Research and Application of Water Control Fracturing Technology by Re-adjusting Seepage Field with Blockage-Pressure Synergy in Tight Oil Reservoirs

Abstract

To address challenges in the Jiyuan Oilfield’s tight oil reservoirs during high water-cut development, specifically a sharp increase in water cut after conventional fracturing and poor oil enhancement from standard measures, a pre-pad fluid water control fracturing technology was proposed. This involves pumping a large-displacement pre-pad of water control material to block water breakthrough channels, forming a “hard baffle” at the fracture tip, forcing the main fracture to redirect during primary fracturing to access lateral remaining oil. Laboratory experiments selected the key QFK series materials: QFK-1 water control gel achieved a viscosity of 1200 mPa·s at 85°C;QFK-2 resin cement showed a viscosity of 55 mPa·s at 25°C, with 9.2% shrinkage and a breakthrough pressure of 15.2 MPa. Based on Cohesive finite element simulation, a finite element model for water control fracturing was built to optimize process parameters. A construction displacement rate of 2.8∼4.0 m3/min achieved a fracture net pressure exceeding 3.4 MPa. With a blockage position ≥25m, the fracture deflection radius was 20∼30m, enabling the fracture to extend from low-stress to high-stress zones, effectively mobilizing lateral remaining oil. Numerical simulations revealed the multiphase interaction laws governing stress field, pressure distribution, and fluid flow under combined blockage-pressure effects, characterized the evolution patterns of diverse water channels, and informed parameter optimization for synergistic blockage-pressure treatments. Differentiated technical systems were established for various high water-cut well types. Field implementation in eight wells resulted in an average incremental oil production of 1.2 tons per well per day and a 21.2% decrease in water cut. The effectiveness is primarily influenced by dynamic and static parameters such as reservoir physical properties, oil saturation, number of previous treatments, and proppant intensity. By significantly enhancing sealing strength and meeting the conditions for new fracture initiation in medium-high water-cut wells in the Jiyuan area, this fracturing measure ultimately achieves effective vertical reservoir stimulation for water control and oil enhancement, providing a new technical pathway for re-stimulation of such wells in tight oil reservoirs.