The Kudu 9A-2 and 9A-3 boreholes were drilled from 1987 to 1988 as follow-up wells to test the extent of the Barremian gas-bearing sandstones encountered in the Kudu 9A-1 well which was drilled in 1974. The reservoir interval is subdivided into a Lower Non-Marine (Lower Gas Sand) and an Upper Marine Unit (Upper Gas Sand). The former includes the main reservoir in Kudu 9A-3 where it is thickest and comprises a medium-grained anhydritic sandstone which is interbedded with terrestrial basalts and volcaniclastic deposits. The massive nature of the sandstones and the presence of high-angle cross-bedding, anhydrite and well-sorted and well-rounded sand grains, suggest an aeolian origin, perhaps in a coastal dune complex. The vertically and laterally associated basalts and volcaniclastic deposits also show features of subaerial deposition. The volcaniclastic sandstones contain a high proportion of well-rounded and well-sorted sand grains in a red iron oxide-stained matrix and similar sand penetrates cracks in the extensively oxidised tops of the basalts. The thickness variations of the aeolian sandstones may relate to the control exercised on their deposition by the basalt topography. The Upper Marine Unit comprises alternations of very fine- to medium-grained sandstone, conglomerate, calcareous claystone, limestone and siltstone which were deposited in nearshore environments as evidenced by the abundance of shell fragments and the trace fossil Ophiomorpha. In addition, high-energy sedimentary structures together with conglomerates and carbonaceous material suggest periodic fluvial sediment supply to the shoreline. The facies that comprise the Lower and Upper reservoir sandstones both have the potential for extensive lateral development.