苏里格气田东部储集砂岩孔隙衬里绿泥石成因及其对物性的影响

There are multiple interpretations of genesis of pore-lining chlorite in diagenesis research on sandstone reservoirs, such as transformation from clay minerals, deposition in pore water and alternation from other minerals. And arguments still exist in opinion about whether pore-lining chlorite resisting compaction or not, pausing cementation or not, protecting pore or not. As a kind of familiar clay minerals in sandstone reservoirs in the eighth member of Shihezi formation in the eastern part of Sulige gas field, close correlation lies between pore-lining chlorite and sandstone reservoir properties. As a result, the applicants will combine all principles and techniques of crystal chemistry, physical chemistry and reservoir geology in this study, setting genesis research of pore-lining chlorite in evolution of diagenetic fluid and diagenetic environment. Based on principles and data of crystal chemistry, the authors will calculate the forming temperature of pore-lining chlorite, and determine ion source of pore-lining chlorite. The applicants will estimate whether diagenetic reactions in certain medium and certain conditions happened or not by thermodynamics calculation. The applicants will study on the forming mechanism of pore-lining chlorite on the basis of diagenetic sequences, evolution of diagenetic fluid and diagenetic environment and ion source. The applicants will also discuss impacts of pore-lining chlorite on reservoir properties by judge whether pore-lining chlorite: ① resist compaction or not, ② pause cementation or not, ③ protect pore of sandstone or not. This study has not only scientific significance on reservoir geology research on pore genesis and pore protection, but also has important reference value on reservoir prediction, tight sandstone gas exploration and development at the similar conditions.

孔隙衬里绿泥石的成因有粘土矿物转化、孔隙水沉淀及矿物蚀变等多种解释，而在能否阻止压实作用、能否抑制胶结作用及能否保存孔隙等方面仍存在争议。作为苏里格气田东部盒8段储集砂岩中常见的黏土矿物，孔隙衬里绿泥石与储层物性密切相关。故本项目综合应用晶体化学、物理化学与储层地质学理论技术，将孔隙衬里绿泥石成因研究置于成岩流体与成岩环境演化之中；依据晶体化学理论和数据，计算孔隙衬里绿泥石的形成温度、判断离子来源；根据热力学计算判断一定成岩介质条件下的成岩反应能否发生。在成岩序列、成岩流体、成岩微环境演化以及离子来源的基础上，研究孔隙衬里绿泥石的成因。通过判断孔隙衬里绿泥石能否抵抗压实作用、能否阻止胶结作用、能否保护孔隙，探讨孔隙衬里绿泥石对储层物性的影响。本项目不仅对于孔隙成因、孔隙保护等储层地质学研究具有重要的科学意义，而且对于类似条件的储层预测、致密砂岩气勘探开发具有重要参考价值。

孔隙衬里绿泥石的成因及其对储层物性的影响成为近年来储层地质学争议的焦点问题之一。 苏里格气田盒8气层组砂岩中发育孔隙衬里绿泥石，在成岩序列、成岩流体、成岩微环境演化以及离子来源的基础上，研究孔隙衬里绿泥石的成因。通过判断孔隙衬里绿泥石能否抵抗压实作用、能否阻止胶结作用、能否保护孔隙，探讨孔隙衬里绿泥石对储层物性的影响。不仅对于孔隙成因、孔隙保护等储层地质学研究具有重要的科学意义，而且对于类似条件的储层预测、致密砂岩气勘探开发具有重要参考价值。. 探讨了长石石英砂岩和岩屑砂岩在成岩流体性质、成岩微环境和成岩产物等方面的差异，结果表明：① 储层中成岩古流体的演化复杂；② 埋深和温度是该区储层成岩环境变化的主导因素； ③ 岩性及原始物质組分的差异不仅影响了局部流体性质和成岩微环境的变化， 而且还导致了成岩反应、成岩序列和成岩产物的差异；④ 受差异成岩作用控制，苏里格气田长石石英砂岩的成岩演化相对简单， 其孔隙特征明显好于岩屑砂岩；⑤ 孔隙衬里绿泥石之上可继续发育硅质胶结；⑥ 一些绿泥石晶体被后期的自生石英晶体包裹，表明孔隙衬里绿泥石难以阻止硅质胶结物的发生，二者的出现先后关系取决于成岩环境的变化。. 绿泥石可包裹高岭石和石英加大边，偶见放射状绿泥石且孔隙较好。认为中成岩Ａ期的钾长石溶蚀、蒙脱石伊利石化、高岭石伊利石化、黑云母水化都会使得矿物体积变小，属于增孔反应，在一定程度上改善储层孔隙；且胶结作用增加储层的抗压实能力，在一定程度上保护了原生孔隙；故在分析胶结作用对物性的影响时，不能简单地归结为破坏性成岩作用。