Study On High - Tech Technology And Model Of Acid Pressure Control Joint

Acid fracturing was a critical technology for putting the well into production, stimulation and stabilizing production in carbonate reservoirs. The effect of acid fracturing directly determined single well controlled reserves, oil field recovery and development benefit. It was a tough problem that how to prolong stimulation validity, increase acid penetration distance and acid etched fracture conductivity in an economic and effective way.Tahe oil field Ordovician Yijianfang formation was a fractured vuggy carbonate reservoir which mainly composed by mud micritic and grain limestones. Due to the influence of macro-thickness, reductive differential stress and high-angle natural fracture, the height of acid fracturing fracture couldn’t be effectively controlled in this formation, and the acid penetration distance fail to achieve the desired goals. It had tried to using conventional fracture height control technology in Yijianfang formation, but the effect was not significant. Therefore, it was an urgent problem that development a novel fracture height control technology and simulation applicating effects based on the geologic characteristic of Tahe oil field.In this paper, based on review plenty of domestic and foreign literatures, summarized conventional fracture height control technology, and approved the unique advantages of artificial barrier technology; proposed a novel fracture height control technology that using gel as artificial barrier, designed the physicochemical property of gel material, optimized a suitable gel system by performance evaluation experiment; developed a simple acid fracturing construction procedure when using gel artificial barrier fracture height control technology.In order to predict the optimum time of separant injection material, established a semi-analytic model of wellbore temperature field. The model consided the coupling process of fluid thermal properties change, tube heat balance and formation non-steady-state transfer heat, based on Laplace transform and Stehfest numerical inversion method, identified the distribution and change of physical space wellbore temperature field in acid fracturing construction. The simulating results were accurate though verification calculation, and this method had certain guiding significance for acid fracturing construction.To analyze the control factor of fracture height extension and evaluat the control effect of fracture height control technology, established a pseudo-three dimensional fracture extension model. Based on the preliminary model research, considered early leakoff and non-symmetrical fluid friction, regarded the COD guidelines as judging criteria of fracture height extension; simulating analyzed the influential factors of fracture extension, including crustal stress, Young’s modulus, fracture toughness, construction rate, leakoff coefficent. Analysis the effect of gel artificial barrier technology and conventional artificial barrier technology based on preliminary studies.The results show that gel artificial barrier fracture height control technology could form high fracture differential pressure, wouldn’t be contolled by formation conditions, bring small formation damage, and had preferred fracture height control effect. In a summary, the gel artificial barrier fracture height control technology is worthy to further apply in oil field.