Field-Development-Plan Optimization of a Giant Field for Recovery Improvement

Abstract

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 171770, “Field-Development-Plan Optimization of a Giant Field for Plateau Extension and Recovery Improvement,” by Youcef Azoug, SPE, and Harshad Patel, Zakum Development Company, prepared for the 2014 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 10–13 November. The paper has not been peer reviewed. To optimize the development plan of a giant carbonate reservoir offshore Abu Dhabi to extend the production plateau and improve recovery, detailed sector models were used to facilitate the large number of required simulation runs. The findings from those sector models were then incorporated in the full-field model (FFM). An optimized field-development plan is proposed, involving an infill drilling strategy and corresponding injection strategy. The injection strategy includes optimization of the future target reservoir pressure, to achieve the best field performance. Introduction The giant field discussed here was discovered in the 1960s. It is located offshore Abu Dhabi and is one of the largest oil fields in the world, covering an areal extent of 1200 km2, with an expected operating life exceeding 100 years. To ensure effective depletion of all regions of this very large field, the field has been managed by subdividing the reservoir into smaller regions. Fig. 1 shows a plan view of the reservoir and its subdivisions. The main crestal area of the reservoir is divided into 80 patterns. A target production rate has been established for each subdivision on the basis of the oil in place in that pattern/region. Sector-Modeling Description and Strategy Because of the large size of the FFM, long execution time is required; 5 to 6 days are typically required for each full simulation prediction case. A large number of predictions are needed to optimize development in such a large area. Therefore, to enable many runs in less time, this study was carried out with a combination of three tools: the FFM, 2D sector models, and 3D sector models. Optimizing Vertical Well Placement Vertical well placement in the reservoir is critical and guided by the water movement. The objective is to choose the best layers for the maximum-reservoir- contact (MRC) horizontal-well placement to ensure the best sweep efficiency and delay water breakthrough at the producers. Several 2D sector models were created from different areas of the reservoir to study the water movement. In both the high-permeability and the low-permeability areas, the study concluded that the best placement for the horizontal drains for producers and injectors is in the bottom layers. This placement delayed water arrival and improved oil sweep.