Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U. Slide — 1

Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U. Slide — 2

Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.

Material Balance Notesfrom Department of Petroleum Engineering Course Notes (2012)

Slide — 3

Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.

"Accounting" Concept of Material Balance:Require all inflows/outflows/generations. (Average) reservoir pressure profile is REQUIRED.Require rock, fluid, and rock-fluid properties (at some scale).

Oil Material Balance:Less common than gas material balance (pressure required).

Gas Material Balance:Volumetric dry gas reservoir (p/z versus Gp (straight-line)).Abnormally-pressured gas reservoirs (various techniques).Waterdrive/water influx cases (always problematic) (i.e., we don't

know the influx, so we use a model).Material Balance yields RESERVOIR VOLUME!

Material Balance — Reservoir Engineering Aspects

(Material Balance Notes — from Department of Petroleum Engineering Course Notes (2012))Slide — 4

Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.

General Concept of Material Balance...

From: Petroleum Reservoir Engineering —Amyx, Bass, and Whiting (1960).

a. Initial reservoir conditions. b. Conditions after producing Np STB of oil, and GpSCF of gas, and Wp STB of water.

Material Balance: Key Issues Must have accurate production measurements (oil, water, gas). Estimates of average reservoir pressure (from pressure tests). Suites of PVT data (oil, gas, water). Reservoir properties: saturations, formation compressibility, etc.

(Material Balance Notes — from Department of Petroleum Engineering Course Notes (2012))

Material Balance — Concept Diagram

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Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.

Average Reservoir Pressure

From: Engineering Features of the Schuler Field and Unit Operation — Kaveler (SPE-AIME, 1944).

Average Reservoir Pressure: Key Issues Must "average" pressures over volume or area (approximation). Pressure tests must be representative (pavg extrapolation valid). Can average using cumulative production (surrogate for volume).

(Material Balance Notes — from Department of Petroleum Engineering Course Notes (2012))

Material Balance — Average Reservoir Pressure

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Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.

Black Oil Material Balance Case: (Example) Note that all fluid functions are given: Np, Wp, and GOR (for Gp). Average reservoir pressure is presumed correct. Authors cite "partial waterdrive" — remains a contentious issue.

Fr

om: A

pplic

atio

n of

the

Mat

eria

l Bal

ance

to a

Pa

rtia

l Wat

erdr

ive

Res

ervo

ir—

van

Ever

ding

en

(SPE

, 195

3).

(Material Balance Notes — from Department of Petroleum Engineering Course Notes (2012))

Material Balance Example — Black Oil

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Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.

"Black Oil" Material Balance: (p>pb )

"Solution Gas Drive" (Oil) Material Balance: (all p)

poi

o

ti N

BB

Ncpp 1

we

iwi

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gi

goi

gssioio

wpgspop

BW

ppScSc

NBm

BB

mNB

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)()1(

)()1(

1

)()(

)(

(Oil Expansion (RB))

(Gas Cap Expansion (RB))

(Water Exp./Pore Vol. Comp. (RB))

(Water Influx (RB))

(Withdrawal (RB))

Oil Material Balance Relations:

(Material Balance Notes — from Department of Petroleum Engineering Course Notes (2012))

Material Balance Relations — Black Oil

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Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.

General Gas Material Balance:

"Dry Gas" Material Balance: (no reservoir liquids )

"Abnormal Pressure" Material Balance: (cf=f(p))

ewinjpg

swpinjpi

i

i

i

ie

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)(1615.51

))((1

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i

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pppczp

zp p

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)(

)1(1 )( fw

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pc

Gas Material Balance Relations:

(Material Balance Notes — from Department of Petroleum Engineering Course Notes (2012))

Material Balance Relations — Dry Gas

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Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.

"Dry Gas" Material Balance: Normally Pressured Reservoir Example Volumetric reservoir — no external energy (gas expansion only). p/z versus Gp yields unique straight-line trend. Linear extrapolation yield gas-in-place (G).

(Material Balance Notes — from Department of Petroleum Engineering Course Notes (2012))

Material Balance Relations — Volumetric Dry Gas

Slide — 10

Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.

"Dry Gas" Material Balance: Abnormally Pressured Reservoir Example Volumetric reservoir — no water influx or leakage. p/z versus Gp yields unique quadratic trend (from approximated MBE). Quadratic extrapolation yield gas-in-place (G).

(Material Balance Notes — from Department of Petroleum Engineering Course Notes (2012))

Material Balance Relations — "Abnormal Pressure" Dry Gas

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Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.

a. Gas Material Balance Plot: p/z vs. Gp — simulated performance. Note effect of aquifer permeability on field performance.

b. Gas Material Balance Plot: p/z vs. Gp — simulated performance. Note effect of displacement efficiency (Ep).

Gas Material Balance: Water Drive Gas Reservoir Pressure (hence p/z) is maintained during production via communication with an unsteady-

state aquifer (this study). Unsteady-State Performance of Water Drive Gas Reservoirs, Agarwal (Texas A&M Ph.D., 1967).

(Material Balance Notes — from Department of Petroleum Engineering Course Notes (2012))

Material Balance Relations — "Water Influx" Dry Gas

Slide — 12

Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.

Volumetric Oil ReservoirsMaterial Balance Notes

from Department of Petroleum Engineering Course Notes (1984)

Slide — 13

Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.(Material Balance Notes — from Department of Petroleum Engineering Course Notes (1984))[Volumetric Oil Reservoirs]

Slide — 14

Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.(Material Balance Notes — from Department of Petroleum Engineering Course Notes (1984))[Volumetric Oil Reservoirs]

Slide — 15

Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.(Material Balance Notes — from Department of Petroleum Engineering Course Notes (1984))[Volumetric Oil Reservoirs]

Slide — 16

Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.

Gas ReservoirsMaterial Balance Notes

from Department of Petroleum Engineering Course Notes (1984)

Slide — 17

Petroleum Engineering 620 — Fluid Flow in Petroleum Reservoirs Fundamental Flow Lecture 3 — Material Balance Concepts

Tom BLASINGAME | t-blasingame@tamu.edu | Texas A&M U.(Material Balance Notes — from Department of Petroleum Engineering Course Notes (1984))[Gas Reservoirs]

Slide — 18