Sedimentology and depositional environment of the Oligocene-Miocene gas-bearing succession in the Yacheng 13-1 field, South China Sea, People's Republic of China

Conference · Tue May 01 04:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6761128

Atkinson, C D; Bloch, S; Scheihing, M H ^[1]

---

1. ARCO Oil and Gas Co., Plano, TX (USA)

The giant Yacheng 13-1 gas field, discovered in 1982, is located in the South China Sea some 70 mi south of Hainan Island. The Oligocene-Miocene reservoir succession accumulated on the shallow-dipping flank of an extensional half-graben basin. The reservoir comprises an at least 800-ft (250-m) thick clastic interval that forms part of a transgressive basin fill. Basin sedimentation commenced with localized fan deltas sourced from the underlying Mesozoic granitic-metamorphic basement and fed directly into a lacustrine environment Paleosols (gleysols, planosols, and possible podzoluvisols) and palynomorphs, together with the textural characteristics of the sediments and the common occurrence of coal, suggest a prevailing humid, but seasonal, paleoclimate and abundant vegetation. Marine transgression into the basin occurred abruptly from the southwest. An elongate marine embayment was formed, the geometry of which served to amplify prevailing tidal currents. Marine processes had a pronounced effect upon the fan deltas, which continued to supply sediment to the basin. Tidal current and wave reworking winnowed and removed much of the unstable lithic components from the sediments, resulting in increased maturity. With continued transgression the basement topography was eventually drowned and the fan delta/shoreface sequences were sealed by shelfal muds and silts. Reservoir quality is controlled by burial diagenesis superimposed on the textural and mineralogical characteristics of the sediments. Poor reservoir quality typifies the immature, poorly sorted, lacustrine, fan-delta deposits, whereas good reservoir quality is characteristic of the texturally more mature, tidally reworked, marine, fan-delta, and shoreface sediments.

• OSTI ID: 6761128
• Report Number(s): CONF-900605--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Journal Volume: 74:5
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030200* -- Natural Gas-- Reserves
Geology
& Exploration
58 GEOSCIENCES
580000 -- Geosciences
ALLUVIAL DEPOSITS
ASIA
CENOZOIC ERA
CHINA
DEPOSITION
EXPLORATION
GEOLOGIC AGES
GEOLOGIC DEPOSITS
MATURATION
MINERAL RESOURCES
NATURAL GAS DEPOSITS
NATURAL GAS FIELDS
RESERVOIR ROCK
RESOURCES
TERTIARY PERIOD