珠江口盆地陆丰凹陷南部文昌组储层发育特征及其控制因素

Characteristics and controlling factors of reservoir development in the Wenchang Formation,Southern Lufeng Sag,Pearl River Mouth Basin

珠江口盆地陆丰凹陷文昌组为裂陷期沉积,裂陷初始期沉积的文五段发育优质储层。为了揭示优质储层成因机理,综合利用地震、钻井、岩心、铸体薄片、扫描电镜和压汞曲线等资料,对凹陷南部LF-A洼文五段的沉积、储层及成岩作用进行了研究。结果表明,LF-A洼文五段主要为辫状河三角洲前缘亚相沉积,岩石类型以长石质石英砂岩和岩屑质石英砂岩为主,储集空间主要为残余原生粒间孔,具有低孔隙度、低-中等渗透率、低-中等排驱压力特征。优质储层主要发育在杂基含量少、成熟度高的厚层河道砂岩中,反映高能环境对优质储层发育的控制。成岩作用对储层的影响主要表现为压实和早期胶结使孔隙减少,而晚期溶蚀有助于改善储层物性。早期构造抬升使文五段在后期未经受上覆地层的强烈压实,使大量原生孔隙得以保存,是优质储层形成的关键因素。

The Wenchang Formation in the Lufeng Sag,Pearl River Mouth Basin,is sedimentary fill deposited in the rifting stage. High quality reservoir was developed in the 5 thMember of Wenchang Formation which was deposited during the early stage of rifting. To uncover the genetic mechanisms of high quality reservoir,various data including seismic,drilling,core,thin section,scanning electron microscope( SEM) images and mercury experiments were integrated to analyze the sedimentary facies,reservoir characteristics and diagenesis of the 5 thMember of Wenchang Formation in the LFA Sub-sag,Southern Lufeng Sag. The research results indicate that the 5 thMember of Wenchang Formation is dominated by deposits of braid river delta front subfacies. Lithic quartz sandstones and feldspathic quartz sandstone are the dominatant rock types. The remnant primary intergranular pores are the main reservoir spaces. The 5 thMember of Wenchang Formation is characterized by low porosity,low-medium permeability,and low-medium displacement pressure. High quality reservoirs mainly present in thick channel sandstones with low lithic content and high maturity,reflecting the control of high energy environment on reservoir formation. The cementation and compaction processes in the early stages of diagenesis decreased porosity,while the dissolution process in the late stages of diagenesis enhanced reservoir property. Structural uplifting process in the early stages prohibited strong compaction by the overburden,making it possible for the preservation of large amount of primary pores,thus was the crucial factor for the formation of high quality reservoirs.