Analysis of Stimulation Effect and Optimization of Stimulation Mode for Ultra-deep Tight Gas Reservoir

Abstract

The Kuqa foreland area tight sandstone reservoir is characterized by ultra-depth, high temperature and high pressure, high earth stress, low porosity and low permeability, developed natural fracture and strong heterogeneity. The effects of fracture acidizing stimulation operation in some wells are not ideal. After fracture acidizing, sand fracturing stimulation is implemented, and the effects are satisfactory. Combined with the reservoir geological characteristics, the specific circumstances of fracture acidizing and sand fracturing stimulation operations as well as analysis on after-fracturing evaluation, the reasons for making the large difference in the effects of fracture acidizing and sand fracturing stimulation is compared and analyzed. According to the analysis results of the difference in the stimulation effects, a targeted stimulation strategy is proposed for different reservoir types, that is, for reservoirs with nature fractures developed and good effectiveness, where the near-well fractures are easy to be activated, taking into account the cost of stimulation, acid fracturing aiming to activate and connect natural fractures is adopted to increase production; for reservoirs with nature fractures relatively developed, the effectiveness is moderate and the activation difficulty is large, in order to activate natural fractures to increase production as many as possible, the fracture-network fracturing is adopted; for reservoirs with nature fractures poorly developed and the effectiveness is poor, the fractures cannot be massively activated, the large-scale sand fracturing aiming to make long fractures and connecting nature fractures of far wellbore area is adopted, or the high angle deviated well or horizontal well can be explored to increase production. These reservoir stimulation schemes improved by this method has achieved ideal effects in the actual operation in Kuqa foreland area. The output after the stimulation is significantly improved compared with the adjacent wells, which provides reference and guidance for the subsequent stimulation mode for tight sandstone reservoirs in Kuqa foreland area.