Reservoir characteristics and its main controlling factors of Dainan1 formation in Yongan Area,Gaoyou sag
Lian Chengbo1, Qu Fang1, Tan Xiucheng1,2, Wang Zhikun3, Wu Liyun4, Zhang Jianliang4, Duan Hongliang4, Gao Guoqiang4
1. School of Resources and Environment, Southwest Petroleum University, Sichuan 610500;
2. State Key Laboratory of Oil-Gas Reservoir Geology & Exploitation Sichuan 610500;
3. Exploration and Development Research Institute of Jidong Oilfield Company, Tangshan 063004;
4. Research Institute of Geologic Sciences, Jiangsu Oil Field, SINOPEC, Yangzhou, Jiangsu 225009
The sandstone reservoir characteristics of Dainan 1 Formation of Yongan area in Gaoyou sag are analyzed based on the data of core,casting film,electron microscope scanning,poroperm analysis and pore image analysis,and the main controlling factors of the reservoir quality are studies from the aspects of sedimentation and diagenesis.The results show that the sandstones are mainly feldspathic litharenite with low compositional maturation,fine grain,and medium-bad sorting degree.The reservoirs are mainly of low porosity and low permeability,and supplemented of medium porosity and medium permeability.The pores are mainly intergranular pores,intergranular dissolved pores,intragranular dissolved pores and moldic pore,with the average pore diameter of 37.53 μm.The throats are mainly the shrink parts of the feasible end faces,then the laminated throat and the curved lamellar throat,with the average throat radius of 10.25 μm,throat pore coordination number of 3,and good sorting.The research indicates that the sedimentary factor is one of the main controlling factors of the sandstone reservoir quality of Dainan 1 Formation of Yongan area in Gaoyou sag,and the sandstone formed in the sedimentary environment with high hydrodynamic intensity has good reservoir quality with large grain and good sorting.Different kinds of diagenesis have different effects on reservoir quality.Compaction and cementation make the reservoir quality become worse,while the dissolution make the reservoir quality become better by producing secondary porosity.The secondary porosity zones are obvious in the depth of 2 500～2 700 and 2 850～2 950 m.