Fault Patterns in Benin River and Makaraba Fields: A Regional Play Type for the Niger Delta: ABSTRACT

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Using 830 km{sup 2} of excellent 3-D seismic data, we determined the fault patterns that are responsible for hydrocarbon entrapment in the Benin River and Makaraba fields, onshore northwestern Niger Delta. Both fields are trapped downthrown to the major listric GbokoMaka growth fault system, which trends E18{degrees}S for over 40 km, and has at least 2000 m of displacement to the southwest. Several major splay faults break off the main trend in a southeasterly direction, creating a series of fault-bounded structural compartments. Each of these compartments opens to the southeast and has a structural attic at the junction of the splay fault with the main fault trend. These compartments create large-scale traps for hydrocarbons migrating from east to west up the gentle regional dip within the Miocene Ughelli depobelt. The Benin River field is trapped in the major compartment between the GbokoMaka fault and the Benin River splay fault. The large Makaraba field is similarly trapped between the GbokoMaka and MakaWest faults. Such traps require an upthrown fault seal at the master fault and a downthrown fault seal at the splay fault. In the Makamba field, the trap potential is enhanced by rollover into the GbokoMaka fault. The same structuralmore » style is also evident along several other major fault trends to the north and the south, and probably represents an important play type in the onshore western Niger delta.« less