Chemical and optical studies carried out on the Kudu 9A-2 and Kudu 9A-3 boreholes revealed that two major intervals of Aptian-Barremian source shales are present below 3800 m and are analogous to oil-prone source intervals in the offshore Bredasdorp basin south of Mossel Bay, South Africa. The intervals were originally wet gas- to oil-prone although, as a result of the high palaeotemperature gradient, they have reached an advanced level of maturation and presently retain only some dry gas potential. Burial history studies show that oil may have been expelled from the shales during the latest Cretaceous and earliest Tertiary and that immediately succeeding structural movements allowed oil to escape updip. Any remaining oil was cracked to gas and wet gas-prone kerogen converted to gas by additional maturation supplied during further burial. The hydrocarbons that were encountered in the reservoir sands in the boreholes were, however, essentially dry. It is therefore quite possible that some, or all, of the gas presently retained in the reservoir formed by the thermal breakdown of pre-existing oil. There is also a possibility that some oil and wet gas could have escaped from the trap and been trapped further updip.