Smart-Well Technology at the SACROC CO2 EOR Project

Abstract

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 100117, "Application of Smart- Well Technology to the SACROC CO2 EOR Project: A Case Study," by J. Brnak, SPE, Kinder Morgan Production Company, and B. Petrich and M.R. Konopczynski, SPE, WellDynamics, prepared for the 2006 SPE/DOE Symposium on Improved Oil Recovery, Tulsa, 22-26 April. Application of smart-field technologies to the SACROC Unit carbon dioxide enhanced oil recovery (CO2-EOR) project in Scurry County, Texas, was studied. A five-well pilot project in early 2005 demonstrated the ability of intelligent-well downhole flow-control valves to restrict or isolate the production of CO2 from breakthrough zones in production wells and to control the distribution of CO2 injection in injection wells. The objective is to reduce unnecessary cycling of CO2 between injectors and producers, improve sweep efficiency, increase oil production, and improve ultimate oil-reserves recovery. This is done with cost-effective, fit-for-purpose intelligent-well systems. SACROC Field The SACROC Unit in Scurry County, Texas, is the seventh largest oil field onshore in North America, with 2.8 billion bbl of original oil in place. Its main producing formation is the Canyon Reef, a Pennsylvanian-aged limestone carbonate and part of a reef complex called the Horseshoe Atoll. It is a highly heterogeneous formation. Permeability within a single well can range from less than 1 md to hundreds of millidarcies. Likewise, porosity can vary drastically. Net and gross thickness can change significantly over short distances. However, average reservoir properties are as follows.Depth = 6,700 ft.Thickness = 259 ft.Porosity = 7.6%.Permeability = 19.4 md. SACROC CO2 EOR Project The SACROC Unit was discovered in 1948 as the Kelly-Snyder field. The field produced under primary depletion with solution-gas expansion as the main drive mechanism. Reservoir pressure declined rapidly, and in 1952, the Kelly-Snyder and Diamond M fields were unitized. In 1954, the operator implemented a crestal waterflood in which water was injected along the center (the spine) of the field. In 1972, CO2 injection was initiated. With limited CO2 supply, the oil-production response to CO2 injection was limited. During water and CO2 flooding, H2S was introduced to the reservoir from sources outside the unit. As shown in Fig. 1, shortly after CO2 injection was initiated, the unit's oil production peaked with rates exceeding 200,000 BOPD. During the following decline, several projects were attempted to halt the decline, but they had little effect. In 1995, a CO2-flood pilot consisting of five-spot patterns was started. This pilot used large CO2-injection volumes at miscible conditions, and the decline of the unit's oil production was halted. In 2001, project acreage under CO2 flooding began to expand rapidly. In response, oil production increased to more than 31,000 BOPD.