| 徐家围子断陷砂砾岩储层纳米-微米级孔隙的形成及其与天然气充注的关系 |
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| 引用本文： | 刘超,陈海峰,王洋,陈掌星.徐家围子断陷砂砾岩储层纳米-微米级孔隙的形成及其与天然气充注的关系[J].地球科学,2018,43(5):1574-1586. |
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| 作者姓名： | 刘超 陈海峰 王洋 陈掌星 |
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| 作者单位： | 1.大庆油田有限责任公司勘探开发研究院, 黑龙江大庆 163712 |
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| 基金项目： | 致密砂岩微-纳米孔喉体系中油赋存特征和可动性研究项目41672116东北石油大学培育基金资助项目NEPUPY-1-03国家十三五科技重大专项"致密油形成条件、富集规律与资源潜力"2016ZX05046-001 |
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| 摘 要： | 松辽盆地徐家围子断陷在沙河子组致密砂砾岩纳米-微米级的孔隙中获得了工业气流，研究纳米-微米级孔隙形成与天然气充注的关系，为勘探选区和"甜点"预测奠定基础.在分析储层岩石学、储集空间和成岩作用特征的基础上，通过储层分类和计算各成岩事件对储层物性的影响，确定了砂砾岩储层的致密成因、微米-纳米级孔隙形成机制.研究认为，断陷早期的快速沉降大量减少储层原始孔隙，在强烈的机械压实作用下，富含粘土和塑性岩屑的"超致密砂砾岩"首先致密，相对富含刚性组分的"致密砂砾岩"受中成岩B期碳酸盐胶结物的充填达到致密，晚期碳酸盐岩胶结开始形成时期对应砂砾岩大规模致密化的时期，这期间原始较大孔隙也逐渐向微米-纳米级转化.结合砂砾岩中方解石胶结物内气液烃包裹体的均一温度和地层埋藏史、热史，推断砂砾岩致密化深度为2 500 m，致密化时期为距今100 Ma.砂砾岩孔隙演化史、源岩生烃史和油气充注史综合研究表明，天然气在储层致密前、后均有充注:初次充注发生在储层致密以前，天然气的生成速率和充注强度低，形成"先成藏、后致密"型构造气藏，斜坡带上倾方向发育微构造形态的部位是"甜点"发育的有利区；成藏高峰发生在砂砾岩致密化之后，天然气"连续"充注，形成不受构造控制的、大面积分布的致密气藏，斜坡带下倾方向邻近生烃中心的河道砂砾岩体是"甜点"发育的有利区.沙河子组砂砾岩储层致密与天然气充注关系综合分析认为，沙河子组主体为"先致密、后成藏"，局部为"先成藏、后致密".
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| 关 键 词： | 致密 砂砾岩 储层 成藏 沙河子组 徐家围子断陷 石油地质 |
| 收稿时间： | 2017-10-01 |
Formation of Nano-Micron Pores in Conglomerate Reservoirs of Xujiaweizi Fault Depression and Their Relationship with Natural Gas Filling |
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| Abstract: | Sandy on conglomerate gas prospecting in Shahezi Formation of Xujiaweizi depression has achieved initial success after several industrial gas flow wells had been drilled in reservoir space of nano-micron size. It is of great importance to determine the relationship between tight reservoir formation and natural gas charge for the exploration plan and "sweet spot" prediction. Based on the analysis of reservoir petrology, reservoir space and diagenetic evolution sequence, principal reasons and formation mechanism of nano-micron pores were determined through calculating the porosity changed by various diagenesis events. It is concluded that the quick subsidence and the huge mechanical compaction in the early diagenetic stage accelerated the damage of primary pores, resulting in the compacting of 'super-tight sandy conglomerates' which are rich in clay and plastic lithic fragments. 'Tight sandy conglomerates' which are rich in rigid components reached the tight grade in the later diagenetic process mainly due to the filling of carbonate cements, thus the formation of later carbonate cements corresponding to the densification threshold, after which the original pores reduced into nano-micron pores greatly. According to analysis of the homogeneous temperature of hydrocarbon inclusion in the calcite cement and burial-thermal history of Shahezi Formation, the compacting of sandy conglomerates happened around 2 500 m in depth and before 100 Ma. According to the comprehensive study of pore evolution history, hydrocarbon generation history and hydrocarbon filling history, gas accumulation occurred both before and after the compacting of sandy conglomerates. Before the compacting of sandy conglomerates, gas generated at a low speed and filled into the reservoir with a weak strength, forming some structural gas pools at the boundary of the depression, and therefore the upward direction of slope where micro amplitude structure developed is the favorable area for prospecting. The peak of gas accumulation occurred after reservoir compacting, characterized by high gas injection strength, forming widely distributed lithologic gas reservoirs, and thus the downdip direction of the slop where distributary channel sandbody developed and closely contact with main source rocks is the potential area for exploration.The comprehensive analysis indicates that the gas pool mainly formed after the reservoir tight with some formed before the reservoir compacting. |
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