Abstract The Bight Basin is a major frontier basin of Jurassic-Cretaceous age, which is currently undergoing renewed exploration interest. Although only limited data is available for understanding the petroleum systems in the basin, several observations indicate that poor fault seal integrity may represent a key exploration risk. The presence of a paleo-oil column in the Jerboa-1 well, interpreted gas chimneys, oil slicks, and asphaltite strandings indicate that seal failure caused by fault reactivation is potentially a significant issue in the Bight Basin. Thus, in this study, we investigated the likelihood that faults in the Bight Basin will undergo sufficient structural reactivation to induce fault seal failure, under the regional in-situ stress field. Fault reactivation risk was assessed for two sets of faults that represent extensional events of Late Jurassic (Sea Lion faults) and Late Cretaceous age (Tiger faults). Analysis of in-situ stress data suggests that the region is currently under a strike-slip or normal stress regime. Interpretation of borehole breakouts from six wells indicates the average maximum horizontal stress orientation is 130°N. Although the magnitudes of the three principal stresses could not be unequivocally constrained, plausible ranges of values were determined based on well data. Pore pressure in wells in the region is hydrostatic except in Greenly-1, where moderate overpressure occurs. This study assesses the risk of fault reactivation using the fault analysis seal technology (FAST) technique. The FAST technique evaluates the increase in pore pressure (AP) required to cause reactivation as a measure of fault reactivation risk. In all cases investigated, faults striking 40(±15)°N of any dip are the least likely to be reactivated. Thus, traps requiring such faults to be sealing are the least likely to be breached. Fault reactivation risk for the strike-slip and normal stress regimes have been plotted in map view on a series of fault orientations for the Sea Lion and the Tiger faults using a range of hypothetical dips. The results for these hypothetical dips clearly demonstrate the importance of knowing both the strike and dip of a particular fault when conducting a three-dimensional fault seal analysis, because the risk can range from relatively low risk at 25° dip to relatively high risk at 70° dip, with differences being more significant for certain fault orientations.

The Sheeprock Mountains are part of a horst of Proterozoic, Paleozoic and Cenozoic sedimentary and igneous rocks located in the transitional region between the Cordilleran fold-thrust belt and the hinterland in the Basin-Range province of west-central Utah. Prominent structural elements in the Sheeprock Mountains are the Sheeprock Thrust, juxtaposing Proterozoic rocks above Paleozoic ones with a stratigraphic separation exceeding 10 km; the Pole Canyon Thrust, thought to be an upper plate imbrication of the Sheeprock Thrust; the Pole Canyon Anticline, a recumbent fold vergent to the northeast and cut by the Pole Canyon Thrust; the east-northeast-striking Indian Springs (tear) Fault; and two low-angle normal faults (the Harker and Lion Hill Faults) which together account for stratigraphic omission of several kilometres. The Pole Canyon Anticline is thought to have developed in the late Mesozoic during propagation of the thrusts parallel to the Indian Springs Fault, and this transport direction is corroborated by minor structures. Fault geometry suggests that the Harker and Lion Hill Faults are younger than the thrusts and probably of late Cenozoic age, although some mid-Cenozoic or even earlier displacement cannot be entirely ruled out. My preferred interpretation of the structural history of the Sheeprock Mountains is consistent with minimal regional extension before the mid-Cenozoic and with the view that crustal shortening in the fold-thrust belt is for the most part unrelated to hinterland extension.

Abstract All of the petroleum accumulations discovered to date in Côte d’Ivoire are along west-northwest to east-southeast trending anticlines bounded by normal faults known as the Lion, Foxtrot, Espoir, and Quebec highs. An analogous positive structural feature, the Grand Lahou high, exists in 1500m+ water depths. Basinward of the Grand Lahou high is the Grand Bassam sub-basin, which may contain rich deep water source rocks and reservoirs. The oldest known reservoirs are Aptian/Albian clastics, which grade up-section from lacustrine to marginal marine. Later Albian and Cenomanian fluvial and shallow marine sediments form additional reservoirs overlying an unconformity dated at 98 Ma. Slope canyon systems did developed during Coniacian time. Additional deep water clastic reservoirs are deposited in Coniacian, Santonian, Campanian, and Maastrichtian times. Less well-developed slope canyon systems have formed reservoirs during the Miocene. Gas prone source rocks have been encountered in middle Albian shales. Oil prone source rocks have been encountered in upper Albian marginal marine shales, upper Albian shallow water limestone, and Cenomanian/Turonian shallow marine shales. Oil geochemistry suggests the presence of a fifth source rock, most likely Albian-Aptian lacustrine shale. Oils reservoired in the western part of the basin appear to originate from lacustrine and marine sources, while oils reservoired in the eastern part of the basin are from exclusively marine source rocks. Future deep water discoveries may be found along the Grand Lahou High or in deeper basinal areas of the Grand Bassam sub-basin. Trap types and reservoirs along the Grand Lahou high would be similar to those found in shallower water along the Lion-Quebec high, consisting of Albian and Cenomanian fluvial and shallow marine sandstones in fault and stratigraphic traps on Albian highs. Other potential accumulations may be found in stratigraphic traps associated with Campanian through Maastrichtian slope canyon systems, which have been identified in shallower water. These same canyon systems feed into the Grand Bassam sub-basin, and may compose slope canyon and basin floor fan sand reservoirs.