Multistage Alternating Injection Closed Acid Fracturing Design Simulation And Application

Multistage alternate phase Acid Fracturing is a technique that the pad fluid and acid are injected alternately into the fracture, which is similar with pad acid fracturing. However, it’s more effective to decrease acid loss and form non-uniform etching fracturing face than pad acid fracturing. Multistage alternate phase acid fracturing has been widely used in carbonate reservoirs as an important stimulation treatment.To satisfy the requirement of optimizing designs. I have completed a computer programs to simulate the Multistage alternate phase acid fracturing procedure. The detailed work as follows:(1) Wellbore temperature field is calculated by using the Eickmerier model; fracture geometry parameter is calculated by using the I.D.Palmer model; The temperature field in hydraulic fractures is stimulated through by the model of fracture temperature field; Acid solution concentration distribution is calculated by the Acid concentration distribution model.(2) Considering the difference of fracturing fluid leak-off and acid leak-off,(we established a)calculation procedure of the fracture fluid leak-off velocity and fluid loss and the acidizing fluid leak-off velocity and fluid loss as the acid wormhole existing in Multistage Acid Fracturing.(3) Modeling and calculating the Acid concentration along the length of fracture, and then we obtaining the acid effective distance. A wormhole mean length and acid leak-off delayed time calculation method is used, as well as the calculation of the filtration.(4) Using these models and Visual Basic language, we develop a Multistage alternate phase-Closed Acid Fracturing program which can calculate such as the temperature, the geometry of fractures, the effective penetration distance, the acid etched fracture conductivity, the stimulation ratio.(5) With field document of T709well in Tahe oilfield, Calculation is made by the established model. Fully considering the effects of formation temperature, acid/rock reaction heat, homo-ionic effect and so on, we can get that the calculation results indicate that the predictions of this program simulation well with the field practice.