Preservation of primary porosity in the Neogene clastic reservoirs of the Surma Basin, Bangladesh

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

OSTI ID:6858969

Ferdous, H S; Renaut, R W ^[1]

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1. Univ. of Saskatchewan, Saskatoon (Canada)

The Surma Basin is a Tertiary sub-basin within the greater Bengal Basin, in N.E. Bangladesh. The Neogene sequence ([approximately]17 km thick) contains the producing hydrocarbon reservoirs with proven gas reserves. These sediments are alternating coarse and fine clastics, representing a complex interfingering of deltaic and marine subenvironments, with the former dominating. The principal reservoir facies are distributary channel-fill sandstones in a lower delta-plain setting. Kailashtila, Beanibazar and Rashidpur, located in anticlinal structures, are major hydrocarbon-producing fields in the E. Surma Basin. Petrographic analysis shows that primary intergranular porosity mainly controls the reservoir quality of these Neogene sands, which occur at a depth of [approximately]3000 m. Most samples show primary pores with about 20% porosity and permeabilities of about 200 mD. The preservation of a higher proportion of primary pores in fine to medium grained sandstones is a result of (1) moderate compaction resulting from overpressuring caused by a higher rate of subsidence and sedimentation, (2) weak cementation, and (3) a general lack of deleterious clays and the presence of some grain-rimming chlorites. The general absence of long and sutured grain contacts also supports these observations. Some of the existing literature suggests that secondary pores are dominant in the Neogene sandy reservoirs of the Bengal Basin; however, they contribute little ([approximately]2%) to the total porosity in the Surma Basin.

• OSTI ID: 6858969
• Report Number(s): CONF-960527-; CODEN: AABUD2
• Journal Information: AAPG Bulletin, Vol. 5; Conference: Annual convention of the American Association of Petroleum Geologists, Inc. and the Society for Sedimentary Geology: global exploration and geotechnology, San Diego, CA (United States), 19-22 May 1996; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
03 NATURAL GAS
BANGLADESH
NATURAL GAS DEPOSITS
PETROLEUM DEPOSITS
SEDIMENTARY BASINS
NATURAL GAS
RESERVES
RESERVOIR ROCK
POROSITY
ASIA
DEVELOPING COUNTRIES
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
MINERAL RESOURCES
RESOURCES
020200* - Petroleum- Reserves
Geology
& Exploration
030200 - Natural Gas- Reserves
Geology
& Exploration