Gas recovery and wireline data provides confirmation of moveable hydrocarbons
Invictus reports that the exploration team has successfully recovered natural gas (predominantly
methane and trace heavier hydrocarbons) to surface from the Pebbly Arkose formation and continued pipe conveyed logging operations due to challenging borehole conditions.
Additionally Invictus says, wireline logging data from gamma ray, density-neutron and resistivity has identified multiple hydrocarbon bearing intervals in the Upper and Lower Angwa reservoir sands, subsequently reaffirming the moveable hydrocarbons observed during initial fluid sample clean-up which showed gas and liquid hydrocarbons flowing through the onboard compositional fluid analyser (CFA).
Prior to the fluid sampling in the Pebbly Arkose formation, analysis of the wireline logs interpreted the
presence of residual gas (low gas saturation below the net pay cutoff). The formation was targeted to
acquire a water sample to assist the calibration of resistivity data and calculation of gas saturation in
the below Upper and Lower Angwa formations.
The recovery of natural gas to surface from a primarily water bearing interval in the Pebbly Arkose
provides confirmation of the presence of hydrocarbons coupled with the wireline log interpretation of
hydrocarbon bearing reservoirs in the Upper and Lower Angwa formations and most importantly
signifies a potential discovery in the Mukuyu field (as per Society of Petroleum Engineers Petroleum
Resource Management 2018 definition section 2.1.1.).
Subsequent evaluation of the Upper and Lower Angwa
Higher than anticipated pressure in the gas leg in the Lower Angwa beneath 3,400mMD where
formation pressures exceed 5,000 psi which required an increase in the mud weight to maintain control
of the well and preserve well barriers whilst drilling.
Connection gases were observed during the drilling of this part of the hole section to Total Depth at
3,718mMD together with high levels of trip gas resulted in the implementation of well control measures
through raising of the mud weight to ensure the safety of the drilling and logging operations and
maintain well integrity.
The raising of the mud weight has subsequently led to high overbalance conditions in the shallower
intervals of this hole section which has resulted in fluid losses and formation invasion by the drilling
fluid which is evidenced by the high pump out volumes required to obtain fluid sample cleanup to
obtain representative reservoir fluid samples. High amounts of overpull are required to free the drill
string and wireline tools from several points along the wellbore resulting in tool damage, together with
holdups and obstructions in the wellbore is typically indicative of hole instability/breakdown.
Subsequent attempts to complete the fluid sampling program on pipe conveyed logging in the Upper
and Lower Angwa reservoirs and the remaining data acquisition program have been hampered by tool
failures. This is primarily related to the conditions, borehole deterioration and compounded by the
duration this hole section has been exposed since drilling of this interval commenced.
Due to the limited availability of replacement fluid sampling tools and risk of successfully completing
the fluid sampling and remaining data acquisition program in the current borehole, the Company has
carefully considered all options to achieve our objectives for the Mukuyu-2 well.
The Exalo Rig 202 is preparing to plug back the existing 8 ½” wellbore section and commence redrilling the 8 ½” hole section with more optimal parameters to approximately 3,400mMD above where the overpressure zone in the Lower Angwa commences.
The Mukuyu-2 vertical sidetrack will be more conducive for conventional wireline
logging operations including the fluid sampling to be conducted in the Upper Angwa and part of the
Lower Angwa reservoirs, providing favourable parameters for a more efficient and economic sidetrack
operation in comparison to the Mukuyu-1 sidetrack well.
The completion of the sidetrack will also allow for the well to be suspended for future flow testing through running the 7-inch liner over this interval and retain the ability to drill, evaluate and test the
remaining portion of the Lower Angwa in 6-inch hole in future operations.
Following the conclusion of the drilling the 8 ½ inch hole section, the well will be logged including
wireline formation testing and final results provided.
The Company anticipates the remaining activities to conduct the sidetrack and wireline logging to take
approximately 21-28 days depending on drilling and logging conditions and is currently funded to
complete these activities
A thorough assessment in conjunction with our service providers was conducted and determined that
plugging back the existing 8 ½ inch wellbore section and conducting a simple vertical sidetrack from
the 9 ⅝ inch shoe (at approximately 1,966mMD) would provide the Company the strongest opportunity
of acquiring valid fluid samples from the well.
Comments from Managing Director Scott Macmillan:
“Further evaluation results continues to reaffirm the presence of moveable hydrocarbons at Mukuyu-2,
evidenced by the recovery of natural gas from the Pebbly Arkose formation and further wireline logging
data interpretations obtained from the Upper and Lower Angwa reservoirs.
“Due to compounding sampling challenges, borehole conditions and well control measures the Company,
in conjunction with our service providers, have determined a simple vertical sidetrack will provide the
strongest opportunity to achieve our remaining Upper and Lower Angwa evaluation objectives.
“The Company is currently funded to conduct and evaluate the planned sidetrack operations, with the
completion allowing the well to be suspended for future flow testing.
I thank our shareholders for their patience as we conduct the sidetrack well and finalise the evaluation
program, I invite you to attend today’s webinar briefing to discuss the initial results and forward plan.”