Polymer Flooding by Hydrophobically Associating Polyacrylamide. (Technology Of Preparation. The Study Of The Processes Of Stability And Degradation).
Authors: Patokina Olga Y. 
Published: October 2015

Growing interest in enhanced oil recovery techniques is evident both in Russia, and worldwide. A number of research studies aimed to find a scientifically proven approach for selection of the most effective reservoir engineering technologies is constantly growing.

One of the most promising methods applied for heavily depleted, flooded oil-bearing formations with scattered, irregular oil saturation is polymer flooding.

Polymer flooding is a physical and chemical method of enhanced oil recovery at flooding by pumping aqueous polymer solutions of various concentrations with high molecular weight into the formation. Aqueous polymer solutions are pumped into the oil-bearing formation in a form of slugs, with water mobility decreased in the area of their penetration, which increases the oil-bearing formation sweep efficiency and, ultimately, improves the recovery factor (RF). At polymer flooding, the slug size depends on the oil viscosity and formation heterogeneity, and is ideally makes to 0.1–0.5 of the formation pore volume. Oil displacement efficiency at filtration of polymer solutions also depends on flow properties of the polymer system.

Since December 2012 in the Perm region a project on polymer flooding on terrigenous formations has been implemented with the use of hydrophobically associating polyacrylamide, with the test site including 2 injection and 20 producer wells. As of May 1, 2015, pumping of 0.1 % polymer solution is being conducted, meanwhile polymer in the amount of 10.8 % of the pore volume of the test field area reservoir has been actually pumped. The amount of polymer solution pumped equals to 154.3 thous. m3.

During this project implementation, subdivisions of the PermNIPIneft branch are performing scientific and engineering support: laboratory researches of incoming inspection of dry polymer and polymer solutions, of reservoir-pressure maintenance system (RPMS) water quality, investigation of properties of formation waters and polymer at the producer well outlet, studying of polymer filtration properties in the bottom-hole formation area, and carry out the complex analysis of current efficiency of polymer flooding, results of laboratory researches, and develop recommendations on further implementation of the pilot project.

Based on the results of the works performed, a set of measures has been developed to introduce changes to the technology of polymer solution preparation and pumping, and the polymer preparation and pumping plant has been upgraded.

This set of measures on scientific support of the polymer flooding project enabled to: Perform selection of standard field samples for laboratory investigations.Determine the optimum time of use of the polymer solutions after preparation (to ensure solution homogeneity and to minimize the destruction degree).Prepare the concentrated solution with the required quality and increase solution homogeneity in the entire reservoir volume.Ensure proper flow, pressure, temperature control at the polymer preparation and pumping plant.Ensure minimum mechanical destruction on a pump supplying the polymer solution to RPMS.Mandatory works have also been determined:Select and install a mixing unit on a water distribution manifold (WDM) to ensure high-quality concentrate mixing with the pumped water upstream of the point of flow distribution among wells.

Today, polymer flooding with hydrophobically associating polyacrylamide is a unique project. Such projects are new both to LUKOIL Group, and in Russia. The work has a significant value – the incremental production in the Perm field is expected to be 5 mln tons, while the RF incremental growth – 18.93 %. Polymer flooding project monitoring, including complex analysis of the process for polymer solution preparation and pumping have been performed by the PermNIPIneft subsidiary and LUKOIL and LUKOIL-Engineering Companies for the first time.