Offshore Polymer/LPS Injectivity Test with Focus on Operational Feasibility and Near Wellbore Response in a Heidrun Injector

Abstract

Increased oil recovery technologies are very important for the large Heidrun field located in the Norwegian Sea. Very harsh climate and stringent environmental regulations render enhanced oil recovery (EOR) projects challenging. One EOR method evaluated for the field is polymer/LPS (Linked Polymer Solution) with the objective to improve the reservoir sweep. An offshore polymer and LPS injectivity test was performed with the objectives to determine the logistical and operational feasibility of handling polymers and to observe the near wellbore response during polymer and LPS injection.Prior to the offshore test, laboratory work was performed to qualify a polymer and a LPS system. A yard test was conducted to test necessary instrumentation and mixing/pumping equipment in preparation for the offshore test. The operation was performed by mixing a 5000 ppm polyacrylamide mother solution onshore, which was then shipped and stored offshore in completion tanks on the platform. The polymer mother solution was then injected downstream the choke on the injection well at a final polymer concentration of 300 ppm and 600 ppm, respectively. The test was done with a stepwise rate increase to switch from matrix to fracture injection. Aluminum citrate (AlCit) cross-linker was added at 300:10 and 600:20 polymer-tocross-linker ratio.A comprehensive sampling and analysis program was performed both onshore and offshore to secure high-quality polymer solution throughout the logistical chain. High-pressure sampling equipment was constructed to sample polymerized injection water at the wellhead. Furthermore, high-quality injection data was obtained through installation of a bottomhole memory gauge into the injector prior to the test.The main results from the offshore test proved the feasibility of storing, mixing, transport and injection of polymer solutions without contamination or unwanted shear degradation of the polymer. Good mixing was obtained by feeding the polymer mother solution into the injection stream. Polymer sampling at the wellhead showed good polymer quality based on viscosity and filter ratio results. Well injectivity improved under polymer/LPS injection compared to water injection due to the opening of existing fractures at lower injection rates.

Rock Lithology-Based Laboratory Protocols and Best Practices for Polymer Screening for EOR Application in Conventional and Harsh Reservoirs

“…Recent review work summarizes the available polymers for use in high temperature and high salinity reservoirs [10,11]. These polymers are mainly based on acrylamide.…”

Extending the Life of Mature Assets: How Integrating Subsurface & Surface Knowledge and Best Practices Can Increase Production and Maintain Integrity

“…Selle et al [22] discuss the development of a polymer injection project on the Heirun platform in the North Sea. They review previously reported application of polymer flood offshore and point out that there were three projects reported in the period prior to 1990 which represents the initial phase of interest in offshore polymer flood.…”

Nanoparticles for Enhanced Oil Recovery: Influence of pH on Aluminum-Cross-linked Partially Hydrolyzed Polyacrylamide-Investigation by Rheology and NMR

“…LPS has been implemented successfully at onshore fields in China , and extensive core flood experiments have showed high recovery potential. ,, However, only one injection pilot has been performed at offshore field . To adapt LPS to offshore conditions, the properties have to be optimized to meet specific requirements regarding pH, salinity and temperature.…”

“…7,9,10 However, only one injection pilot has been performed at offshore field. 45 To adapt LPS to offshore conditions, the properties have to be optimized to meet specific requirements regarding pH, salinity and temperature. Physicochemical properties have been studied by rheology and dynamic light scattering (DLS).…”