Oil-based fluids (invert emulsion fluids) have for many years been the fluid of choice for use in challenging hole sections. These fluid systems can bring many advantages, including optimal shale stability, low torque and drag, good resistance to contamination, and high drilling rates. One of the challenges of utilizing an invert emulsion fluid, however, has been the increasing level of environmental concern and legislation associated with its use. These challenges have driven the search for a high performance water-based fluid that will provide oil-based fluid performance and be environmentally acceptable in all offshore areas of the Egyptian Mediterranean Sea.

A novel, environmentally compliant high performance water-based fluid (HPWBF) system has been developed that has proven to be extremely inhibitive and highly lubricious.

Use of this new HPWBF system has helped operators to drill some of the most reactive shales in the Egyptian Mediterranean Sea while avoiding the high cost and safety risks associated with "skip and ship" operations. This performance is coupled with excellent cuttings integrity, increased temperature stability and good hole-cleaning properties. In the application of this system, the engineered approach matches fluid requirements with local clay characteristics, environmental regulations and operational objectives.

A HPWBF was chosen to drill Petrobel's well Karam-1 with a great success. The fluid was utilized to drill 334 meters of 12¼" hole section through the very challenging highly reactive formation of Kafr El-Sheikh stratum. The following conditions existed for this operation:

  • Fluid must be water-based to meet environmental stipulations

  • The shale section would be exposed for up to 10 days while logging

  • Bottomhole temperature is 230°F

  • Approximately 100 m 17½" rat hole existed below the 13 3/8" casing

This paper discusses the technical challenges and highlights the criteria for the proposed fluid system and the successes achieved in this well.

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