珠江口盆地深水气田储层差异及主控因素

Reservoir property differences and main controlling factors in deep-water gas field,Pearl River Mouth Basin

为了分析珠江口盆地荔湾气区同一深水盆底扇两相邻气田的储层物性差异及主控因素,综合利用铸体薄片、扫描电镜、物性及压汞等分析资料,对2个气田的岩石组分、微观孔隙结构和宏观物性特征进行对比分析,探讨沉积及成岩对储层质量差异的控制作用。研究结果表明:1)储层质量宏观上受控于沉积作用,A气田位于扇体远端,粒度较细,分选好;B气田靠近扇根位置,粒度较粗,分选差,粒间充填泥质杂基,沉积组分差异对储层物性有一定影响。2)造成储层质量差异的主要原因是受不同埋深影响引起的差异化成岩作用。受深埋藏强压实作用,塑性组分含量高的储层,粒间泥质杂基易挤压变形,降低储层的原生孔隙体积;黏土矿物中伊利石和伊/蒙混层多呈丝缕/丝片状充填于粒间和次生孔隙中,导致储层渗透性大幅度降低。研究成果对区域深水盆底扇的油气勘探开发具有一定借鉴指导意义。

Two adjacent gas fields have different reservoir properties in the same deep-water basin-floor fan in Liwan gas area of Pearl River Mouth Basin.To clear the main controlling factors,we comparatively analyzed rock composition,microscopic pore structure,and macroscopic physical properties of the two gas fields based on injecting thin sections,SEM observations,physical property,and mercury injection test,and then explored the impact of sedimentation and diagenesis on reservoir qualities.The results showed that:1)The reservoir quality is generally controlled by sedimentation.A gas field in the fan end is characterized by a fine grain size and is well-sorted;however;B gas field in the fan root is characterized by a coarser grain size,worse-sorted,and intergranular muddy matrix;2)Differentiated diagenesis caused by different burial depths is the main controlling factor of reservoir qualities.Under the action of deep burial and strong compaction,intergranular argillaceous matrixes are easy to extrude and deform in the reservoir with high plastic component content,reducing the reservoir's primary pore volume.At the same time,the illites and illite-smectite mixed-layers in clay minerals are mostly in the form of strands/silk sheets and fill the intergranular and secondary pore spaces,significantly reducing reservoir permeability.The study can be used for reference in oil-gas exploration and production in deep-water basin-floor fans.