混合气藏类型划分及成藏模式探讨

混合气藏是常见的天然气藏类型,实用的类型划分及成藏模式的建立是该类气藏定量研究的基础。根据端元气的来源,对混合气藏类型进行了划分,并结合实例建立了相应的成藏模式。研究结果表明,常见的混合气藏可划分出两大类4小类:(1)异源混合气藏,指不同气源岩(灶)生成天然气的混合,其中包括异源岩混合气藏和异源灶混合气藏两类;(2)同源不同阶混合气藏,按母质类型分为煤型不同阶和油型不同阶两类。对塔里木、鄂尔多斯、四川等盆地典型气藏解剖结果证明,多套有效气源岩、沟通圈闭和源岩(灶)的通道是异源混合气藏形成的基础;而气源岩多期次演化生气、持续有效的圈闭是同源不同阶混合气藏形成的重要条件。分析认为,具有多套源岩供气的轮南凸起、川东高陡褶皱带是发育异源混合气藏的有利地区;而成藏过程复杂的库车坳陷则是同源不同阶混合气藏发育的有利地区。

Investigation on classifying types and forming patterns of gas-mixed reservoirs

Gas-mixed reservoirs are prevalent in gas-bearing basins.Classifying types and establishing reservoir-forming patterns are significant to quantitatively investigation and exploration for source-mixed gas.Based on types of end-member gases and their sources,the gas-mixed reservoirs were classified under two types including four sub-kinds gas-mixed reservoirs,and the corresponding reservoir-forming patterns by investigating typical gas reservoirs were established.The gas-mixed reservoirs include hetero-source gasmixed reservoir and hetero-stage gas reservoir.The hetero-source gas-mixed reservoir whose gases came from different source rocks or kitchens could be subclassified hetero-source-rock gas reservoir in which gases came from different source rocks and hetero-source-kitchen gas reservoir in which gases came from different source kitchens.The hetero-stage gas reservoir whose gases came from different thermal maturity of one source rock includes coal-type and oil-type hetero-stage gas reservoirs,gases came from different thermal maturities of coal-type precursor and oil-type precursor material respectively.Each kind of gas-mixed reservoir was selected from Tarim,Ordos or Sichuan basins in China and their geological conditions,formation mechanism and main controlling factors were investigated particularly.Conclusions were drawn that multi-source and pass-ways connecting sources(kitchens) and trap are indispensable factors for hetero-source gas-mixed reservoir,while for hetero-stage gas-mixed reservoir,multi-phase generating gas processes and sustaining effective trap are indispensable.Hetero-source gas-mixed reservoirs could be found in Lunnan arch of Tarim Basin and eastern Sichuan Basin where multi-series source rocks exist.Hetero-stage gas-mixed reservoir could be easily found in Kuche depression and the source rock bearing here has complex processes of generating gas.