Characteristics of breccia lava reservoirs and analysis of their dominant factors: case study of the Xushen gas field located in the Songliao Basin

Breccia lava is a type of rock in transition between volcanic clastic rock and lava. Its physical properties are comparatively special, while the nature of its genesis and the formation of reservoirs, deposits and concentrations vary considerably. In order to discover the different genesis for breccia lava reservoirs, our study has been carried out on breccia lava for its rock constituents, structures, diagenesis and reconstruction from tectonic movements to mineral depositions. From our analysis, we conclude that the main type of reservoir is a secondary emposieu, where rock compositions, structures, diagenesis and tectonic action are the major contributing factors to the deposition of breccia lava and its properties. Diagenesis constrained the extent of conservation of the primary pore of breccia lava and produced secondary porosity. The roles of tectonics were played out through the formation controlling tectonic fissures inside breccia lava and affected the impermeability of breccia lava fluids. The constituents of lava rock determine directly the type of diagenesis and its response to tectonic action. At the time of appropriate rock composition and structures, constructive formation occurred to breccia lava. Breccia lava also responded proactively to tectonic movements, forming the best quality collective reservoir agglomerations of vast spaces and strong permeability.