| 梁正中,张晓磊,宫焕然,郝志磊,庞锦莲.榆林-神木地区流体压力场演化及页岩气成藏过程动态分析[J].地质找矿论丛,2025,40(2):206-216 |
| 榆林-神木地区流体压力场演化及页岩气成藏过程动态分析 |
| Dynamic analysis of fluid pressure field evolution and shale gas accumulation process in Yulin-Shenmu area |
| 投稿时间：2025-03-03 修订日期：2025-04-16 |
| DOI：10.6053/j.issn.1001-1412.2025.02.008 |
| 中文关键词: 有机质 压力演化 页岩气 山西组 鄂尔多斯盆地 |
| 英文关键词:organic matter pressure evolution shale gas Shanxi Formation Ordos Basin |
| 基金项目:国家自然科学基金项目(编号:42062011)、陕西省科学技术厅重点研发计划(编号:2024GX-YBXM-511)、榆林市科技局项目(编号:22RCYPJB0103)和陕西高校青年创新团队(编号:2022-37)资助。 |
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| 中文摘要: |
| 鄂尔多斯盆地上古生界主要发育一套良好的过渡相煤系页岩,国内外学者认识到其页岩气具有良好的勘探开发前景。对于盆地东北部榆林-神木地区上古生界的流体动力演化及天然气运聚成藏机理已有大量论述,但鲜见区内异常压力的形成与页岩气富集成藏耦合关系的报道。本文在研究区及周缘过渡相页岩气形成、保存条件分析的基础上,结合有机地球化学和岩石学、含气量等测定分析,以压力变化特征为主线,重点剖析二叠系山西组页岩成烃成藏直至逸散的演化过程,并探讨地层压力的控藏作用。研究结果表明,榆林-神木地区泥页岩全区分布,厚度较大,有机碳含量较高,普遍处于中高成熟阶段,整体有利于页岩气藏的形成富集。山西组泥页岩层系现今以弱超压和常压为主,基于构造热演化模拟及流体压力演化史划分出区内泥页岩生烃增压、卸载减压、调整定型的三阶段。古超压形成与晚侏罗世-早白垩世盆地生烃高峰页岩气聚集期相一致,早白垩世末期地层抬升剥蚀降压伴随着页岩气藏的散失或破坏。古超压流体支撑对埋藏压实具有抑制作用,使得页岩储层保存相对较高的孔隙度,可形成超压微裂缝。超压地层能量高,游离气含量高,气藏整体含气性更好。在地层压力由超压降为常压或低压的过程中页岩含气量降低,同时导致赋存类型的转换。结论认为,盆地东北部上古生界压力场演化与页岩气富集保存相互协同作用的研究值得深入,对厘清整体非常规气分布规律及确定勘探方向具有重要的理论和实际意义。 |
| 英文摘要: |
| In the northeastern Ordos Basin,a set of marine-continent transitional shale in coal system of Upper Paleozoic group is well developed. Scholars consider that the shale has potential for gas exploration and development. Dynamic evolution of Upper Paleozoic fluid and the mechanism of gas accumulation and storage have been extensively discussed,but the coupling relationship of formation of the abnormal pressure with shale gas reservoir has been rarely reported. Based on analysis of the shale gas accumulation and storage in periphery of the study area,combined with organic geochemical,petrological data,and gas content measurement,this paper follows the major line of the pressure change characteristics to stress discussion of generation of hydrocarbon,formation of reservoir,and dissipation in the shale of Permian Shanxi Formation,and stratum pressure-control of reservoir. The results show that thick muddy shale is widely Distributed in the whole Yulin-Shenmu area and contains higher organic carbon and generally remains at amedium-high mature stage,thus is favorable for shale gas generation and accumulation. At present,the muddy shale is under weak super-pressure and normal pressure condition. Based on tectonic thermal evolution simulation and fluid pressure evolution history,gas accumulation in the shale is divided into three stages:hydrocarbon generation-pressure increase, unloading -pressure decrease and adjustment-finalization. Paleo-super-pressure formation coincided with late Jurassic-early Cretaceous peak of hydrocarbon generation,and the early Cretaceous uplift of strata led to erosion and loss of the gas from the shale and destruction of the reservoir. Support of the paleo-super-pressure constrains burial compaction of the strata,and keep higher porosity of the reservoir,resulting in formation of micro-fissures. Stratum with super-pressure and high energy contains large volume of free gas and the gas-bearing behavior of reservoir is better. Pressure of the stratum changes from super to normal or low leading to decrease of gas content of the stratum and transformation of reservoir type. According to the mentioned above,study on coordination of Upper Paleozoic pressure field evolution in the northeast basin with the shale gas enrichment and storage should be deepened,which can clarify distribution law of abnormal gas and is theoretically and practically significant to determine future prospecting direction. |
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