Study of casing design in controlled annular mud level drilling and synergy potential with drilling fluid technology.

摘要

Controlled Annular Mud Level (CAML), is a dual gradient drilling technology developed to face the challenges of drilling deep and ultra-deep water wells. It consists of a submersible system which includes a mud return line and subsea pump system in order to circulate the mud out of part of the riser. This allows to vary the mud level inside the riser as required to have a precise bottom hole pressure control. The empty level in the riser, reduces the hydrostatic pressure, and allows to use heavier drilling fluid density. The use of heavier drilling fluid generate a pressure profile that can allow drilling longer sections.;In this paper, a case study is done to evaluate how CAML drilling impacts casing design. Drilling fluid's density, casing seat depth, kick tolerance, burst, collapse and tension loads, riser collapse and u-tube effect are the main factors investigated to evaluate CAML potential and limitations for optimizing casing design. A sensitivity analysis is also done to evaluate how the fluid's rheological properties and flow rates impacts casing design, and how drilling fluid technology can be synergized with CAML drilling to improve casing design. The results show a great potential for CAML drilling in terms of reducing casing design costs and synergy with drilling fluid's technology.