Natural gas accumulation in the basin–mountain transition zone, northwestern Sichuan Basin, China
Natural gas accumulation in the basin–mountain transition zone, northwestern Sichuan Basin, China
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DOI：
10.1016/j.marpetgeo.2021.105305
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发表时间：
2021-08
影响因子：
4.2
通讯作者：
Di Xiao;Long Wen;Ya Zhang;Chen Xie;X. Tan;Jian Cao
中科院分区：
文献类型：
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作者：
Di Xiao;Long Wen;Ya Zhang;Chen Xie;X. Tan;Jian Cao
盆山过渡带是油气勘探的重要地区。为了更好地了解该区油气成藏过程和机制，对龙门山皮埃蒙特中二叠统栖霞组进行了研究。研究表明，冲断带栖霞组天然气（即，匡山梁、河湾场等地区）为下寒武统原油裂解产物。储层中充满了大量的沥青，这反映了强烈的充油作用。但由于后期大气沃茨的侵入对油气藏的破坏，天然气藏并不丰富。相反，在推力前缘（即，双峪石地区）和前隆带（即，九龙山地区储层沥青含量少，天然气含量高，油气保存良好。天然气主要来源于中二叠统烃源岩干酪根裂解，但也有少量下寒武统原油裂解气混入。冲断前缘和前隆带位于变形较小的地区，由于地层中既有腐泥型烃源岩又有腐殖型烃源岩和储集层，因此有利于天然气的聚集。认为盆山过渡带（超）深层油气资源可能是全球勘探的重要目标。
The basin–mountain transition zone is an important area for hydrocarbon exploration. To better understand the process and mechanism of hydrocarbon accumulation in this area, the middle Permian Qixia Formation at the piedmont of the Longmenshan Mountains, northwestern Sichuan Basin, China, was investigated. It is showed that natural gas in the Qixia Formation in the thrust belt (i.e., the Kuangshanliang and Hewanchang areas) was derived from lower Cambrian strata by oil cracking. The reservoirs are filled with amounts of bitumen, which reflects strong oil charging. However, the gas accumulation is not rich, which is due to the later destruction of hydrocarbon accumulations by the invasion of meteoric waters. In contrast, in the thrust front (i.e., the Shuangyushi area) and forebulge belt (i.e., the Jiulongshan area), the reservoirs contain few bitumens and large amounts of natural gas, which is indicative of good preservation for hydrocarbon accumulation. The natural gas was mainly derived from kerogen cracking in middle Permian source rocks, although it was mixed with a small amount of lower Cambrian-derived oil-cracking gases. The thrust front and forebulge belts occur in areas of lesser deformation, and thus are favorable for gas accumulation, due to the strata containing both sapropel- and humic-type source rocks and reservoirs. It is generalized that hydrocarbon resources in (ultra-)deep strata in the basin–mountain transition zone may be an important target for exploration worldwide.