Integrated fault seal analysis and risk assessemt: Okan and Meren Fields, Nigeria

Conference · Mon Jan 01 04:00:00 EST 1996 · AAPG Bulletin

OSTI ID:6859634

Eisenberg, R A ^[1]; Brenneman, R J ^[2]; Adepoju, A A ^[3]

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1. Chevron Petroleum Technology, Co., La Habra, CA (United States)
2. Chevron Overseas Petroleum Co., San Ramon, CA (United States)
3. Chevron Nigeria Ltd., Lagos (Nigeria)

Integration of production, geochemical, seismic, well log, and structural data provides important constraints on the sealing capacity and dynamic behavior of fault juxtaposed reservoirs in Okan and Meren fields, offshore Nigeria. Correlations were found between pressure decline histories, juxtaposed fluid types, oil composition, fluid contact relationships, fault sealing/leaking condition, and estimates of the composition of the fault gouge. Fault plane sections defined reservoir juxtapositions and potential cross-fault spill points. Smear gouge ratios calculated from E-logs were used to estimate the composition of fault-gouge materials between juxtaposed reservoirs. These tools augmented interpretation of seal/nonseal character in proved reservoirs and were used to quantify fault seal risk of untested, fault-dependent closures. In the Okan Field juxtapositions of the G-, H, L-, M, and O-sands were analyzed. Smear gouge ratios correlated to fluid contact relationships and pressure decline histories within these juxtaposed reservoirs empirically calibrate sealing potential. The results of these analyses were then used to interpret production-induced fault seal breakdown within the G-sands and to risk seal integrity of fault-dependent closures within the untested 0-sands in an adjacent, upthrown fault block. Within this fault block the presence of potential fault intersection leak points and large areas of sand/sand juxtaposition with high smear gouge ratios (low sealing potential) limits column heights and potential reserves within the O-sand package. In the Meren Field the E- and G-sands are juxtaposed, on different pressure decline, geochemically distinct, and are characterized by low smear gouge ratios. In contrast, the G- and H-sands, juxtaposed across the same fault, contain similar OOWCs and are characterized by high smear gouge ratios.

• OSTI ID: 6859634
• Report Number(s): CONF-960527--
• Conference Information: Journal Name: AAPG Bulletin Journal Volume: 5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
020300 -- Petroleum-- Drilling & Production
AFRICA
DEVELOPING COUNTRIES
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC DEPOSITS
MINERAL RESOURCES
NIGERIA
OFFSHORE SITES
OIL FIELDS
PETROLEUM
PETROLEUM DEPOSITS
PRODUCTION
RESOURCE ASSESSMENT
RESOURCES