Evaluation of Injection Well Stimulation as Applied to a Large Micellar/Polymer Project

Abstract

This paper deals with completion techniques applied to a large (407-acre or 1.6 km2) micellar/polymer flooding project. Injectivity and vertical conformance in wells completed openhole by solid-block shooting and hydraulic sand fracturing are compared. Openhole hydraulic sand fracturing appears to give better injectivity and vertical conformance than openhole shooting. Introduction Marathon Oil Co. currently operates a large micellar/polymer project in southern Illinois. This commercial-scale test, known as the M-1 Maraflood (trade mark) Project, lies in Secs. 15, 16, 21, and 22, T6N, R13W, Crawford County, IL, and encompasses approximately 407 acres (165 ha) of the main Robinson sand reservoir (Fig. 1). This Pennsylvanian-age sand is an example of stream channel deposition from a meandering river with migrating point bars. The reservoir lies about 950 (290 m) subsurface, and sand thickness varies from zero on the eastern flank of the project to about 60 ft (18.3 m) near the center (Fig. 2). Both multiple sand bodies stacked one above the other and isolated sand lenses found above and/or below the main sand occur in the M-1 project. Average reservoir characteristics are shown in Table 1. The Robinson sand reservoir was discovered in 1906 and experienced rapid and extensive development. Production during the first few years declined as the solution gas energy dissipated. Early attempts to reduce production decline consisted of air and gas injection and application of vacuum to producing wells. The project area subsequently was producing wells. The project area subsequently was developed for waterflooding on 10-acre (4-ha) spacing during the 1950's. Following a successful waterflood, oil production rates declined to a low level. In 1974, Maraflood development began. As indicated in Fig. 2, the project has been developed as two distinct areas; one on 2.5-acre (1.0-ha) spacing and the other on 5.0-acre (2.0-ha) spacing. Project development, including all wells and facilities, neared completion on Sept. 30, 1976, when a contract was executed between the U.S. Energy Research and Development Admin. (now DOE) and Marathon for cooperative funding of the project. This paper presents the history of injectivity problems, presents the history of injectivity problems, subsequent stimulation, and evaluation. Past experience has shown that injection of micellar solution is difficult unless the wellbore is undamaged and the micellar solution has been filtered and delivered to the wellbore uncontaminated. Analysis of injectivity problems requires a basic understanding of the recovery process. For the M-1 project, micellar/polymer process. For the M-1 project, micellar/polymer flooding is referred to as the Maraflood oil recovery process when used as described in Marathon's more process when used as described in Marathon's more than 100 patents covering the process. It typically consists of injecting between 5 and 15% PV of a micellar solution that displaces oil in a miscible-like manner and leaves a very low residual oil saturation. Micellar solution is displaced by a mobility buffer, normally a polymer-thickened water, to ensure adequate mobility control and provide good sweep efficiency. Finally, the mobility buffer is followed by drive water to complete the project. JPT P. 777