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, sub-homogeneous 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.
