Application of an Alternative Material to the Portland cement for the Cementing of Wellbore Top Casings of Subsea Wellhead
The Offshore Drilling Operations are moving to deep waters due to the continued demand for Fossil Fuels and the depleting Continental Shelf reserves. This has posed several new problems to the offshore or subsea engineers in the design of the various systems and equipment to be used for the exploration and exploitation of deep water resources due to harsh environmental conditions at deep oceans. One of the most affected systems due to this environmental condition is Subsea Wellheads or Subsea Wellhead/Conductor Systems experiencing more fatigue induced damage problems than their application in continental shelves. Subsea Wellhead serves as an access to the wellbore while the conductor is to sustain the wellbore integrity in all phases of an offshore field development until Plugging and Abandonment. In this paper, a case study on the application of alternate material, i.e. a Marine-Grade Resin for securing the wellbore top casings than the API Class G cement grout is studied at a deep water field named ‘Kikeh’ which is located offshore Sabah, East Malaysia in the South China Sea. This is to overcome various dis-advantages of the Portland cement in deep water oil/gas well applications. A model of a Semi-Submersible Drilling with Drilling Riser System was developed in ORCAFLEX to obtain the Bending Moment, Shear Force and the Effective Riser Tension at the mudline. The obtained results were then used to estimate the fatigue life of a De-Coupled 3D CAD Model of Soil – Wellhead/Conductor System developed in Creo Parametric 2.0 in ANSYS Static Structural Analysis Module. It has been found that the application of Marine-Grade Resin as an alternative return material is producing better fatigue life than placing the API Class G cement returns inside the annulus.