Peripheral Pattern Waterflood Performance, Sholem Alechem Fault Block "E" Unit

Abstract

Abstract Predictions of primary performance and five-spot water-flood performance were made early in the life of the Sholem Alechem fault block "E" field. A fieldwide secondary-recovery unit was formed near the end of primary depletion and the reservoir was water flooded using a peripheral injection pattern. By comparing the five-spot waterflood prediction with the actual peripheral waterflood performance, we established that five-spot predictions of oil recovery, water production and water injection can be used to determine the same performance characteristics throughout the life of a peripheral water flood. Accomplishing and determining fill-up are necessary for the satisfactory operation of a peripheral water flood in a previously depleted reservoir. Methods of positively determining fill-up as well as inconclusive indications of fill-up are discussed. After fill-up it is possible to make a pore-volume calculation of waterflood reserves utilizing flood-front data and new saturation conditions, which will serve as a check on the previous estimates of waterflood reserves. Introduction The Springer Sims sand reservoir in the fault block "E" area was initially produced in 1948. The reservoir was developed on 10-acre spacing, and the unitized area includes 47 wells. Reservoir characteristics are included on Table 1.The reservoir is a portion of the Springer anticline structure, which has been separated by major faulting. A combination of normal block faulting followed later by reverse faulting together with sand development has divided the area into several essentially closed reservoirs. The Sholem Alechem fault block "E" unit (SAFBEU) was formed from the oil-producing portion of an essentially separate reservoir. The area is closed on the north by a fault and sand development, on the west by a fault. on the east by sand development and on the south by a water-oil contact. This is shown in Fig. 1.The reservoir originally had a gas cap and an aquifer. During primary depletion the reservoir produced principally as dissolved-gas-drive reservoir with some gas-cap expansion. Although some water was produced from down-dip wells and there was a noticeable encroachment of water before unitized operations began. there was no appreciable recovery resulting from the water influx. During 1953 the unitization engineering subcommittee evaluated primary and five-spot waterflood performance for the proposed unit area. These predictions and actual production during the primary and waterflood phases of operation are shown on Fig. 2. JPT P. 537ˆ