冷湖七号和南八仙渐新统混积岩储层特征对比分析 

Contrastive analysis of Oligocene peperite reservoir characteristics
of No.7 Lenghu and Nanbaxian structure

杨勇 赵为永 史玉成

1．中国石油青海油田公司井下作业公司，甘肃 敦煌 736202 2．中国石油青海油田公司勘探开发研究院，甘肃 敦煌 736202

Downhole Operation Company, Qinghai Oilfield Company, PetroChina, Dunhuang 736202, China Research Institute of Exploration and Development, Qinghai Oilfield Company, PetroChina, Dunhuang 736202, China

渐新统下干柴沟组下段是柴北缘中部地区油气勘探的主要目标，弄清该区储层发育的控制因素是深入评价的基础。文中根据铸体薄片、普通薄片及岩屑录井等资料，对该区冷湖七号和南八仙构造的岩石学特征进行了对比分析。研究表明，该区大量发育陆源碎屑、碳酸盐、硬石膏的混合沉积，但是由于水体咸度的不同，在冷湖七号的滨浅湖混积岩中硬石膏含量较高，颗粒主要为基底式胶结；而南八仙构造地处辫状河三角洲前缘相带，因河流的稀释作用，混积岩中硬石膏体积分数很低，颗粒为孔隙式-基底式钙质胶结，原生孔喉较为发育，有利于后期酸性流体的溶蚀改造。由于2种类型混积岩的初始孔隙度及孔喉演化模式不同，最终引起2个地区含油气丰度的巨大差异。

The lower interval of Oligocene Xiaganchaigou Formation is an important prospecting object in the central areas of northern Qaidam Basin. Finding out the factors controlling the reservoir property is prospecting basis. Based on the normal thin sections, cast thin sections and drilling data, the rocks characteristics of No.7 Lenghu and Nanbaxian structure were analyzed in this paper. Study shows that the mixed deposits such as terrigenous clastic, carbonate and anhydrite are found very common in this area. But because of different salinity, the content of anhydrite is high in shore shallow lake facies peperite of No.7 Lenghu structure. Particles are mainly base type cementation. The salinity of Nanbaxian structure located in delta front facies belt is lower because of the great amounts of water input by the rivers and there is little anhydrite in peperite. Particles are mainly pore type-base type calcium cementation. The initial porosity in Nanbaxian is much higher than that of No.7 Lenghu, which is in favour of the later dissolution of acidic fluid. Because the initial porosity and pore throat evolution model for two types of peperites are different, there is great difference in the oil and gas abundance of two areas.

10.6056/dkyqt201305006