延安地区长7段页岩气成藏富集条件及发育模式

蒲泊伶; 王凤琴; 王克; 孙建博; 李艳霞; 时保宏; 赵卫卫; 郭小波

doi:10.12029/gc20220313002

延安地区长7段页岩气成藏富集条件及发育模式

The enrichment conditions and model of shale gas reservoir in the Chang 7 member of Mesozoic Yanchang Formation in Yan'an, Ordos Basin

摘要

摘要:
研究目的 鄂尔多斯盆地中生界延长组长7段页岩具有岩性岩相、沉积厚度变化快、有机质丰度高但成熟度偏低、黏土含量高、地层普遍低压—常压的特点，对长7段页岩开展页岩气富集条件及发育模式的研究，利于探寻适合长7页岩气勘探开发的地质理论，以期对该地区下一步勘探工作提供指导，进一步完善陆相页岩气地质理论。
研究方法 基于钻井、岩心和分析测试资料，从生烃条件、储集条件、保存条件等方面，对长7段页岩气成藏富集条件进行了系统研究，建立页岩气富集发育模式。
研究结果 研究认为：（1）研究区长7页岩有机质丰度高，TOC基本大于1.5%，且处于大量生油气阶段，Ro基本在0.8%~1.3%，生气潜力较大；（2）黏土矿物含量高，基本在40%~60%，利于页岩气吸附，具有吸附气产出的特征；（3）相对稳定的构造背景是页岩气得以保存的重要条件；（4）页岩气富集模式可分为页岩与砂质纹层互层式和厚层富有机质页岩式两种模式，砂质纹层有效改善页岩储层物性，连续沉积的厚层富有机质页岩是气保存的重要形式。
结论依据对长7页岩气富集特征的解剖，将长7页岩气富集规律总结为“两大一多”的特征：生气潜力大、连续厚度大、砂质纹层多。

Abstract:
This paper is the result of oil and gas exploration engineering.
Objective The Chang 7 shale of Mesozoic Yanchang Formation in Ordos Basin is characterized by rapid changes of lithologies and lithofacies, thick, high abundance but low maturity of organic matter, high clay content and low-normal strata pressure. The study on shale gas enrichment conditions and development model of the Chang 7 shale is beneficial to explore the geological theory suitable for the exploration and development of Chang 7 shale gas, in order to provide guidance for the next exploration work in the region and further improve the geological theory of continental shale gas.
Methods Based on drilling, core analysis, and test data, the accumulation and enrichment conditions of the Chang 7 shale gas were systematically studied from the aspects of hydrocarbon generation conditions, reservoir conditions and preservation conditions, and the enrichment and development model of shale gas was established.
Results The results show that: (1) Chang 7 shale in the study area has high organic matter abundance, TOC is basically greater than 1.5%, and is in the oil and gas generation window, Ro is basically between 0.8% and 1.3%, and has the geological conditions of shale gas generation; (2) The clay mineral content is high, basically 40%-60%, which is beneficial to shale gas adsorption and has a certain adsorbed gas production; (3) The relatively stable tectonic background is an important condition for the preservation of shale gas; (4) The enrichment model of shale gas can be divided into two types: interbedded shale and sandy lamina type, and thick organic-rich shale type. The sandy lamina effectively improves the physical properties of shale reservoirs. The thick organic-rich shale deposited continuously is an important form of gas preservation.
Results Based on the dissection of the enrichment characteristics of Chang 7 shale gas, the enrichment law of Chang 7 shale gas is summarized as "two large and one many": large gas generation potential, large continuous thickness and many sandy laminas.

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