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Borehole-Image Log Interpretation in the Wara and Burgan Palaeotransport System, Greater Burgan Fields, Kuwait
(1) Field Development Group (S&E Kuwait), Kuwait Oil Company, Ahmadi, Kuwait.
(2) Data and Consulting Services, Schlumberger, East Ahmadi, Kuwait.
The Wara and Burgan Sandstones are a major oil producer in Kuwait. In our study, the formations have been characterized using cores, borehole images and open hole log data from 16 wells. Five lithofacies were determined: (1) massive, cross-bedded and low-angle sandstone units; (2) structureless, cross-bedded and low-angle argillaceous units; (3) interbedded sand and shale heterolithic units; (4) structureless and laminated shale units; and (5) undefined carbonate units.
The palaeotransport direction was analyzed separately for the Wara Sandstone and four Members of the Burgan Sandstone, which are the 3 Sand Upper (3SU), 3 Sand Middle (3SM), 3 Sand Lower (3SL) and 4 Sand (4S). Results showed bi-modal and tri-modal distribution of palaeocurrents for some intervals, in agreement with previous interpretations for this field. For the first time, we have identified a main source of sediment from 1350 (40% of the footage) and 2500 (32% of the footage) with a high variation (standard deviation = 1200) for the Wara Sandstone.
In 3SU member of the Burgan Formation, 150 was the dominant palaeocurrent direction (45% of the footage), whereas in member 3SM, the palaeocurrent direction is toward the 450 (50% of the footage). In member 3SL, palaeocurrents show a trimodal distribution, with the main trends towards 600 and 100 (40% of the footage) and a minor trend towards 2800 (29% of the footage). Finally in member 4S, the main palaeocurrent direction is towards 650 (49% of the footage).
Eighteen faults were identified with strike azimuths that range from 3100 to 3450 and dip azimuths that range from 2200 to 2550 (72% of the footage). The NW-SE strike azimuth fits well with the structural trend of the Greater Burgan fields, which consist of three giants Burgan, Magwa and Ahmadi fields.
The combination of fault (NW-SE trend) and palaeocurrent distribution (mostly with a NE trend) compartmentalizes the reservoir.