The Study For Kinetics Behavior Of High Viscosity Acid-rock Reaction

After more than50years of research and development, a variety of carbonatereservoir deep-acid-fracturing technologies with purpose of controlling acid fluid loss,reducing the acid-rock reaction rate are formed in the world. Different types ofhigh-viscosity acid systems have been widely used in the deep acid fracturingtechnology. The chemical reaction between high viscosity acid and rock directlydetermines the etching effective distance and etching fracture conductivity ability. Sothe acid-rock reaction of high-viscosity acid system is the core research ofdeep-acid-fracturing technology and it is important to predict the effect of acidfracturing and guidance technology program.There are few studies on the mechanism of the viscosity influence on theacid-rock reaction in currently, and the understanding of acid-rock reaction withdifferent viscosity acids is elementary. It is because the type of liquid, thecharacteristics of the flow pattern and acid-rock reaction of high-viscosity acid systemis quite different from conventional low-viscosity acid system. When usingconventional experimental test, the simulation acid-rock reaction result is quitedifferent from the actual situation, and the results are usually error. Therefore, invent anew experimental method that suits for the kinetic behavior of high-viscosity acidacid-rock reaction is very necessary. Meanwhile, study on the viscosity influence onthe acid-rock reaction mechanism and related laws so as to establish a consideringacid viscosity acid-rock reaction kinetic theory model.Based on the indoor experimental simulation of acid-rock reaction with thehigh-viscosity acid system, by the analysis of the adaptability, this paper established anew experimental method suits for the kinetic behavior of high-viscosity acidacid-rock reaction which can use for the different viscosity acids acid-rock reaction study.Combining theory and principles of fluid mechanics, chemical reaction kinetics,this paper researches viscosity influence mechanism of the acid-rock reaction andobtains the acid viscosity and mass transfer coefficient relationship to establish twoacid-rock reaction kinetic models considering acid viscosity in the reservoir fractureand the acid-rock reaction experiment. This paper also analyze the H~+mass transfercoefficient and acid-rock reaction rate distribution law and the effective etchingdistance in reservoir fracture by using the model. The study results in this paper are asfollows:1. Systematic study of the conventional acid-rock reaction simulationexperimental methods, combining the chemical reaction engineering theory andmixing principle, this paper designed and developed a new different viscosity acidssystem acid-rock reaction simulation experimental method. Based on the method, thispaper studies the correlation law between the acid concentration, temperature andflow rate with different viscosity acids acid-rock reaction rate by laboratoryexperiments.2. Binding the Prandtl boundary layer theory to establish the relationship of theformation fractures and acid-rock reaction experimental boundary layer distributionand the acid viscosity. Simulate the distribution and flow pattern of acid in theformation fracture boundary layer and define the applicable acid viscosity for therotating disk experiments.3. Combined with collision theory of reaction and diffusion kinetics theory of H~+diffusion coefficient and solution viscosity relationship, using the basis experimentalvalues in chemical principle, the relational expression between H~+diffusioncoefficient and acid viscosity, temperature and concentration was obtained.4. Based on double membrane mass transfer principle of mass transfer theory, themathematical model of Laminar and turbulent with convective mass transfercoefficient and viscosity relationship in formation fractures, acid-rock reactionexperiments was established. Calculate and analyze the acid viscosity, acid emission,fracture width and acid flow pattern influence on H~+mass transfer coefficient bysimulating.5. Study on the acid-rock reaction mechanism of the formation fractures andacid-rock reaction experiments, combined with H~+mass transfer coefficient equationchemical reaction kinetics theory, establish the acid-rock reaction considering the acidviscosity kinetics theory model of formation fractures and acid-rock reaction simulation experiment.6. By the analysis of the apparent viscosity of power law fluid and the formationfracture flow shear rate, via viscosity and shear time fitting relational expression toobtain the acid viscosity variation law in the formation fractures. Application of theconsidering acid viscosity acid-rock reaction kinetics theoretical model to simulatedifferent viscosity acid H~+mass transfer coefficient and acid-rock reaction rate alongthe fracture length direction distribution and to evaluate the impact of the acidemission with the viscosity change of the effective role of the etching distance.The purpose of this paper is to invent a simulation experimental method suitablefor the high-viscosity acid acid-rock reaction, to explore high-viscosity acid acid-rockreaction mechanism, to establish the relationship law of acid viscosity and acid-rockreaction and to perfect the high-viscosity acid system acid-rock reaction dynamicsbasic theory. Whether it is for the promotion of the development of the basic theory ofacid fracturing of carbonate reservoirs, or for improving the deep-acid-fracturingtechnology application effect of the carbonate reservoirs with high viscosity acid, it isof important theoretical and practical significance.