Managed Pressure Drilling fills a key void in the Evolution of Offshore Drilling Technology

摘要

This paper speaks to offshore applications of specializedrnequipment developed for the practice of underbalancedrndrilling (UBD) where the intent is not to achieve a true staternof underbalance at any point in a well’s drilling program. Thernintent is not to produce hudrocarbons while drilling ahead.rnInstead, the intent is to apply well-proven UBD tools andrntechnology for the purpose of more precisely managingrnwellbore pressure(s) and annulus returns while drillingrnoverbalanced in marine environments.rnSuch technology as been coined Managed PressurernDrilling (MPD) or Pressure Management While Drillingrn(PMWD). By either label, such technology is uniquelyrnapplicable to remediate or eliminate entirely a number ofrndrilling-related problems the offshore industry faces today.rnSeveral recent offshore-focused technology transferencernvenues have identified MPD as Enabling Technology for:rnLow-Head or Near-Balanced Drilling.rnVariations (3) of Dual Gradient Drilling.rnTop Hole Drilling alternative to Pump & Dump.rnDeepwater Drilling with a Surface BOP.rnPressurized Mud Cap Drilling.rnReverse Circulating.rnDrilling with Casing.rnA tool developed for the safe practice of underbalancedrndrilling is required for all applications of MPD. Specifically, arnRotating Control Head, aka Rotating Control Device, orrnsimply, Rotating Head. Many in the industry prefer to use thernword ‘head’ when describing the tool as a reminder that it is tornbe used on the head of BOP stack (atop the annular)) and notrnin lieu of any component of a typical BOP stack. (APIrnRecommended Practice 53).rnIn 1995, only about 10% of working land rigs used a RCHrnfor any purpose during a well’s drilling program. Today thernvast majority of land drilling programs in the U.S. and Canadarnuse a RCH at some point in each well’s drilling program, forrnone reason or another. For whatever the purpose the tool wasrnused, a significantly better “well control incident” track recordrnhas resulted, this compared to those onshore wells drilled withrna conventional open-to-the-atmosphere drilling nipple atop thernBOP.rnA Rotating Control Head and a dedicated choke manifoldrnaffects a closed and pressurizable mud returns system whilerndrilling ahead. This is a required feature not only for the safernpractice of underbalanced drilling, but also for ManagedrnPressure Drilling. Offshore variations of this tool have beenrndeveloped and proven to practice UBD and MPD in marinernenvironments.rnDrilling in marine environments with a “closed &rnpressurizable” mud returns system and particularily where thernintent is not to invite hydrocarbons influx - offers relativelyrnlow hanging fruit to overcome a litany of obstacles tornconventional offshore drilling.rnAbout one-half of the remaining offshore resources ofrnhydrocarbons, gas hydrates excluded, are economicallyrnundrillable with conventional tools and methods. Thernpercentage “undrillable” increases with water depth. Drillingrnrelated obstacles to greater economic viability include:rnLoss circulation/differentially stuck pipe.rnSlow ROP.rnNarrow Pore-to-Fracture pressure marginsrnnecessitating excessive casing programs and requiring larger,rnmore expensive drill ships to bouy.rnShallow geohazards when drilling top holes riserless.rnFlat time spend circulating out riser gas, kicks, etc.rnFailure to reach TD objective with large enough hole.rnEssentially all of the drilling-related obstacles to economicrnviability of offshore wells can be addressed, to one degree orrnanother, with a technology that offers more precise wellborernpressure management and control while drilling ahead. That’srnMPD.rnBecause MPD focuses not on producing hydrocarbonsrnwhile drilling ahead and a full UBD surface/downhole “kit of