库车坳陷东部下侏罗统致密砂岩储层特征及主控因素

塔里木盆地致密砂岩气分布广、勘探潜力大,是今后勘探的重要前瞻性领域.库车坳陷东部下侏罗统砂岩储层普遍致密,加强其储层特征及主控因素的研究,对指导下一步的天然气勘探开发具有重要意义.为了揭示了塔里木盆地库车坳陷东部下侏罗统致密砂岩储层的发育规律及主控因素,通过铸体薄片、阴极发光、扫描电镜、激光共聚焦等测试手段并结合测井资料,研究了储层的岩石学特征、孔隙结构特征和物性特征.结果表明,该区储层岩石类型以岩屑砂岩为主,岩石成分成熟度低,结构成熟度中等;孔隙结构主要为中孔细喉和小孔微喉,孔隙连通性较差;孔隙度大部分为4%~12%,平均为8.12%,有效空气渗透率主要为(0.1~3)×10-3μm2,属于典型的致密砂岩储层.在此基础上,综合分析了致密储层与沉积作用、成岩作用、构造作用的关系.研究认为,储层的物性受沉积作用、成岩作用、构造作用等的共同影响,其中主控因素是受沉积作用控制的粒度、成岩作用中的压实作用和构造压实作用.

Reservoir Characteristics and Main Controlling Factors of the Lower Jurassic Tight Sandstone in Eastern Kuqa Depression

The tight sandstone gas of Tarim Basin has a large distribution and great exploration potential, which is an important prospective exploration field of the basin in the future. The Lower Jurassic sandstone in eastern Kuqa depression is commonly tight. It is important for the further exploration and development to strengthen the study of its reservoir characteristics and the main controlling factors. In order to reveal the controlling factors and development mechanism of the Lower Jurassic tight sandstone reservoir in eastern Kuqa depression, by use of the tests of casting section, cathodeluminescence, scanning electron microscope and laser confocal microscopy are applied, together with the geological and logging analyses. The lithology, pore structure characteristics and physical properties are carried out in this paper. The results show that lithic sandstone is the main reservoir rock type, and the rock composition maturity is low while the textural maturity is of medium degree. The pore structure is mainly mesoporous with fine throat and micropore with fine throat. Majority of the porosity values ranges from 4% to 12%, with an average of 8.12%, and the effective air permeability is mainly (0.1~3)×10-3μm2; On the basis of the comprehensive analyses of sedimentation, diagenesis and tectonics of tight reservoir strata, the studies suggest that the reservoir physical property is mainly controlled by sedimentation, diagenesis and tectonism. The main controlling factors are granularity and compaction.