长庆油田特低渗透油藏中高含水井调堵压裂技术

长庆油田特低渗透油藏进入中高含水期后受储层高渗带影响，常规重复压裂存在含水率上升、增产幅度低等问题。为解决该问题，根据典型油藏长期注采开发实际，采用油藏三维地质建模方法，结合加密井生产资料，研究了中高含水油井调堵压裂增产机理，分析了不同调堵压裂参数对油井重复改造效果的影响，提出了“前置调堵控含水、动态多级暂堵压裂提单产”的重复压裂技术思路。通过室内试验，研发了PEG-1凝胶，凝胶主剂质量分数为5%～10%时，可保持较高水平的凝胶强度；优化注入排量为1.5 m3/min，注入量为300～600 m3，可在裂缝深部40～80 m处封堵高渗条带；优化动态多级暂堵压裂技术，缝内净压力提高到5.0 MPa以上，实现了压裂裂缝由低应力区向高应力区扩展，以动用侧向剩余油。现场试验结果表明，实施调堵压裂后单井日产油量平均增加1.07 t，含水率降低9.0百分点，实现了中高含水井重复压裂“增油控水”的目的。该调堵压裂技术为长庆油田特低渗透油藏中高含水井重复改造提供了新的技术途径。 

Fracturing Technologies with Profile Control and Water Shutoff for Medium and High Water-Cut Wells in Ultra-Low Permeability Reservoirs of Changqing Oilfield

Due to the influence of the high-permeability zone, the water cut will increase and reservoir stimulation results are poor when conventional refracturing is implemented in the ultra-low permeability reservoirs of Changqing Oilfield at the medium and high water-cut development stage. Focusing on the long-term injection-production development practices of typical reservoirs and infill well production data, this paper uses 3D geological modeling to analyze the stimulation mechanism of fracturing with profile control and water shutoff in medium and high water-cut oil wells. The influences of fracturing parameters on the effect of?repeated stimulation were studied, and a refracturing concept hinging on “profile control and water shutoff in the pad adding stage to control water cut and dynamic multistage temporary plugging fracturing to improve single-well production” was advanced. PEG-1 gel was developed through laboratory experiments and when the mass fraction of its main agent achieved 5%-10%, gel strength would be maintained at a high level. With an optimal injection flow rate of 1.5 m3/min and an injection volume of 300-600 m3, the high-permeability zones at the fracture depth of 40-80 m could be effectively plugged. In this way, the dynamic multistage temporary plugging fracturing technology was optimized. As a result, the net pressure in the fractures was increased to above 5.0 MPa, fractures extended from the low-stress zone to the high-stress zone, and the production of the oil remaining laterally was thereby produced. Field test results showed that average daily oil production improvement per well was 1.07 t/d and water cut was reduced by 9 percentage points after the measure was implemented, which indicated that the goal of increasing oil production while controlling the water was accomplished by refracturing the medium and high water-cut wells. The proposed fracturing technology with profile control and water shutoff provides a new technical concept for the repeated stimulation of medium and high water-cut wells in ultra-low permeability reservoirs of Changqing Oilfield.