中国北方页岩气成因类型、成气模式与勘探方向

Genetic types,generation models,and exploration direction of shale gas in northern China

与南方相比,中国北方页岩气的成藏条件更复杂,成因类型更多,成气特征差异更大,但目前对北方页岩气的成因分类比较粗糙混乱,成气模式不统一、不完整,还未明确其分布规律和勘探方向,在北方寻找页岩气,直接套用南方的找气思路行不通。采用广泛调研与典型解剖相结合的综合分析思路,制定了基于成因机制、母质类型、演化阶段的页岩气三级分类方案,以此为标准建立了实用完整的页岩气成因类型判别标准模板,明确了北方存在原生油型生物气、次生煤型生物气、高成熟—过成熟油型气等9种不同成因类型的页岩气;选取典型样品,通过归纳、对比、拟合、对接、组装,建立了一套统一实用的反映页岩演化成气规律的定量通用模式;梳理分析北方页岩气的分布规律,总结出在纵向上依据成熟度演化阶段分层,平面上依据演化程度分带的有序连续分布特征,提出了北方页岩气勘探采取"分类勘探,分步实施,各个击破"原则,以煤型页岩气和生物页岩气为主要勘探领域,首先考虑中生界煤系地层的成熟、高成熟—过成熟煤型页岩气和湖相有机泥页岩的次生油型生物页岩气为重点勘探对象,其次,对新生界煤系地层和湖相有机泥页岩以寻找次生生物页岩气和原生生物页岩气为主要目标。该研究成果对北方页岩气勘探开发具有指导作用。

Compared with southern China,the shale gas accumulation conditions are more complicated,with more genetic types and greater differences in gas-forming characteristics in northern China. However,the classification of the shale gas genesis in northern China is relatively rough and chaotic,with gas-forming model being different and incomplete. The distribution law and exploration direction are not clear yet. Therefore,it is neces-sary to gain a deeper research to apply the idea of finding gas directly in southern China. Based on the comprehensive analysis of extensive research and typical anatomy,a three-level classification scheme of shale gas based on genetic mechanism,parent material type and evolution stage was established. Based on this standard,a practical and complete standard template for identifying the genetic types of shale gas was established. It is clear that there are nine different genetic types of shale gas in northern China,such as primary oil-type biogas,secondary coal-type biogas,high-mature-over-mature oil-type gas. Typical samples were selected,and a set of unified and practical quantitative general model reflecting the evolution of shale into gas was established by induction,comparison,fitting,docking and assembling. By analyzing the distribution law of shale gas in northern China,it is concluded there are stratified evolution stages in the longitudinal direction,and ordered continuous distribution features on the plane according to the degree of evolution. It is proposed that the shale gas exploration in the north adopts the principle of"classified exploration,step-by-step implementation,and various breakdowns".Coal shale gas and biogenic shale gas are the main exploration areas,and the mature,high mature-over mature coal shale gas in Mesozoic coal-bearing strata and secondary oil-type bio-shale gas of lacustrine organic mud shale are the key exploration objects. For Cenozoic coal-bearing strata and lacustrine organic shale,the main target is to search for secondary biogenic shale gas and primary biogenic shale gas. The results of this study have a guiding role in the exploration and development of shale gas in northern China.