An Assessment of Conductor Casing Design in Relation to a Titled of Offshore Monopod Fixed Platform

Abstrak

Refer to several sources of SNI, API, Canada nor US Regulations; an overall definition of conductor casing is not only designed as a large pipe to support the well, wellhead and completion equipment and hole stability for initial drilling operation, but also as a conduit pipe to allow circulation of drilling cutting to surface. In most practice of drilling through an offshore fixed platform, conductor pipe is set by driving with hammer, where the depth is set whenever blow per foot (BPF) of driving has reached 80% of hammer capacity, or the force of hammer has reached 80% of conductor strength. This practice does not assess formation integrity below conductor pipe, to assure strong enough to support circulation of drilling cutting throughout surface drilling section operation or not; but have assured as a competent rock to support drilling operation until production life. Practically, a requirement of formation integrity below conductor casing shoe to allow circulation is not an ultimate criterion to be achieved for drilling operation, unless if any shallow gas risk from the geophysical survey result. In relation to common fixed platform condition, conductor casing for a well shall be designed independently from the platform structural integrity. However, a case for Monopod Fixed Platform; position of conductor depth has taken critical impact to the platform integrity during drilling operation. Conductor shall be set deeper enough to case weak formation to assure no loss circulation during drilling, as the loss circulation will obstruct formation integrity that hold the monopod's structure. The impact of loss circulation to the structural pipe of Monopod was outstanding, and abnormal or never happen in the past for similar drilling operation. This paper contains comprehensive discussion of conductor casing requirement for the safest and the most economic drilling operation until end of production life without jeopardizing fixed monopod platform integrity and regulation compliance from various reference of conductor casing requirement, also will debrief drilling loads consideration in existing designing method of Monopod Fixed Platform and recommendation or room improvement from drilling operation side for future designing method of Monopod Fixed Platform to anticipate shallower conductor casing setting depth for drilling.