Numerical Simulation Of Acid Indication In Acidic Fracture

Carbonate reservoir is one of the important oil and gas reservoir in the world. Recently, oil and gas production of carbonate reservoir has reached more than60%of the total production. As a result of some characteristics of carbonate reservoir and dual advantages of acid fracturing, acid fracturing has become one of the mainstream technology for them to efficiently developing. The main parameters (acid etched fracture conductivity and fracture length) which control the acid fracturing effect are closely related to acid flow and reaction process. If the acid fluid in the fracture occurs within the fingering phenomenon, on the one hand, it will strengthen acid fluid non-uniform etching on fracture surface, on the other hand, it will reduce the acid fluid loss rate and delay the acid rock reaction rate, so it can improve acid fracturing effect.Although the domestic and foreign scholars extensively studied the fingering phenomenon, which mostly occurs in Hele-Shaw Cell and porous medium, but we will study the acid fingering which occurs in fracture. And there are large differences between them. In view of this, this article firstly started mechanism of fingering.Then we simulated and analyzed influence factors of acid fingering from physical and simulation experiments. The main works that had been done in this thesis were summarized in following aspects,(1) In order to further reveal the essence of fingering phenomenon, we constructed a physical-mathematical model of acid fingering in fracture, and carried on the analysis of the mechanical mechanism.(2) By improving the existing physical simulation device, using home-made device conducted12set of physical simulation experiments of acid fingering under the condition of high temperature, and mainly discussed the effect of temperature on the morphological characteristics of the fingering.(3) Through researching multiphase flow simulation at home and abroad, a acid fingering evolution numerical simulation method which based on the VOF method was firstly developpment. It has the pertinence, economic, rapid, accurate and reproducible, etc.(4) The "VOF model+UDF" method was successfully simulated acid fingering firstly. And the influence of the gravity, viscosity ratio, acid injection rate, density difference, formation temperature and fracture surface roughness on acid fingering also had been studied.At last,in order to analyze multiple factors for the above several factors, the orthogonal design was used, and the effect curve and significance rank were obtained.To sum up, we successful completed the physical and numerical simulation of acid fingering, and comprehensively analyzed the influence factors of acid fingering. And on this basis, seveal suggestions of acid fracturing design and construction optimization were presented.