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A series of studies was conducted to determine a suitable site for enhanced geothermal systems (EGSs) in mainland China. First, the Xujiaweizi (XJWZ) area in the Songliao Basin in northeastern China was identified to possess several features indicating a huge potential for hot dry rock (HDR) resource development from the aspects of tectonics, geology, geophysics, and geothermics. Then, a hydraulic fracturing model based on the real geological and logging data of well YS-2 and field fracturing experience in this region was established, and the geometric dimension and flow conductivity of the induced fracture were imported into a 3D hydrothermal coupled model established using TOUGH2-EOS1. The electricity generation potential of the fractured reservoir using three horizontal well production patterns is evaluated. Finally, three enhanced methods are proposed and discussed based on the simulation results. Results indicate that HDR resources in the XJWZ area demonstrate a significant potential for development from the aspect of geology. The Yingcheng Formation is selected as the potential target formation. The gel-proppant fracturing method is adopted in consideration of the undeveloped natural fractures in the target formation. The generalized EGS reservoir region possessed a considerable length of 600 m. The maximum production flow rate is determined to be 1 kg/s. The water flow impedance is relatively high during the heat production process for economic exploitation. Such an EGS reservoir has poor electricity generation capacity. A naturally fractured reservoir with a higher temperature should be targeted for electricity generation.

Coalbed methane (CBM) reservoir with Lower Young's Modulus, higher Poisson's ratio, and lower permeability is different from conventional sandstone reservoir in composition, structure, tectonic and mechanical property, therefore, the fracturing technique and mechanism are much more different. Qinshui Basin located in the southeast of Shanxi Province is of simple synclinorium structure, less of faults, and it has up to 10 layers of coal seams, total thickness 1.2-23.6m and the maximum 6.5m. By far, No.3 and No.15 coal seam of Qinshui Basin have been developed for CBM production, depth from 600m to 900m, and the rank of the coal are mainly meager-lean coal and anthracite. No.3 coal seam of Shanxi Formation is 0.53-7.84m thick, gas content 11.94m 3 / t on average, mainly semi-bright coal and semi-dull coal, reservoir pressure gradient 0.7149MPa/100m on average, well-testing permeability 1.589mD on average, Langmuir volume 39.03m 3 /t on average, Langmuir pressure 2.902 MPa . No.15 coal seam of Taiyuan Formation is 0.6-9.9m thick, gas content 12.45m 3 /t on average, mainly bright coal and semi-bright coal, reservoir pressure gradient 0.7727MPa/100m on average, well-testing permeability 1.14mD on average, Langmuir volume 40.91m 3 /t , Langmuir pressure 2.5417 MPa.Through optimizing the fracturing designs, evaluating fracturing fluid systems and implementing control measures, a set of 'network fracturing' treatments with casing injection, high displacement and activated water fracturing fluid as key techniques were developed and applied successfully for coalbed methane in Qinshui Basin with the rate of success more than 95%. The study also showed that the multi-fracture treatment by plugging perforation with plastic ball can be used in separate layer treatment of coalbed methane reservoir. Furthermore, variable injection rate and slug injection of proppant can also be used to achieve the purpose of controlling extension of fractures. In five years,1264 layers (at 1096 wells)were treated by using this fracturing technology in QinShui Basin, and the gas production rate is over 2000 m 3 /d in 60% fracturing wells. SPE 167108 Coal-bearing formationThe basin has up to 10 layers of coal seams, total thickness 1.2-23.6m and the maximum 6.5m. Although the basin undergo Indosinian, Yanshan and Himalayan movement when coal forming, the No.3 coal seam of Shanxi Formation and the No.15 coal seam of Taiyuan Formation are substantially stable 2 . The No.3 coal seam is 0.53m-7.84m thick, with the thickest in southeast, and the No.15 coal seam is 0.6m-9.9m thick, with the thicker in the north and south and the thinner in the central and west. Coal seam depth 3The depth of Taiyuan and Shanxi Formation is controlled by the ring syncline and local Cenozoic rift. The depth increases from Edge outcrop to the central part of the basin, being shallow in north-east-east-southeast, deep in the central. The formation within 1000m is in the north of the basin (mainly located in four areas of Taiyuan-Yangquan, xiangyuan-Changzhi, Qinshui-Yangchen...