塔里木盆地秋里塔格构造带深部碎屑岩储层特征及控制因素

塔里木盆地秋里塔格构造带近期取得了天然气勘探的重大突破,但是目前对于埋藏深度较大的下白垩统巴什基奇克组碎屑岩储层的形成机制及控制因素尚不十分清楚。为了给该区下一步的勘探目标优选与油气开发提供技术支撑,基于已获得的钻井、岩心录井、薄片分析等资料,结合测井和生产测试资料,探讨了秋里塔格构造带巴什基奇克组储层的特征及控制因素。研究结果表明:①巴什基奇克组储层岩性以岩屑砂岩为主,次为长石岩屑砂岩,石英、长石含量低,岩屑含量高,成分成熟度低,结构成熟度中等;②储集空间以残余原生粒间孔和粒间溶孔为主,次为裂缝,具有"排驱压力高、孔喉半径小、进汞量小、细孔喉"的孔隙结构特点,属于低孔隙度、低渗透率孔隙型储层;③储层发育受沉积作用、成岩作用、构造作用、巨厚膏盐层分布和埋藏深度的综合影响,其中岩相、溶蚀作用和构造挤压是主要的控制因素,溶蚀作用与构造挤压造缝是储层储集性能得以改善的关键;④储层孔隙的演化模式可划分为早期浅埋粒间孔发育、早成岩期强胶结孔隙缩减、早表生期溶蚀增孔、中成岩期孔隙持续保持、晚期裂缝沟通孔隙改善储层性能等5个演化阶段。

Characteristics and controlling factors of deep-buried clastic reservoirs inthe Qiulitage structural belt,Tarim Basin

A great breakthrough was recently achieved in the Qiulitage structural belt, Tarim Basin, but no better understandings have ever been obtained of the accumulation mechanism and controlling factors of the Lower Cretaceous Bashijiqike Fm Clastic reservoirs. In order to provide technical support for further exploration target optimization and oil & gas development in this study area, we, based upon the drilling, core logging, thin section analysis data and other well logging and test information, discussed the characteristics and controlling factors of reservoirs there. The following results were achieved. (1) The rock types of the Lower Cretaceous Bashijiqike Fm are dominated firstly by lithic sandstones, and secondly feldspar lithic sandstones, characterized by a low amount of quartz and feldspar, high content of debris, low compositional maturity, and medium textural maturity. (2) The reservoir spaces include primarily inter-granular pores, inter-granular dissolution pores and secondary fractures. The reservoir rock physical property was bad, which suggests a reservoir of low porosity and low permeability. The pore structure is featured by high discharge pressure, small pore throat radius, small amount of mercury, and fine pore throat so that low-porosity and low-permeability porous reservoir was eventually formed there. (3) The reservoir properties are affected by sedimentation, diagenesis, tectonic action, gypsum rock layers and burial depth, etc., among which lithofacies, dissolution and tectonic compression are the main controlling factors, while corrosion and structural extrusion are the key factors to favorable reservoir properties. (4) The reservoir evolution mode is divided into five stages, i.e., long-term shallow-buried inter-granular pore development, strong cementation and pore reduction during the early diagenetic period, dissolution and pore-enhancement during the early supergene period, continuous maintenance of pores during the middle diagenetic period, and fractures connecting pores to improve reservoir performance during the late diagenetic period.