摘要
四川盆地下寒武统广泛发育一套膏盐岩,主要沉积于早寒武世龙王庙期。基于四川盆地深井及实测剖面中膏盐岩的识别和统计,发现下寒武统有川南和鄂西两大聚盐区,最厚达690.40m;川南聚盐区西部以含泥含云质石膏岩类和含膏砂泥岩类为主,东部及颚西聚盐区主要为含膏白云岩类。结合前人研究,认为膏盐岩发育于浅水缓坡沉积环境,有潮上萨布哈和缓坡蒸发两类成因。通过对川南聚盐区储盖匹配关系及后期构造与膏盐岩封盖性分析,表明下寒武统膏盐岩与盐下震旦系优质的白云岩储层在空间上具有良好的匹配关系;四川盆地边界大断裂及边界外寒武系的抬升暴露让膏盐岩在盆地外封盖性失效,而在盆地内膏盐岩的封盖性较好。威远气田解剖表明有膏盐岩分布的威远地区成藏,而无膏盐岩分布的资阳地区气藏被破坏,显示了下寒武统膏盐岩在四川盆地油气成藏中具有重要的作用。
The gypsum rocks which mainly deposited during Longwangmiao Period of the Early Cambrian are widely developed in Sichuan Basin. Based on the identification and statistics of gypsum rocks from the deep drill cores and outcrops, we found that there are two salt concentrated areas： Chuannan salt concentrated area and E＇xi salt concentrated area. The thickest gypsum rock unit is 690. 40m in the areas. The lithologies are argillaceous and dolomitic gypsum rocks in the western Chuannan area, and gypsum dolomites in the eastern Chuanuan area and the E＇ xi area. In combination with previous studies, we suggest that the gypsum rocks deposited in shallow ramp environments. Two types of genetic models were put forward： tidal sabkha model and ramp evaporation model. The relationship of reservoir to cap, posttectonic and the sealing of gypsum rock in Chuannan salt concentrated area was analyzed in the paper as well. It is shown that the cap of Lower Cambrian gypsum rocks and the Sinian dolomite reservoir are well matched spatially. The sealing of Lower Cambrian gypsum rock is effective in Sichuan Basin. However, it loses sealing effectiveness outside the basin because of the basin boundary faults and the uplift exposure of Cambrian. The case study on Weiyuan gas field indicates that gas accumulates where the gypsum rocks are distributed in Weiyuan area. In contrast, there is no gas accumulation without the distribution of gypsum rock in Ziyang area. The evidence also supports that the gypsum rocks have an important role in the process of gas accumulation in the Sichuan Basin.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2014年第3期718-726,共9页
Acta Petrologica Sinica
基金
中国地质调查局地质调查工作项目(1212011220758)
国家自然科学基金重点项目(40739901)联合资助
关键词
下寒武统
膏盐岩
封盖有效性
威远气田
四川盆地
Lower Cambrian
Gypsum rock
Sealing effectiveness
Weiyuan gas field
Sichuan basin
