Environmental Statement - Maersk Oil

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Balloch Field Development Environmental Statement
Section 2 Proposed Development
and when required. The BOP is made up of a series of hydraulically‐operated rams that can be closed
in an emergency from the drill floor and also from a safe location on the rig.
2.4.5. WELL DESIGN
A detailed well design and completion strategy has yet to be finalised for the Balloch production
wells. However, each well is expected to follow the design outlined in Table 2‐7 and Figure 2‐10.
Table 2‐7 Balloch well completion details.
Hole section Depth (MDBRT in ft) Section length (m) Drilling fluid
36” 815 71 Seawater with viscous sweeps
17½” 3,092 694 Seawater with viscous sweeps
12¼” pilot* 9,630 1,993 OBM
12¼” 9,006 1,862 OBM
8½” 9,220 61 OBM
*The 12 ¼” pilot hole will only be drilled in the appraisal well / initial production well.
The top hole section (36”) of the wells will be drilled with seawater and hi‐vis sweeps to an
approximate depth of 815 ft measured depth below rotary table (MDBRT) and a 30” x 20” conductor
will be set and cemented. The 17½" section of the well will be drilled directionally with seawater and
hi‐vis sweeps, building to approximately 15 degrees inclination by total depth at 3,092 ft MDBRT. A
13 3 /8 ” casing will then be run and cemented in place.
A 12¼” appraisal pilot hole is planned from the 13 3 /8 ” shoe as part of the first production well. This
will be drilled using +/‐ 11.4 ppg Versaclean Oil Based Mud (OBM) and logged. The well will be drilled
to an angle of 38 degrees. Target depth (TD) of the pilot hole is currently planned at +/‐ 10,040 ft
measured depth (MD). The pilot hole will then be abandoned before setting a kick off plug across the
13 3 /8 ” shoe.
The main target 12¼” hole section will be drilled using +/‐ 11.4 ppg Versaclean OBM and logged. The
trajectory will gradually build angle, entering the top sand at 34 degrees at approximately 9,006 ft
MDBRT. The section will be secured with 9 5 /8” casing.
It is planned to continue drilling with +/‐ 10.9 ppg OBM and log with logging while drilling (LWD) in the
8½” hole to TD at the currently planned +/‐ 9650 ft MDBRT. A 7” liner will then be cemented.
It is intended to complete the well by perforating the 7” liner below a production packer tied back to
the surface with 4½” x 5½” tubing. The well will be completed with a gauge mandrill, chemical
injection feature, gas lift valve and sub‐surface safety valve (SSSV). Following completion, the well
will be suspended as per industry best practice and will await hook up for production. At this time
there are no foreseeable well interventions planned for the Balloch wells.
The Balloch wells will be drilled and completed in accordance with Maersk Oil’s Well Operations
Standards.