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Technical Paper: Deepwater Batchset Operations Through the Magnolia Shallow Water Flow Sand
Paper 92289
Abstract
ConocoPhillips is developing the Magnolia field with a Tension Leg Platform (TLP) in 4674 ft of water in Garden Banks (GB) block 783 in the Gulf of Mexico. Three wells were drilled at the eventual TLP site to discover and appraise the field prior to sanction of the development plan. Field development plans required drilling an additional six wells at the TLP site where a shallow water flow (SWF) zone is present. The development plan included batch drilling and casing the SWF interval prior to deepening any of the wells to total depth.
The Magnolia batchset program was successfully conducted in 2002 using the Ensco 7500 dynamically positioned semi-submersible drilling vessel. The six well batchset program was drilled at less than the Authority For Expenditure (AFE) cost estimates with zero lost workday cases.
The batch set program included jetting 36 in. casing to 246 ft below mudline (BML), directionally drilling a 26 in. hole to 3264 ft BML while building hole angles up to 17°, and running and cementing 20 in. casing with verified cement returns to the mudline. The SWF sand interval was drilled and cased without “Top Setting” a cemented casing string above the SWF zone. Although individual exploratory wells have been drilled and cased without top setting casing previously, the Magnolia field is the first deepwater field with a SWF zone to be developed in this manner.
Pre-planning for the SWF zone addressed directional drilling issues, water base mud (WBM) design, cement formulation and placement procedures, and logistic supply to the drilling rig. Each well required three 89 ft joints of 36 in. casing, 81 joints of 20 in. casing, 40,730 bbls of blended WBM, and 6,760 ft3 of cement. Five supply vessels were used to provide logistic support for the operation.
This paper will focus on the extensive planning process and the operational aspects of performing a batchset drilling program through a SWF sand in a deepwater environment.
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