Control Factors on the Formation of Effective Rreservoirs in Tight Sands: Examples from Guang’an and Sulige Gasfields
详细信息
- 责任者：Li Yilong (Branch of Ordos ; Research Institute of Petroleum Exploration & Development ; PetroChina ; Beijing 100083 ; China) ; Jia Ailin
- 刊名：Acta Petrolei Sinica
- 出版年：2013
- 卷期：34(1)
- 关键词：致密砂层 ; tight sands ; 砂岩储集层 ; sandstone reservoirs
- 页码：p.71-82
- 图表：illus., 3 tables, 23 refs.
- 分类号：1003
- issnNo：ISSN0253-2697
- isbnNo：CN11-2128/TE
摘要
Among widely-distributed low-permeability and low-porosity tight sand gas reservoirs,there usually develop some local reservoirs with relatively higher qualities.In order to understand control factors on the genesis of favorable tight gas reservoirs,we comparatively studied tight gas reservoirs in two intracratonic basins(Sichuan and Ordos Basin) in the sense of depositional fractionation and diagenesis.Sedimentary and diagenetic characteristics of the Xujiahe Formation in Guang’an,Sichuan Basin and the He-8 and Shan-1 members in Sulige,Ordos Basin were examined in detail.The results showed that:(1) the sedimentary heterogeneity determined by differences in provenance and hydrodynamic environments affects diagenesis significantly,which forms a basis for the formation of effective reservoirs."Coarse-lithofacies" sandstones in stacked high-energy channels are thought to be favorable to forming high-quality reservoirs;(2) compaction and cementation are the main causes of reservoir quality reduction;(3) rigid and coarse grains such as quartz may contribute to retaining more initial intergranular pores by resisting compaction during early diagenesis,which can be pathways for diagenetic fluids in late diagenesis,but quartz overgrowth in a coal-measure acidic diagenetic environment may largely reduce the reservoir quality during late diagenesis;(4) authigenic clay minerals may reduce the permeability of reservoirs,while clay coatings may help retain initial intergranular pores by preventing quartz overgrowth;and(5) secondary dissolution controlled by dissolvable minerals,diagenetic fluids and fluid pathways is the main cause for enhancing reservoir quality.As for the studied tight gas reservoirs,sandstone diagenesis is strongly controlled by the initial heterogeneity derived from sedimentation process,which consequently controls the formation of favorable reservoirs as well.In order to predict the distribution of favorable reservoirs,sedimentary characteristics should be carefully studied.
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