Evaluation And Production Simulation Of Hydraulic Fracturing By Stimulated Reservoir Volume In Shale Gas Revervoirs

The development of shale gas reservoirs in our country is paid more and more attention and seen as an important part to modify the energy structure, since the supply of energy is inadequate in our country and the development of the shale gas increases quickly in other countries. In the past two years, the development of the shale gas in our country is so fast that the daily gas production in falling representative area achieves15×104m3/d and the cumulative gas production reaches7300×104m3, this bring us expectation and hope. However, the conditions of conducting large volume hydraulic fracturing operation should be needed to develop shale gas reservoirs. One of these conditions is complex fracture network and methods to express it in computer; another is to understand thoroughly the permeate mechanism in shales. Since the permeate method not only include Darcy flow in large pores and channels but also desorption process and diffusion process in small pores and channels, all of these mechanisms make a unimaginable complex permeate condition. Therefore, how to solve the above two questions is a necessary way to achieve shale gas production prediction.First, this paper conducts lots of tests on outcrops in Sichuan Xujiahe shale play, including mineralogical analysis, rock density test, horizontal terrestrial stress test, triaxial stress test and tensile strength and shearing strength test, etc. The results show that the shale in Sichuan Xujiahe shale play can generate a fracture network after large volume stimulation on the basis of results of horizontal terrestrial stress, Young's modulus and Poisson ratio, rock brittleness. The shale is easily fractured in the horizontal direction on the basis of results of tensile strength and shearing strength. Through summarizing the fracture number, fragments and fracture surface density after fracturing using silent agent, a new criterion to judge the possibility to create fracture network is developed. Second, on the basis of black oil model and mass conservation law, we use the dissolved gas to replace the adsorbed gas and using Fracman to generate the discrete fracture network, so the single medium model to simulate shale gas production is modified. Compared with the double hole single permeability model, both of them yield reasonable result, which means the modified single medium model is appropriate to simulate shale gas production. Third, simulate the effect of matrix permeability, artificial fracture parameters, natural fracture parameters and adsorbed gas volume on shale gas production. The results show that the production is in proportional to matrix permeability, artificial fracture length, artificial fracture number, natural fracture conductivity, natural fracture connection and adsorbed gas volume, and is inversely proportional to natural fracture interval. The order to influence the production is obtained through orthogonal test method and proved by analytic hierarchy process and Plackett-Burman (BP) test method. With large amounts of simulations, the calculated plate for quick parameter determination is created. Through practicing the effects of different factors on the shape and size of the stimulated reservoir volume using BP artificial neutral network method, the quick parameter determination for any condition can be achieved. Finally, simulate the real shale gas reservoir A. Through comparison of horizontal well production and vertical well production, horizontal well is more appropriate to develop the shale gas reservoir. The fracture parameters are also optimized to provide theoretical guidance to the development of this reservoir.