Invictus Energy Ltd. identified a potential discovery in Mukuyu field from the Mukuyu-2 well in Cabora Bassa basin, Zimbabwe.
Mukuyu-2 was drilled to confirm a working hydrocarbon system in the basin and test multiple stacked targets within the greater Mukuyu structure to also confirm a commercial discovery (OGJ Online June 26, 2023).
Natural gas (predominantly methane and trace heavier hydrocarbons) was recovered to surface from the Pebbly Arkose formation. Wireline logging data from gamma ray, density-neutron, and resistivity has identified multiple hydrocarbon-bearing intervals in Upper and Lower Angwa reservoir sands, subsequently reaffirming moveable hydrocarbons observed during initial fluid sample clean-up, which showed gas and liquid hydrocarbons flowing through the onboard compositional fluid analyzer.
Formation pressure exceeded 5,000 psi in the Lower Angwa’s gas leg beneath 3,400 m MD. This pressure required an increase in mud weight to maintain control of the well and preserve well barriers while drilling. Connection gases were observed during drilling of this part of the hole section to total depth at 3,718 m MD. Also observed were high levels of trip gas. Well-control measures were required by increased mud weight which resulted in high overbalance in the shallower intervals of the hole section. This overbalance resulted in drilling fluid losses and formation invasion which led to high overpull to free the drill string and wireline tools, resulting in tool damage.
Due to the limited availability of replacement fluid-sampling tools and risk of successfully completing fluid sampling and remaining data acquisition in the current borehole, Invictus will plug back the existing 8 ½-in. wellbore section and conduct a simple vertical sidetrack from the 9 ⅝-in. shoe (at about 1,966 m MD). The vertical sidetrack is the best option to acquire valid fluid samples from the well and will facilitate conventional wireline logging operations.
Completion of a sidetrack will also allow the well to be suspended for future flow testing by running a 7-in. liner over this interval. Subsequent operations will have the option to drill out a 6-in. hole to evaluate and test the remaining portion of the Lower Angwa.
Exalo Rig 202 is preparing to drill the sidetrack. Following the conclusion of drilling the 8 ½-in. hole section, the well will be logged including wireline formation testing. The company anticipates that sidetracking and wireline logging will take 21-28 days, depending on drilling and logging conditions.
Cabora Bassa basin lies onshore in the Zambezi Valley in Muzarabani, 300 km northeast of Harare. The 250,000-acre SG 4571 license is in its second exploration period which runs to June 2024. Prospective resources are 20 tcf of gas and 845 million bbl of conventional gas-condensate.
Invictus is operator with 80% interest.