A Field Test of Microemulsion Flooding, Chateaurenard Field, France

Abstract

Summary A pilot test of microemulsion flooding was conducted in a single five-spot pattern in the Chateaurenard field in France. The test had to accommodate a 40-mPa·s (40-cp) oil viscosity and a regional pressure gradient across the pattern. A very clear oil bank was observed, resulting in a substantial increase in oil production. Introduction Société Nationale Elf Aquitaine (Production) is conducting a microemulsion/polymer flooding pilot test in its Chateaurenard field in the southern part of the Paris basin. This project involves the participation of the Inst. Franç du Pétrole, and it has been partially funded by the Commission of the European Communities. The primary objectives of the pilot are to (1) demonstrate the efficiency of the process under field conditions, (2) develop the technology involved in such an operation, and (3) assess the economics of fieldwide extension. The permeability of the unconsolidated sand reservoir is very high, and the connate water is fresh. Both of these factors are favorable for micellar flooding application. The oil is relatively viscous [40 mPa·s (40 cp)]. Even though the oil saturation is far from residual, the well effluents have a high water cut due to poor areal efficiency of oil displacement by water. A microemulsion flooding scheme, with its readily achievable mobility control, appeared to offer a feasible recovery mechanism. However, the injection of viscous fluids limits the injection rate and requires a higher concentration of chemicals. The Chateaurenard oil viscosity is above the limit of 20 to 30 mPa·s (20 to 30 cp) mentioned in some publications.1,2 The well arrangement is a 10´103-m2 (2.5-acre) inverted five-spot pattern with one observation well. The pilot area was determined through coring, logging, and interference testing. These data indicated an initial pressure gradient across the pattern. Three separate injection phases compose the process: microemulsion, polyme, and chase water. Microemulsion was formulated using field crude and water. Injection was initiated in Feb. 1978 and followed by polymer concentration started in April 1979 and led to chase water in Nov. 1979. The polymer buffer has been overdimensioned somewhat to test specifically the efficiency of the microemulsion, without interference from poor mobility control following it. A significant response was observed from the producing wells 2 months after the start of operations. In this paper we present pilot design, performance, and an interpretation of the results. Field Description The Chateaurenard field, outlined in Fig. 1, is part of the Neocomian (Lower Cretaceous) oil reservoirs found in the southern part of the Paris basin. They are located 100 km (62 miles) south-southeast of Paris; the oil-bearing zones extend over an area of 20 km2 (7.7 sq miles).