Facies analysis, sequence stratigraphy and hydrocarbon habitat prospectivityof the PindigaFormation and FikaShale, Gongolasub-basin, northern Benue trough, Nigeria

Abstract

Outcrop based sequence stratigraphic studies have been conducted on the Pindiga Formation and Fika Shale of the Gongola sub-basin, Northern Benue Trough, Nigeria. This has implications for hydrocarbon play identification in the basin especially at the intermediate temporal position where the poorly studied, recently delineated Sandy members occur. The approximately 600 m thick interval was subjected to detailed facies, depositional environment, and depositional trend analyses as well as marking out of major bounding surfaces based on 17 measured stratigraphic sections. Sequence stratigraphy analysis led to the delineation of one depositional sequence (DS), shared with the underlying formations and two complete 2nd order sequences using Depositional Sequence III model. Dark grey to black shales of the late Transgressive Systems Tract (TST) to early Highstand Systems Tract (HST) in the three Depositional Sequences constitute potential source rocks. Lowstand Systems Tract (LST) sandstones deposited in fluvial and tidal channels as well as bayhead delta make up potential reservoir rocks within DS2. The TST and HST of DS1 and DS2 contain potential reservoir rocks including tidal bar, estuary mouth and shoreface to nearshore sandstones. Potential intra-formational seals comprise the late TST and early HST mudstones of DS1, the early HST mudstones of DS2 and a regional top seal is provided by DS3, which consists entirely of the Fika Shale. These depositional sequences consist of varied lithologies and their relative temporal and spatial distribution promises high potential for further exploration in the basin.