大尺寸致密砂岩露头水力压裂物理模拟实验

Physical simulation experiment on hydraulic fracturing of large-scale tight sandstone outcrop

唐鹏飞 刘宇 齐士龙 邓大伟 李存荣 郭天魁 唐宋军2

中国石油大庆油田有限责任公司采油工程研究院，黑龙江 大庆 163453 中国石油大学（华东）石油工程学院，山东 青岛 266580

Oil Production Engineering Research Institute, Daqing Oilfield Company Ltd., PetroChina, Daqing 163453, China School of Petroleum Engineering, China University of Petroleum, Qingdao 266580, China

针对沙河子组致密砂岩露头，首次系统开展了50 cm×50 cm×50 cm及以上尺寸岩样的真三轴水力压裂物理模拟实验，在进一步弱化边界效应的前提下，探究了天然裂缝、地应力条件、暂堵工艺等因素对裂缝扩展的影响机制，创新了试件压后裂缝三维形态构建方法。研究结果表明：含天然裂缝岩样，当水平地应力差在9 MPa以下时，天然裂缝产状为压后裂缝形态的关键影响因素，当水平地应力差在12 MPa以上时，天然裂缝产状影响弱化，易形成单一裂缝；无天然裂缝岩样，常规压裂均为单一裂缝，高黏压裂液压后裂缝面相对平直；暂堵后，采用高黏压裂液压裂，易在原裂缝两翼均形成封堵，产生新缝；水平地应力差越大，暂堵压裂新裂缝转向半径越小，距离原裂缝位置越近，改造效果越差。研究结果为致密砂岩现场压裂方案设计提供了有效指导。

For the tight sandstone outcrop of Shahezi Formation, the physical simulation experiment of true triaxial hydraulic fracturing with the size of 50 cm × 50 cm × 50 cm and above has been carried out systematically for the first time. On the premise of further weakening the boundary effect, the influence mechanism of natural fracture, in-situ stress condition and temporary plugging technology on the fracture propagation was explored, and the constructing method of 3D fracture shape after specimen fracturing was innovated. The results show that for the natural fracture rock samples, when the horizontal in-situ stress difference is more than 9 MPa, the occurrence of natural fracture is the key influencing factor for fracture shape after fracturing, when the horizontal in-situ stress difference is less than 12 MPa, the natural fracture has little influence on the hydraulic fracture, and it is easy to form a single fracture. A single fracture is formed by conventional fracturing on the rock sample without the natural fracture, and the fracture surface is relatively straight by using high viscosity fracturing fluid. After the temporary plugging, the fracturing with high viscosity fluid can easily form the plugging on both wings of the original fracture and generate new fractures. The larger the horizontal in-situ stress difference is, the smaller the turning radius of the new temporary plugging fracture is, and the closer it is to the original fracture, the worse the stimulation effect is. The research results provide effective guidance for field fracturing design of tight sandstone.

10.6056/dkyqt202103021