December 2002, further work from this project is continued as Project 463

Purpose of the project is to obtain data that describes shear rams capabilities for shearing drill pipe that is used while drilling a well. This study was designed to answer the question “Can a given rig’s BOP equipment shear the pipe to be used in a given drilling program at the most demanding condition to be expected?” Briefly, this can only be demonstrated conclusively by testing. Seven of the fourteen cases in this mini-study opted not to test to confirm capabilities; another had insufficient data to draw a definitive conclusion. Of the seven tested, five successfully sheared and sealed (71%) based on shop-testing only. If operational considerations of the initial drilling program were accounted for, shearing success dropped to three of six (50%). Based on the results obtained, two of the rigs modified their equipment to enable shearing and sealing on the drill pipe for their program.

This mini-study examines data from physical tests that were conducted on shear ram capabilities. The purpose of this study was to get a snapshot of shearing capabilities of rigs that are working on the OCS (subsea BOP’s). The data contained in this mini-study was obtained during rig acceptance work from 7 drilling rigs that are capable of drilling in water depths between 450 feet and 10,000 feet. The continuation of this project can be found in Project Number 463, Shear Ram Capability Study (West Engineering Services) and further describes BOP manufacturers’ use of the Distortion Energy Theory shear equation to predict the forces necessary for pipe shearing.

The study discusses the following:

	The Shear-Blind Ram test procedures contained in API Spec 16A
	The testing procedures and acceptance criteria used to conduct the shear tests.
	Additional pressures that should be considered for shearing pipe.
	Findings:
	5 of 7 rigs successfully sheared pipe and sealed the well bore in shop tests (or 2 of 7 failed).
	When operational considerations were accounted for, shearing success dropped to 3 out of 6.

Other Observations:

	West was involved in acceptance reviews on 14 rigs, 7 of those rigs did not examine shearing capabilities.
	2 rigs modified their BOP equipment after testing the shearing capabilities.
	The drill pipe referenced in API Spec 16A is not representative of that used on 5th generation drilling rigs. That pipe in use is generally heavier and thicker.
	Old and new drill pipe (of the same grade) may take differing pressures to shear.
	West wrote "It appears that at least some of the rigs currently in operation have not considered critical issues necessary to ensure that their shear rams will shear the drillpipe and seal the wellbore."

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Last Updated: 08/11/2008, 07:53 AM