Performance of multifunctional viscous slickwater for enhanced oil recovery in tight oil reservoirs

Economically recovering oil from tight/shale reservoirs requires extensively developed propped fracture networks and rock matrices with sufficient oil mobility, which imposes higher demands on the fracturing fluid. This study develops a DME-aided viscous slickwater (MEVS) that addresses these dual challenges. During hydraulic fracturing, DME reinforces viscoelasticity through hydrophobic association, significantly improving proppant-carrying capacity without substantially increasing viscosity, thereby enabling the creation of extensive propped fractures. After hydraulic fracturing, DME minimizes surfactant adsorption and deepens wettability alteration, thereby enlarging the water-wet zone of rock matrix to enhance oil recovery via imbibition and increased oil relative permeability. Laboratory evaluations using a visualized rough fracture model reveal that the fluid elasticity can be quantified using the Weissenberg number, and then used to predict the proppant transport performance at a specific flow condition during hydraulic fracturing. In-situ NMR and pressure transmission tests confirm that DME can mobilize oil in different-sized pores from the tight rock and significantly enhance oil recovery through water imbibition, meanwhile accelerating the pressure propagation by two orders of magnitude and enlarging the surfactant-modified zone. Field applications demonstrate that MEVS can successfully carry 400 kg/m 3 proppants at 10 m 3 /min without plugging issues, and triple oil production comparing to wells using the conventional slickwater. This work establishes an integrated fracturing-EOR approach and provides a laboratory-based method to optimize the pumping schedule in field operations.