Acidic Acid Flow Simulation And Fingering Characteristics Analysis

For low-permeability reservoirs,especially dense carbonate reservoirs,acid pressure reforming is often used to increase single well production,and the effect of acid pressure depends on the acid-induced fracture conductivity and the distance of acid etching,both of which are associated with cracks.The flow characteristics of the acid are related.Therefore,the numerical simulation method is used to study the flow law of acid liquid in acid fracturing cracks.With the help of the powerful fluid dynamics software,the flow of acid liquid is simulated and analyzed.Through investigation,it has been found that the predecessors have few studies on the flow of acid in acid fracturing cracks,and the research method is mainly based on a flat plate model for experimental research.This model has some differences with the actual acid fracturing cracks.Most of the researches on fingering and fingering are directed at the flow of fluid in porous media,but there is less research on fingering in acid fracturing.The mathematical model of acid flow in acid fracturing is established,and the continuity equation,momentum equation and energy equation of acid flow are obtained.Through the mechanical mechanism analysis of acid fingering in acid fracturing,the acid liquid is deduced In the flow rate equation,the rate formula can be found to affect the flow of acid factors: the geometry of the fracture,fluid viscosity,fluid density,and random factors in the experiment.The mechanism of finger pointing triggering is summarized: fluid properties,interfacial tension,wall wettability,and random factors.The fracture horizontal roughness model was established based on the actual geometry of the crack wall.A section near the entrance to the fracture was selected for simulation.The leading edge distance,leading edge velocity,displacement efficiency and the maximum flow rate of the acid are the characterization parameters of the acid flow.The effects of roughness,viscosity ratio and injection displacement on the flow of the acid were studied.The study found that there are differences in the flow characteristics of the smooth wall surface and the rough surface,and the effect of the roughness on the flow of the acid is not a monotonous linear relationship;the effect of the viscosity ratio on the flow of the acid is the boundary line of 50 and is divided into a rapid rise phase.In the gentle rise phase,the filtration will shorten the length of acid-etched cracks and will reduce the effect of acid etching.Through comprehensive tests,it is found that the injection displacement is the main factor affecting the flow of acid,followed by the roughness and viscosity ratio.Based on the characteristics of perforation acid pressure,a vertical perforation model of cracks was established.The leading edge distance,leading edge velocity,displacement efficiency,and D/H are the characterization parameters of acid flow.Gravity,viscosity ratio,density difference,number of perforation clusters,perforation cluster spacing,and injection displacement are studied separately for acid flow.The study found that high displacement can make the acid flow deeper into the cracks and increase the acid etching distance;the presence of gravity makes the acid flow along the bottom of the fracture and will reduce the number of branches of the acid front and change from the original multi-finger flow.The viscosity ratio is 50 points,showing two different changes before and after;the greater the density difference,the more obvious the flow characteristics of the acid along the bottom of the crack;the single cluster has the largest flow distance and the perforation cluster The influence of the finger process on the acidity was small;the distance of the leading edge of the acid liquid increased with the distance between the clusters,and the distance between the clusters was 6 m.Displacement is the main factor affecting the flow of acid.The research shows that the injection displacement is maximized under the premise of considering the construction cost,so that the acid can be etched farther;the density difference between the acid liquid and the pre-liquid is properly adjusted,the density difference should not be too large,and the gravity is used to increase the acid.The flow distance of the liquid;the ratio of the viscosity of the front liquid to the acid liquid should be greater than 50 to increase the finger-in effect of the acid liquid.In this paper,the flow behavior of acid fluids in acid fracturing and the sticking characteristics of acid liquids are studied to help understand the flow law of acid fluids in acid fracturing and the low-permeability reservoirs,especially dense carbonate reservoirs.The acid-pressure modification of the layer provides good guidance.