柴北缘中部下干柴沟组下段成岩演化与储层评价

Diagenetic evolution and reservoir assessment about the lower part of Xiaganchaigou formation in the central areas of northern Qaidam Basin

根据普通薄片、铸体薄片、扫描电镜、储层物性等资料,分析了下干柴沟组下段的孔隙结构和成岩演化特征,建立了成岩序列与孔隙度演化模型.根据沉积相、地层等深图以及孔隙度演化模型,在柴达木盆地北缘中部地区划分出6种成岩相:浅湖-强压实相、滨湖-强压实相、冲积平原-强压实相、滨湖-中等压实相、三角洲前缘-较弱压实相、辫状河道-弱压实相.综合分析认为,继承性的古隆起及其斜坡带上的三角洲前缘-较弱压实相,储层物性较好,同时靠近生烃凹陷,成为油气运聚的有利区.

Based on normal thin sections, cast thin sections, SEM analysis, porosity and permeability analysis data, pore structure and diagenesis of the lower part of Xiaganchaigou formation were studied. The paragenetic sequence and porosity evolution model were creat.ed. Finally, six kind of diagenetic facies were termed according to sedimentary facies, bottom contour map and porosity evolution model： shallow-lake faces-tight compaction zone, lackshore faces-tight compaction zone, fluvial plain faces-tight compaction zone, lakeshore faces-middle tight compaction zone, delta front faces-weak compaction zone, braided channel faces-weak compaction zone. The reservoir property of early calcite cemented siltsandstone and fine sandstone located in the inherited swell is the best because these sandstones are weak compacted and strongly dissolved. This kind of reservoir is next to the generating depression, thus becoming the hopeful prospecting areas where oil and gas migrated and amassed.