Fracturing Technology of Real Time Control Guarantees Highly Efficient Exploitation of Shale in Weiyuan Gas-Field, SW China

Abstract

Production history fitting in Weiyuan shale gas shows that the length and height of supporting fractures are short, which limits the long-term conductivity of fractures. Due to the limited volume of reconstruction, the production decreases rapidly, which makes it difficult to achieve the purpose of economic and effective exploitation. In view of the above problems, an enhanced hydraulic fracturing technology (EHFT) which has been verified and applied is proposed to increase effective SRV. according to the different characteristics of shale reservoir, EHFT optimizs the performance parameter of fracturing fluid and matchs different modes of proppant injection, which can be classified in 4 major patterns, including modes of proppant injection in long/short slug type and densifying proppant injection in long / short slug type. First, based on brittleness evaluation and mineral composition, and combined with interpretation results of the natural fracture, the pumping plan is made according to the design goal. Then, modes of proppant injection is adjusted and optimized in real time through the construction curve and micro-seismic data during fracturing. The hydraulic fracture propagates along the dominant channel in the process of fracturing and there is the risk of the fracture communicating with the adjacent well. The fracture control technology of multi cluster perforating can effectively avoid it. Through field application, the following conclusions are drawn: (1) For reservoirs with high clay content, high viscosity fracturing fluid is recommended to improve the fracture width and reduce the complexity of construction; modes of proppant injection in long slugs of low concentration can control the construction scale, improve quality of proppant per meter, establish continuous fracture support and improve the long-term conductivity; modes of proppant injection in short slug type can control the fluid loss and avoid the occurrence of complex conditions, which is especially suitable for reservoir with natural fracture. (2) In the process of fracturing, the combination of various modes can achieve good results through real-time analysis and judgment. (3) The effectiveness of EHFT is verified by construction parameters, fracturing curve and micro-seismic monitoring. The construction scale (total volume of fracturing fluid) is reduced by 10%; quality of proppant per meter is increased by 10-20%; the fluctuation range of construction pressure is controllable/small; and the SRV and micro-seismic events are significantly increased. (4) The test production of well A which is the highest in Weiyuan is 71.2×104m3 with this technology. EHFT is suitable for the complexity of shale reservoir reconstruction. Multiple modes of real-time control can reduce the occurrence probability of complex conditions, improving the effective SRV and achieving efficient fracturing. Most importantly, the technology is feasible and effective in the overall goal of cost reduction and efficiency increase