Energy Reports (Nov 2022)
Physical simulation experiment method of water breakthrough mechanism and plugging effect of horizontal well in tight reservoir
Abstract
Horizontal wells have become a key technology for the economical and effective development of tight reservoirs. In production, water cut increases rapidly, and even waterflooding is prominent. The mechanism of water breakthrough and the analysis of the water plugging effect are still tricky problems worldwide. Based on the reservoir characteristics of the typical tight oil area in Changqing oilfield, a physical simulation method of water breakthrough and plugging effect of segmented fractured horizontal wells was established based on the parallel connection of double cores and large-scale physical simulation system, and the mechanism of water breakthrough and water plugging effect of horizontal wells were studied. The results show that natural fractures or dynamic fractures are the main factors affecting the characteristics of water breakthrough. The end and waist of staged fractured horizontal wells are the main parts of water breakthrough. Water breakthrough points gradually increase in production, showing multi-direction. The overall water cut decreases after the water-prone area is plugged. Specifically, in this study, water plugging was implemented when the water cut of the horizontal well rose to 91%, and the water cut of a breakthrough part was reduced to about 60% after plugging, which played a good role in controlling the overall water cut. Oil displacement efficiency increased from 32.5% before plugging to 36% after plugging, rising by 4.5 percent. In addition, the duration of oil production increase in horizontal well after water plugging is not long, mainly because of the formation of water injection dominant channel between the injection well and horizontal well fracture before plugging. At this time, the resistance primarily exists in the water-affected area, and the Jamin effect caused by imbibition is the main factor of resistance; then, the swept volume is difficult to expand.
