Low-Salinity Polymer Flooding in a High-Temperature Low-Permeability Carbonate Reservoir in West Kuwait

Abstract

While polymer flooding has widely been used as a successful technology to improve mobility control and sweep efficiency in many oil reservoirs, its applicability under harsh temperature/salinity conditions and in low-permeability reservoirs has prohibitively remained a challenge. This study was aimed at investigating the feasibility of low-salinity polymer flooding in a very challenging reservoir located in Kuwait with low permeability (< 10 mD), high temperature (113°C), high salinity (~239,000 ppm), high hardness (~20,000 ppm), and carbonate mineralogy. The evaluation was conducted through a series of systematic laboratory studies including polymer rheology, thermal stability, and transportability using coreflood tests. Our results highlight that the common constraints may be overcome by careful selection of polymer/cosolvent/pre-shearing and appropriate design of low-salinity polymer flooding.

Capillary Desaturation Tendency of Hybrid Engineered Water-Based Chemical Enhanced Oil Recovery Methods

“…The limitations of standalone PF can be overcome by combining it with EW or LSW, and this has been given the term 'hybrid engineered water polymer flooding' (EWPF). The effectiveness of EWPF in carbonates has been proven by various experimental [61][62][63][64][65] and numerical modeling [66][67][68][69] studies. EWPF provided incremental recovery of 10% OOIP from carbonate cores in experiments by Al Sofi et al [70].…”

“…EW aids in altering the carbonate rock wettability by desorption of acidic crude oil components [71,72], and PF helps in providing stable oil bank displacement by creating a favorable mobility ratio [73]. The adsorption and chemical degradation of HPAM polymer is also reduced in the presence of EW, and therefore, less polymer is required to achieve a desired viscosity [62]. A 30-50% reduction in polymer concentration can be achieved by combining EWF and PF, due to a higher solution viscosity and lower polymer adsorption under low-salinity settings [62,65,74].…”

“…The adsorption and chemical degradation of HPAM polymer is also reduced in the presence of EW, and therefore, less polymer is required to achieve a desired viscosity [62]. A 30-50% reduction in polymer concentration can be achieved by combining EWF and PF, due to a higher solution viscosity and lower polymer adsorption under low-salinity settings [62,65,74].…”

Updated Perceptions on Polymer-Based Enhanced Oil Recovery toward High-Temperature High-Salinity Tolerance for Successful Field Applications in Carbonate Reservoirs

“…Furthermore, Al Murayri et al [ 184 ] indicated that the most common deterrents under the HTHS conditions are low-permeability carbonates, which may be addressed by carefully selecting the polymer/ solvent/ co-solvent, pre-shearing, and suitable design of low salinity polymer-based cEOR [ 184 ]. They demonstrated that injecting polymer at 113 C in a reservoir with less than 10 mD permeability was possible in their investigation, which was a long-term stability test [ 184 ]. Based on the composition of the injected brine, rheological tests revealed that when the polymer solution had a viscosity of 2–3 cP, a stable flood could be achieved with 2500–4000 ppm polymer.…”

“…Based on the composition of the injected brine, rheological tests revealed that when the polymer solution had a viscosity of 2–3 cP, a stable flood could be achieved with 2500–4000 ppm polymer. As a result, combining thorough laboratory tests and design with low-salinity water floods proved to be extremely beneficial [ 184 ].…”