Simulation Study On Acidification And Acidization

The abundant oil gas total resources contain in carbonate reservoirs, but, the carbonate reservoir characteristics with multilayers, uneven damage and high heterogeneity, these features cause different physical properties among these layers. So, the diverting measures must be taken during the acidizing process in order to achieve stimulation yield. Self-diverting acid technology is a novel acidizing stimulation technology in carbonate reservoirs with multilayer systems, it could achieve longitudinal uniform stimulation in anisotropic reservoir relying on its superior characteristics "variable viscosity, reducing leakoff, retardance reaction velocity, lowing damage", many domestic and foreign oil field have applied diverting acid technology and achieved significant stimulation yield. In recent years, many schoolars have devoted to the researches on performance evaluation of diverting acid, change mechanism of viscosity, diverting performance and treatment in field, but, the systematic researches on law of change viscosity, process of diversion and leakoff of diverting acid are very rare, lead to a certain degree blindness and randomness of diverting acid in actual application.In this paper, reviewed plenty of domestic and foreign literatures, formed diverting acid based formula by many experiment researches, tested the synthesized performance of novel diverting acid system, conducted many theoretical studies on the basis of this system, including the viscosified law of diverting acid, the process of diversion, the development and leakoff of acid etched wormhole.The major workloads and achievements of this paper are as follow:(1)Firstly, preferred main additives of diverting acid through laboratory experiments, including diverting agents, iron stabilizers, corrosion inhibitors, and the compatibility is approved between diverting agents and others additives, then formed diverting acid basic formula based on these laboratory experiments.(2)Then, tested the overall performance of novel diverting acid through laboratory experiments, including apparent viscosity, high temperature corrosiveness, dissolution rate, acid-rock reaction speed and diverting performance.the results proved this novel diverting acid oblect the following characteristics:corrosion retardance, variable viscosity, reducing leakoff, retardance reaction velocity.(3)On the basis of laboratory experiment studies and acid-rock reaction kinetics, proposed using the similarity of change trend between error function and viscosity variation to research viscosified law during porous media of this novel diverting acid, then developed variable viscosity law of this novel diverting acid system in porous media based on the results of laboratory experiments.(4)On the basic studies of diverting acid viscosifiy effect, developed a diverting model and diversion judging criteria of this novel diverting acid. Then established simulating programs to simulate the flow separately and calcaulate the acid rate in each layer, and make contrast analysis with regular acid, the results proved the diverting effect is well, and achieve uniform acidizing in multilayers carbonate reservoir. (5)0n the basic studies of diverting acid leak-off mechanism, taken the viscosified effect into consideration of wormhole extended model and leak-off model of regular acid, established simulating programs to simulate the law of diverting acid wormhole extension and leak-off, and make contrast analysis with regular acid, the results proved the wormhole of diverting acid less branches, small bore diameter than regular acid, and leak-off control effectiveness is remarkble than regular acid.Proposed innovativly using the similarity of change trend between error function and viscosity variation to research viscosified law during porous media of this novel diverting acid in this paper, then taken the viscosified effect into consideration of diverting model, wormhole extended model and leak-off model of regular acid, researched diverting acid flow separately effect, simulated acid rate during acidizing treatment in multilayers carbonate reservoirs, development of acid etched wormhole and acid leakoff volume. These aspects have a certain degree guiding significance during diverting acid treatment in field.