As proved from both experimental tests and field applications, diversion agents can effectively plug the previously artificial fractures or natural fractures to create reorientation fractures, which can improve diversion efficiency and stimulated reservoir volume (SRV). However, the temporary plugging mechanism and its influencing factors were still unclear.
In light of this, a fracture temporary plugging evaluation system was proposed by this study, which holds large fracture scale, and high pressure-bearing capability. Hence, this setup can meet the requirements of plugging tests. Moreover, in order to enhance the experimental accuracy, the 3D printing technique was introduced, which can reproduce the real surface morphology of acid-etched fracture. Based on the newly designed setup, some experiments were performed to study the plugging rules of fibers and the combination of fibers and particulates. Furthermore, the inner plugging mechanisms of the different cases were also analyzed.
Experimental results show that the pure fibers and the combination of fibers and particulates both can achieve favorable plugging effect. In addition, the plugging processes of pure fibers can be summaried as follows: 1) The carrier fluid with fibers flow into the fracture model and a small amount of fibers remain in the fracture. 2) Fibers begin to adhere to the fracture surface with a small fracture width. 3) The previously attached fibers capture the subsequently injected fibers to bridge plugging. 4) The bridging plugging extend to the entrance and eventually form a tight plugging zone. Furthermore, when the diameter of particulates is less than the half of fracture width, the plugging mechanism is similar as that of pure fibers. When the diameter of particulates is larger than the half of fracture width, the plugging mechanism is completely different from that of pure fibers. The big particulates will firstly be bridging and plugging at the location with a small fracture width.
This study reveals the temporary plugging mechanism of diversion agents within acid-etched fracture, which provides an insight of optimizing temporary plugging fracturing design.