碎屑岩盆地天然气成藏及分布序列

随着勘探程度的提高和非常规天然气研究的深入，多种聚集机理类型的天然气及其相互关系逐渐成为了研究焦点，即当煤、泥页岩等不同类型和成熟度的烃源岩与物性复杂变化的储层夹、互层存在时，煤层气、页岩气、根缘气、常规储层气等不同类型气藏将同时发育而形成基于气源岩的天然气机理及分布序列。通常情况下，常规储层气藏形成时的优先顺序晚于煤层气、页岩气、根缘气等非常规类型，处于天然气成藏与分布序列的顶端，加之非常规类型天然气聚集的成藏下限条件较之常规储层气藏要低。因此常规气藏的发现预示着非常规类型气藏的发育。由于盆地类型及其地质条件差异较大，不同类型天然气的分布及其资源量规模配比也表现出较大的不同。结合盆地勘探实践及理论研究认为，不同机理类型天然气之间存在相互关联和连续过渡，并由此建立了碎屑岩盆地不同类型天然气发育的地质模式。

NATURAL GAS ACCUMULATING AND DISTRIBUTION SPECTRA IN CLASTIC BASINS

With the improvement of exploration degree and progress of unconventional gas accumulations study,variety of natural gas accumulations with different accumulating mechanisms and their relations are becoming scientific research focuses. When various type of source rocks (coal measures and shale) with different thermal maturity coexist with complex reservoirs with continuous changing physical property,different types of gas accumulations,such as coal-bed methane,shale gas,tight gas and conventional gas accumulations,can occur in the form of gas accumulations spectra in the same basin. Generally,conventional gas accumulations formed after those unconventional gas accumulations (coal-bed methane,shale gas,basin-centered gas or source-contacting gas),positioned on the top of natural gas accumulation spectra,which might imply the occurrence of other unconventional gas accumulations in the same basin due to their reservoir conditions required for unconventional gas accumulations forming are not so constrained like conventional gas accumulations. Different basin types and geologic conditions lead to different resource proportion among different types of gas accumulations within the basin. The theoretic analysis as well as practical examples anatomy indicates one type of gas accumulation can transfer to the other one if accumulating conditions change,which provide clues to construct the natural gas distribution model in clastic basins. This finding can be quite useful in predicting gas accumulations distribution and guiding their exploration in clastic basins.