松辽盆地深层火山岩气藏地质特征及评价技术

松辽盆地深层火山岩天然气藏勘探获重大突破,表明火山岩作为储集体,在适宜条件下,只要有良好的生、储、盖组合,就可以成藏.松辽盆地深层火山岩气藏具有以下地质特征:①发育烃类和非烃类两大类气藏,前者因密度偏轻,多分布干与次级深断裂伴生且埋藏较浅的火山岩中,后者则分布干与超深断裂伴生且较深的火山岩中;②下白垩统沙河子组煤系气源岩、营城组火山岩和登娄库组泥岩构成良好生储盖组合,控制主要火山岩气藏的分布;③火山口与爆发相火山岩多沿深大断裂分布,故深大断裂控制较大型火山岩气藏分布;④与深大断裂相伴的裂缝带控制火山岩气藏富集高产带分布;⑤深凹陷区溢流相火山岩堆积最厚,且与烃源岩大规模接触,只要具备储集条件,成藏前景更好.火山岩气藏的评价技术可概括为三步法:①重、磁、震联合反演确定火山岩分布;②用地震属性反演等多种方法预测火山岩储集体分布;③用流体预测等综合方法预测含气火山岩分布.对松辽盆地深层火山岩气藏特征与评价技术的总结有益于指导陆上其他盆地火山岩勘探.图11表2参31

Geological features and evaluation techniques of deep-seated volcanic gas reservoirs, Songliao Basin

The significant breakthrough of natural gas exploration in deep-seated volcanic rocks of Songliao Basin demonstrates that volcanic rocks as reservoirs can form natural gas accumulations where excellent source-reservoir-seal associations exist. This paper reveals several features of volcanic gas accumulations: (1) Two types of reservoirs including hydrocarbon and non-hydrocarbon are developed, the former is organic and usually trapped in shallower volcanics associated with sub-deep-seated faults, the latter is mainly inorganic and accumulated in deep-seated volcanics associated with large-scale deep-cut basement faults. (2) The Lower Cretaceous Shahezi coal series source rock, Yingcheng volcanics and Denglouku mudstone form good source-reservoir-seal associations, which control the major volcanic plays. (3) Volcanic crater and eruptive facies spread along deep-seated faults, so discordogenic faults control the distribution of larger-scale volcanic gas reservoirs. (4) Fracture zones, accompanied with large-scale faults, control the distribution of high-yield zones. (5) Effusive volcanic rocks in deep part of sags have huge thickness and contact extensively with source rock, so the gas accumulation potential is promising if reservoirs exist. Evaluation techniques can be summarized into three steps: (1) Determining of volcanic rocks distribution by joint inversion of gravitational, magnetic and seismic data; (2) Predicting the distribution of volcanic reservoirs by multiple methodologies; (3) Prediction on distribution of gas-bearing volcanic rocks by integrated methods including gas detention.