渤海海域石臼坨凸起东北缘沙河街组一段+二段砂砾岩储层差异定量表征

为了探究砂砾岩储层物性差异的成因，以石臼坨凸起东北缘秦皇岛19-A构造和秦皇岛29-B构造沙河街组一段（沙一段）+沙河街组二段（沙二段）为例，通过岩心、铸体薄片、岩石物性、全岩分析、流体包裹体等资料，定量分析了砂砾岩储层的差异、控制因素以及孔隙演化过程。研究结果表明：①沉积作用控制了不同构造的岩性差异和原始物性差异，是其主要因素。秦皇岛29-A构造沙一段+沙二段主要发育扇三角洲中砂岩、粗砂岩夹薄层砾岩储层，粒度相对较细，砾岩比例小（约为2%），粒间以少量泥质为主，物性好，原生孔隙为主。秦皇岛29-B构造沙一段+沙二段主要发育扇三角洲含生物碎屑的砾岩与中砂岩、粗砂岩互层的储层，粒度较粗，砾岩比例高（约为57%），粒间以大量方解石、白云石等胶结物为主，物性差，次生孔隙发育。受控于沉积作用的差异，秦皇岛29-A构造沙一段+沙二段储层原始孔隙度为32.7%，秦皇岛29-B构造储层原始孔隙度为29.6%。②不同沉积作用影响下，砂砾岩储层经历了差异成岩演化。在长期碱性→酸性→短暂碱性的流体演化过程中，秦皇岛29-A构造经历了较强的压实作用（损失孔隙度为16.2%，孔隙度损失率为47.1%）和较弱的胶结作用（损失孔隙度为5.5%，孔隙度损失率为15.5%）；秦皇岛29-B构造经历了较弱的压实作用（损失孔隙度为10.1%，孔隙度损失率为35.6%）和较强的胶结作用（损失孔隙度为14.9%，孔隙度损失率为53.2%）。2个构造均经历了相近的强烈溶解作用（秦皇岛29-A构造增加孔隙度为8.3%，增孔率为24.7%；秦皇岛29-B构造增加孔隙度为7.2%，增孔率为25.8%）。③孔隙定量演化揭示，不同构造的储层孔隙演化过程具有明显的差异性。

Q uantitative characterization of differences in glutenite reservoir in the Member 1 and 2 of Shahejie Formation in the northeastern margin of Shijiutuo uplift,Bohai Sea

To explore the cause of differences in the physical properties of glutenite reservoirs, taking the Member 1 and 2 of Shahejie Formation in the QHD 29-A structure and QHD 29-B structure in the northeastern margin of Shijiutuo uplift as examples, this paper quantitatively analyzes the differences, controlling factors and process of the pore evolution of glutenite reservoirs by cores, casting thin sections, rock physical properties, whole rock analysis, and fluid inclusions. The research results show that: (1) Sedimentation controls the differences in the lithologies and original physical properties of different structures, which is the main factor. The reservoirs consisted of the gritstone intercalated by thin-layer conglomerates and fan-delta medium sandstone are mainly developed in the Member 1 and 2 of Shahejie Formation in the QHD 29-A structure, characterized with relatively fine grain size, a small proportion of conglomerate (about 2 % ), a small amount of intergranular clay, and good physical properties, dominated by primary pores. The reservoirs formed by the medium sandstone containing bioclasts and fan-delta conglomerate interbedded with gritstone are mainly developed in the Member 1 and 2 of Shahejie Formation in the QHD 29-B structure, characterized with relatively coarse grain size, a high proportion of conglomerate (about 57 % ), dominated by plenty of intergranular cements such as calcite and dolomite, showing poor physical properties and the development of secondary pores. Controlled by the differences in sedimentation, the original porosity of the Member 1 and 2 of Shahejie Formation in the QHD 29-A structure is 32.7 %, and it is 29.6 % for the QHD 29-B structure. (2) Under the influence of different sedimentary processes, glutenite reservoirs have undergone differential diagenesis evolution. In the fluid evolution process of long-term alkalinity→acidity→short-term alkalinity, the QHD 29-A structure experienced strong compaction (porosity loss of 16.2 %, porosity loss rate of 47.1 % ) and weak cementation (porosity loss of 5.5 %, porosity loss rate 15.5 % ). The QHD 29-B structure experienced weak compaction (porosity loss of 10.1 %, porosity loss rate of 35.6 % ) and strong cementation (porosity loss of 14.9 %, porosity loss rate of 53.2 % ). Both structures have experienced similar strong dissolution (the porosity increased by 8.3 % for the QHD 29-A structure, with the porosity increasing rate of 24.7 %; the porosity increased by 7.2 % for the QHD 29-B structure, with the porosity increasing rate of 25.8 % ). (3) The quantitative evolution of pores reveals that there are obvious differences in the evolution process of pores in reservoirs in different structures.