Study On Acidification Capacity Of Carbonate Matrix Based On Fractal Theory

Matrix acidizing is a major stimulation measure for carbonate reservoir. It is widely applicable for recent years. This paper aims at the study of matrix acidizing production, the major works are as following:According to the research for nearly thirty years about the acid wormhole and the fractal method, this paper analyzes the factors which have strong influences on the wormhole propagation and the wormhole growth models. In addition, this paper describes the origin of the fractal method and its development. Based on these theories, the author discovers the problem needed to be research:the effects of different fractal dimension for the permeability, skin factor and production. Then, based on the mechanisms the wormhole created and the wormhole propagation characteristics this paper discusses the theory of reaction between rock and acid. A wormhole propagation model is developed and the sensitive analysis is illustrated. As can be seen that large injection rate, low concentration acid system with some additives can make wormhole longer, which increases the efficiency of acidizing. Combining with the fractal theory, A new wormhole fractal permeability model is developed. This model is verified to match the experiment results well and a sensitive analysis is provided. As can be seen that larger tortuous fractal dimension corresponds to lower permeability, larger fractal dimension corresponds to larger permeability, larger porosity corresponds to larger permeability. A new skin factor model considering the pressure drop on wormhole is established to introduce the fractal dimension into skin factor. An analysis between these two models is discussed. Also, a sensitive analysis including tortuous fractal dimension, fractal dimension and porosity is shown. Based on the models above, the calculation for steady-state vertical well production is developed. Case study is given. On the basis of numerical study and sensitive analysis, some instructive conclusions and advices may be drawn, as can be seen that larger tortuous fractal dimension corresponds to lower production, larger fractal dimension corresponds to larger production, larger porosity corresponds to lower production.Matrix acidizing in carbonate reservoir is a complicated program which refers to different disciplines. There are many problems needed for further discussion.