致密砂岩岩相组合约束下成岩作用差异及成因—志靖-安塞地区延长组长8油层组【中深层复杂油气储层专辑】
- 收稿日期:
2023-06-02
- 网络出版日期:
2023-10-23
摘要: 【目的】储层成岩作用的差异性,是影响储层非均质性特征的重要因素之一,制约了致密砂岩油气的分布预测,文章以志靖-安塞地区长8致密砂岩为研究对象,明确储层在岩相组合约束下成岩作用的差异性及成因。【方法】综合运用铸体薄片观察与鉴定、阴极发光(CL)、扫描电子显微镜(SEM)、碳氧同位素分析、激光剥蚀等一系列技术手段。【结果】研究结果表明,志靖-安塞地区长8致密砂岩储层可以分为三种岩相组合类型。Ⅰ型粉砂岩-细砂岩相夹泥质岩相组合与Ⅲ型细砂岩-粉砂岩-泥质岩相组合中,粉砂岩相粒度细,云母含量高,压实作用强烈,方解石胶结物在靠近泥质岩相的位置处大量发育,形成时间早,孔隙水受压实作用从泥岩向临近砂体排出,为方解石胶结物的形成提供物质来源;Ⅱ型细砂岩-中砂岩相组合中厚层砂体内部发育的方解石胶结物形成时间晚,主要与有机质演化有关;Ⅰ型和Ⅱ型岩相组合内部常见石英胶结物的发育,主要由长石溶蚀和黏土矿物转化提供硅质来源;溶蚀作用发育在岩石粒度较粗,塑性颗粒含量低的位置,该位置具有良好的流体运移通道。【结论】明确了研究区成岩作用的差异性及成因,为储层非均质性成因的进一步研究提供重要依据。
Diagenesis Differences and Genesis under the Constraint of Tight Sandstone Lithofacies Combination:in Chang 8 Member of Yanchang Formation in Zhijing-Ansai Area
- Received Date:
2023-06-02
- Available Online:
2023-10-23
Abstract: [Objective] Different reservoir diagenesis has a significant effect on reservoir heterogeneity, and limits the ability to predict the presence of oil and gas in tight sandstone reservoirs. [Methods] In the study area, the constraints of lithofacies combinations causing differences in diagenesis in Chang 8 tight sandstone in the Zhijing-Ansai area were clarified by observation and identification from thin sections, cathodoluminescence (CL), scanning electron microscopy (SEM), C and O isotope analysis, and laser ablation. [Results and discussion] The reservoir sandstone comprises three lithofacies combinations: type I is siltstone or fine sandstone interbedded with argillaceous rock; type II is fine-to-medium sandstone; and type III is fine sandstone/siltstone/argillaceous rock. The fine particles of the siltstone facies have high mica content, and the rock is strongly compacted. The reservoir contains a large amount of near-argillaceous calcite cement that was developed early. The mudstone is rich in pore water with high concentrations of calcium ions and bicarbonate ions. When the mudstone overlying and underlying the reservoir sandstone is deeply buried, overcompaction causes the muddy and clayey sediments to discharge mineralized water into the sandstone, affecting its diagenesis. The supersaturated calcium carbonate thus forms a dense carbonate cement at the sandstone-mudstone interface. The calcite cement developed in the type II sandstone facies combination was formed later: this is mainly due to the later evolution of organic matter influenced by the decarboxylation of organic matter in the source rocks. The conversion of clay minerals in source rocks occurs when the pore water containing calcium ions undergoes lateral advection along highly permeable pathways, entering the reservoir and providing a material source for the development of calcite in the thick sandstone. Quartz cement is usually developed within the type I lithofacies and is mainly provided by the dissolution of feldspars and the transformation of clay minerals which are the source of silica. The dissolution process usually develops in regions of the rock with relatively coarse particle size and low plastic particle content, thus providing good fluid migration channels. [Conclusions] The differences and origin of diagenesis in the study area are clarified, providing an important basis for further research on the origin of reservoir heterogeneity.
赵慧, 葸克来, 操应长, 辛红刚, 淡卫东, 李弛. 致密砂岩岩相组合约束下成岩作用差异及成因—志靖-安塞地区延长组长8油层组【中深层复杂油气储层专辑】[J]. 沉积学报. doi: 10.14027/j.issn.1000-0550.2023.096
Diagenesis Differences and Genesis under the Constraint of Tight Sandstone Lithofacies Combination:in Chang 8 Member of Yanchang Formation in Zhijing-Ansai Area[J]. Acta Sedimentologica Sinica. doi: 10.14027/j.issn.1000-0550.2023.096
Citation: |
Diagenesis Differences and Genesis under the Constraint of Tight Sandstone Lithofacies Combination:in Chang 8 Member of Yanchang Formation in Zhijing-Ansai Area[J]. Acta Sedimentologica Sinica. doi: 10.14027/j.issn.1000-0550.2023.096
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