Field test of volume fracturing for horizontal wells in Sulige tight sandstone gas reservoirs, NW China

Based on the development degree of natural micro-fractures, rock brittleness and two-direction stress and other geological conditions of the Sulige gas field, the feasibility of using volume fracturing to increase production was analyzed and verified by field test. The Sulige gas field, a typical tight sandstone gas reservoir, has developed natural micro-fractures, with fracture complex index of 0.3−0.5, rock brittleness index distribution in the 36−52 and two-direction stress heterogeneity factor of 0.17. From the development experiences of unconventional gas reservoirs abroad, the geological conditions in the Sulige gas field is suitable for volume fracturing. Through lab experiments and pilot field tests, a volume fracturing technology for horizontal wells has been developed, which features “fracturing with low-viscosity liquid, carrying proppant with high-viscosity liquid, combination of multi-scale proppants, and massive fracturing at a high injection rate”. The technique had been applied in 42 wells of the Sulige tight gas field by the end of 2013. The initial production of wells treated by this approach is 1.2 times that of the adjacent wells treated by conventional fracturing, indicating that the technique can enhance the production of the horizontal wells in the Sulige gas field substantially.