The Pilot Test of ASP Combination Flooding in Karamay Oil Field

Abstract

Abstract The chemical screening and chemical formulation studies were discussed in this paper, and the pilot test results as well for the ASP combination flooding pilot test in Karamay EZ District. Also the designing strategies of the ASP process were included in this paper. The ASP pilot test started from August 21,1995 with the beginning of NaCl brine pre-flush in order to condition the reservoir, then followed by ASP slug and Polymer slug. The post-water injection was applied after the designed chemical injections. The 24%OOIP incremental oil recovery was achieved in the whole test area with about 25%OOIP incremental oil recovery for the central production well. Introduction Karamay oil field was discovered in late 50's. It has been developed about 50 years so far. It's very urgent to find the technologies to keep the oil production high and cost low because the majority of the producing wells are in high water-cut production period. The ASP flooding method (alkaline/surfactant/polymer flooding) was adapted in EOR project of Karamay EZ District after both of computer modeling and pre-lab studies. The computer modeling results showed that the chemical flooding technologies were suitable for EOR process in our target pilot area, and the surfactant involved chemical processes had more potential advantages than others. Meanwhile the Alkaline/ Surfactant/ Polymer flooding method was found to be the best combination chemical flooding process for Karamay EZ District EOR project from the pre-lab study's results. The ASP combination flooding is defined as a combination flooding system of alkali, surfactant and polymer. The ASP technologies were well studied during the 80's, and proved to be an effective method for improving oil recovery process for certain reservoires1. During the 80's to 90's, the ASP combination flooding studies were conducted in Daqing and Shengli oil field, and the results were very good from both laboratories and fields2. Also the ASP combination flooding technologies were widely studied focusing on Karamay reservoir conditions from late 80's to late 90's3,4. The field test started on August 21, 1995, a very exciting results were achieved which were as good as we expected after three-year field operation. The lowest water-cut period lasted for 20 months for the test area and for 14 months for the central production well. By the end of December in 1998, the incremental oil recovery was 23.15%OOIP with the water-cut of 92.4% for the whole test area, and 24.25%OOIP incremental oil recovery with the water-cut of 90.2% for the central producer5. Also 25%OOIP incremental oil recovery was obtained by the end of June in 1999 for the central well and 24%OOIP for the pilot area. So it's very lucky and important for us to learn the best experiences from the pilot test for conducting ASP combination flooding project in highly heterogeneous conglomerate reservoirs. Pilot Area Properties The pilot test area was located in the north of EZ District of Karamay oil field which is 10 km away from Karamay city. The pilot pattern is an inverted 5-spot pattern including 4 injection wells and 9 production wells which covers about 0.031 km2. See Figure 1. The well spacing between injector and producer is 50 m and 70.7 m between two producers. A central well was used for evaluation purposes. There were 8 wells for controlling injection and production balance for the test area; also there were 6 wells outside the test area, which forms a hexagon water injection boundary for the test pattern. S73+S74, the target zone, belongs to the main channel deposits of fanhead, featured with good oil preservation conditions, continuous oil zone distribution, good rock connectivity and good reservoir properties, sedimentary thickness of 19.5~24.5m, glutenite reservoir thickness of 15.0~22.0m. Also the Table1 and Table 2 show the water and oil properties of the pilot test area respectively.