The business drive is to deliver projects as fast as possible in a prudent manner. Acceleration needs to be balanced against the risk of a sub optimal development. Parallel working on appraisal and project definition is one answer. This article describes some subsurface-surface interface processes used to accomplish this acceleration successfully. The development consists of a number of non-conventional fields characterized by deep often geo pressured carbonates encased in salt and charged with light but sour hydrocarbons. On primary depletion these reservoirs would only recovery a limited amount. Under a miscible gas flood with the right enrichment agents and pressures, the recovery can be significantly improved.
The Harweel cluster is a new oil province that has recently been brought on stream by Petroleum Development Oman (PDO).The cluster, see figure 1, which currently comprises 7 different fields containing 9 reservoirs, is located 80km south west of existing infrastructure at Birba. The cluster is being developed in a phased manner, see figure 2, in order to manage appraisal and deliver early production. One of the objectives of the 1st phase was to gather information to determine whether a miscible gas injection project would be feasible in these fields [references 1 & 2].Miscible gas injection will significantly increase production. Subsequent phases will involve full field primary development followed by the stepwise implementation of miscible gas flooding. The first phase has demonstrated the viability of miscible gas flooding from the information gathered. The second and third phases of the project have been selected and defined through the information gathering phase from Phase 1.
The development consists of a number of non-conventional fields called "the stringers" due to their appearance on seismic and geological cross-sections, see figure 3.The reservoirs are essentially Pre-Cambrian heterogeneous carbonate slabs floating and encased in salt and charged with light but sour hydrocarbons. On primary depletion these reservoirs will only recover some 10% of the oil in place. A successful miscible gas flood will potentially bring this up to as high as 50% of the volumes originally in place. However the inherent subsurface uncertainty, see figure 4, of these reservoirs needs to be narrowed to ensure feasibility and satisfactorily define a development. Further appraisal is required to underpin the feasibility of the proposal to all stakeholders.
