Abstract
Abstract
The field is a very mature field. 30 years after its production start-up, it is now producing with an average water-cut of 84 %. This paper presents the continuous adaptation efforts deployed throughout the years to further valorise resources, in response to the growing maturity of the field.
Well activation started very early, first through ESP's, then by full field gas-lift implementation. As an answer to an important depletion of some reservoirs, a water injection scheme has been implemented as early as 1979. In 1997, a major field revamping campaign was performed to implement an EOR technique which proved to be very efficient: tertiary gas injection after water flooding. After the first horizontal wells, drilled in 1994, ever increasing well architecture complexity allows now to target more and more precisely heterogeneities, to produce residual oil pockets, and to develop tight reservoirs. A 3D seismic acquired in 1995 has opened the path for quadruple and quintuple multilateral wells.
At the current maturity level, field management appears as the next challenge. The complex gas scheme, which comprises at the same time gas production, gas lift, gas injection, gas recompression and gas export, needs constant arbitration between activation gain and tertiary recovery.
In parallel, a global water management policy must be set up, as the water disposal network is more and more heavily loaded. A water management study is currently under the way, to review long term fluid production predictions, surface facilities limitations, and long term reliability of disposal well, and to screen for solutions, ranging from reservoir and well control to surface facilities de-bottlenecking.
Introduction
In 1972, one year after the creation of the UAE Federation, Total was granted a concession to develop a field offshore Abu Dhabi. At that time, the life span of the field was estimated to 15 to 20 years. Today, 30 years later, oil is still being produced, and will continue for many years to come. In order to achieve such a result, extensive and continuous efforts have been deployed throughout the years to further develop resources, in response to the growing maturity of the field. A remarkably large variety of means and techniques has been deployed all along its development to curb the production decline and extend the life of its installations, such as phased development, secondary reservoirs development, well activation, production mechanism optimisation, use of emerging technologies, understanding of heterogeneities, field management, equipment replacement and upgrading.
Background
The field is a large NE-SW anticline, affected by NW-SE trending faults. The stratigraphic sequence encountered comprises a thick calcareous platform succession from Permian to recent. Depositional environments range from shallow marine to supratidal. Limestone, dolomite, anhydrite and shale are the most common lithologies encountered. The field comprises 2 main reservoirs of Upper Jurassic Age, respectively called Upper and Lower reservoirs, one secondary reservoir of Lower Cretaceaous age, and one marginal, Middle Jurassic, reservoir.