Enhancement of the Economics and Safety of PMCD Operations

Managed Pressure DrillingApplication AnswersEnhancement of the Economics andSafety of PMCD OperationsChallengePressurized mud-cap drilling (PMCD), one of a number of discrete variants of managed pressure drilling(MPD), allows drilling to continue during conditions of severe or total fluid losses in highly depleted orcavernous formations. A characteristic of this technique is the need to kill the well before pulling thebottomhole assembly (BHA) out of the hole, often a lengthy and expensive process, especially if severaltrips are required. The challenge is to provide a means of tripping pipe without the need to kill the well,thereby improving both the safety and the economic aspects of the operation.Use of the downhole deployment valve (DDV ® ) tooleliminates the need for killing the well to make trips andallows safe and efficient installation of anirregularly shaped BHA.ConstraintsWhen drilling wells using PMCD techniques, inmany cases wells which had been undrillableuntil the advent of this technology, severalconsiderations must be examined:• While losses of sacrificial drilling fluids (typicallywater or sea water) are understood, the loss ofthe annular viscous mud cap will occur whentripping pipe and this occurrence can be anextreme economic disadvantage.• A rotating control device (RCD) is required toseal around the tubular to allow fluid injectionunder pressure.• Adequate sources ofwell control fluids mustbe maintained. Duringoffshore operations, thesacrificial fluid is normally seawater, but water supplies in onshoreoperations may be inadequate, resulting inexcessive fluid costs.• The need to kill the well prior to pulling pipeshould be eliminated in order to improve theeconomics of the process.• The need for snubbing operations must beeliminated, if possible, to improve personneland operational safety, as well as to optimizeoverall economics.© 2008-2010 Weatherford. All rights reserved.

Managed Pressure DrillingFeatures, Advantages and Benefits• The DDV ® tool performs the function ofa downhole lubricator, enabling the safeinstallation of long and complex assemblies into,and retrieval from, the well.• Using the DDV tool saves the time requiredto kill the well and maintains the well duringtripping. This improvement trims operational timeand reduces the use of kill fluid, benefiting welleconomics.• When tripping out of the hole, the pipe is pulledwith stripping techniques while using an RCD toa point above the DDV tool, but below the pipelight point. The valve is then closed and testedby bleeding off above the valve. The surfacepressure is brought to zero and the pipe trippedat conventional rates under fully safe operatingconditions.• When running in the hole with an irregularlyshaped BHA, the BHA is tripped normally to theDDV tool depth. The mud cap is reestablished,as needed, and the casing pressured to equalizeacross the valve. The valve is then opened andthe BHA run to bottom in “pipe heavy” conditionswhile using standard stripping techniques.• Thus, both tripping out of and into the hole ismuch faster and safer with resultant economicimprovements.• BHAs and tubular materials are handled atsurface with conventional techniques, enhancingboth personnel and operational safety.• Running or pulling of the pipe below the DDVtool is done in “pipe heavy” conditions, therebyallowing all such operations to be performed withconventional stripping methods—the need forsnubbing is eliminated.• By eliminating the need for killing operations andpumping well control fluids to allow pipe tripping,a beneficial economic impact can be made interms of reducing fluid costs and the expenseof maintenance on the pumping equipmentnormally associated with PMCD operations.Operational Outline• Install the DDV tool as an integral part of thecasing, setting immediately above the problemzones, and cement in place with standardmethods.• Run cleanout string; drill out cement and floatshoe.• Leave the DDV tool in the open position and drillahead until the need for PMCD is established.• Establish PMCD conditions and drill ahead untila trip out of the hole is needed.• Using standard stripping methods, pull the BHAto a point above the DDV tool.• Close the DDV tool by applying pressure tothe closing line and then test the DDV tool bybleeding off above it.• Bleed off surface pressure and trip the drill stringat standard trip speeds.• Change the BHA, as necessary, and run innormally to a point directly above the DDV tool.• Establish mud cap, as needed, and pressure upthe casing and pipe to equalize across the DDVtool, and then pump through it.• Apply pressure to the opening line to open theDDV tool; run the BHA to bottom and continueoperations.3© 2008-2010 Weatherford. All rights reserved.

Managed Pressure DrillingSecure Drilling SM services: offering an alternative to conventional drilling methodswhen drilling hazards, formation damage and speed are of particular concern.Our Secure Drilling services incorporate several drilling techniques—including air,managed pressure and underbalanced drilling—and associated technologies tooptimize drilling performance, minimize formation damage and mitigate hazards.The no-snub, no-kill answer.weatherford.comWeatherford products and services are subject to the Company’s standard terms and conditions, available on requestor at weatherford.com. For more information contact an authorized Weatherford representative. Unless notedotherwise, trademarks and service marks herein are the property of Weatherford. Specifications are subject to changewithout notice. Weatherford sells its products and services in accordance with the terms and conditions set forth in theapplicable contract between Weatherford and the client.© 2008-2010 Weatherford. All rights reserved. 5807.01