Managed Pressure Drilling with Solids-Free Drilling Fluid Provides Cost- Efficient Drilling Solution for Subsea Carbonate Gas Development Wells

摘要

The development of the Kanowit Field in offshore Sarawak, Malaysia requires the drilling of two subsea development wells using a semi-sub rig. Previous experience identified the need for solids-free drilling fluid to ensure maximum reservoir productivity and so that the quality of the produced gas is within required specifications. High reservoir pressure requires the use of high-density solids-free drilling fluids, but associated costs and the high probability of losing large volumes to the fractured carbonate reservoir made this option unsuitable. A more cost-effective option was to use a less-dense solids-free drilling fluid and utilize managed pressure drilling (MPD) to be able to compensate for the difference in density with backpressure. MPD mitigated the loss circulation risk by controlling the level of overbalance to the minimum and MPD early kick and loss detection capabilities, used in conjunction with a statically underbalanced drilling fluid, also allowed for the collection of actual geopressure environment data that aided in the decision making process. Both wells were completed and tested with a maximum potential flow rate that exceeded the technical potential in initial projections. The successful deployment of MPD with solids-free drilling fluids proves its technical and economic feasibility in carrying out subsea development drilling through carbonate reservoirs prone to severe circulation losses.