William B. Gogarty

Enhanced oil recovery through the use of chemicals-Part 2

Chemical enhanced oil recovery (EOR) includes processes in which chemicals are injected to improve oil recovery. Chemical methods are one of three categories of EOR, the others being thermal and miscible. The different processes in these categories are defined by the Crude Oil Windfall Profit Tax Act of 1980. A comparison of field project activity in the three categories is shown. Thermal activity is the highest, followed by chemical. The number of chemical projects more than doubled between 1980 and 1982. Miscible CO/sub 2/ injection accounts for most of the miscible category. Projects in the chemical category are broken down further in terms of the three chemical EOR methods. Micellar/polymer projects are those in which surfactant is injected into the formation. Polymer projects refer to a spectrum of uses including near-wellbore treatments, complete polymer-augmented waterfloods, and a combination of both. Caustic refers to projects where alkali is injected to increase pH and to produce surfactants in situ. With all three chemical EOR methods, activity has increased significantly between 1980 and 1982.

A Field Test of Micellar Solution Flooding

A field test was conducted using a micellar slug for tertiary oil recovery in the Robinson sandstone of the Henry reservoir in southeastern Illinois. The origin of the sandstone was nonmarine fluvial, with 20 percent porosity and 200 md permeability. The micellar slug contained petroleum sulfonate, crude column overhead, isopropanol, nonylphenol, sodium hydroxide and water (500 ppM total dissolved solids). Pusher 500 was the thickening agent in the following polymer flood. The flood water was treated with sodium hydroxide before mixing with the polymer to remove divalent cations. A 63 percent recovery of oil in place after waterflooding was realized.