长岭断陷东部火山岩气藏成藏条件及成藏模式

Formation Conditions and Reservoir-forming Patterns of Volcanic Rocks,Eastern Changling Depression

长岭断陷东部火山岩气藏具有储量规模大、丰度高、气层厚度大、储集物性好、单井产量高的特点,是深层天然气勘探的重点领域。通过对该区火山岩气藏成藏要素研究,认为下白垩统沙河子组湖—沼相暗色泥岩和煤系地层为主力烃源岩;营城组上部中—酸性火山喷发岩为主要储集层,储集空间以次生孔隙和裂缝为主;断裂和不整合面是油气运移的主要通道。根据长岭断陷火山岩气藏成藏特征,总结出3种成藏模式,即构造成藏模式、构造—岩性成藏模式和火山岩岩性成藏模式,其中构造—岩性复合型成藏模式为研究区最主要成藏类型。

Volcanic gas reservoirs in eastern Changling depression are characterized by large scale reserves, high abundance, good physical properties and high single-well production, and are the main area of deep gas exploration. The analysis on the key elements of the volcanic gas reservoirs reveals that the major source rocks are dark mudstone and coal layers of lacustrine and paludal facies of Lower Cretaceous Shahezi Formation. The major reservoirs are neutral and acid volcanic rocks on top of the Yingcheng Formation, and the reservoir space is induced pores and fractures. Fault and uncomformable surface are the main path for hydrocarbon migration. According to the characters of volcanic gas reservoir, three kinds of reservoir forming models are generalized, they are structure-type reservoir forming model, strueture-lithology type reservoir forming model and lithology-type reservoir forming model. Structure-lithology type is the most important pattern.