三塘湖盆地侏罗系油藏中溶蚀对异常低压的控制作用

Controlling function of feldspar dissolution for abnormal low-pressure in Jurassic reservoir of Santanghu Basin

应用岩心、薄片、扫描电镜、储层物性和黏土矿物X衍射等资料,研究了三塘湖盆地侏罗系储集层的岩石学特征,发现中下侏罗统低压油藏中长石大量被溶蚀,高岭石非常发育,占全岩的3%～16%,平均为9.6%。研究表明,长石溶蚀过程中,伴随着高岭石的形成,地层水被消耗,孔隙中流体含量降低,储层孔隙体积增加了约1%,孔隙流体压力平均降低了2MPa,说明长石溶蚀作用是中下侏罗统油藏压力降低的重要影响因素。

The data from core, slice, SEM and XRD were used to study the characteristics of the Jurassic reservoirs in Santanghu Basin. In the Lower-Middle Jurassic low pressure reservoir, lots of feldspars were dissolved, the content of kaolinite is from 3% to 16%, and the average value is 9.6%. During the formation of kaolinite, the formation water was abundantly consumed, and fluid content in pores decreased. The porous space increased by 1%, and the average value of fluid pressure almost decreases by 2MPa during feldspar dissolution. So, feldspar dissolution is the most important factor for declining of the reservoir pressure in the Lower Middle Jurassic reservoir of Santanghu Basin.