靖边南上古生界储层特征及优质储层主控因素分析

Research on reservoir characteristics and favorable reservoir's dominated factors of upper paleozoic in south of Jingbian area

靖边南区块位于靖边气田南部,其显著特点是上、下古生界复合含气。上古生界含气层系有石盒子组盒8段、山西组山1、山2段和本溪组,其中以盒8段、山2段为主力含气层段。由于该区上古生界仍处于开发评价阶段,对其砂岩储层基本特征及主要控制因素认识不甚清楚,严重制约了该区上古生界规模开发的进程。通过岩心、铸体薄片、粒度分析、扫描电镜、毛管压力分析等分析测试手段,从成岩作用和成岩相角度,探讨了靖边南区块上古生界盒8、山2段致密砂岩储层的主要控制因素,认为:(1)该区上古生界储层总体表现为低孔低渗,但局部存在较高渗透性储层形成大面积含气有利区;(2)首次对各种成岩作用与孔隙演化关系进行了定量分析,认为压实作用对盒8储层孔隙影响大于山西组储层,而胶结作用导致的孔隙减少则是山西组大于盒8段储层;溶蚀作用在增加孔隙方面以盒8段储层最高;(3)靖边南区块上古生界储层物性受沉积环境、成岩作用影响,储层非均质性较强,但广泛存在的高角度裂缝与水平缝共同构成的裂缝体系与叠置高渗砂体相匹配,有利于天然气富集成藏。

The obvious feature of south Jingbian gas field is contains gas both in upper pale-ozoic and lower palaeozoic. The upper paleozoic gas-bearing series includes the Member 8 of Shihezi formation, the Member 1 and 2 of Shanxi formation and Benxi formation, the Member 8 of Shihezi formation and the Member 2 of Shanxi formation are main gas bearing formation. This area is still in development evaluation phase, the recognition of the sand for-mation basic features and main controlling factors is not clear, which seriously limits the process of the upper paleozoic scale development. Through core,casting thin sections,grain size analysis, scanning electron microscope, capillary analysis etc methods, the tight Member 8 of Shihezi formation and the tight Member 2 of Shanxi formation main controlling factors are studied from diagenesis and diagenetic facies view in this area, conclusions： （ 1 ）This area upper paleozoic formations generally are low porosity and low permeability, but some large area of favorable gas-bearing areas formed in local high permeability formations; （2）The first time, all kinds of diagenesis and pore evolution relations are quantitative analysed, the results show that compaction has more effect on the pore of Member 8 of Shihezi formation than on Shanxi formation, cementation causes more pore reduce in Shanxi formation than in the Member 8 of Shihezi formation, dissolution creats more pore in the Member 8 of Shihezi formation; （3） The physical properties of this area upper paleozoic formations are affected by sedimentary environment and diagenesis, its heterogeneity is strong, but the extensive frac-ture systems are composited of high angle fractures and horizontal fractures match high per-meability sand body, the favorable areas natural gas enrich to reservoir.