A Research Of Acid Fracturing Flowback Control Of Carbonate Reservoir

Acid fracturing is an important technology to improve the oil recovery of low permeability reservoir,especially carbonate reservoir.In the process of acid fracturing of carbonate rock,a lot of reaction heat is generated by chemical reaction between acid and rock,which affects the temperature distribution in the well,and then the filtration and flowback of acid.The acid fracturing flowback is a very important link in the acid fracturing process,which directly affects the fracturing effect,the fracture length and conductivity.Because the flowback problem is very complex,there is no mature theory of acid fracturing flowback.The field flowback is mainly determined by experience,which has great blindness and randomness.In this paper,a systematic study on fracturing fluid flowback is carried out,focusing on the influence of wellbore and fracture temperature and acid concentration on acid fluid filtration after acid fracturing.A twodimensional model and a numerical model of acid fluid filtration are established.Based on the calculation of filtration,a forced fracture closure model is established,and the acid fracturing flowback system is optimized.The research results have theoretical significance for fracturing flowback.The main research contents are as follows:First of all,based on the research status at home and abroad,this paper summarizes and summarizes the current situation of wellbore temperature field and acid concentration field model research,and establishes and solves the model according to the geological characteristics of carbonate reservoir.Secondly,considering the influence of temperature,acid concentration and other factors on the acid filtration,on the basis of fluid mechanics and material balance theory,the model of forced fracture closure is established,and the calculation method of wellhead pressure drop and fracture closure time is given.Finally,according to the parameters of carbonate reservoir and construction conditions,the flowback rate of fracturing fluid is optimized,and the design principle and method of flowback scheme are established.Guide the site to carry out backflow operation.