Mikuyu: Invictus Can ‘Feel’ the Oil, but Can’t Evaluate It

Invictus Energy’s Mukuyu-1 wildcat, onshore Zimbabwe, has drilled through sequences the company considers highly prospective.

But the operator can’t run wireline tools to determine the extent of hydrocarbon accumulations because of the deterioration in the hole at the much desired, deeper section.

The option now is to sidetrack the hole: plug back the existing 8½” wellbore section to seal off hydrocarbon zones and leave the well in a safe state prior to and commencing the re-drill of the upper 8½” hole section to approximately 3,500metres Measured Depth (MD).

The London listed explorer says that its first well in Zimbabwe’s Cabora Bassa Basin was successfully deepened to 3,923 metres MD, “encountering additional elevated gas shows and fluorescence through to total depth”

Mudlog (pre-wireline logging) results of the Upper Angwa formation, suggest it is thicker than pre-drill estimates with a potential for thickness of over a 900metre gross interval, h which, the company says, “bodes well for future prospectivity in the Cabora Bassa Basin”.

But after “reaching TD, the borehole was prepared to run wireline logs, however, due to a deterioration in borehole conditions, the tools were unable to pass below a depth of approximately 3,030mMD where the primary fluid sampling targets are located. As there is likelihood of losing tools and not meeting the objectives of the well, the decision has been made to sidetrack^ the Mukuyu-1 well in order to complete our evaluation and obtain a fluid sample”.

Forward plan Exalo Rig 202 is preparing to plug back the existing 8½” wellbore section to seal off hydrocarbon zones and leave the well in a safe state prior to and commencing the re-drill of the upper 8½” hole section to approximately 3,500mMD. This will provide sufficient information to calibrate the deeper sections of the original Mukuyu-1 wellbore. The sidetrack well (Mukuyu-1 ST-1) will be drilled to a slight updip location to the north of Mukuyu-1, with a lower mud weight and solids content mud system (approximately 1,500psi reduction in overbalance), which will improve the logging conditions and chances of successfully obtaining a fluid sample. Following conclusion of sidetrack drilling, the well will be logged, including wireline formation testing, with final results to be provided. The Mukuyu-1 ST-1 well will then be suspended for potential future testing.