库车坳陷克拉苏构造带白垩系储集层多期溶蚀物理模拟

Physical Simulation of Multi-Period Dissolution in Cretaceous Reservoirs of Kelasu Tectonic Belt, Kuqa Depression

含油气盆地深层—超深层储集层孔隙成因及保存机理争议较大,以塔里木盆地库车坳陷克拉苏构造带超深层白垩系巴什基奇克组为例对此进行探讨。利用高温高压溶蚀模拟研究区储集层所经历的三种成岩环境下地层流体的溶蚀特征,结果表明,早成岩表生期饱和CO_2大气淡水溶蚀作用显著,易于溶蚀长石质及碳酸盐类矿物,石英矿物相对难溶;早成岩浅—中埋藏期咸化环境碱性溶蚀作用次之,石英、钾长石及钠长石均发生不同程度的溶蚀;中成岩深埋藏期少量有机酸溶蚀作用较弱,主要表现为沿缝网溶扩、石膏溶解和方解石沉淀。总体以前两期溶蚀作用为主,现今储集层残余粒间孔及粒内溶孔面孔率为2%～4%,占储集层总孔隙度的50%～80%.对于埋深超过5 500 m的储集层,溶蚀作用的实验模拟较合理地解释了溶蚀孔隙成因,有助于全面认识克拉苏构造带超深层优质储集层的成因,为西部盆地前陆冲断带深层—超深层多期构造运动下储集层研究提供依据。

There are lots of disputes on the pore genesis and its preservation mechanism in deep-ultra?deep reservoirs in petroliferous ba?sins.Taking the ultra?deep Cretaceous Bashijiqike formation in the Kelasu tectonic belt of Kuqa depression in Tarim basin as an example,the paper makes an in?depth discussion.High?temperature high?pressure dissolution simulation experiments are performed to study the dis?solution characteristics of the formation fluids under 3 different diagenetic environments.The results show that during the early diagenesis supergene period,the dissolution of CO2?rich meteoric freshwater was very significant,which was easy to dissolve feldspar or carbonate min?erals and quartz was a little bit difficult to be dissolved.During the early diagenetic shallow-medium burial period,alkali dissolution in sa?line environment took the second place,and quartz,potassium feldspar and albite suffered from the dissolutions of different degrees.During the middle diagenesis period the dissolution of organic acid was weak,which was characterized by the dissolutions along fractures,gypsum dissolution and calcite precipitation.The dissolutions during the early diagenesis period are dominant.The surface porosities of reservoir re?sidual intergranular pores and intragranular dissolved pores range from 2%to 4%,accounting for 50%~80%of the total reservoir porosity.For the reservoir with the burial depth over 5 500 m,the experimental simulation of the dissolution can reasonably explain the causes of the dissolved pores,which helps to fully understand the genesis of the ultra?deep high?quality reservoirs in the Kelasu tectonic belt and pro?vides basis for the study on deep-ultra?deep reservoirs with multi?period of tectonic movements of the foreland thrust belts in the western basins of China.