| The Central Canyon-Channel Gasfield in Qiongdongnan Basin is the first deep-water large-scale gas field
discovered by self operated exploration in China sea area, which is an important support for the production of oil and gas
fields in the western South China Sea. Influenced by the large-scale decline of global sea level, the basin had sufficient
sediment sources during the deposition of the upper Miocene Huangliu Formation, and incised turbidity channels called
the Central Canyon-Channel (CCC) developed through the whole basin. In order to reasonably formulate the gas field
development plan, based on the core analysis data and engineering test data, the petrology, physical property, and pore
structure of the CCC sandstone of Huangliu Formation in Ledong Sag-Lingshui Sag were revealed, and the reservoir
types were classified and the control factors for the difference of reservoir characteristics were explored. The results show
that: (1) The lithology of the CCC is dominated by siltstone and fine sandstone. The pore space is dominated by
intergranular pores, followed by intergranular and intragranular dissolution pores. The pore throat size varies from
medium to micro, being different among different development blocks. (2) Based on the physical property, fluidity,
petrology, productivity, lithology and pore structure, the CCC reservoir can be divided into four types: good, medium,
poor and tight. The quality of the CCC reservoir gradually improves from west to east: the good reservoir is distributed in
the Lingshui X, ZX blocks, the medium reservoir is distributed in the Lingshui Z block, the poor reservoir is distributed in
the Yacheng A, B blocks, and tight reservoir is distributed commonly in a small amount in all blocks. (3) Hydrodynamic
conditions primarily control the CCC reservoir quality. Compaction and carbonate cementation reduce pore throat.
Abnormal overpressure inhibit the compaction process and retain intergranular pores. These factors together determine the
distinct variation in the pore structures among different development blocks. This research will provide a new visual angle
that is beneficial for the optimization of exploration targets and development plans of the CCC Gasfield. |
