Restudy of the Formation Mechanism of the Da’anzhai Condensate Gas Reservoir in the Bajiaochang Structure, Middle Sichuan Basin
详细信息
- 责任者：Chen Shijia (Southwest Petroleum University ; Chengdu 610500 ; China) ; Liu Chaowei
- 刊名：Natural Gas Industry
- 出版年：2013
- 卷期：33(9)
- 关键词：凝析气 ; condensate gas ; 油气藏形成 ; reservoir formation ; 四川盆地 ; Sichuan Basin
- 页码：p.29-35
- 图表：6 illus., 2 tables, 28 refs.
- 分类号：1003
- issnNo：ISSN1000-0976
- isbnNo：CN51-1179/TE
摘要
The Da’anzhai condensate gas reservoir in the Bajiaochang structure is the only one large-scale condensate gas reservoir in Middle Sichuan Basin,so the study of its formation mechanism is of great significance to a better understanding of the hydrocarbon accumulation there.In view of this,according to carbon isotopic compositions of crude oil and natural gas,this paper studied the origins of hydrocarbons,analyzed the formation mechanism based on the distribution of faults and hydrocarbons,and finally discussed the influences of natural gas on the enrichment of hydrocarbons in this study area.The following results were obtained.(1)In those wells close to the faults,abnormal characteristics were presented from carbon isotopes of natural gas and crude oil as well as C4-C7 light hydrocarbons in condensates,which discloses that the gas obviously came from the underlying Upper Triassic Xujiahe Fm.(2)The intensity of such gas invasion is controlled by the distribution and size of faults.The formation of the condensate gas reservoir in the Bajiaochang structure benefited from the faults which connect the source rock of the Xujiahe Fm and the Da’anzhai reservoir.The resulted mass invasion of gas from the Xujiahe Fm into the Da’anzhai oil reservoir changed the original gas-oil ratio,so that a gas-invasion condensate gas reservoir was formed.(3)Comparatively,the gas invasion appears weak in the adjacent Jinhua structure with small-scale faults,where hydrocarbons were found with high gas-oil ratios instead of condensate gas in some wells.(4)Natural gas is the primary drive for the migration and accumulation of oil in the Da’anzhai tight reservoir,influencing oil enrichment degree and oil-well productivity of such a low amplitude water-free tight reservoir in this study area.
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