Study of Slick Water and Its Application in Spatial Fracturing Fractured Carbonate Formations

Slickwater is a fracturing fluid widely used in fracturing unconventional petroleum reservoirs such as shale gas reservoirs and tight oil reservoirs. Slick water has low viscosity and high penetration performance which are helpful in enhancing the complexity of natural fractures. Generally speaking, deep fractured carbonate reservoirs have matrix rocks of poor physical properties and strong inhomogeneity, and fractures are the main spaces and channels for the petroleum to stay and flow through. Therefore, increasing the volume of rocks being fractured is the key to produce more petroleum, and this goal can be achieved by performing spatial fracturing with fracturing fluid composed of low viscosity slick water, gel and converting acid. Low viscosity and high injection flow rate help activate more natural fractures in rocks. In this paper the evaluation of a new slick water containing polymers is discussed. Laboratory study and numerical simulation were combined to ascertain the working mechanisms of slick water in spatial fracturing. It was found that:1) the new polymer slick water has good drag reducing property, and is able to reduce the fraction and drag acting on the pipe string, thereby realizing high flow arte injection and improving stimulation efficiency. 2)Complex fractures are generated with injection of slick water at high flow rates, and the connectivity of the fractures is enhanced by forming acid-etched wormholes by the injection of low-viscosity acids. Alternated injection of slick water (hydraulic fracturing) and low-viscosity acid (acid etching) gives birth to networked fine fractures. By applying these studying results in field operations, the well AT3x has acquired daily oil production rate of 35 m³ and daily gas production rate of 50.3×10⁴ m³, providing a new technical reference for stimulating complex deep high temperature reservoirs in China.