Design and History Matching of a Very Large Waterflood/Miscible Gas Flood Model of the Northwest Fault Block, Prudhoe Bay, Alaska

Abstract

Abstract Prudhoe Bay, located on Alaska’s North Slope, is the largest field discovered in North America. Over eight billion barrels of oil have been produced since the start of production in 1977. Four major waterflood/miscible water-alternating-gas (WAG) flood projects are in progress in the Prudhoe Bay field. This paper describes the construction of a model representing one of these projects using a combination of stochastic and deterministic tools, and input data from the major field owners (ARCO, BP and Exxon) by personnel from multiple companies. These techniques produced porosities and permeabilities that required only minor modifications to obtain an excellent history match for the Northwest Fault Block (NWFB) area of the Prudhoe Bay field. The historical production period matched in this study included primary, secondary waterflood and tertiary miscible WAG flood mechanisms. During the history matching process, proper representation of the well’s perforation and wellwork history and the existence and extent of flow barriers (e.g. shales) were important to achieving a good match. Fluxes between the NWFB and the remainder of the field were a dominant force in some predictive cases, emphasizing the importance of field-wide reservoir management. The model demonstrated a close link between overall production and management of voidage replacement requiring a good balance between productivity gains associated with reservoir fracture treatments and injection rates.