reservoir engineering aspects of unconventional resources

Petroleum Engineering 612 — Unconventional Oil and Gas Reservoirs Module — Reservoir Engineering Aspects of Unconventional Resources

Tom BLASINGAME | [email protected] | Texas A&M U.

Tom BLASINGAMEPetroleum EngineeringTexas A&M University

College Station, TX 77843-3116 (USA)+1.979.845.2292 — [email protected]

Reservoir Engineering Aspectsof Unconventional Resources

Pressure Transient Analysis (PTA):Identifying Practical Aspects

of Time-Pressure AnalysisIncluding Flow Regime Diagnostics

Slide — 90


Tom BLASINGAME | [email protected] | Texas A&M U. Slide — 91

Reservoir Pressure — Value Proposition

Discussion:●Characterize reservoir performance without wellbore pressure effects.●Diagnose offset behavior. (i.e., "well-to-well fracture interaction" ("frac-hits"))●Diagnose production interference. (… induced or natural fractures, faults, etc.)

Rate and pressure functions vs. time,multi-well interference.(Source: SPE 187180)

Rate and pressure functions vs. time,Examples of "Frac-Hits."(Source: URTeC 2670079)



Reservoir Pressure — Influence of Uncertainties

Discussion:●Wellbore phase segregation → bias in surface pressures (shut-ins).●Surface pressure issues. (… temperature compensation, operations, etc.)●Location of pressure sensor. (… the wellhead, "before the curve," etc.)●Mechanical issues. (… e.g., downhole gauges not properly set, leaks, etc.)

(ptf)meas , (pwf)meas, and (Ttf)meas vs. time,(Source: IJGGC 2013 (Liebscher))

(ptf)meas and (Ttf)meas vs. time.(Source: PETSOC-97-35)

Wellhead Temperature

Casing PressureTubing Pressure



Reservoir Pressure — Implications of Errors and Inconsistencies

Discussion:● (inconsistencies) ptf influenced/biased by operational practices.● (inconsistencies) Downhole measurements less affected by operations.● (errors) Gauge failure (rare) or gauge losing calibration (uncommon).

Rate and pressure functions vs. time.(Source: URTeC 1934785)

Rate and pressure functions vs. time.(Source: URTeC 1934785)



Reservoir Pressure — Need to Continuously Monitor Reservoir Pressures

Discussion:●Surface pressures (ptf) necessary for operations and choke management. ●ptf → pwf conversion has uncertainty that may bias analysis/interpretation.●The clarity and resolution of pwf data make these data essential.●pwf data represent the "ground truth" for the in-situ reservoir pressure.

Comparison: (pwf)meas and (pwf)calc vs. time. (Source: SPE 178608)



Discussion: Marcellus PA Cases (normalized to similar derivative shape)●Very strong grouping for all three wells — unique character.●Grouping = f(permeability, well completion, fracture conductivity).●3 (three) wells shown in this collection.

Time-Rate-Pressure Analysis — Normalized RTA (Marcellus Example)

1:2 Slope(Compound

LinearFlow)

"Normalized" Material Balance Time

"Nor

mal

ized

" In

vers

e Pr

oduc

tivity

Inde

x

1:4 Slope(low FcD)

Groupof

3 wells

InverseProductivity

Index

Derivativeof Inverse

ProductivityIndex



Discussion: Montney PTA Cases (normalized to similar derivative shape)●These trends are grouped according to derivative character.●Grouping = f(permeability, well conditions, fracture conductivity).●Note that each shape has at least 2 wells that make up that group.

1:2 Slope(high FcD)

"Normalized" Time

"Nor

mal

ized

" Ps

eudo

pres

sure

Dro

p

1:4 Slope(low FcD)

1:4 Slope(low FcD)

Group 1(3 wells)

Group 2(3 wells)

Group 3(2 wells)

PseudopressureDrop

PseudopressureDerivative

Time-Pressure Analysis — Normalized PTA (Montney Example)



Time-Rate-Pressure Analysis — PTA (SPE 145463 (Mayerhofer))

Mayerhofer, M. J., Stegent, N. A., Barth, J. O., & Ryan, K. M. (2011). Integrating Fracture Diagnostics and Engineering Data in the Marcellus Shale. Society of Petroleum Engineers. doi:10.2118/145463-MS (http://dx.doi.org/10.2118/145463-MS)

a.Gas production rates and flowing tubing pressures show communication between the two wells.

b.First post-frac buildup (final interpretation with dual-porosity slab interpretation and DFIT matrix permeability).

c.Second post-frac buildup after 5 months of production affected by Well 1H offset production (dual-porosity slab interpretation with DFIT matrix permeability).



PTA Cases in Bakken (Oil Shale) [SPE 162473 (Kurtoglu)]K

urto

glu,

B.,

Torc

uk, M

.A.,

& K

azem

i, H

. (20

12) P

ress

ure

Tran

sien

t Ana

lyse

s of

Sh

ort a

nd L

ong

Dur

atio

n W

ell T

ests

in U

ncon

vent

iona

l Res

ervo

irs. S

ocie

ty o

f Pe

trol

eum

Eng

inee

rs. d

oi:1

0.21

18/1

6247

3-M

S.



Reservoir Pressure — Quantifying Pressure Interference (SPE 191407)

Pressure response due to Well 3H being "put-on-production" (or POP'd).

Chow Pressure Group (pressure derivative function)For all for 4 wells due to Well 3H being "POP'd."

Pressure interference response in Well 4H. Pressure interference response in Well 6H. Pressure interference response in Well 5H.(due to Well 3H POP) (due to Well 3H POP) (due to Well 3H POP)

reservoir engineering aspects of unconventional resources

Documents