柴窝堡凹陷中二叠统芦草沟组储层控制因素与发育模式

为明确柴窝堡凹陷中二叠统芦草沟组有利储层分布规律,综合利用岩心、岩石薄片、X射线衍射和扫描电镜等测试资料,结合构造演化及沉积体系分布特征,系统分析了芦草沟组储层特征与控制因素,建立了储层发育模式。研究结果表明:芦草沟组储集空间主要以溶蚀孔隙和微裂缝为主,以超低孔超低渗、超低孔特低渗储层为主。紧邻伊林黑比尔根山的近岸水下扇扇中砂砾岩原生孔隙度较低,成岩早期受垂向、侧向压实作用的共同作用,储层更加致密;近岸水下扇扇缘砂砾岩在成岩早期主要受垂向压实作用影响,侧向压实作用影响较弱,成岩后期经历烃源岩释放的酸性流体强溶蚀作用,形成了较多的粒间、粒内溶孔,为油气聚集最有利的沉积相带;浊积扇砂体夹于半深湖—深湖相厚层烃源岩内,发育一定的溶蚀孔隙,为油气勘探的“甜点”储层。研究成果为柴窝堡凹陷部署勘探井提供了重要的地质依据。

Reservoir Controlling Factors and Development Model of Middle Permian Lucaogou Formation in Chaiwopu Sag

In order to work out the distribution pattern of favorable reservoirs in Middle Permian Lucaogou Formation in Chaiwopu Sag, the reservoir characteristics and controlling factors of Lucaogou Formation were systematically analyzed and the reservoir development pattern was established according to the test data such as core, rock slice, X-ray diffraction and scanning electron microscope, in combination with the characteristics of tectonic evolution and sedimentary system distribution. The study results showed that the reservoir space of Lucaogou Formation was dominated by dissolved pores and micro-fractures, and was mainly composed of reservoirs with ultra-low porosity and ultra-low permeability. In the nearshore subaqueous fan adjacent to Yilinheibiergen Mountain, the primary porosity of glutenite at the fan center was low and the reservoir was denser due to vertical and lateral compaction in the early diagenetic stage. The glutenite at the margin of the nearshore subaqueous fan was mainly subjected to the effect of vertical compression while the effect of lateral compaction was weak in the early diagenetic stage. The strong dissolution effect of acidic fluids released from source rocks in the late diagenetic stage made more inter-granular and intra-granular dissolved pores, form the most favorable sedimentary facies belt for hydrocarbon accumulation. The sandbody of turbidite fan was sandwiched in the deeper or deep lacustrine thick source rocks, developed with dissolved pores, forming a "sweet spot" reservoir for oil and gas exploration. The study results provide an important geological basis for the deployment of prospecting wells in Chaiwopu Sag.