鄂尔多斯盆地东部奥陶系风化壳储层特征及主控因素分析

Characteristics and Key Controlling Factors of Ordovician Weathering Karst Crust Reservoir in the Eastern Part of Ordos Basin

鄂尔多斯盆地东部奥陶系风化壳储层岩石类型以含膏模孔的细粉晶白云岩为主。储集空间主要为溶孔,溶孔的充填程度及类型决定了储层物性的好坏。充填物类型决定储集空间的好坏,方解石充填对储集空间破坏性较大,但充填白云石由于其自身晶粒较粗,发育晶间孔,对储集空间具有建设性作用。对盆地东部风化壳储层发育的表征形态及孔洞充填物的硫同位素、化学成分、激光碳氧同位素、锶同位素特征的分析表明,盆地东部岩溶孔洞中充填的方解石主要形成于裸露风化期,而白云石则是埋藏期压释水岩溶的产物,提出中深埋藏期的压释水岩溶是有利储层形成的关键因素。

It is shown that silt-sized crystalline dolostone with moldic-pores are common in the Ordovician weathering karst crust reservoir in the eastern part of Ordos Basin. The pore space is mainly dissolved in the reservoir and the quality of reservoir is controlled by the filling degree and pore style. Calcite filling may have some destruction but have some construction to reservoir space due to relatively large crystal grains of filling calcite with intercrystal porosity. The analysis result of weatherJng karst crust reservoir and pore fills has shown that the fill- ing calcite deposited during the hyperdiagenesis expose phase while the dolomite is the product of compactionrelease water karst duimg burial time. It is put forward that the key controlling factor of favorable reservoir lie on the compaction-release water karst during middle- to deep-burial phrase.