Minas Surfactant Field Trial Tests Two Newly Designed Surfactants with High EOR Potential

Abstract

Abstract Caltex Pacific Indonesia (CPI) recognizes the enormous potential that a large scale tertiary enhanced oil recovery (EOR) project like Light Oil Steam Flood or Surfactant Flood can have on extending the operations in Minas oil field well into the 21st century. With 4.5 billion barrels of remaining target oil, a successful tertiary EOR process will have a significant economic impact on future operations. Tertiary projects are capital intensive and carry a high degree of risk, however, decision analysis (DA) studies for Minas indicate they have tremendous upside potential. In depth EOR screening identified two major processes for potential application in this high temperature, shallow reservoirs: Surfactant Flooding and Light Oil Steam Flooding. A successful Surfactant Field Trial in Minas will pave the way to potentially implement the process in several CPI fields in the Central Sumatra Basin. The Minas Surfactant Field Trial is a unique project where two new low-cost surfactant systems, Lignin II and Synthetic Petroleum Sulfonate, have been specifically designed for Minas reservoir conditions. Lab tests indicated significant and comparable recovery from both systems in Berea and field cores. They are ready to be tested in the field for the first time. Four different polymers, designed to provide a favorable mobility ratio in displacing the surfactant, will also be tested to select the most cost-effective system for Minas' high temperature environment. The purpose of the Field Trial is to validate the lab results, reduce the range of technical and economic uncertainties associated with recovery efficiency and field operations, and select the most cost-effective surfactant for field scale application. The Surfactant Field Trial area is a 4.3 acre, 5-spot pattern utilizing 4 injectors and one central producer. Five sampling wells and four observation wells will be drilled to monitor the flood performance in both the A1 and A2 sands. The evaluation of flood results have been based on actual log and core data collected before, during and after surfactant injection. A reservoir simulation model will be used to history match production performance and to scale up the process for field wide performance predictions. The selected finite difference simulation package is equipped with surfactant and polymer options. This paper will discuss both reservoir and facility aspects of the Surfactant Field Trial design and implementation. In the future, actual recovery efficiency of both surfactant systems will be reported and compared to performance predicted from laboratory test results & reservoir modeling. Historically surfactant floods have not been viewed favorably due to their high cost & moderate recovery1. However, the low cost of production of Lignin II and Synthetic Petroleum Sulfonate may change the way we view surfactant flooding if their high recovery is proven in the field trial. Introduction & Overview The giant Minas Oil Field, located in the central Sumatra basin, is a faulted transgressional anticline approximately 28 km long by 10 km wide. Shown in Figure 1, Minas is one of the largest oil fields in Southeast Asia, with estimated original oil in place of about 9 billion barrels. Discovered in 1944 and placed on production in 1952, Minas has produced over 4.2 billion barrels of oil to-date. The primary reservoir consists of five major sand bodies within the Sihapas Formation, designated as A-1, A-2, B-1, B-2, and D sands. A Minas type log displaying the Sihapas sand package is shown in Figure 2. These sands have an average total gross thickness of approximately 260 feet and lie at a depth of about 2000 feet sub-sea.