埋藏(机械)压实—侧向挤压地质过程下深层储层孔隙演化与预测模型

Deep Reservoir Pore Evolution Model of a Geological Process from Burial Compaction to Lateral Extrusion

早期长期浅埋、后期快速深埋以及晚期强烈的侧向挤压作用是西部前陆盆地共性地质演化过程,受此地质演化过程影响,明确深层储层孔隙、孔径、喉径等参数的演化特征并进行定量评价,对油气勘探具有重要意义。开展成岩物理模拟实验,并与实际地质分析相结合,定量评价与预测了库车坳陷克拉苏构造带白垩系深层储层的孔隙类型与演化特征。研究结果认为,研究区深层储层的孔隙类型、含量变化及演化规律可划分为4个阶段,其中第3个演化阶段即深层储层快速埋藏后的早期阶段是孔隙度和渗透率提高的重要阶段,是此类地质过程下深层有利储层形成的关键时期。构造侧向挤压与成岩压碎破裂造缝、次生溶蚀两种改造机制,改善了深层储层的储集性、提高了渗透性,进而建立了深层储层孔隙预测模型。定量揭示出库车坳陷克拉苏构造带在埋深7 000~8 000 m甚至更深层段,储层孔径、喉径增大并保持,仍发育有效储层。

Early shallow burial for a long time,the late quickly buried deep and lateral extrusion in western foreland basin are common geological evolution process in China. Affected by such geological evolution process,a high-quality reservoir can be formed in deep horizon. Clearing this kind of reservoir parameters such as porosity,pore diameter and throat diameter of evolution characteristics and quantitative evaluation,it has great significance for oil and gas exploration. Based on analysis of diagenetic physical modeling experiment,combined with the actual geological research,the evolution of deep-reservoir porosity in a foreland basin can be divided into four stages： 1） long-term,shallow burial;2） a transition from shallow burial to rapid,deep burial; 3） early,rapid,deep burial; and 4） late,rapid,deep burial. Of these,the third stage is crucial to the improvement of deep-reservoir porosity and permeability,and thus to the formation of favorable reservoirs. The two kinds of transformation mechanism are tectonic lateral extrusion and particles broken crack. Deep reservoir porosity prediction model has been established. Reservoir pores and pore throats show a significant increase at a burial depth of 7 000-8 000 m.