD= various, no CDf cases.

d. Type Curve: CfD=5, CDf = various.

(04 December 2002)

b. Type Curve: CfD=1, CDf = various.

c. Type Curve: CfD=2, CDf = various.

e. Type Curve: CfD=10, CDf = various.

f. Type Curve: CfD=1x103, CDf = various.

PETE 689 (02C) — Pressure Transient Testing Slide — 23

Well Test Analysis — Fractured Wells (1)

Type Curve: Various CfD (Cinco-Samaniego). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 24

Well Test Analysis — Fractured Wells (2)

"Pseudoradial flow" skin factor correlation for a fractured well (Cinco-Samaniego). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 25

Well Test Analysis — Fractured Wells (3)

Type Curve: CfD=2, various CDf cases. (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 26

Well Test Analysis — Fractured Wells (4)

Type Curve: CfD=1x103, various CDf cases. (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 27

Well Test Analysis — Dual Porosity Reservoirs

a. Type Curve: ω,λ= various, pss interporosity flow.

b. Type Curve: λCD= 1x10-1, pss interporosity flow.

c. Type Curve: λCD= 1x10-4, pss interporosity flow.

d. Type Curve: ω,λ= various, transient interporosity flow.

e. Type Curve: λCD= 1x10-1, transient interporosity flow.

f. Type Curve: λCD= 1x10-4, transient interporosity flow.

(04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 28

Well Test Analysis — Dual Porosity Reservoirs (1)

Type Curve: Pseudosteady-State Interporosity Flow (Onur, et al format). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 29

Well Test Analysis — Dual Porosity Reservoirs (2)

Type Curve: Transient Interporosity Flow (Onur, et al format). (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 30

Well Test Analysis — Dual Porosity Reservoirs (3)

Type Curve: λCD= 1x10-4, pss interporosity flow. (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 31

Well Test Analysis — Dual Porosity Reservoirs (4)

Type Curve: λCD= 1x10-4, transient interporosity flow. (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 32

Well Test Analysis — Scaling Pressure transient analysis "sees" the reservoir as a volumeaveraged set of properties. New solutions/models will also have this view of the reservoir — but, quantifying heterogeneity may (or may not) be possible by the analysis of pressure transient test data. Scaling will remain a major issue — regardless of the mechanism used to analyze reservoir performance. From: Simulator Parameter Assignment and the Problem of Scaling in Reservoir Engineering — Halderson (1986).

(04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 33

(Formation Evaluation and the Analysis of Reservoir Performance)

Module for:

Analysis of Reservoir Performance

Pressure Transient Testing End of Presentation T.A. Blasingame, Texas A&M U. Department of Petroleum Engineering Texas A&M University College Station, TX 77843-3116 (979) 845-2292 — [email protected] (04 December 2002)

PETE 689 (02C) — Pressure Transient Testing Slide — 34