低渗透油藏裂缝转向重复压裂技术研究

发布时间：2018-12-29 07:51

【摘要】：低渗透油田增产的主要措施是压裂。初次压裂后单井产量逐渐递减,必须依靠重复压裂来提高产量。目前W油田重复压裂井所占比例逐年增大,且存在增油效果逐年变差的趋势,严重影响低渗透油田的开发效益。为了经济有效地动用低渗透油气田储量,应尽可能地提高重复压裂增油效果。为此开展了重复压裂造新缝机理、裂缝延伸规律及现场施工工艺为主要内容的同井同层重复压裂技术研究。本文分析和研究了油井初次压裂后地应力的变化趋势,确定裂缝转向的极限应力差值为8MPa。建立了重复压裂前的渗流场和应力场数学模型,根据物模实验当井筒附近应力发生反转,反转后应力差超过3MPa时重复压裂不经封堵可直接压开新缝。研究了应用有限元技术建立了不同射孔方位、不同施工参数条件下裂缝转向数值模型技术,证明水平两向应力差值小于4MPa,与水平最大主应力成一定夹角定向射孔时,可产生初始方向沿射孔方向起裂并逐渐转向最大主应力方向的有效转向裂缝。根据机理研究结果,形成W油田重复压裂井选井选层、压裂时机优选方法。通过分析不易实现裂缝转向重复压裂井,得出采取增大施工规模或酸洗裂缝壁面、提高裂缝导流能力措施,可以提高重复压裂效果。矿场应用效果良好,试验井措施有效率89.0%,增油效果达初次压裂84.3%以上;对比以往重复压裂井,单井初期增油强度提高36%,高含水井压后含水下降39.7%,起到了良好的效果,对低渗透油藏重复压裂裂缝转向工艺技术提供了现实指导。
[Abstract]:Fracturing is the main measure to increase production in low permeability oil fields. The production of single well decreases gradually after initial fracturing and must be improved by repeated fracturing. At present, the proportion of repeated fracturing wells in W oilfield is increasing year by year, and there is a tendency of increasing oil production effect to become worse year by year, which seriously affects the development benefit of low permeability oil field. In order to produce the reserves of low permeability oil and gas fields economically and effectively, the effect of increasing oil production by repeated fracturing should be improved as much as possible. In this paper, the mechanism of new fracture formation, fracture extension rule and field operation technology of the same well and the same layer are studied. In this paper, the variation trend of in-situ stress after initial fracturing is analyzed and studied, and the limit stress difference of fracture turning is determined to be 8 MPA. The mathematical models of seepage field and stress field before repeated fracturing are established. According to the physical model experiment, when the stress in the vicinity of wellbore reverses and the stress difference after inversion exceeds 3MPa, the new fracture can be opened directly without plugging if the stress difference is more than 3MPa. The numerical model of crack steering under different perforation azimuth and different construction parameters is established by using finite element technique. It is proved that the horizontal two-direction stress difference is less than 4MPa and directional perforation is at a certain angle with the horizontal maximum principal stress. An effective steering crack can be produced in which the initial direction cracks along the perforation direction and the direction of the maximum principal stress is gradually shifted. According to the results of mechanism study, the formation of the reservoir selection of W oilfield repeated fracturing well and the optimal selection method of fracturing time. By analyzing that it is not easy to realize fracture turning to refracturing well, it is concluded that measures to increase the scale of operation or pickling fracture wall and to improve fracture conductivity can improve the effect of repeated fracturing. The effect of field application is good, the effective rate of test well is 89.0, and the effect of oil increase is over 84.3% for the first time fracturing. Compared with the previous repeated fracturing wells, the initial oil increasing intensity of single well is increased by 36%, and the water cut of high water cut well decreases by 39.7% after compression, which has a good effect, and provides practical guidance for the technology of refracturing fracture turning in low permeability reservoir.
【学位授予单位】：东北石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE357

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