新疆塔河油田下奥陶统碳酸盐岩缝洞型油气藏特征

The characteristics of Lower Ordovician fissure-vug carbonate oil and gas pools in Tahe oil field, Xinjiang

塔河油田奥陶系油气藏位于塔里木盆地沙雅隆起阿克库勒凸起西南部斜坡 ,是一个储量近 2× 10 8t的超大型油气藏。自1997年发现以来 ,经 2年多的滚动勘探开发 ,已建成产能 2 0 0×10 4 t。油气藏的储集层属古风化壳碳酸盐岩叠加改造缝洞型储集体 ,纵向上可划分为 3个叠加—改造岩溶作用带 (风化残积表生岩溶带、渗流加潜流岩溶带、潜流岩溶带 ) ,是基岩经历多次构造运动抬升并多次产生岩溶改造而成 ,因而纵向上多期岩溶作用 (表生、渗流、潜流 )叠置 ,并在平面不同位置叠加改造 ,形成了非常复杂、纵横向储集性能变化极大的缝洞型储集体 ,在距风化壳顶面之下 2 5 0m深度以内呈层状展布 ,非均质性极强。储集体为泥、微晶灰岩 ,基质岩块不具孔渗能力 ,储集空间以缝洞为主 ,发育受古构造、古岩溶地貌及水系发育等控制 ,平面上形成多个组合类型。受储集体控制 ,油气层也呈层状展布。古风化壳缝洞型油气藏类型有层状凝析气藏、层状凝析气顶层状油藏、低饱和重质油藏 ,均属正常温压系统 ,具多期成藏特点 ,无统一底水 ,以弹性驱和溶解气驱为主 ,多数单井经酸压产量高。

The Ordovici an oil-gas pool of Tahe oil field is located in the southwest slope of Akekule salience in Shaya uplift, Tarim basin. It's a super large-scale oil-gas pool w ith about 2×10~8t OOIP. Through the progressive exploration and development of more than 2 years since being found in 1997, a production capacity of 200×10~ 4t/y has been built up there. The reservoir of the oil-gas pool belongs to supe rimposed-reconstructed fissure-vug type of paleo-weathering crust carbonate r ocks. It can be divided into weathering-sedimentary hypergene, vadose zone plus undercurrent and undercurrent karst belts etc, in vertical. The above three su perimposed and rec onstructed karst belts are formed by basement rocks, which have undergone many t imes of u plifting by tectonic movement and karst transformation. In vertical orientation, it has many stages of karst (hypergene, vadose and undercurrent) superimposed o n the different locations of the plane, and has formed very complicated, superim posed and reconstructed fissure-vug types of reservoir with obviously changeabl e reservoir performance in vertical. On the plane, reservoir beds are spread by layer 250m below the top of weathering crust with strong heterogeneity. The stor age space of the reservoir is dominated by fissure and vug, and controlled by an cient structure, ancient karst land features and water system growth etc. The fi ssure and vug growth of the reservoir varies obviously and can be formed into ma ny reservoir combination types. The basement rocks are mudstone, and matrix lime stone with no porosity and permeability. Controlled by reservoir, the hydrocarbo n zone is also distributed by layer. The types of oil-gas pool include paleo-w eathering crust fissure-vug type of stratified condensate gas reservoir, paleo -weathering crust fissure-vug type of stratified oil reservoir with stratifie d condensate gas cap, paleo-weathering crust fissure-vug type of black oil poo l with low saturability. Most single well has high output after being acid fract ured. The oil-gas pool has normal temperature and pressure system, and possesse s many stages of petroleum formation. The oil-gas pool is driven mainly by elas tic drive and dissolved gas drive and it has no unified bottom water.