This project is to review and compare manufacturer’s shear testing criteria and results, review equipment failures, review ram configurations, and make recommendations. WEST was commissioned by the United States Minerals Management Service (MMS) to perform the Shear Ram Capabilities Study. The main goal of the study was to answer the question “Can a rig’s blow-out preventer (BOP) equipment shear the pipe to be used in a given drilling program at the most demanding condition to be expected, and at what pressure?” Shear rams may be a drilling operation’s last line of defense for safety and environmental protection. The Code of Federal Regulation, Title 30 Mineral Resources, diverter and BOP are a requirement for drilling operations to proceed safely and environmental responsible. Therefore, on operator is responsible to assure the BOP shear rams will reliably shear the drill pipe in the particular operational conditions. Drill pipe properties have been improved to support drilling operations, last longer and reduce probability of drill pipe failure. The improvements in drill pipe properties particularity increased material strength and ductility have also resulted in higher forces required to shear the drill pipe. Drill pipe diameter and wall thickness is periodically optimized, requiring increased diligence concerning shearing ability. Increased water depths in combination with drilling fluid density and shut-in pressure contribute to a BOP having to generate additional force to affect a shear. Data from three BOP shear ram manufacturers and one drill pipe manufacturer were collected for analysis in the study. Drill pipe mechanical properties considered significant in the study were yield strength, ultimate strength, and ductility. Indictors of the ductility are Charpy Impact and Elongation% values where higher values generally indicate increased ductility. The Distortion Energy Theory shear force equation is discussed throughout the report and is as follows:

      F=0.577xSYxArea

      Where: SY = drill pipe material yield strength (PSI)

      [Area = cross-sectional area of the drill pipe, (SQ. INCH)]

The Distortion Energy Theory shear equation method, while being reasonable, was found not to consistently predict the highest actual shear forces.

Actual and Calculated Shear Force vs Elongation, sorted by Pipe Grade and then cross sectional area.

Actual and Calculated Fit Shear Force, S-135 Material, Sorted by the cross sectional area of the Drill Pipe.

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