Field: Geographe (Otway basin)
Well: Geographe-4 ERD well (simulations were also utilized during drilling and completion of 4 other wells: Geographe-5, Thylacine North-1, Thylacine North-2 and Thylacine West-2)
Operation type: drilling and completions
Reservoir: normally pressured
Conditions: harsh to moderate
Location: Bass Strait, Southern Australia
Rig: Diamond Ocean Onyx (Victory class)
Case: dynamic rig heave limit calculated during well planning and utilized when Installing liners and completion strings
“Heavelock Solutions provided advanced dynamic rig heave limit modelling that enabled the engineering and operations team to have confidence the floated liner could be run to bottom. It was important to utilize the available weather windows and honour the geomechanical model to ensure wellbore stability and well control were maintained during operations. The operation was a success and the observations during the liner run matched the modelled expectation.”
- Paul Berry, Senior Drilling Engineer -
Beach Energy Limited
Beach Energy - Otway Basin
RISKS/CONCERNS
Drilling and completion operations in the Otway Basin are subject to moderate to harsh weather conditions. Concern for heave-induced surge and swab was flagged high in the risk register, particularly over the winter months. Accurate rig motion criteria were deemed to be required to lower the operational risk and to optimize the uptime, i.e. to reduce Waiting on Weather (WOW) and safely run the liners without wellbore stability issues, including a ~4400m floated 9-5/8” liner.
Risks - floated 9-5/8" liner installation
The following risks related to exceeding swab-surge margin were identified:
• Unable to circulate through the liner due to flotation of the string and thus minimal set-down weight available to run the liner to depth (+/- 30klbs string weight at TD expected). If the pressure margins had been exceeded and circulation into the liner required, it is very likely the string would not be recoverable and contingent side-track would thus be required
• Losses throughout overburden section requiring annulus to be re-filled
• Stuck liner, very likely the string would be have unrecoverable and contingent side-track of >3000 metres would be required in addition to fishing operations. Anticipated that it would have taken 20-25 days to get the well to a point to be able to re-run 9-5/8” liner
• Requirement to have high confidence the liner will run to bottom within a weather window where the geomechanical constraints would be honoured
TOILOR-FIT SIMULATIONS
Beach Energy recognized that Heavelock Solutions offered a very good business case - to utilize tailor-fit surge & swab simulations that would take into account rig heave motion, well trajectory, downhole pressure margins, well fluids, weather data at location, completion components, casingand well geometry as well as other parameters in order to determinetrue limits for rig heave throughout the whole operation.
CONCLUSIONS
Advanced surge & swab simulations from Heavelock Solutions provided tailored and fit-for-purpose weather criteria that reduced operational risks and potential NPT related to Waiting On Weather during installation of the floated 9-5/8” liner in the Geographe-4 well.
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