Tahe Oilfield Vuggy Carbonate Reservoir Depth Of Acid Fracturing Technology

Acid fracturing is an important stimulation technique for carbonate formation, which is widely used in the oil field. Fracture and hole are easily developed in carbonate reservoirs. Because of the existence of fracture and hole, the leakoff theory of Fractured and Holing Reservoir (FHR) is obviously different from isotropic reservoirs or general fractured reservoirs. The temperature field of acid flowing in the borehole and the fracture is the basis for calculating the in-situ parameters. Acidizing fluid system is the best important material in acid fracturing. It is the key to research acidizing fluid system adapting to high-temperature and deep reservoir in order to guarantee the success of acid fracturing. In addition, with the help of various methods for postfrac evaluation are the basis of analyzing acid fracturing effect, improving the design level of following acid fracturing. All of these contents comprise the major substance for TaHe FHR acid fracturing technique.According to the practical need of TaHe acid fracturing, this article mainly discusses the FHR acid fracturing design theory and acidizing fluid system. The main achievements acquired in this paper lie in the following:(1) Taking account of fracture fluid percolate along natural fracture and matrix, the analytic leakoff model of fracture fluid in the limited fractured layer is set up.(2) Based on the tri-medium percolation characteristics of the FHR, the leakoff model of fracturing fluid in the tri-medium reservoir is set up and the analytical solution is given.(3) The model of wormhole growth and acid flowing in the wormhole is set up and the calculation method of leakoff with acidizing wormhole is put forward.(4) Establishing the temperature field numerical model about borehole, leading the leakoff calculation method of FHR fluid, improving the temperature field calculation model about aicd flowing in the fracture.(5) High viscosity gel acid system and low friction emulsified acid system is developed for the need of acid fracturing about the high-temperature and deep reservoir and it was successfully used in the acid fracturing of TaHe oil field.(6) Adapting postfrac pressure fall analysis, production matching analysis, well test evaluation and acoustic emission fracture supervision , the comprehensive analysis about acid fracturing was carried on.Based on the researches on FHR technique, we get some useful conclusions in this thesis.(1) A great deal of fracturing fluid loss into the formation during the initial stage and major loss along the nature fracture, the impact of nature fracture should be considered during the leakoff's calculation of fractured reservoir.(2) The tri-medium leakoff model well describes the characteristics of FHR leakoff of fracturing fluid, and it can be extended to solve the problems of multi-medium leakoff or percolation.(3) Acidizing fluid mainly losses through the wormhole, the length of acidizing wormhole is the major affecting acid leakoff, properly icrease acid viscosity can slow down the growthrate of the wormhole length, so as to reduce the acid leakoff efficiently.(4) Improved foil-dimensional temperature numerical model can be better used in FHR's acid fracturing design.(5) The high viscosity gel acid system and low friction emulsified acid system can attain the requirement of TaHe oil field Ordovician system's FHR deep acid-fracturing reconstructed.(6) Adapting postfrac pressure fall analysis, production matching analysis, well test evaluation, acoustic emission ground fracture supervision etc, the comprehensive evaluation of acid fracturing will be beneficial to objectively and actually determine the fracture parameter.