Abstract
Through a tightly integrated collaboration between an operator and a service company, the world's northernmost horizontal well was successfully drilled and tested. Set in the Barents Sea at 73° latitude 350km from Hammerfest, this project de-risked a future commercial field development plan for the Wisting field, which holds some of the largest known oil reserves in the Barents Hoop Area.
All three major well objectives were achieved: (1) proving drillability by landing the horizontal well approximately 250m from the seabed (a record for subsea wells) and geosteering for 1400m across several fault blocks, (2) performing a well test within a long interval of reservoir exposure (over 460m) to prove the added productivity of horizontals, (3) acquiring appraisal information: reservoir data in new blocks, estimated oil / water contact (OWC), geomechanical properties, etc.
This well was outside the envelope achieved before, and such an extended reach drilling (ERD) operation required a customized well engineering approach at every step.
In addition, the hole design was adopted to cater for the drillstem test (DST) string. Different casing designs, string designs and operating parameters were screened in dedicated studies, looking at equivalent circulating density (ECD), torque and drag, hole cleaning, prior experience and contingencies.
A combined 3D subsurface, pressure and stress model was built, calibrated to drilling observations, core data and leak off tests and then used as input for subsequent studies (mud window, rock strength for drill ability).
The geometry required a constant 9°/30m dogleg from kickoff (no tangent section) to land at reservoir depth. Any interval where that performance was not achieved would have resulted in overshooting the reservoir (too deep).
An oil-based mud design was adopted for several reasons, and a dedicated lost circulation material (LCM) strategy established to manage potential losses in the reservoir matrix, in fractures or faults.
Important planning and operational considerations were given to safety and logistics, and no issues resulted in this remote and environmentally sensitive area.
The mud motor strategy selected after careful engineering simulations landed the well at the reservoir depth, before geosteering near-horizontally for the required 1400m. The partnership has gained invaluable information about the drill ability of such wells in Wisting.
Several fault blocks could be accessed with a long horizontal, giving a positive impact on the field economics.
