| Acid fracturing is an important stimulation treatment of carbonate reservoir, it has been used widely at home and broad. The secret of acidizing is that the etching surface which acid reacting with rock has left has great conductivity that makes fluids flow into well more easily.Evaluation of acid fracturing treatment is mainly up to the acid eched fracture conductivity and effective distance of acid-rock reaction. Alternating Phase Fracture Acidizing was presented by Coulter et al in 1976—the fracture is created by a pad fluid injection at first, and then acid and additional pad fluid are injected alternately. Spot-practice make us known: Alternating Phase Fracture Acidizing is an effective stimulation. Characteristics of decreasing fluid loss and uneven etching pattern are superior to the pad acid fracturing.With the theory of acid fracturing and digital simulation, and considering actual situation of Alternating Phase Fracture Acidizing, we finished work as following:(1) Wellbore temperature model and fracture temperature model is calculated; Pwseudo 3D fracture Propagation model is calculated; effective distance of live acid model is calculated.(2) Considering the difference of fracturing fluid leakoff and acid leakoff and acid leakoff delayed time, calculation procedure of leakoff velocity and fluid loss are presented in Alternating phase acid fracturing.(3) Wormhole average length and acid leakoff delayed time for interface movement model are presented.(4) Interface movement physical model and interface movement mathematical model are presented, considering acid leakoff delayed time.(5) Using these models, we develop alternating phase fracture acidizing software which fully considering the effects of formation temperature, acid/rock reaction heat, homo-ionic effect, acid fingering effect, wormhole effect and acid leakoff delayed and so on.(6) With field document of Puguang 9 well in northeast of sichuang, we calculated in the way of different injected series and different interval liquid flow and have found better construction scheme. It is close to the results of FRACPROPT 10.1 software. Field practice indicated that stimulation effect is prominence with the construction scheme. |
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