塔中地区志留系柯坪塔格组砂体类型及储集性

塔中地区志留系柯坪塔格组下沥青砂岩段是以海滩-浅海陆棚为主的沉积体系，具有海侵背景下受风暴控制的海滩-浅海陆棚沉积模式，上沥青砂岩段以潮坪沉积为主，并有部分海滩沉积，横向相变明显，垂向交互叠置。塔中地区柯坪塔格组砂体类型主要为前滨-临滨砂体、浅海浅滩砂体、低潮坪砂体、潮汐水道砂体等。浅海浅滩和前滨-临滨砂体物性好于潮坪砂体。沉积作用以及沥青充填程度对成岩的综合影响是控制后期优质储集层成因的主要因素。沥青充填空间主要为原生孔隙，存在一定程度的沥青二次生烃，产生的较大量有机酸可以溶解砂岩的一些物质，现今原油产层的孔隙为原生孔隙和次生孔隙混合类型，次生孔隙内很少见残留沥青。塔中地区岩性油气藏的勘探取得了一定进展，柯坪塔格组下沥青砂岩段滨滩-浅海陆棚砂体是岩性地层圈闭勘探的重点。

Sand bodies and their reservoir quality in the Silurian Kepingtage Formation in Tazhong area,Tarim Basin

In the Silurian Kepingtage Formation in Tazhong area, Tarim Basin, the lower bitumen-bearing sandstone interval is a shore-neritic depositional system and controlled by storm under transgression. The upper bitumen-bearing sandstone interval is mainly a tidal flat depositional system with some foreshore and nearshore facies laterally contacted or vertically lapped. The sand bodies in the Kepingtage Formation are shore sand, neritic, flat and tidal channel sand body, respectively. The shore-neritic depositional sand bodies could be the better reservoirs. Depositional process and bitumen-filling degree are the main factors controlling reservoir quality. The bitumen-filling pores are primary pores. There was some extent of secondary maturity of the bitumen, which leads to organic acid related dissolution in the sandstones. The pore types in the current pay layer are primary pore and secondary pore complex. The bitumen is absent in the secondary pores. The shore-neritic sandbodies are the important sandstones in lithologic-stratigraphic traps in this area.