Sweep Efficiency of Surfactant Flooding Processes

Abstract

JPT Forum articles are limited to 1,500 words including 250 words for each table and figure, or a maximum of two pages in JPT. A Forum article may present preliminary results or conclusions of an investigation that the present preliminary results or conclusions of an investigation that the author wishes to publish before completing a full study; it may impart general technical information that does not warrant publication as a full-length paper. All Forum articles are subject to approval by an editorial committee. The recent National Petroleum Council study1 of the potential for enhanced oil recovery estimates possible reserve additions through application of emerging technology. In analyzing the potential for surfactant processes, the NPC study assumes that volumetric sweep efficiencies for such processes would be no higher than those obtained from a prior waterflood. This assumption considers the only oil available for tertiary recovery to be the residual waterflood oil in the swept zones. Zones of higher oil saturation thus are eliminated. Since many surfactant flooding processes utilize a viscous slug followed by a polymer solution, one might anticipate that such processes could yield higher volumetric sweep efficiencies. An analysis of produced chlorides from a Maraflood™ oil recovery process test in the Bradford Third sand of Pennsylvania supports· this position. Danielson et al.2 have reported previously on this test. The Bingham project was carried out on a 4 7 -acre tract in the Bradford field, McKean County, Pa., allowing a unique opportunity to estimate increased sweep efficiency from an analysis of produced chlorides. This is possible for two reasons. First, the connate water contained a high chloride ion concentration (150,000 ppm), while all injected flood water was fresh (150 ppm chloride or less). No produced water was recycled during waterflood operations, thus avoiding what would otherwise be a serious complication in the analysis of produced chlorides. Second, the same wells and patterns were used for this surfactant, or micellar flood, as were used for the waterflood, eliminating the possibility of increased volumetric conformance because of pattern changes.