Gas Reservoir Gas Reservoir Compartmentalization in Compartmentalization in Lowstand Prograding-Lowstand Prograding-

Wedge Deltaic Systems: Wedge Deltaic Systems: Oligocene Frio Formation, Oligocene Frio Formation,

South TexasSouth TexasUrsula Hammes, Bureau of Economic Geology, Jackson School of Geosciences, University of Texas

Contributors and SponsorsContributors and Sponsors Frank Brown (sequence stratigraphy)Frank Brown (sequence stratigraphy) Bob Loucks (sequence stratigraphy)Bob Loucks (sequence stratigraphy) RamRamóón Trevin Treviñño (geology)o (geology) Patricia Montoya (geophysics)Patricia Montoya (geophysics) Randy Remington (geophysics)Randy Remington (geophysics)

STARR ProjectSTARR Project Western Geco (seismic)Western Geco (seismic) IBC PetroleumIBC Petroleum Railroad Commission (logs, production data)Railroad Commission (logs, production data)

OUTLINEOUTLINE Develop exploration model for OligoceneDevelop exploration model for Oligocene Frio deltaic lowstand sands.Frio deltaic lowstand sands. Assess exploration potential of growth-Assess exploration potential of growth- faulted basins.faulted basins. Establish structural and stratigraphic Establish structural and stratigraphic architecture.architecture. Define reservoir compartmentalization.Define reservoir compartmentalization.

DATADATA3-D seismic data set.3-D seismic data set.Well logs.Well logs.Production and engineering analyses.Production and engineering analyses.

Regional OverviewRegional Overview

Schematic NW-SE Cross SectionSchematic NW-SE Cross Section

Frio Formation (Oligocene): Prograding wedge deltaic sediments and Frio Formation (Oligocene): Prograding wedge deltaic sediments and slope and basin-floor fansslope and basin-floor fans

Modified from Bebout and Loucks (1981)

On-shelf deposits(highstand and

transgressive sands)

Off-shelf deposits(lowstand sands)

Mobile shale ridge

Basin-floor fans

Pleistocene

Anahuac

sfsf sf

PwPw

Pw

sf

Pw

sf

Sea level

?

Pw

sfsf

Frio Formation

Study AreaStudy Area

Study Area and Regional TectonicsStudy Area and Regional Tectonics20 Miles30 Km

Corpus ChristiCorpusChristi

Bay

Outer Limit ofTexas State Waters

Salt DomesStudy Area

Exploration in Growth-Exploration in Growth-faulted Subbasins faulted Subbasins

Growth-Growth-faulted faulted

subbasins subbasins in Corpus in Corpus

Christi areaChristi area Oso Bay

Laguna Madre

PADRE ISLANDMUSTANG ISLAND

GrassFlats

Aransas Pass

PORTLAND

CORPUSCHRISTI

PORT ARANSAS

1

2

3 3

44

5

6 0 5 mi

Faults cutting Frio Fm.are generalized

5 km0

TEXAS

QAd2176c

Idealized Cross SectionIdealized Cross Section

1

3 4 5

??

?

Unexpandedolder deep-water systems

?

Incipient intraslopesubbasin no. 6

Shingled turbiditeson clinoform toes

?

??

?

?2

6

~1000 ft~1 mi

NW SE

Strike LineStrike Line

SW NE 0

500

1000

1500

2000

2500

3000

ms twt

Prograding wedge

Slope Fan Complex

Anatomy of a growth-faulted Anatomy of a growth-faulted subbasinsubbasin

3rd-order sequence composed of three mini-basins set up by growth faults

New 3rd-order sequence

Mobile shale

Mobile shaleMobile shale

N

Seismic survey outline

• Major growth faults (blue, green)• Antithetic and synthetic crestal faults (yellow)• Orthogonal fault (red)

Red Fish Bay Fault MapRed Fish Bay Fault Map

NN

Strike LineStrike LineSW NE 0

500

1000

1500

2000

2500

3000

ms twt

Prograding wedge

Slope Fan Complex

Dip LineDip Line0

1

500

000

2

500

000

3

500

000

1

2

0

1

500

000

2

500

000

3

500

000

1

2

Crestal Faults

Prograding Wedge Prograding Wedge ExplorationExploration

Depth Structure at mfs 3 (2460 ms)(Below 34 sand)

Contour Interval: 30 ft

ft

Top ProgradingTop ProgradingWedge StructureWedge StructureMapMap

20Miles

C.I. = 40 ftpw = lowstand

prograding wedge

Isopach map of Frio Formation showing inferred sediment input (red arrows) and depocenters (blue

contour fill) along growth faults (yellow)

Section of Red Fish Bay S5-Benchmark Charts

LST:ivf

LST:ivf

LST:ivf

4 & 5 pw’s

LST:ivf

7000

7500

8000

8500

9000

9500

10,000

10,500

11,000

11,500

12,000

12,500

13,000

13,500

4 & 5 slopefans =3 sf system

Sub-basinfloor

Camerina sp.

Cibicides hazzardi

Marginulina texana

Nonion struma

HST

TST

Lithostratigraphic“Frio” boundariesare diachronous

10A10B9

76

13

23

2725

28

17 181921

20

3132

33

35

4042

41

47

48

M iogupsinoidesTST

HST

HST

TST

TST

Base of Shelf

Distal HST

6

25.2 Ma

m fs = m cs

TS

T1

mfs = mcsT1

TS

39

8

14 15

22

34

363738

44

43

45

46

2930

3 LST:pw

28.58 Ma

Nodosaria blanpedi,Discorbis “D”

&Anomalina “F”

cocoaensis

28.26 Ma

27.51 Ma

26.62 Ma

Bolivina m exicana27.33 Ma

25.98 Ma

25.2 Ma

25.59 Ma

Marginulina idiomorpha,M. vagulata, H. howei

24.78 Ma

28.0 Ma

27.49 MaHackberry unconformity

2 TS

25.38 Ma

4

T1

28.5 Ma

T1

5

3 LST:bff28.4 Ma

28.6 Ma28.5 Ma

top sf and local mcs

top bff and local mcs

T1

3

4

5E

3

4

4

43

5D

5C

5BHST

4 & 5 pw’s withthin distal 4 HST’s

and TST’s

TST

Logsection

selectedfrom well

Depositional sequences,systems tracts, and surfaces

2nd orderB ased on local subb asin

(T/R cycles)3rd order# with some

component 4th orders

Age ofStratal surfaces (M a)

Approximatemicrofossil biozones

(benthics)SP R es.

Compositelog

Pay zones

3\4

2 TST

2 LST

AOI

Cross Section – Dip LineCross Section – Dip LineA A'

-100 SP 20-100 SPn orm 20

ILD 30.3ILM 30.3 -1 00 SP 20-1 00 SPno rm 20

0 G R 150-100 SPnorm 2 0

SFL 30.3 -100 SP 2 0 SFLA 30.3

Well A Well CWell B Well D Well F

ILD 30 .3-100 SP 200 G R 150

-100 SPnorm 20

-100 SP 200 G R 150

-100 S Pnorm 20

SED 30 .3

Well E

0

0

1 mi

1.5 km

Cross Section - Strike LineCross Section - Strike Line

B B'Well A Well B Well C Well D Well E Well G Well H Well I Well J Well K Well LWell F

0

0

2 mi

3 km

-100S P

20

-100SPnorm

20

0.3ILM

3ohm .m -100S P

20

-100S Pnorm

20

0.3S N

3ohm.m -10 0S P

20

-100SPnorm

20

0.3ILM

3ohm.m -100SP

20

-100SPnorm

20

0.3ILM

3ohm.m

0.3SFLU

3

-100S P

20

-100SPn orm

20

0.3ILM

3ohm .m

0.3S FLU

3

-100SP

20

-100S Pnorm

20

0.3ILM

3ohm .m

0.3S FLA

3

-100SP

20

0GR

150

0.3ILM

3ohm.m

-100S Pnorm

20

-10 0SP

20

-100SPnorm

20

0.3ILM

3ohm .m -100S P

20

0G R

150

0.3ILD

3ohm .m

-100SPn orm

20

0.3SE D

3ohm .m

-100SP

20

-100S Pnorm

20

0.3ILM

3ohm .m

0.3S ED

3

0G R

150 0.3ILM

3ohm.m -100SP

20 0.3ILM

3ohm.m

STRIKE SECTIONSTRIKE SECTION

Reservoir Engineering and Reservoir Engineering and Production AnalysisProduction Analysis

Production history and characteristicsProduction history and characteristicsReserve calculationsReserve calculationsReservoir compartmentalizationReservoir compartmentalizationVolumetrics estimationVolumetrics estimationReservoir pressure performanceReservoir pressure performance

Initial Bottom-hole PressureInitial Bottom-hole Pressure8,500

9,000

9,500

10,000

10,500

11,000

11,500

In itia l Bottom H ole P ressure (psi)

Sand 35

Sand 36

Sand 38

Sand 39

Sand 40

Sand 42

Sand 43

Sand 44

L ithostaticP ressure G rad ient

343_M cM oran_2Feb. 1977

H ydrosta ticP ressure G rad ient

342_M cM oran_2N ov. 1979

334_M cM oran_1N ov. 1971

352_M cM oran_1Jun. 1977

342_Phoenix_1Jul. 1970

351_M cM oran_1N ov. 1978

343_M cM oran_1Feb. 1971

344_M cM oran_2Apr. 1975

345_M cM oran_1Aug. 1973 342_Phoenix_1

Jul. 1970

343_M cM oran_1Feb. 1971

344_M cM oran_2Apr. 1975

343_M cM oran_2M ar. 1976

344_M cM oran_1Sep. 1984

344_M cM oran_1Jan. 1972

345_C orpus_1Jun. 1986

343_M cM oran_3D ec. 1980

342_M cM oran_2Jun. 1979

345_C orpus_1Dec. 1982

344_Brock_1Apr. 1984

O verpressure zone

Hydrocarbon Phases by RegionHydrocarbon Phases by Region

North Area74.4%

South Area25.6%

Natural Gas: 47.8 BCF

North Area60.8%

South Area39.2%

Condensate: 1,328 MBC

North Area5.4%

South Area94.6%

Water: 1,055 MBC

N

North Area

South Area

Reservoir Drive MechanismReservoir Drive Mechanism

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

0 250,000 500,000 750,000 1,000,000

Cumulative Gas Production (MMCF)

Bot

tom

Hol

e Pr

essu

re/Z

(psi

) Well 422_Energy_6 – Sand 35

Cumulative Gas Production (MMCF)

Bot

tom

Hol

e Pr

essu

re /

Z (

psi)

Weak

Moderate

Strong

P/Z plot for a waterdrive gas reservoir

Source: Miller, 2002

Well X – top sand

Reservoir Reservoir CompartmentalizationCompartmentalization

Reservoir Compartmentalization Reservoir Compartmentalization IndicatorsIndicators

100,000

10,000

1000

1001 10 100 1000 10,000

3000

2000

1000

0

2500

1500

500

0 1000 2000 3000 4000

Homogeneousreservoir

Compartmentalizedreservoir

Homogeneousreservoir

Compartmentalizedreservoir

Time (days) Cumulative gas production (MMcf)

(B)(A)

After Jenkin (1997)

Red Fish Bay CompartmentsRed Fish Bay Compartments

0

1000

2000

3000

4000

5000

6000

7000

0 900,000 1,800,000 2,700,000 3,600,000 4,500,000 0 1,800,000 3,600,000 5,400,000 7,200,0000

1000

2000

3000

4000

5000

6000

7000

Cumulative gas production (Mcf)Cumulative gas production (Mcf)

Zone A Zone B

Reservoir CompartmentsReservoir CompartmentsNorth Area South Area

Production and Pressure HistoryProduction and Pressure History

0

2600

5200

7800

10,400

0

700

1400

2100

2800

Jun-80 Jun-84 Jun-88 Jun-920

1500

3000

4500

6000

Jun-70 Jun-72 Jun-74 Jun-76 Jun-78 Jun-800

2100

4200

6300

8400

Zone A Zone B

Production AnalysisProduction AnalysisTVDFeet

ILD

SN

3

30.3

0.3 ohm.mSP

10VSH_BEG

20-100

TVDFeet ILD

30.3 ohm.mSP

10VSH_BEG

20-100

m fs

3rd-order m fs3rd-order m fs

m fs

We ll 1 We ll 2

(A)

(B)

10000

9500

Log and systemstracts characteristics

Trap styles

CONCLUSIONSCONCLUSIONS Compartmentalization of Frio reservoirs is due to interplay of Compartmentalization of Frio reservoirs is due to interplay of

sediments and tectonics.sediments and tectonics.

Compartments are related to different sandstone bodies Compartments are related to different sandstone bodies deposited at different times and to a common sandstone body deposited at different times and to a common sandstone body that has several pressure compartments defined by fault that has several pressure compartments defined by fault segregation.segregation.

Sequence stratigraphic correlation established framework for Sequence stratigraphic correlation established framework for distribution of sand compartments.distribution of sand compartments.

Best reservoirs occurred in late lowstand to transgressive Best reservoirs occurred in late lowstand to transgressive deposits.deposits.

Fault mapping from 3-D seismic provided crucial evidence to Fault mapping from 3-D seismic provided crucial evidence to define compartments.define compartments.