Sloss Micellar Pilot: Project Design And Performance

Abstract

Introduction Amoco Production Company is conducting a tertiary micellar pilot flood in a high-temperature (200 degrees F) reservoir in the Sloss Field, Kimball County, Nebraska. The well arrangement is an isolated nine-acre normal five-spot pattern (Figure 1). The primary objectives of the pilot are:to demonstrate that the recovery method mobilizes and efficiently displaces the tertiary oil remaining after waterflooding andto establish technology which will permit reliable projections of fieldwide performance. This pilot flood is "unconfined" with respect to the perimeter of the pilot area, the pilot injection-withdrawal ratio (IWR) being slightly greater than unity. Because of this factor, the flow configuration, i.e., streamline geometry, is different from that for a fieldwide flood. A portion of the tertiary oil recovery will come portion of the tertiary oil recovery will come from outside the pilot area. From an interpretability standpoint it is important that the pilot flow paths and area contributing to the pilot pilot flow paths and area contributing to the pilot production remain as constant as possible with production remain as constant as possible with time. To achieve this, the pilot design and operation were based on maintaining the IWR of each injector-producer pair constant with time. The design sequence of injection consists of four fluids: preflush water, micellar, polymer, and, finally, chase water until termination of the process. The micellar formulation was designed to process. The micellar formulation was designed to efficiently displace tertiary oil and be stable at the reservoir temperature of 200 degrees F. The mobilities of the micellar and polymer were adjusted so that they were approximately equivalent to the mobility of the tertiary oil-water bank. To be able to adequately interpret pilot performance, a good reservoir description is performance, a good reservoir description is required. Therefore, prior to initiation of micellar injection, a comprehensive program was conducted to obtain a reservoir description. The program consisted of coring, logging, production program consisted of coring, logging, production tests, pressure transient tests, pulse tests and tracer injection. In addition, a geological study was made. A detailed reservoir description of the area affected by the pilot flood was obtained. With this description, micellar flood performance predictions were made to determine expected injectivities and oil recovery and response. Micellar injection was initiated on February 26, 1977. Polymer injection commenced on March 30, 1977, and is still in progress. A definite tertiary oil response has occurred. In this paper, pilot performance through mid-January, 1978, is summarized. performance through mid-January, 1978, is summarized. MICELLAR FLUID FORMULATION AND TESTING The Sloss Muddy J reservoir conditions are basically amenable to micellar flooding. The porosity is 17 percent, the permeability is 80 md, the inplace water is fresh (TDS = 2500 ppm, hardness = 50 ppm) and low salinity water is available (TDS = 260 ppm, hardness = 25 ppm). The high temperature (200 degrees F) of this reservoir makes it a unique pilot. The National Petroleum Council study of 1976 projected temperatures Petroleum Council study of 1976 projected temperatures of only 170 degrees F for current technology. In particular, thermal stability of polyacrlyamide molecules has not been tested under actual high temperature reservoir conditions. The micellar fluid for the Sloss pilot was designed by going through a series of tests similar to that described earlier. Principal components finally selected for these tests were Amoco Mahogany AA sulfonate (62% active), isopropyl alcohol (IPA), Dow pusher 700 polymer, Great Salt Lakes Minerals and pusher 700 polymer, Great Salt Lakes Minerals and Chemical Corporation sodium chloride, and Sloss fresh water. These were chosen on the basis of availability, performance, and stability. Similar laboratory systems performance, and stability. Similar laboratory systems have been extensively studied.