Investigating Fault Propagation and Segment Linkage Using Throw Distribution Analysis within the Growth Faulted Agbada Formation of Ewan and Oloye Fields, Northwestern Niger Delta
Throw distribution analysis of the key stratigraphic surfaces (sequence boundaries and maximum flooding surfaces) across fault has allowed detailed investigation of the tectonic history within the Ewan and Oloye fields, northwestern Niger delta. The structure in the studied area is dominated by a growth fault system that strikes east-west and dips basinward (to the south). The growth faults are characterized by broad convex-basinward plan-view geometry, decreasing in dip with depth. Generally, the faults are active down to 2000 m depth before they die out or sole into the underlying shale. The hanging-wall blocks of growth faults are deformed into broad rollover anticlines, with some synthetic and antithetic faults initiated from the anticline crests, and fault splays off major faults, further complicating these structures. Stratigraphic key surfaces within the syn-faulting succession range in age from 16.7 to 10.35 Ma.
Periods of maximum throw are established from 2-Dimensional throw distribution attribute maps recording throw of growth strata. Throw distribution for individual faults are variable, interpreted to be due to fault initiation propagation and linkage. Throw variations seen within the segmented faults indicate some general features such as:- i) throw typically decreases upwards, suggesting that the interpreted segmented faults are behaving as kinematically coherent system, ii) variation in the throw distribution occurs over time. iii) there is considerable variation in the throw distribution at different time interval (horizon interval for the whole fault system, iv) linkages between fault segments are achieved by tip-to-fault linkage. Within the growth interval, fault propagation and segment linkage (lateral and vertical) are important features of the fault system. Fault interaction and linkage may be due to constructive and destructive interference pattern of stress field distribution within the fields.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009