Water Shutoff and Conformance Improvement for Lamadian Oilfield in Daqing Using a Novel Polymer System: Experimental Study, Simulation, and Pilot Tests

Abstract

Abstract Primary recovery and extensive waterflooding lead to preferential pathway for the water between injectors and producers, resulting in low sweep efficiency and lower oil recovery. The Lamadian Oilfield in Daqing has been waterflooded for 50 years, where various methods have been tried to reduce the high water-cut. This paper presents a novel water conformance control system that has been successfully applied to reduce water-cut and increase the oil production from Lamadian Oilfield. The polymer system containing swelling particles and delayed polymer gelling agents to form plugs and block high permeability channels was tested in the laboratory through sandpack and coreflood experiments at reservoir temperature using injection brine from the Lamadian Oilfield. With injection concentration of polymer ranging between 1200-4500 ppm and crosslinker between 1200-1600 ppm, the experimental tests showed formation of strong plugs in-situ with delayed time of 4-18 days. This system also had low polymer/crosslinker's retention. The lab-measured parameters for rock-fluid interaction were used as input in a history-matched numerical reservoir simulator. Several scenarios with different injection schemes were simulated to investigate the volume of plugs formed, maximum distance travelled by the gelling agents from the injectors before forming plug, and their impact on the surrounding production wells. Simulation results showed that the formation of the plug was the most robust at the front of the crosslinker-polymer system, and the region between the injectors and the front showed formation of secondary plugs by the particles. An optimal scenario was selected for pilot tests. Field tests for 2 well groups with a total of 16 wells started in December 2021 that were successfully completed by April 2022. Field test results show the targeted high-perm channels were blocked, resulting in a significant increase in oil production (up to 15%) in the majority (71%) of the surrounding producers and a drop in water-cut (1-3%). The oil production rates of the surrounding producers maintained a stable increasing trend, indicating the long-lasting effect of the plugs on the displacement of the remaining oil. This work presents a novel polymer conformance control system with low injection viscosity, long and tunable gelation time, good plugging strength, and long-term stability under reservoir conditions to effectively shutoff high permeability channels/zones for robust in-depth conformance control.