Study On Seepage Theory And Single Well Numerical Simulation Of Shale Gas Reservoir

As shale gas reservoirs are different from conventional gas reservoirs in reservoir forming condition, reservoir characteristics and percolation mechanism, its development method is also different from the conventional gas reservoirs. Because of the limitation of technology, the development of shale gas in China is still in the initial stage. Especially the understanding of the mechanism of shale gas reservoir is still insufficient. The above factors have greatly restricted the development of shale gas reservoir economically and effectively. Therefore, the research of complicate seepage flow in shale gas reservoir has great theory significance. At the same time, comparing with other fossil energy, shale gas can reduce most of the pollutions. Therefore, the research of complicated seepage flow also has great practical significance.Nonlinear seepage theory and numerical simulation technology are the premise and foundation of developing shale gas reservoirs effectively. This paper has established a mathematical model and a numerical model of gas-water two phase considering characteristics of adsorption, desorption, diffusion, seepage. With the help of models above, the percolation mechanism of shale gas reservoirs was known and analyzed deeply. Then did single well numerical simulation research of shale gas reservoirs by shale gas module of Eclipse numerical simulation software. After that, the effects of reservoir parameters and operation parameters on gas production rate and gas recovery were demonstrated. Finally, ordered various parameters by orthogonal test method according to the influence on cumulative gas production from strong to weak.The main achievements of this dissertation are as follows:(1) Based on a large number of literature research home and aboard, this paper researched the reservoir characteristics, storage characteristics and percolation mechanism of shale gas thoroughly. This could be treated as theoretical foundation of performance description in shale gas reservoirs.(2) Based on the percolation characteristics of shale gas reservoirs, the mathematical model of gas-water phase flow which considered the Langmuir adsorption, the Fick diffusion and the Darcy flow was established. By using a full-hidden finite difference method, the numerical model of the mathematical model mentioned before was completed.(3) By using Eclipse numerical simulation software, the shale gas single well numerical simulation model was established and the sensitive parameters of gas reservoir were analyzed. The results showed that, the production of horizontal well increased gradually with the increasing of the Langmuir pressure, the permeability in fracture system, the Langmuir volume, the inter porosity flow coefficient and the diffusion coefficient. But matrix permeability has little effect on gas production. The order of the influential parameters on the gas production, which was justified by the orthogonal experimental method, the effect from strong to weak is: the fracture permeability, the inter porosity flow coefficient, the diffusion coefficient, the Langmuir volume, the Langmuir pressure, the matrix permeability.(4) The sensitive parameters of construction parameter were also analyzed using Eclipse numerical simulation software. The results showed that, single well production gradually increased with the increasing of the vertical angle. The vertical wells were unable to complete commercial development of shale gas reservoirs due to low yield. Along with the increasing of the horizontal well spacing, the single well gas production gradually increased, but the recovery rate decreased gradually. With the increasing of horizontal well course length, the increasing of fracture half-length and the decreasing of BHP, single well gas production increased gradually. The order of the influential parameters on the gas production, which was justified by the orthogonal experimental method, the effect from strong to weak is: the bottom hole flowing pressure, the fracture half-length, the fracture distance, the spacing of horizontal wells, the course length of horizontal section.