构造活动及层序格架约束下的沉积、成岩作用对储层质量的影响——以松辽盆地南部大情字井地区葡萄花油层为例

Impact of sedimentation and diagenesis upon reservoir quality under constraint of tectonic activities and sequence stratigraphic framework——A case study of Putaohua oil layer in Daqingzijing area of southern Songliao Basin

利用钻测井、岩心、岩石薄片、电镜扫描和室内分析化验等资料,基于层序地层学理论,展开了对松辽盆地南部(松南)大情字井地区葡萄花油层沉积作用、成岩作用和构造活动对储层质量控制作用的研究。结果表明,葡萄花油层层序格架主要由低位体系域和湖侵体系域组成,低位体系域主干分流河道砂岩和岔道口砂岩的储层质量最好,湖侵体系域水下分流河道次之。层序格架约束下的沉积作用控制不同体系域沉积微相的纵横向展布及砂体发育规模差异。垂向上,低位体系域上部砂岩的发育规模大、连通性好,为相对优质储层的发育层段;平面上,主干分流河道砂岩和岔道口砂岩的储层物性相对较好。成岩压实作用是导致葡萄花油层砂岩低渗透化的直接因素,层序格架控制低位体系域砂岩和湖侵体系域砂岩早期成岩环境的差异,导致湖侵体系域砂岩的碳酸盐胶结相对更强。溶蚀作用的强度主要受控于储层物性好坏、油源断裂展布及距油源断裂距离。研究区葡萄花油层的相对优质储层主要受控于层序格架、沉积作用、成岩作用及构造活动4者的耦合作用,即临近油源断裂或被多条油源断裂夹持的低位体系域中上部主干分流河道是相对优质储层发育的主要部位。

The impact of sedimentation,diagenesis and tectonic activities upon reservoir quality in Putaohua oil layer of Daqingzijing area,southern Songliao Basin,was studied based on sequence stratigraphic theories through analyses of drilling and logging data,core and thin section observation,SEM images as well as lab testing results. The result shows that the sequence stratigraphic framework of Putaohua oil layer is mainly composed of a low stand system tract and a lake transgression tract,with the former containing some high-quality sandstone reservoirs in distributary channels and forks of the main stream and the latter with quality sandstone reservoirs in underwater distributary channels. Sedimentation constrained by the framework was found to control the vertical and horizontal distribution of sedimentary microfacies and the scales of sandbodies in these system tracts. Vertically,sandstone layers at the upper part of the low stand system tract are large in scale and good in connectivity,thus contain relatively high-quality reservoirs; and horizontally,reservoir properties of the main distributary channel sandstone and fork sandstone are better for oil and gas accumulation. Diagenesis andcompaction were suggested to be the direct reason behind the low-permeability of Putaohua oil layer,while the sequence stratigraphic framework,which controlled an early diagenesis environment in both system tracts,was regarded to be a factor that strengthened to some extent the carbonate cementation of sandstone layers in the lake transgression system tract.The range and extent of dissolution there were thought to be determined by the properties of reservoirs,distribution of source rock-rooted faults and distance to these faults. Relatively high-quality reservoirs in the oil layer were controlled jointly by four factors,namely the sequence stratigraphic framework,sedimentation,diagenesis and tectonic activity,i. e.the main distributary channels at the central and upper part of the low stand system tract that were near to the source rock-rooted faults or bounded by the faults served as the major spots for high-quality reservoirs to take shape.