Research on Calculation Methods for Parameters of Injection Layers in Downhole Oil-Water Separation Injection-Production Wells

The downhole oil-water separation and injection-production technology enables direct separation of produced fluids within the wellbore, where separated water is directly reinjected into the injection layer while low-water-cut production fluid is lifted to the surface. This technology enables simultaneous production and injection within the same wellbore, achieving the dual utilization of a single well. As the system incorporates both injection and production layers downhole, conventional wellhead measurements of liquid/oil production rates and water content fail to accurately characterize zonal performance. Leveraging the distinct mechanical behavior and dynamometer card signatures of hydraulic feedback pumps, a methodology has been developed to isolate injection-layer parameters by eliminating interference from production pump loads, rod inertia, and vibration effects. Key parameters including reinjection pressure, flow rate, and apparent water injectivity index are derived from surface dynamometer load data and pump operational parameters. The calculated downhole production-injection data enable real-time monitoring of injection-layer absorption capacity evolution, tubular string integrity, and pilot-area injection-production ratios, facilitating timely anomaly detection and dynamic parameter optimization to maintain optimal operational efficiency. Field implementation across 90+ wells has demonstrated effective production adjustments guided by this methodology, yielding significant improvements in both reservoir development outcomes and economic returns.