Steam-Drive Project in the Schoonebeek Field, The Netherlands

Abstract

Abstract In Sept., 1960, a steam-drive project was started in the solution-gas drive area of the Schoonebeek field. A pattern of three five-spots and one four-spot was selected covering an area of 65 acres. The pay in the project area has good lateral continuity and dips slightly to the northeast; it is about 80 it thick and permeability increases from 1,000 md at the bottom to approximately 10,000 md at the top. The oil originally in place was 12.6 X 10 bbl. The oil has an in situ viscosity of about 180 cp. At the start of the steam drive the cumulative primary production due to solution-gas drive amounted to 4 percent of the oil originally in place. Reservoir pressure had dropped to about 120 psi and no significant primary reserves remained. Some 113 million bbl of steam (all steam quantities are expressed in barrels of water vaporized) have been injected, resulting in production of an additional 4.1 X 10 bbl of oil, or 33 percent of the oil originally in place. This corresponds to a cumulative oil-steam ratio of 0.37 bbl/bbl. It appears that the steam preferentially moves updip while liquids are produced mainly from downdip wells. Observations indicate that the steam flows through only the upper part of the formation. The lateral steam distribution in the pattern is unsatisfactory since several production wells hardly reacted and, hence, contributed little lo the oil production. Production performance and results from material balance calculations agree satisfactorily with the results of large-scale laboratory experiments. On the basis of these experimental results the steam drive, together with a cold water follow-up, is expected to bring ultimate recovery to a value of at least 50 percent of the oil originally in place. No serious production problems have been encountered. However, due to mechanical failure, two old production wells and one injection well had to be replaced. An extension of the steam drive in this area is, under construction. Introduction The Schoonebeek oil field, discovered in 1943 and developed after World War II, is situated in the eastern part of the Netherlands. The main oil reservoir in this field is the Valanginian sand. A completely sealing fault divides this reservoir into two areas (Fig. 1): the southwestern part of the sand body where primary production is obtained by means of a solution-gas drive, and the remainder where edge-water drive is the production mechanism. In the greater part of the field the reservoir consists of a single, unconsolidated sand body. The net thickness ranges from 30 to 100 ft and the top is between 2,400 and 2,800 ft below sea level. Formation permeability varies from approximately 10,000 md at the top to values of the order of 1,000 md at the bottom, and porosity is about 30 percent. The reservoir contains a paraffinic oil of 25 deg. API gravity with an in situ viscosity of 160 to 180 cp. Initial oil saturation was high (85 to 90 percent). The relatively large quantity of oil in place (more than 10' bbl), and the low ultimate primary recoveries expected from this field -approximately 15 percent stock-tank oil initially in place (STOIIP) for the water-drive area and 5 percent STOIIP for the solution-gas drive area - clearly indicate ample scope for secondary recovery. Because reservoir and crude characteristics made this field suitable for thermal secondary recovery, a hot-water drive project was started in the water-drive area about 10 years ago. A few years later a steam drive and an in situ combustion project were started in the solution-gas drive area. This paper deals with the performance of the steam-drive project, which was started in Sept., 1960, and which is still in operation.