Evaluation of Horizontal, Radial, and Vertical Injection Wells in a Pilot Steamflood

Abstract

SPE Member Abstract A unique pilot steamflood incorporates one horizontal, one radial, and three vertical steam injection wells. The horizontal and radial wells were designed to alleviate steam override and improve sweep efficiency. The horizontal injector is a medium radius well with 400' of completion in the horizontal section. The radial well has four completed, near-horizontal, ultra-short radius laterals drilled within a short vertical section. The vertical injectors are conventional completions, with perforations in one or two sand lobes. Production data from offset producers, injection profile data, produced fluid and downhole temperature data, and a comprehensive log suite conducted on three temperature observation wells were used to compare the three injection strategies. While a significant increase in oil production has not yet been seen, changes in water production, cut and flowline temperature provide clear indications that many of the offsets are being affected by steam injection. The pilot steamflood is located in a 5-acre area in the southwest portion of Unocal's Bremer lease, Midway Sunset Field. The steamflood targets the Mio-Pliocene age Potter formation, a highly permeable sand comprised of massive debris and grain flows deposited as proximal submarine fans. The pilot and surrounding areas have been cyclically steamed for over 10 years. The pilot steamflood has been in place for just under 2 years. In addition to comparisons within the pilot area, comparisons are also made with the eastern portion of the lease which has been successfully steamflooded for over 10 years. The horizontal injector has efficiently heated a very localized, previously unswept, portion of the thick, subhomogeneous reservoir being steamflooded. To date, the radial well has been used as a huff-n-puff producer. Despite the short steam injection periods, producers surrounding the well have responded dramatically. Observation well data, rates from offset producers, and temperatures in the offset producers confirm that the vertical injectors are distributing heat and affecting oil production less effectively than the horizontal and radial methods. Introduction Unocal's Bremer Fee is located in the northern portion of the Midway Sunset Field, approximately 35 miles west of Bakersfield, California (Figure 1). The property consists of 360 acres entirely within Section 16, T31S, R22E, MDB and M. Approximately 180 acres are productive. Current production averages 5,000 BOPD from 247 producing wells. Although the Marvic, "D" Channel and Spellacy horizons have been produced sporadically, all production from the lease is currently from the Potter formation. Primary development began in 1968. Cyclic steaming in the southwestern area of the lease was initiated in 1976. Up until initiation of the pilot steamflood in 1990, the area had been successfully produced under cyclic stimulation only. Steamflooding in the northeast portion of the lease was initiated in the late 1970's, with a major expansion in 1980–1983. At the start of the pilot steamflood project, log-derived oil saturations in unswept areas were close to initial, implying that significant steam channeling had occurred during cyclic operations. This, along with comparisons with the successful steamflood in the northeast, provided the incentive for steamflooding in the southwest. P. 7^