Thermal field development often requires trials or pilots to unlock additional oil recovery. "A" East (ALE) is a thermal EOR oil development project located on the Eastern Flank of the South Oman Salt Basin. An initial/ongoing development phase in the upper part of the reservoir primarily consists of Cyclic Steam Stimulation (CSS) followed by steam drive. Aiming to increase the field's total ultimate recovery, the next development phase was conceived to target the more viscous oil (up to 200,000 cP) in deeper zones, deemed too challenging in the first phase.
Many concepts were evaluated, however "Cross Top Down Steam Drive" (X-TDSD) was ranked as the most favorable option to address the development uncertainties. Similar to the Steam Assisted Gravity Drainage (SAGD), the injection wells will be positioned above the production wells. However unlike SAGD, the injectors will be placed perpendicular (cross) to the producers. Additionally, the XTDSD will assess the approach of utilizing a combination of steam flooding at the top, using vertical wells, and a gravity drainage process at the bottom using horizontal wells.
The X-TDSD trial scope includes the drilling and completion of two horizontal injectors, three horizontal producers, and three vertical observation wells. These will be accommodated within the existing infrastructure. The acceleration of the three observation wells reduced some of the main uncertainties prior to executing the horizontal wells. These included structural geology, stratigraphy, and grain size analysis for sand control requirements.
The success of the X-TDSD trial depends not only on reservoir properties, but also on the well and reservoir operating strategy. A clear plan for operating parameters and real-time surveillance were incorporated into the project development plan. Permanent production and injection monitoring are included, to facilitate systematic adjustment of the well parameters. This aims to optimize steam chamber development during the pilot's operating life. Flexibility was incorporated in the wells and facility design to accommodate the six planned modes of operation, as described later.
This paper will focus on the design details, which required integrated input from several disciplines.