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Abstract: Pores, cavities and fractures are well-developed in deep volcanic reservoirs. The simultaneous break and extension of multi-fractures in treatment caused early stage sand-block, low fracturing success ratios, small treatment scales, and bad stimulation results. Based on the geologic characteristics of the deep volcanic rocks, this paper establishes a fracturing break and extension model of volcanic rocks, introducing with time-relevant leaking factor, peak factor and modulus factor. The model is used to better describe the process of initiation and extension of major fractures and micro-fractures. On this basis, the evaluating method for the “three highs” of pump off pressure gradient, near well friction resistance and leakoff coefficient is studied, and through field practices, integrated processing measures are formed: use rubber plugging to deal with near-well high friction resistances, use silts to seal natural fractures, adjust prepad fluid ratios, and inject multi-section silt slugs. The success ratio of volcanic rock gas reservoir fracturing is raised to 90.0% from the past 36.0%. [Copyright &y& Elsevier]

In this study, Shengli fault depression, Tangyuan fault basin, and northern Songliao Basin in Yitong-Yilan fault zone of Heilongjiang province are considered the research areas for geothermal anomaly. Based on the temperature of the deep thermal reservoir, the hydrothermal fluid channel, caprock thickness, and the mode of heat transfer, which are the main factors controlling the geothermal reservoir formation, we examined geothermal resource system of the underground HDR in this area. First, we inversed the aeromagnetic data, calculated the Curie isotherm depth, analyzed the geothermal distribution characteristics, and estimated the temperature of the deep heat source. Second, we applied the controlled source audio frequency magnetotelluric (CSAMT) and magnetotelluric (MT) methods to obtain the deep electrical structure of the study area. We determined the thickness of the caprock and the hydrothermal fluid channel. Finally, we obtained the borehole geothermal steady-state temperature measurement data and water sample chemical analysis data from the logging temperature curves of 24 wells to infer the mode of heat transfer. Based on the results, we built a model of the geothermal system of the sedimentary basin in this area. The results show that the depth of Curie isotherm in the study area is 17–39 km. The resistivity of sedimentary caprock in the north of Songliao basin is low, and there exists a deep heat source, which is mainly thermal convection. In contrast, in Shengli and Tangyuan fault basins, heat conduction is dominant. Based on the geothermal system model, we conclude that the area from Daqing to Lindian in Songliao basin has a thermal-convection-dominated sedimentary basin geothermal system. Heat exchange is realized by the upwelling of mantle-derived thermal materials through fracture channels. The thick sedimentary caprock reduces the heat loss. It can be a target for sustainable development and utilization of HDR. [ABSTRACT FROM AUTHOR]