牛圈湖油田侏罗系储层控制因素分析

Analysis on Control Factors of Jurassic Reservoir in Niu Quanhu Oilfield

通过铸体薄片观察和大量的岩矿测试资料分析,系统地研究了储层性质的控制因素。三塘湖盆地牛圈湖油田侏罗系近物源快速堆集的三角洲储集砂体泥杂基含量高和高岭石发育(西山窑组)是储层低渗的主要原因,其中头屯河组与齐古组泥杂基以粘土膜的方式缩小孔隙喉道,使储层低渗,西山窑组泥杂基和泥质转化的高岭石杂乱充填于孔隙中,造成储层低渗;成岩压实作用是储层低孔的主要因素,砂岩成分成熟度低、早期成岩胶结弱、异常低压使侏罗系砂岩易被压实;溶蚀作用对储层增孔作用不大,只是增加少量的颗粒溶孔,同时产生的副矿物高岭石使储层进一步低渗。根据侏罗系储层的岩性、物性、含油性及电性综合分析,中侏罗统西山窑组有效储层的孔隙度大于11.0%,渗透率大于0.5×10-3μm2。

By observation of thin - section of the cast and test data analysis of a large number of rock - minerals, reservoir control factors are systematically studied. The main reason that the permeability of reservoir is low is high shale content and kaolinization of delta reservoir sandbody that Jurassic near source accumulated quickly in Niu Quanhu oilfield in San Tanghu basin. Of which low permeability of reservoir resulted from pore throat shrinking caused by argillan in mud of Toutun river formation and Qigu formation, pores are filled with kaolinite transformed from mud in J2x, which causes the low permeability of reservoir. Diagenetic compaction is the dominated factor of low permeability. Low maturity of sandstone component, weak diagenetic cementation at early stage and abnormal low pressure make the Jurassic sandstone easily compacted; solution cant increase porosity of reservoir besides increasing a little particle solution opening, paramineral kaolinite formed simultaneously make the reservoir permeability lower. Based on the overall analysis of lithology and physical property and oil - bearing property, porosity of available reservoir in middle Jurassic J2x formation is over 11.0%, permeability is over 0.5 × 10^-3 μm^2.