差异胶结作用引起的储层物性差异成因分析:以白音查干凹陷达尔其扇三角洲为例

Analysis on the causes of difference of reservoir physical properties caused by differential cementation:A case study of Daerqi fan delta in Baiyinchagan Sag

扇三角洲为陆相沉积盆地中的一个重要沉积体系,多数具有良好的油气储集能力。通常情况下,盆地中发育的扇三角洲具有相近的物性,扇三角洲前缘分流河道储层物性好,席状砂物性较差。然而,达尔其油田相邻的2个扇三角洲的物性出现了较大差异,达尔其西扇三角洲出现了分流河道物性差异与相控储层理论相悖的现象。利用偏光显微镜镜下薄片观察、岩芯物性分析与测井等资料,研究了该区储层岩石的孔隙类型以及成岩过程中压实和胶结作用对储层物性的影响,分析2个相邻扇三角洲储层物性差异及达尔其西扇三角洲河道物性差的原因,认为干旱气候和地壳抬升作用、盐湖沉积阶段和盐类沉积时间差异是形成2个扇三角洲物性差异的关键因素。研究成果为解释达尔其油田2个扇三角洲储层物性剧烈变化和差异提供了重要依据。

Fan deltas are an important depositional system in continental sedimentary basins,and most of them have good oil and gas storage capacity.Generally,the fan deltas developed in the basins have similar physical properties.The physical property of distributary channel in the fan delta front is good,while that of the sheet sand is poor.However,the physical properties of the two fan deltas adjacent to the Daerqi oilfield are quite different,and the physical properties of distributary channel in the west fan delta of Daerqi are contrary to the theory of phase-controlled reservoir prediction.Based on the thin section observation under polarizing microscope,core physical property analysis,log data and other materials,this essay studies the pore types of the reservoir rock,the influence of compaction and cementation on reservoir physical properties in the diagenetic process,analyzes the causes for the reservoir physical property differences between the two adjacent fan deltas and the reason for the poor channel physical property in the west fan delta of Daerqi,and puts forward that arid climate,crustal uplift,the difference of salt lake sedimentation stage and salt sedimentation time are the key factors accounting for the physical properties differences of the two fan deltas.The research results can provide an important basis for the drastic changes and differences of reservoir physical properties in the two fan deltas in the Daerqi oilfield.