Improved Oil Recovery by Polymer, Surfactant and Low Salinity Water Flooding Applied for Gullfaks field (Statfjord-I1 Segment) Based on applied Reservoir Simulation.

Most of the energy used all over the world come from fossil fuel in which hydrocarbons which are non-renewable sources of energy contribute in large percent. Recently most of oil fields are tertiary phase of recovery. As a result, more techniques for improving the recovery of hydrocarbons (oil) remained in the reservoir after primary and secondary recovery phases have to be applied. This work is based on reservoir simulation to improve the oil recovery of the Gullfaks field (Statfjord I-1 segment) by applying various IOR methods including well placement optimization, chemical injection based on surfactant, polymer and low salinity water flooding. The simulation from the base case with three wells, two producers (C-16 and A-36) with one injector (A-41), resulted into the recovery factor of 37.89% from May 1992 to January 2001. When the production time was extended up to 2032, the base case attained a maximum recovery factor of about 46.39%. Low salinity was applied as a secondary method to the base case, the recovery factor was observed to increase from 37.89% to 40.10%. New case with five wells (three producers and two injectors) was proposed, and the simulation was performed up to 2035, oil recovery of about 64.79% was achieved which is significantly improved compared to the base case. Polymer and surfactant injection were implemented from the proposed case for a duration of 15 years, unfortunately a minor effect on the oil recovery was observed. The observed improvement in the oil recovery factors were about 0.2% and 0.1% by surfactant and polymer injection respectively. This alternative was therefore rejected, and the low salinity method which was observed from the base case to provide improvement in the oil recovery was adapted. Low salinity water flooding technique with various salt concentrations from 500ppm to 30000ppm were implemented as secondary and tertiary method. In all these cases significant improvement in oil recovery was observed compared to waterflooding and other chemicals applied . Based on simulation results of oil recovery, incremental oil and gas produced and NPV analysis, low salinity waterflooding has been proposed as the best IOR method for Statfjord I-1 segment . As part of recommendation further studies including other chemical injection such as alkaline flooding, assisted surfactant polymer flooding (ASP), surfactant injection in salt water and other methods with appropriate reservoir and fluid data from the respective field is very important