Pressure dynamic characteristics of oil wells in the carbonate reservoirs of tidal flat facies reconstructed by acid fracturing

Carbonate reservoirs of tidal flat facies are characterized by the development of dissolution pores and natural micro-fractures. Fracture network induced by acid fracturing can greatly improve the physical properties of the reservoirs around the well and change the flowing regimes of reservoir fluid. The pressure behavior model for the oil well in the carbonate reservoir of tidal flat facies reconstructed by acid fracturing was established based on concept of effective acid fracturing, combined with the phenomenon that no fracture-vug characteristics is reflected in the early pressure response of actual acid fracturing oil well. Then, the pressure solution in the real space was obtained using Laplace transformation and Stehfest numerical inversion. Finally, the effects of and the fracture-vug characteristics, boundaries of reservoir, the reconstruction degree and range of acid fracturing on the pressure behavior were analyzed. It is shown that there is obvious transitional flow between the reservoir reconstructed by acid fracturing and the unreconstructed reservoir, the transitional flow is under the joint control of reconstruction degree and reconstruction range. The application result of the new model to the oil well in the carbonate reservoir of tidal flat facies reconstructed by acid fracturing proves the feasibility of the assumption of effective acid fractured volume, provides a new idea for the evaluation of acid fracturing effect, and guides the preparation of schemes and measures in the late stage, e.g. the acidizing and plugging removal and the repeated acid fracturing.