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

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.

Evaluating Factors Impacting Polymer Flooding in Hydrocarbon Reservoirs: Laboratory and Field-Scale Applications

“…A common method to compare the two mobility values is the use of the mobility ratio. This is defined as the ratio between the mobility of the displacing phase and that of the displaced phase [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. In all secondary and tertiary recovery applications, the displaced phase is the oil, whereas the displacing phase is the injected fluid that is being used to displace the oil.…”

“…First, it has a low viscosity value, which is comparable to or sometimes even less than that of oil. This can result in the water having a lower resistance to flow compared to oil, which, in turn, creates channels through the oil zone—a phenomenon referred to as viscous fingering [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ]. Secondly, depending on the water saturation and the wettability, the water can have a higher permeability than the oil.…”

“…Many studies have investigated the use of polymers for different applications in laboratory-based experiments. These experiments investigated either the ability of a specific or a newly synthesized polymer to improve oil recovery or the impact of a specific parameter on polymer performance and degradation [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ]. The majority of polymer flooding experiments conducted on polymer flooding EOR can be classified as core flooding experiments, polymer flooding in fractures, polymer application in microfluidics, or reservoir simulation of polymer flooding.…”

“…This can be achieved by creating a new phase with unique properties, the most important of which is viscosity. It is important to note that many reservoir simulators do not take into consideration polymer degradation based on the change in conditions, assuming an ideal polymer [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ].…”

“…Anand [ 37 ] evaluated the use of water-alternating polymer to enhance polymer pattern performance and optimize polymer utilization through reservoir simulation. Lu [ 38 ] used lab-measured parameters of a synthesized polymer to run a simulation in order to optimize polymer flooding in the Daqing field. Simulation results were used as a precursor to an actual field testing.…”