Simulation Study On Acrylic Acid Closed Acid Pressure Process

As an effective means for the second modification of existed fracturing and acid fracturing, closed acid fracturing technology is widely used to increase production of carbonate reservoir at home and abroad, which makes it worth in-depth research and extension. At present, the indoor experimental researches of closed acid fracturing technology have been mature and have had a good application and development in site construction. In return, it provides technical support for oilfield production at home and abroad.However, the optimization of closed acid fracturing construction parameters is much insufficient in the simulation study. The determination of construction parameters (such as closed length, Acid injection displacement, acid liquid) mostly rely on personnel’s field experience, has not formed a complete and scientific optimization design method.In order to form a set of methods to optimize the design of closed acid fracturing technology, this paper had carried out gelling acid closed acid fracturing simulation studies through indoor experiments and numerical simulations. Moreover, this paper was mainly focused on the changes of fracture width, acid etching fracture conductivity, fracture closure simulation and the effect of closed fracture acidizing.(1) Combined with3D laser scanner, ultrasonic scanning, energy spectrum analysis, acid etching experiments and conductivity test, the work obtained acid rock reaction ability and acid etching fracture conductivity before and after acidizing. From the aspects of experiment, the improving effect of closed acid fracturing to near wellbore closure area is testified. Experiments show that it has more significant effect for lower conductivity fracture;(2) After deducing Palmer pseudo3D fracture extension model and acid flow reaction model,2D distribution of acid fracture width is achieved by solving numerical model;(3) Acid fracture closure model is established to simulate the closed characteristics of acid fracturing under different closure stress. Besides, the final distribution of fracture width is calculated out, and the closed area length is figured out through the changes of acid concentration distribution and conductivity;(4) Closed acidizing displacement, the dosage of acid and its injection time are determined through analyzing factors influencing the change of etching pattern and closed acid etching fracture conductivity before and after closed fracture acidizing model;(5) With sufficient indoor experiment and numerical simulation method, this paper systematically calculated the fracture width and conductivity under different construction displacement and dosage of acid. According to the requirements of reasonable production, the most optimal closed acid fracturing design scheme is screen out, thus forming a set of simulation method that optimizes construction parameters of closed acid fracturing.