Petroleum system evaluation of the world’s deepest (>5000 m) volcanic reservoirs, Sichuan Basin, China

IF 2.7 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

AAPG Bulletin Pub Date : 2024-04-01 DOI:10.1306/12152322045

Di Xiao, Yu Yang, Long Wen, Benjian Zhang, Ran Liu, Ya Li, Xiucheng Tan, Jian Cao

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Abstract

Large-scale hydrocarbon accumulations have rarely been found in volcanic reservoirs around the world. This study documents large gas accumulations in Permian reservoirs in two areas of the Sichuan Basin, southwestern China, that include the deepest (>5000 m) volcanic reservoirs yet identified worldwide. Petroleum system elements differ in these deep volcanic accumulations between the Jianyang and Zhougongshan areas within the basin. In the Jianyang area, natural gas was derived mainly by the cracking of oil from Cambrian source rocks. Accumulations are overpressured stratigraphic traps spatially controlled by the distribution of a welded tuff reservoir with high porosity and high permeability. In contrast, low-porosity and low-permeability welded lapilli tuff and welded breccia reservoirs have lower gas saturations and are not productive. In the shallower Zhougongshan area, gas was generated by the cracking of kerogen in middle Permian source rocks. Regional tectonism formed normally pressured structural traps in fractured basaltic reservoirs. Multistage tectonism likely breached seals and allowed oil and gas to escape, reducing the scale of the accumulations in this area. Key factors influencing the large-scale accumulation and preservation of natural gas in the study area include development and preservation of adequate reservoir quality as well as tectonic history favorable to maintain seal integrity in brittle rocks. Our results provide guidance for the exploration for similar reservoirs in other areas.

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中国四川盆地世界最深（大于 5000 米）火山岩储层的石油系统评价

在世界各地的火山岩储层中很少发现大规模的油气聚集。本研究记录了中国西南部四川盆地两个地区二叠纪储层中的大型天然气储量，其中包括目前世界上发现的最深（大于 5000 米）的火山岩储层。在盆地内的简阳和周公山地区，这些深层火山岩储集层的石油系统要素各不相同。在建阳地区，天然气主要由寒武纪源岩中的石油裂解而来。积聚区是超压地层陷阱，空间上受高孔隙度和高渗透率的焊接凝灰岩储层分布控制。相比之下，低孔隙度和低渗透性的焊接青灰凝灰岩和焊接角砾岩储层的气体饱和度较低，产量不高。在较浅的周公山地区，天然气是由中二叠纪源岩中的角质裂解产生的。区域构造作用在断裂玄武岩储层中形成了常压构造陷阱。多期构造作用很可能破坏了封隔，使油气外泄，从而缩小了这一地区的储集规模。影响研究区天然气大规模聚集和保存的关键因素包括开发和保存足够的储层质量，以及有利于在脆性岩中保持密封完整性的构造历史。我们的研究结果为在其他地区勘探类似储层提供了指导。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

AAPG Bulletin 工程技术-地球科学综合

CiteScore

6.60

自引率

11.40%

发文量

审稿时长

4.8 months

期刊介绍： While the 21st-century AAPG Bulletin has undergone some changes since 1917, enlarging to 8 ½ x 11” size to incorporate more material and being published digitally as well as in print, it continues to adhere to the primary purpose of the organization, which is to advance the science of geology especially as it relates to petroleum, natural gas, other subsurface fluids, and mineral resources. Delivered digitally or in print monthly to each AAPG Member as a part of membership dues, the AAPG Bulletin is one of the most respected, peer-reviewed technical journals in existence, with recent issues containing papers focused on such topics as the Middle East, channel detection, China, permeability, subseismic fault prediction, the U.S., and Africa.