塔里木盆地桑塔木断垒带奥陶系裂缝特征及成藏意义

塔里木盆地塔北隆起桑塔木断垒带奥陶系碳酸盐岩储层油气资源丰富,裂缝在油气藏的形成中起很重要的作用。通过大量的岩心观察和统计,发现取心段平均裂缝密度为3.3条/m,以小的半充填的斜交缝为主;裂缝主要发育2个带,第1条发育带位于不整合面之下,厚20～50m;第2条裂缝带与第1条相距约100m。通过分析化验资料的观察和分析,认为主要发育2期构造裂缝;综合分析测井、试油和构造等多方面的研究成果,认为裂缝的发育程度主要受断裂、不整合面和岩性等因素控制。裂缝发育程度与油气关系密切,裂缝发育区域油气高产的可能性大。裂缝发育于油气大规模运聚之前,为油气成藏提供通道。同时定量分析了裂缝对储层的贡献,认为其为储层提供一定的储集空间和绝大部分渗透率。 

FRACTURES OF THE ORDOVICIAN LIMESTONE AND THEIR RELATIONSHIP WITH HYDROCARBON ACCUMULATION IN THE SANGTAMU FAULT BELT OF THE TARIM BASIN

Sangtamu fault belt was located at Tabei uplift in Tarim basin. A lot of oil and gas resource was discovered in the Ordovician limestone of buried hill. Reservoirs are pore-fracture type. Many fractures were developed in the reservoirs. Average fractures density in cored inteval is 3.3 strap per meter. The fractures are characterized by small, oblique and half-filled ones. Two belt of fractures were vertically developed with the first one located under uncomformity surface. Its thickness is 20～50m. The second one is located below 100m of the first belt. Its thickness is 50～80m. In different position of fault belt, development level of fractures is different, and fracture is more developed inside the fault belt than the outside. Unconformity surface and lithology infleunced the vertical distribution of fractures. There is close relationship between hydrocarbon accumulation and fractures. The location with little fractures is poor for oil and gas production. Fractures are principal contributor of permeability and porosity of ressrvoirs. They supplied for 99.4% of total permeability and 12% of total porosity.