Preliminary Study on a Strong Sand-Carrying and Low Damage Viscoelastic Slickwater Under a Wide Shear Range

ABSTRACT Slickwater or linear gel is often used for fracturing development in tight sandstone reservoirs. As it carries sand into the formation through the wellbore, its sand-carrying performance changes with the continuous change of liquid shear rates. In this paper, a new type of viscoelastic slickwater is proposed, which avoids the problems of low sand-carrying capacity of conventional slickwater and large damage of guar. Through theoretical calculation, taking the injection rate of 10 m3/min as an example, the maximum shear rate of fracturing fluid in wellbore and fracture is 884.82 s−1 and 8.33 s−1 respectively. Viscoelastic slickwater polymer is physically cross-linked and reversible associated to form a network structure. It has excellent shear resistance at different shear rates (0.01∼1000 s−1). The intersection point of viscoelastic modulus is lower than 0.021 Hz, and the viscoelastic performance is excellent. Under the low shear rates of fracture (0.01∼10 s−1), the performance of viscoelastic slickwater suspended sand is excellent, and the equilibrium height of sand bank is lower than 26.7% of fracture height. Under the high shear rates (10∼1000 s−1) in the wellbore, its viscosity is high, and the friction reduction rate can reach 81.59%. In addition, it breaks quickly, the amount of residue is low, and the conductivity can be retained by more than 90%. Under field application, the sand concentration of the system is as high as 300 kg/m3, and the production of vertical well after fracturing can reach 0.96 tons/day in more than one year. Viscoelastic slickwater can realize friction reduction and sand carrying at the same time, which has the value of popularization and application. INTRODUCTION The tight sandstone reservoir has features of tight lithology, low porosity, and low permeability, and others, mainly secondary porosity, and high feldspar and cuttings content. Due to low reservoir pressure coefficient, its natural productivity is low (Wang et al., 2022; Zhong et al., 2022). Compared with conventional reservoirs, tight sandstone reservoirs have staggered pore distribution and poor connectivity, high water saturation, strong stress sensitivity, and limited recovery by conventional oil displacement methods (Xie et al., 2022; Dong, et al.,2019). Therefore, new unconventional reservoir stimulation technologies and measures are urgently needed.