Conventional Reservoirs Unconventional Reservoirs spacing, reservoir model type (dual vs. single porosity),

(Reservoir Engineering Aspects of Unconventionals) | PETE 631 - Petroleum Reservoir Description)

Petroleum Engineering 631 — Petroleum Reservoir DescriptionReservoir Engineering Aspects of Unconventional Reservoirs — A Brief Introduction

Slide 1

Conventional Reservoirs Unconventional Reservoirs (Shale)● Localized structural trap ● "Continuous-type" deposit● External HC sourcing ● Self-sourced HC● Hydrodynamic influence ● Minimal hydrodynamic influence● Porosity important ● Porosity may not be important● Permeability > 0.1 md ● Permeability << 0.1 md● Permeability ≠ f(p) ● Permeability = f(p)● Traditional phase behavior (PVT) ● Complex (HP/HT) PVT● Minimal extraction effort ● Significant extraction effort● Significant production history ● Limited production history● Often late development life-cycle ● Early development life-cycle● Few wells for commerciality ● Many wells for commerciality● Base reserves on volumetrics ● Base reserves on analogs ● Assess entire prospect before drilling ● Prospect driven by drilling ● Boundary-dominated flow (months) ● No boundary-dominated flow

● Traditional reserves methods ● Traditional reserves methods

Conventional Versus Unconventional:

?

Attributed to Brad Berg(Anadarko Petroleum Corporation)



Slide 2

b.Nelson, P.H.: "Pore-throat Sizes In Sandstones, Tight Sandstones, and Shales," AAPG Bulletin, v. 93, no. 3 (March 2009).

c.Loucks, R.G., Reed, R.M., Ruppel, S.C., and Jarvie, D.M., 2009, Morphology, Genesis, and Distribution of Nanometer-Scale Pores in Siliceous Mudstones of the Mississippian Barnett Shale: Journal of Sedimentary Research, v. 79, p. 848-861.

a.Archie, G.E.: "Introduction to Petrophysics of Reservoir Rock," Bull., AAPG (1950) 1-34.

d.Florence, F.A., Newsham, K., Rushing, J.A., and Blasingame, T.A.: "Improved Permeability Prediction Relations for Low Permeability Sands," paper SPE 107954 presented at the 2007 SPE Rocky Mountain Oil & Gas Technology Symposium held in Denver, CO, U.S.A., 16-18 April 2007.



Slide 3

TD Panel • So We Frac'd the Well, Now What? • Tom Blasingame (Texas A&M U.)

b.Schematic of "fracture stages" in a multi-fracture horizontal well.

c.Schematic of flow regimes which occur in a multi-fracture horizontal well (note linear and bilinear flow regimes).

a.Schematic of hyperbolic-exponential DCA approach.

d.Example of modern decline curve diagnostics (qDb-functions) used forproduction forecasting and estimation of EUR.



Slide 4

b.Phase diagrams of confined and unconfined heavy gas condensate mixture (Pedersen et al, 1989). (vertical( red) line is the reservoir temperature).

a.Critical point suppression due to pore size (various gases).

b.The percentage of liquid drop out (% by volume) of a heavy gas condensate mixture (Pedersen et al, 1989) at 400⁰F. (400⁰F is reservoir temperature — see plot at left).

PVT: (Issues/Challenges/Solutions?)● Undersaturated oil, pb suppression

(nano-pore volumes/distributions).● Volatile oil/critical fluid, nano-volume

effects less an issue (IFT/pc).● Gas condensates — composition issues/ variations in pCrit and TCrit.● Need molecular dynamics work to resolve/validate PVT in nano-pores.

From

:Sa

pman

ee, K

. (20

11).

"Effe

cts

of P

ore

Prox

imity

on

Beh

avio

r an

d Pr

oduc

tion

Pred

ictio

n of

Gas

/Con

dens

ate,

" M

.S. T

hesi

s, U

nive

rsity

of

Okl

ahom

a, 2

011.

From

:Sa

pman

ee, K

. (20

11).

"Effe

cts

of P

ore

Prox

imity

on

Beh

avio

r an

d Pr

oduc

tion

Pred

ictio

n of

Gas

/Con

dens

ate,

" M

.S. T

hesi

s, U

nive

rsity

of

Okl

ahom

a, 2

011.



Slide 5

b.Pressure gradient after 8 months (top) and 10 years (bottom) of production (Note times for different regimes, this is a relatively high permeability shale analog case).

a.Freeman, C.M., Ilk, D., Moridis, G.J., and Blasingame, T.A.: "A Numerical Study of Performance for Tight Gas and Shale Gas Reservoir Systems" paper SPE 124961 presented at the 2009 SPE Annual Technical Conference and Exhibition, New Orleans, LA, USA, 4–7 October 2009.

b.Typical transient response where PSS is seen in the SRV (Note times for different regimes, this is a relatively high permeability shale analog case).

Modeling: (Grand Challenges)● Fully integrated (not coupled) geo-

mechanical/flow simulation model.●Models may not be properly "parameter-

ized" — no data to validate.● Statistical versus deterministic models

(system is "too complex")?● Use models to establish/validate/bound

drainage volumes.● Use models to constrain assumptions

about geomechanics/fluid flow.

From

:K

APPA

Con

sort

ium

on

Unc

onve

ntio

nal R

esou

rces

(Dra

ft pr

ojec

t do

cum

ent)

7th

Febr

uary

201

1 (w

ww

.kap

paen

g.co

m).

From

:K

APPA

Con

sort

ium

on

Unc

onve

ntio

nal R

esou

rces

(Dra

ft pr

ojec

t do

cum

ent)

7th

Febr

uary

201

1 (w

ww

.kap

paen

g.co

m).



Slide 6

b.Time match of (calculated) bottomhole pressures .

c.Cumulative oil match of oil rate using 80- and 800-acre spacings.

a.Time match of oil (green) and gas (red) rate performance. Note thatthe match substantially degrades after the shut-in (reservoir effect?).

d.Plot of EUR versus well spacing (drainage area) for example case.

From

:Ilk

, D.,

Bro

ussa

rd, N

.J.,

and

Bla

sing

ame,

T.A

.,: "

Prod

uctio

n A

naly

sis

in th

e Ea

gle

Ford

Sha

le

—B

est P

ract

ices

for D

iagn

ostic

Inte

rpre

tatio

ns, A

naly

sis,

and

Mod

elin

g,"

pape

r SPE

160

076

pres

ente

d at

the

2012

SPE

Ann

ual T

echn

ical

Con

fere

nce

and

Exhi

bitio

n he

ld in

San

Ant

onio

, TX,

08-

10 O

ctob

er 2

012.



Comment: Left plot yields time required to estimate EUR (~12-32 months). The "hyperbolic" (or "constant b") flow regime is required to estimate EUR.

[all data obtained from publicly available sources — Dry Horizontal Shale Gas Wells ONLY]

From

:Hec

kman

, T.L

., et

al (

2013

): B

est P

ract

ices

for R

eser

ves

Estim

atio

n in

U

ncon

vent

iona

l Res

ervo

irs —

Pres

ent a

nd F

utur

e C

onsi

dera

tions

, Key

note

pr

esen

tatio

n pr

esen

ted

at th

e 20

13 S

PE U

ncon

vent

iona

l Res

ourc

es

Con

fere

nce,

The

Woo

dlan

ds, T

X (U

SA),

10-1

2 A

pril

2013

.

Slide 7



Comment: Results vary when segregated by geological area, completions, spacing, etc. Analyses represent an attempt to quantify the RANGE of values.

From

:Hec

kman

, T.L

., et

al (

2013

): B

est P

ract

ices

for R

eser

ves

Estim

atio

n in

U

ncon

vent

iona

l Res

ervo

irs —

Pres

ent a

nd F

utur

e C

onsi

dera

tions

, Key

note

pr

esen

tatio

n pr

esen

ted

at th

e 20

13 S

PE U

ncon

vent

iona

l Res

ourc

es

Con

fere

nce,

The

Woo

dlan

ds, T

X (U

SA),

10-1

2 A

pril

2013

.

[all data obtained from publicly available sources — Dry Horizontal Shale Gas Wells ONLY][P90/P50/P10 EUR Comparisons (Modified Hyperbolic Model with 30 year max life)]

Slide 8



What Keeps Us (Reservoir Engineers) Up at Night:●Stimulation/Fracture Geometry:

■Well spacing, reservoir model type (dual vs. single porosity), etc.?■ Does the SRV change with time (specifically, does it shrink)?

●Reservoir Model:■ Validity of dual /k models, enhanced k pods, fracture networks?■Model selection has a significant impact on POTENTIAL well spacing.■ Can we predict/incorporate influence of natural fractures?■ Is effort on geomechanics (really) going to lead to better understanding?.

●Data Collection:■ Taking data to validate model, or using model to guide development? ■ Downhole data — expensive — but are there any viable alternatives? ■ Poor data → poor engineering and poor modeling.■ Petrophysical data ( , k, pc) — scale, validity, integration?■ Role of "distributed" data? (temperature, pressure, rates, etc.)

●Process:■ No "cowboy-ing" the choke — develop a choke plan and stick to it!■ Incorporating artificial lift from inception! (including modeling)■ Use modeling to interpret performance and constrain parameters.■ Focus on what we can measure; use that as a basis for modeling.■ Start to consider statistics in addition to mechanistics.

Slide 9

Documents

Conventional Reservoirs Unconventional Reservoirs spacing, reservoir model type (dual vs. single porosity),