柴达木盆地北缘马西气藏储集层研究

Study of Maxi gas reservoir in northern margin of Qaidam Basin

柴达木盆地北缘马西气藏古近系渐新统下干柴沟组下段储集层,形成于辫状河三角洲沉积环境,储集层岩石类型主要为细粒砂岩、中粒砂岩和粉砂岩。砂岩以岩屑长石砂岩为主,其次为长石岩屑砂岩。碎屑岩颗粒分选性中等—好,胶结类型以接触—孔隙式为主,接触关系以点接触为主。砂岩储集孔隙类型以原生粒间孔为主,属于大孔隙,以粗喉道为主。储集层孔隙度平均为25.21%,渗透率平均为963.52×10-3μm2,综合评价为高孔高渗的好储集层。

The gas reservoir in the lower part of the Lower Ganchaigou Formation （ E13 ） in Oligocene in the Maxi gas pool in the northern margin of the Qaidam Basin was formed in braided river delta sedimentary environment. The rock type of reservoir mainly includes fine sandstone, medium sandstone and siltstone. Lithic feldspar sand-stones account for the largest proportion, while feldspar lithic sandstones the second. The separation of fragment grains is medium or good. Contact or pore cementations are common. Point contact is the leading contact type. Primary intergranular pores are dominant in sandstone reservoirs, featured by big pores and coarse throats. The average porosity and permeability of the reservoir are 25.21% and 963.52×10-3μm2, respectively, indicating for a good reservoir with high porosity and permeability.