Since 2025, Changqing Oilfield’s newly developed pre-blocking water control fracturing technology for high water-cut wells has been expanded to 33 wells under the “stabilization ballast” project in mature fields. Daily oil output per well increased from 12 tons to 46 tons, while the average water cut dropped from 84.8% to 70.3%. This marks enhanced adaptability of the technology, providing a crucial tool for tapping remaining oil and improving ultimate recovery in mid-to-high water-cut reservoirs.

A New Tool for Flow Field Reconfiguration in High Water-Cut Reservoirs

As key fields such as Jing’an and Jiyuan in northern Shaanxi enter mid-to-high water-cut stages, contradictions in waterflooding have intensified due to strong reservoir heterogeneity, complex multi-stage fractures, and reduced adaptability of development policies. Conventional measures offer limited well selection, and demand for water control fracturing has become urgent. However, conventional in-layer water control fracturing remains a global technical challenge, plagued by difficulties in determining blocking positions under stress changes, poor coupling of conventional blocking agents with old fractures, and uncertainties in collaborative flow field reconstruction in low-permeability reservoirs.

Since 2023, Changqing Oilfield’s mature field recompletion technology team has pursued original breakthroughs under CNPC’s “Ballast Technology Demonstration & Promotion” program. Guided by a “five-layered” technical concept, the team focused on improving waterflooding effectiveness, enhancing reservoir utilization, and reconfiguring fracture-induced flow fields. They precisely mapped stress field changes after long-term injection and production, defined a “high-strength fracture plugging + forced diversion + secondary fracture layout” model, and revealed the mechanism of “pre-blocking to divert water lines, enlarge sweep volume, and activate lateral residual oil.”

The team developed the QFK composite plugging agent, featuring low viscosity, low shrinkage, high adhesion, and high compressive strength, capable of significantly enhancing fracture plugging and enabling lateral fracture initiation. They created a new process model integrating “large-volume plugging + high-strength stage pre-blocking + multi-stage temporary diversion fracturing” to reconfigure the flow field, markedly reducing water cut and increasing oil output. This filled a domestic gap in residual oil tapping technology for high water-cut wells.

Currently, the technology has expanded from demonstration zones in Jiyuan and Jing’an to broader northern Shaanxi. To date, 62 wells have applied it, reducing water cut from 80.0% to 70.7%, raising per-well output from 0.4 tons to 1.3 tons, and adding 14,000 tons of incremental oil. The team has filed 8 patent applications (2 authorized) and is developing 1 technical standard. Moving forward, they will focus on high water-cut well groups, establish selection criteria, upgrade plugging materials, accelerate process standardization, and position the technology as a core recompletion solution (2.0) for mature fields under new conditions.