Re-fracturing Considerations of Horizontal Well Multi Stage Fractured Completions in Mid Permeability Formations

The oil and gas industry in Russia started facing a complex problem of productivity decline from horizontal multi stage fracture completed wells drilled in the low to mid permeability reservoirs. To enhance hydrocarbon flow from these formations, aggressive production using artificial lift is supported with active water flooding. Nevertheless, operators have acknowledged that the horizontal well multi stage fracture (HW MSF) completions do not live to their expectations.The application of HW MSF completions started in 2008, but widespread acceptance followed several years later. Today, in Russia, about 300 horizontal wells are drilled and completed annually bringing the total number of HW MSF to more than 1200 wells. All these wells are potential candidates for re-fracturing treatments and re-completion, but while re-fracturing of vertical wells is a well proven success in Russia, the industry today has no clear understanding how to address the multitude of potential productivity difficulties in HW MSF.During the work published in this paper, the team has analyzed all the known potential engineering problems and technical risks and clearly defined the domains of further investigation and set recommendations on measurements that are needed to understand the impact of re-fracturing. The analysis was based on field measurements made, analytical calculation and numerical simulations, modeling in all details the key processes defining the productivity of HW MSF completions. The results indicate that pressure influenced stress changes in a mostly isotropic system and resulting fracture placement within the horizontal wellbore are key contributors to the complexity of the problem.The paper presented here is a genuine attempt for the industry streamline further search for solutions and novel methodology to effectively re-fracture the existing completion systems and bring these wells to profitable production.