Research Of Crack Closure Law And Seepage Mechanisms

In recent years, with the deepening of the oil and gas field exploration and development, the exploration and development of fractured reservoirs has a very important strategic position in our country. New proven reserves of complex fractured reservoir has increased year by year in the proportion of total proven resources, by the way the output also has increased. But efficient development of the fractured reservoir is very difficult. Because in fractured reservoirs mining process, although the pre-mining capacity is high, after a period of exploration, the gas production of most wells decrease rapidly. Field analysis shows the main reasons is that in the fractured reservoir oil and gas are produced in great quantities and the pressure of the fluid inside the fracture system drops rapidly, causing the crack opening decreases, and fracture permeability decreases. In addition, it is not easy to recover if the reservoir fracture is closed under the force. Even if gas injection and other measures are taken to restore the formation pressure in the late production, the permeability of the fracture will also become weak. So a lot of rock matrix residual oil and gas can’t be mined and the recovery in the block is low.Therefore, this paper is based on petroleum engineering, petroleum geology, rock mechanics and seepage theory, it combines the experimental study and computer numerical simulation. It studies the law of reservoir fracture surface morphology, fracture closure rule, and does systemic research on the seepage flow characteristic of the fracture fluid, mainly completing the following several aspects of content:(1) System describes the basic characteristics of the reservoir fracture combined with western region A, including different kinds of classification methods, reservoir cracks characterization parameters, a variety of identification methods and the influencing factors of reservoir fracture development;(2) The regularity of the fracture closure and the percolation characteristics are carried by theoretical and experimental studies. So we can analyze the dynamic variations of fracture permeability and crack width under different pressure environment;(3) Combining reservoir fracture closure experiment and the simulations, it verifies the variation of the stress distribution, the velocity field and the pressure field in the three stages of the fracture closure;(4) Based on the factors of seepage in the real fracture space, simulations show us the real fracture roughness and width with their effects on seepage;(5) This paper discusses the closed rules of fractures In the bottom of the well during the production process and the effects of the closure on developing fractured reservoirs, on the basis of the combination of laboratory experiments and numerical simulation of crack closure and it’s percolation characteristics.This study offers a further understanding of the fracture closure mechanisms and seepage law, which has important guiding significance and practical value in determining fractured reservoir development methods and production rates, evaluating fractured reservoirs of oil and gas production variation accurately and improving the production capacity of fractured gas reservoir and oil recovery, and provides reference for similar fractured reservoirs.