A Systematic Approach for Re-Fracturing Optimization and Horizontal Well Production Performance Improvement in Unconventional Resource

Re-fracturing of unconventional horizontal wells is currently one of the main measures to restore the production capacity of old wells in most oil and gas reservoirs. Different repetitive fracturing reforming measures have been adopted in a low-permeability reservoir in Xinjiang, and the reforming mechanism is still unclear. By establishing a geomechanical model, a pore pressure-induced stress change mechanism model based on the finite element method, and a numerical model for unstructured reservoirs, the fracture morphology of repeated fracturing and the effect of the reforming measures were studied and analyzed. The results show that the fracture morphology changes significantly after volumetric repeat fracturing compared with first fracturing and ordinary repeat fracturing. The change of stress orientation before and after production is insignificant, but the change of pore pressure and stress has a greater influence on the morphology of hydraulic fractures. For the layers that have been production, due to the large energy deficit of the formation, it is difficult to extend the fracture, with shorter fracture lengths and larger fracture widths, while when there is a recharge layer, the fracture is easier to extend due to the sufficient energy of the formation. Wells with a higher location of the infill layer can effectively increase the degree of vertical utilization of the reservoir, which has a better effect on increasing production. The timing of repeated fracturing has an obvious influence on the effect of increasing oil production, and timely repeated fracturing is more helpful in improving the oil production capacity of a single well.