Design Testing of a Blowout Preventor and Controls System For Drilling in 1,000 Feet of Water
Authors: Peterman C.P. 
Published: December 2007

This paper describes the design considerations forselecting a blowout preventer control system and associatedhandling techniques required for drilling in 1,000 ft ormore of water from a semi-submersible drilling vessel. Design, manufacture, fabrication and assembly testing havebeen completed. This system is described and a summaryof test information is included. The control system is entirely hydraulic using eitherhose or remote pilot operated circuits, depending onresponse time required for each control. A steelwire-reinforced hose bundle was designed and built in onecontinuous length to allow operation without extra support orguidelines. Handling techniques have been developedwhich should allow the control equipment to be run andretrieved without pulling the marine conductor. A unique unitized triple ram blowout preventer unitwas designed and built so that the over-all height of thedrilling control wellhead could be reduced to allow it tobe used with existing vessels. Other components such asthe control panel, hose reel, kill and choke line assemblesand underwater hydraulic connectors are discussed.

Introduction

The problem was to secure a blowout preventer systemcapable of drilling in all water depths up to 1,000ft or more. Previously used control systems werereviewed to determine what blowout preventer experiencewas directly applicable and what modifications or newdevelopments would be required. In addition, this studytook into account the sea conditions existing along theWest Coast where this system will be tested. Maximumstorm conditions in this area include wave heightsexceeding 40 ft, current in excess of 3 ft/sec and windsin the range of 100 mph. Continuous operation underthese conditions is not a requirement, but the equipmentselected must survive the wave forces and rig motionwhich may occur during these storms. As explained inthe report, the primary control linkage between theblowout preventer stack and the vessel is to be attached tothe marine conductor. Successful operation of the marineconductor is assumed during the discussion of thisprimary control linkage. This report reflects the effects of sea environment onthe controls, reviews the developments required anddescribes the final system which is now awaiting drillingtests. This review places many of the significant designfactors for a subsea blowout preventer system andassociated operating techniques in one place. There maybe disagreement with the equipment and techniquesselected, but the effect of the severe environment (depthand sea conditions) on the design should be appreciated. Hopefully, additional design criteria concerning thevitally important blowout preventer operation will bepresented by others as it is revealed both by experienceand study. Analytical solutions for design problems were usedseveral places. Some of these data are to display theorder of magnitude to be expected rather than to be usedfor detailed design. In some cases data are restricted toa particular item, good only for that item but furnishingcharacteristics which may be expected from similar items. Many times, however, simple tests provided adequatedesign information with much less effort. For instance, fullscale tests of the control circuits were used to evaluatethe feasibility of remote, pilot operated hydrauliccontrols. Design data for the control hose bundle wereobtained by subjecting a full-sized prototype bundle tomaximum forces calculated to exist during actualoperation. Finally, full scale land assembly tests of theequipment were accomplished to further check handlingand operational characteristics.

General Description

The equipment to be used in this blowout preventersystem will be identified in ascending order, from thesub sea wellhead to the control equipment located on thedrilling vessel. A symmetrical four line system will beused to guide the blowout preventer stack and otherdrilling equipment to the wellhead. One of the basicdesign criteria was that the control system should be inplace and fully tested on the spider beams of the vesselbefore the stack was lowered into position. Theblowout preventer stack will normally be lowered andretrieved while attached to the marine conductor.

JPT

P. 1023ˆ