The 2nd Eocene dolomite reservoir in the Wafra field is an attractive target for enhanced oil recovery (EOR) because of its large resource base and low primary oil recovery. Primary oil recovery is low because of heterogeneity, low oil gravity, and lack of significant aquifer support. Screening studies and numerical simulations indicate that steamflooding is the most attractive EOR method in terms of reserves and economics. Key technical challenges in steamflooding the 2nd Eocene reservoir include reservoir heterogeneity, relatively high reservoir pressure, scale deposition and corrosion due to rock-steam interactions, and uncertainty regarding the location and impact of barriers to vertical steam migration.

A pilot steamflood was designed to test the viability of steamflooding the 2nd Eocene. The pilot location was selected based on a number of criteria including reservoir quality and proximity to existing steam generation facilities. Several pattern configurations were evaluated based on their ability to depressurize the reservoir and to yield timely information, taking into account steam availability considerations. Based on these considerations, a configuration of seven 2.5-acre inverted 7-spot patterns was chosen for the pilot. Steam injection rates were designed to yield steam breakthrough after approximately one year of steam injection.

A robust surveillance plan was developed to collect the data necessary to satisfy the pilot objectives and to understand the critical reservoir uncertainties. The surveillance plan was carefully considered in the well and surface facilities designs to ensure that all required measurements could be made with minimal impact on operations. Reservoir simulations indicate that a significant amount of fluid influx will occur from the reservoir surrounding the pilot after steam breakthrough, thereby obscuring the steamflood production response. For this reason a dense array of observation wells was designed to monitor reservoir temperatures and saturations and to provide enough information to understand fluid movement, steam chest development, and steamflood recovery factors in the presence of this influx. A thorough understanding of these mechanisms will be crucial for making future steamflood expansion decisions.

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