optimized recovery from unconventional reservoirs: how ... · shale gas production analysis...

Optimized Recovery from Unconventional Reservoirs: How Nanophysics, the Micro-Crack Debate, and Complex Fracture Geometry Impact Operations

• Near Wellbore

• Well-to-Well

• Field Development

150 ft

1000 ft

miles

Ne

t p

rese

nt

valu

e

Completion Technology

Ne

t p

rese

nt

valu

e

Pressure Maintenance

Ne

t p

rese

nt

valu

e

Spacing / Geometry

Optimized Recovery from Unconventional Reservoirs

Liquids from Shales

Milind Deo, Ph.D.Professor and ChairChemical Engineering

Palash Panja, Ph.D.Post-Doctoral ResearcherEnergy & Geoscience Institute

• Probability density functions (PDFs)• Obtained using Monte Carlo simulations

kmRsiℓfpiCfdRs/dppwfng

Oil Recovery from Shales1 yr 10 yrs 20 yrs Economic Rate

5 bbl/d/fracture

*Xf Km Km Km

Km *Xf *Xf Rsi

Rsi Rsi Rsi *Xf

Pi dRs/dp dRs/dp Pi

dRs/dp Pi Pi Cf

*Pwf ng Cf dRs/dp

ng Cf *Pwf *Pwf

Cf *Pwf ng ng

Symbol Property

Km Matrix perm

Xf Hydraulic Fracture spacing

Rsi Initial dissolvedgas oil ratio

dRs/dp Slope of dissolved GOR

Pi Initial pressure

ng Gas rel. perm exponent

Cf Compressibility

Pwf Producing BHP Only 2 of the variables are operationally

controllable parameters

Most important

Least important

Ranking

Bryony Richards, Ph.D.Senior PetrologistEnergy & Geoscience Institute

• Pressure – 15,000 psi• Temperature 300oF• High-resolution Volume and

Pressure Measurements

Absolute permeability

1 Day, 200 nD 14 days, 5 nD

Relative permeability

Shale Interrogator

Manas Pathak, Ph.D.Energy & Geoscience Institute

rockporerock

Micro

rockporerock

Nano

Surface Interaction

At the Nano-scale, permeability is not a rock property but also depends on fluid-rock interaction

rockporerock

Nano

rockporerock

Nano

RestrictionMolecular Dynamics

Dro

p b

elo

w b

ub

ble

po

int

Bubble point is suppressed in nano-pores

Shale Gas Production Analysis

Cumulative production and production rate

where depends on:– Pressures (bhfp, pore or reservoir pressure)– Reservoir quality/ GIP (permeability, porosity)– Gas properties (viscosity, compressibility, equation of state)– Productive fracture surface area

t

CqtCQ

p

p 21,

pC

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 2 4 6

pro

du

ctio

nra

te (

bsc

/ye

arf)

time (years)

0

200000

400000

600000

800000

1000000

1200000

0 1 2 3

cu

mu

lati

ve p

rod

uc

tio

n (

ms

cf)

sqrt(time) years^0.5

Ian Walton, Ph.D.Research ScientistEnergy & Geoscience Institute

Gas Production Model

• Measure the production coefficient• Estimate pressures, porosity etc• Infer productive fracture surface area

Productive fracture surface area in the Barnett: 1-5 MM sq ft.

0

1

2

3

4

5

6

7

8

9

10

0 100 200 300 400 500

Su

rfac

e a

rea

(MM

sq

ft)

matrix permeability (nD)

Typical Productive Fracture Surface For Barnett Wells

poor producer

average producer

good producer

Estimate of Productive Fracture Surface Area

Example15 transverse hydraulic fracs each 200 ft high and 500 ft across

Frac surface area = 2*15*200*500 sq ft= 3 MM sq ft

Mass balance

• Frac fluid: Frac surface area ~ 100 MM sq ft

• Proppant: Propped frac surface area ~ 1-5 MM sq ft

Estimate of Created Fracture Surface Area

• Gas is produced from the volume defined by extent of primary fracture network

• Most of the fracture fluid resides in the large secondary fracture network and is eventually imbibed into the matrix

Large scale slickwater fracturing is very inefficient: thevolume of the productive fractures represents only asmall percentage of the volume of the fluid pumped.

Productive Reservoir Volume

Oil Recovery from Shales1 yr 10 yrs 20 yrs Economic Rate

5 bbl/d/fracture

*Xf Km Km Km

Km *Xf *Xf Rsi

Rsi Rsi Rsi *Xf

Pi dRs/dp dRs/dp Pi

dRs/dp Pi Pi Cf

*Pwf ng Cf dRs/dp

ng Cf *Pwf *Pwf

Cf *Pwf ng ng

Symbol Property

Km Matrix perm

Xf Hydraulic Fracture spacing

Rsi Initial dissolvedgas oil ratio

dRs/dp Slope of dissolved GOR

Pi Initial pressure

ng Gas rel. perm exponent

Cf Compressibility

Pwf Producing BHP Only 2 of the variables are operationally

controllable parameters

Most important

Least important

Ranking

Greater penetration, lower fracture density?

Idealized Conception

www.halliburton.com

Lower GRV, higher fracture density?

Plausible Complexity

www.drillingcontractor.org

Interaction with hoop stress

Interaction with natural fractures

Interaction with bedding

Lans Taylor, Ph.D.Research ScientistEnergy & Geoscience Institute

Large Scale Geologic Controls on Hydraulic Stimulation

John McLennan, Ph.D.Associate Professor of Chemical EngineeringEnergy & Geoscience Institute

Mechanical Stratigraphy for Hydraulic Stimulation

Does bedding plane slip explain diffuse zones of micro-seismicity during frac jobs?

Jim Rutledge, SLB Microseismic Services, “The Signature of Shearing Driven by Hydraulic Opening”, HGS Mudrocks Conf. 2015

Systematic Chaotic

North Sea

Karoo, S. Africa

Photo: Alan Cooper, www.otago.ac.nz

Compressional Crossing

Process Zone

Material 1

Material 2

Material 1

Material 2

σK1 σK1

σT σT

Modified from Renshaw & Pollard, 1995

Rigid but compressible vs.Flexible but incompressible

Initial condition

Vertical loadunconfined

Vertical loadlateral confinement

σHflexible > σHrigid

as Poisson Ratio decreases, Young’s Modulus increases

Rigid

Flexible

Rigid

Flexible

Rigid

Differential Motion

Con

stan

t st

ress

Con

stan

t st

rain

How is present day stress influenced by basin form and topography?

Does creep enhance stress heterogeneity?

FLEXIBLE

RIGID

FLEXIBLE

RIGID

FLEXIBLE

RIGID

Pressure

Shale

Sandstone

Sandstone

Sandstone

Shale

Shale

Horizontal Stress Magnitude

MostCompressive

LeastCompressive

Stratigraphic arrangement matters


MostCompressive

LeastCompressive

FLEXIBLE

RIGID

Shale

Sandstone

FLEXIBLE

RIGID

Shale

Sandstone

Sandstone

Hydraulic Fracture

FLEXIBLERIGID

Shale

Un

ifo

rm P

ress

ure

thin sandencasedin shale

thin shaleencasedin sand

Co

arse

nin

g u

pw

ard

se

qu

en

ceC

oarse

nin

g u

pw

ard se

qu

en

ce


MostCompressive

LeastCompressive

FLEXIBLE

RIGID

Un

ifo

rm P

ress

ure

Shale

Sandstone

FLEXIBLE

RIGID

RIGID

Shale

Sandstone

Sandstone

Hydraulic Fracture

Different placement of horizontal wells will lead to different hydraulic fracture patterns

Net PressureNet Pressure

Finite Element

Behavior of gradational interfaces

Direct measurement

Discrete Element Models

Curvature Analysis

SLB: Dynel2DCourtesy of Laurent Maerten

1) Input horizon 3) Stress prediction2) Bending model

Curvature for Unconventional Targets

Rigid layers isolated

Flexible layers isolated

Dislocation Analylsis

(Maerten, et al., AAPG Bull, 2006)

Fault Locking

Regional / Counter-regional Faulting

1972 2017
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optimized recovery from unconventional reservoirs: how ... · shale gas production analysis...

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