| Acid not only can dissolve fracture wall to produce uneven etching, but also penetrate the fracture wall to form wormhole when acidizing implemented in carbonate reservoir with natural fractures. Acid-rock reaction heat produced through such a series of process and can put effect on the temperature distribution of underground. Acid-rock reaction kinetics is very sensitive to temperature, constant of reaction rate increased with the temperature as exponentially, even the temperature has important effect on the threshold temperature which is needed in the reaction between weak acid and rock. So aiming at the acidizing characteristics of carbonate rocks with natural fractures, studying the temperature distribution of underground and leak-off situation have significant value to improve the acidizing design level.The main work is as follows:(1)Based on the review of related literatures both home and abroad, paper concludes and summarizes the current models of temperature of wellborn, formation, fracture and wormhole propagation, analyses the main drawback of those models in the process of establishment and solution.(2)Aiming at the the convection and diffusion of vertical wellborn and horizontal wellborn and the heat conduction of formation to wellborn during the injection, this paper established the model of temperature fields of vertical wellborn, gave a convenient semi-analytical solution which was composed of exponential function and zero-order Bessel function through Laplace transform and Stehfest numerical inversion. Finally practical calculation found that the heat conduction of formation is important to the wellborn(3)Based on the convection and conduction between connection and formation, chemical heat in the horizontal wellbore, this paper established the model of temperature fields of formation, gave a semi-analytical solution which was composed of exponential function and nonzero-order Bessel function through Laplace transform and Stehfest numerical inversion. Also it simulated and analyzed the influence of injection time, displacement, reaction heat, injection temperature, formation porosity on temperature distribution and variation.(4)This paper builded natural fracture acidizing temperature by equations of mass conservation, energy conservation, the changing of fracture width and acid migration, simulated and analyzed the influence of injection time, displacement, temperature, fracture height on temperature based on finite difference method, simulated and analyzed the influence of fracture net pressure, initial fracture width on leak-off. This model is fairly accurate on the prediction of the fracture temperature distribution and can provide certain theoretical basis on the selection of the additives of acid.This paper achieves certain innovation on the temperature of formation during model of establishment and solution. The results have importance to design level of acidzing simulated and select acid system more responsible. |
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