Development of Low-Permeability Carbonate Reservoir by Use of Horizontal Wells in Mature South Umm Gudair Field in the Neutral Zone–A New Approach

Abstract

Abstract The South Umm Gudair (SUG) oil field located in the Neutral zone between Kuwait and Saudi Arabia has produced since 1968 from an active water drive carbonate reservoir of Lower Cretaceous age. The lower zones are homogenous intervals of higher permeability which appear to be sufficiently swept by natural water drive over a period of time. The upper zones of the reservoir are more heterogeneous and have lower permeability in the range of 50-150 millidarcies. These upper zones are relatively thin and are bound by tighter intervals that act as effective barriers to the natural water drive system. Due to the presence of barriers and low permeability intervals, these zones have been poorly swept resulting in significant volumes of by-passed oil remaining in these parts of the reservoir. The new approach of exploiting these reserves by drilling and completing 4 horizontal and 2 horizontal side track (HST) wells targeting the lower permeability portions of the reservoir in the SUG field since January 2004; have yielded considerable success in extracting significant incremental oil production with the added benefit of very low water cut. This success has led to field development plan to recover un-swept oil reserves from these low permeability zones. This paper summarizes the various aspects of field development plan taking into consideration geology, reservoir data and production data while highlighting the successes of the new horizontal and HST wells in the low permeability reservoir portions of the SUG field.