top show signs of a leak, the well is still substantially full of drilling mud near the bottom of the well, and the drill pipe is in a better position, near the bottom of the well, to control the leak and begin repair operations.

Observation 2.6: The use of a production liner rather than the long string could have allowed for the use of a rotating liner hanger to improve the chances of good cement bonding; allowed for the use of a liner top packer to add a barrier to annular flow near the bottom of the well; allowed for the omission of the differential fill tube, which would remove a potential failure mechanism for the float collar; potentially made the negative test simpler to conduct and interpret; and configured the well to better control and repair a leak in the liner by leaving the well filled with drilling mud to a greater depth and by placing the drill pipe at a greater depth in the well during the test.

RECOMMENDATIONS

Margins of Safety

Summary Recommendation 2.1: Given the critical role that margins of safety play in maintaining well control, guidelines should be established to ensure that the design approach incorporates protection against the various credible risks associated with the drilling and completion processes.

Recommendation 2.2: During drilling, rig personnel should maintain a reasonable margin of safety between the ECD and the density that will cause wellbore fracturing.

There is no standard for this margin of safety. As a guide until a reasonable standard is established, industry should design the ECD so that the difference between the ECD and the fracture mud weight is a minimum of 0.5 ppg. In the event that a sufficient margin of safety cannot be maintained, the open section of the well should be plugged and alternative drilling or completion methods used in which the required safety margin can be maintained. Additional evaluations and analyses should be performed to establish an appropriate standard for this margin of safety.

Verifying Barrier Integrity

Summary Recommendation 2.3: All primary cemented barriers to flow should be tested to verify quality, quantity, and location of cement. The integrity of primary mechanical barriers (such as the float



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