After suspending our operations in Azerbaijan in 2012, we resumed our drilling program on the offshore Absheron Block with the stated goal of bringing this gas field onstream early – by 2021 – and at lower cost through a concurrent and dynamic appraisal of the reservoir extension with a view to future development phases. To meet that goal, it was decided to build an Early Production System (EPS) well with two “branches”, one for appraisal and one for development, which will eventually be tied into our partner SOCAR’s existing facilities.
Drilling two wells in one
Located above a deeply-buried sandy reservoir, the operational zone features complex geology, which we had already encountered in 2011 when we drilled the ABX-2 exploration well (plugged and abandoned in early 2018). From that experience it made sense to opt for a two-in-one solution for drilling the high-pressure ABD-001 well to reduce the duration and hence the cost of achieving both appraisal and development objectives while also allowing to complete the well as early as possible.
Drilling began in May 2018 and was completed in November 2019 for a total duration of 552 days. Well ABD-001 consists of:
- An appraisal/downdip branch, targeting reservoirs Fasila B and D in the down-dip to the northeast to identify the fluids contact interfaces and better delineate the extent of the reservoir for subsequent development phases, down to 7,411 m.
- A development/updip branch, kicking off from the existing well to the Fasila B and D reservoirs and drilled in the up-dip to the southwest, from a depth of approximately 4,500 m down to approximately 6,803 m.
A drilling architecture of the highest complexity
Accordingly, the architecture of this well consists of no fewer than ten sections in the base case (when considering both branches), with extremely limited clearances and tolerances for the running of the various casings and liners.
To cross through a shallow pressurized “fizzy water” layer at approximately 900 m subsea, a dual gradient MRR (Mud Recovery without Riser) System was successfully utilized for drilling and for the subsequent 22-inch casing operations. The existence at approximately 3,000 m subsea of a barrier of poorly-consolidated creeping/flowing shale called for rapid isolation to prevent inflows, loss of the drilling assembly and to ensure the well’s structural stability.
In both branches of the well, variations in the reservoir pressure increased the risk of differential sticking of the drill string due to uneven pressure distribution around the drill pipe. The first branch proved to be particularly challenging, however after changes to specific mud properties and applying certain drilling techniques, the branch objectives were eventually met, and in the process breaking the record for being the longest well ever drilled in the Caspian Sea (7,411m).
Representing Total’s first subsea completion in Azerbaijan and an excellent achievement, the subsequent development branch was drilled and completed with minimal non-productive time (NPT).
The Absheron project challenges in Azerbaijan
- The Caspian Sea is a landlocked body of water, and therefore there is a short supply in the number of rigs suitable for high-pressure drilling and able to operate to drill to depths up to 7,500 m. This constraint forced us to utilize a new build semi-submersible rig operated by a local rig contractor which we were not familiar with.
- With the project being fast-tracked, there was a tremendous amount of effort from the team to be ready for operations, including awarding as many as fifty new contracts and starting up a new logistics base ahead of equipment delivery, not to mention all the engineering required to drill and complete such a complex well.
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