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.
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