气田水三维荧光特征对天然气运聚的指征——以川中—川西地区二叠系—三叠系气田水为例

Indication of natural gas migration and accumulation by three-dimensional fluorescence characteristics of gas field water: A case of gas field water in the Permian-Triassic in the central-western Sichuan Basin

依据气田水芳烃荧光光谱的三维形态、激发光强度及指纹图谱特征等,研究四川盆地川中—川西地区二叠系—三叠系天然气的运移路径与聚集规律。川中—川西地区二叠系—三叠系气田水具有(凝析)气藏影响特征,存在基峰、双峰与异峰等3大亚类7种三维荧光特征的气田水,以基峰亚类中的稳定型为主。二叠系—中下三叠统地层水与上三叠统须家河组地层水三维荧光特征有较大差异,前者主要受高—过成熟的下古生界海相泥页岩及上二叠统龙潭组煤系所生烃类的影响;而后者主要受其自身烃源岩成熟度差异与有机质类型差异的影响。气田水三维荧光特征研究表明,磨溪构造上二叠统—中下三叠统气藏以垂向运移聚集为主,雷口坡组以下气藏的天然气主要来自龙潭组煤系,而雷口坡组气藏还存在膏盐岩层段生成的天然气;平落坝构造须家河组气藏的天然气主要通过构造中南部的断裂运移而来,平面上储集层非均质性强烈。

The Permian-Triassic natural gas migration paths and accumulation patterns in the central-western Sichuan region are studied based on the three-dimensional shape,exciting light intensity and fingerprint characteristics of aromatic hydrocarbons fluorescence spectra of gas field water.The Permian-Triassic gas field water in the central-western Sichuan Basin has（condensate） gas reservoir impact characteristics,and has three subclasses（base peak,double peak and odd peak,mainly the stable type of base peak subclass） and seven types of three-dimensional fluorescence characteristics.Three-dimensional fluorescence characteristics of the water of the Permian to Middle and Lower Triassic differ from that of the Upper Triassic Xujiahe Formation.The former is mainly influenced by hydrocarbons from high to over mature Lower Paleozoic marine shale and Upper Permian Longtan Formation coal,while the latter is mainly by its own source rock maturity differences and organic matter type difference.Research on the three-dimensional fluorescence characteristics indicates that the Upper Permian Middle and Lower Triassic reservoirs in the Moxi structure mainly accumulate gas from vertical migration;gas in the reservoirs below the Leikoupo Formation originates mainly from the Longtan Formation coal,while the Leikoupo Formation gas reservoir includes gas from gypsum-salt rock section;gas in the Xujiahe gas reservoir in the Pingluoba structure is mainly migrated from central-southern faults and the reservoirs have strong heterogeneity on plan.