临汾—运城盆地上古生界演化、改造及油气资源潜力分析

Analysis on Evolution,Modification and Hydrocarbon Resources Potential of the Upper Paleozoic in the Linfen—Yuncheng Basin

临汾—运城盆地位于山西省中南部,属新生代汾渭地堑系的一部分。以往勘探表明,该地区新生界缺乏有效烃源岩和有利生油条件,油气资源潜力不容乐观。但近年来邻区鄂尔多斯盆地、沁水盆地等上古生界天然气勘探的持续突破,为该地区前新生界油气勘探提供了重要启示。本文通过地震、重磁资料解释,并结合近年来区内钻孔资料,较全面地刻画了盆地上古生界的赋存分布状况,指出石炭系—二叠系主要分布在临汾坳陷中—北部和峨嵋隆起区西北部。由周邻露头资料推测,该盆地上古生界煤系烃源岩较为发育,有机质达到中等—高成熟演化阶段。结合后期改造、埋藏史和生烃史模拟、保存条件分析等,认为盆地北部临汾凹陷为煤层气或常规天然气勘探的较有利选区。

Objectives: The aim of this study is to examine the favorable target area for hydrocarbon exploration of Upper Paleozoic in the Linfen-Yuncheng Basin. Previous exploration demonstrates the Cenozoic hydrocarbon resources potential is not optimistic for lack of effective source rocks as well as other favorable conditions for reservoir forming.Whereas recent continuous breakthroughs of natural gas exploration in Upper Paleozoic strata of adjacent areas such as the Ordos Basin and Qinshui Basin etc. provide significant implication for pre-Cenozoic exploration in the Linfen-Yuncheng Basin.Methods: Based on gravity and magnetic data,combined with plenty of data from borehole drilling in recent years,the distribution pattern of Upper Paleozoic beneath Cenozoic strata is reconstructed. The quality of potential source rock was evaluated by pyrolysis experiment and maturity data.Results: It shows the Carboniferous- Permian systems mainly developed in the central-northern part of the Linfen depression and northwestern part of E 'mei uplift. Inferred from neighboring outcrops,the hydrocarbon source rocks are well developed in this basin. The maturity of organic material generally reaches middle-high thermal evolutionary stages.Conclusions: Integrated analysis of post-sedimentary modification,burial history,hydrocarbon-generating history and preservation conditions and so on,the Linfen sag located in the northern part of this basin is selected as a relative favorable area for coalbed methane or conventional natural gas exploration.