Managed Pressure Drilling -- What Is It Anyway?
Originally appreared in:SPEcIAL FocUS:MANAGED PRESSUREDRILLINGMarch 2007 issue, pgs 27-34.Posted with permission.Managed pressure drilling—What is it anyway?There are many ways to determine the downhole pressure environment limits andmanage the annular hydraulic pressure profile.Kenneth P. Malloy, Stress Engineering ServicesIn the conventional drilling circulation flow path, drilling fluid exits the topof the wellbore open to the atmospherevia a bell nipple, then through a flowlineto mud-gas separation and solids controlequipment, an open vessel approach.Drilling in an open vessel presents difficulties during operations that frustrateevery drilling engineer. Annular pressuremanagement is primarily controlled bymud density and mud pump flowrates.In the static condition, bottomholepressure (PBH) is a function of the hydrostatic column’s pressure (PHyd). Inthe dynamic condition, when the mudpumps are circulating the hole, PBH isa function of PHyd and annular frictionpressure (PAF), Fig. 1.In an open-vessel environment, drilling operations are often subjected tokick-stuck-kick-stuck scenarios that significantly contribute to Non-Productive Time (NPT), an add-on expensefor many drilling AFEs. In an openvessel, pressures cannot be adequatelymonitored unless the well is shut-in.So, well-control incidents are predicatedon increased flow, where precious timeis wasted by pulling the inner bushingsto check for flow. In that short time, theinflux volume becomes larger and can bemore difficult to manage. The recentlydeveloped Managed Pressure Drilling(MPD) method offers better ways tocontrol PBH .UNDERBALANCED DRILLINGMPD originates from a few specifictechnologies developed by its forbearer—underbalanced drilling. In additionto improved rate of penetration, the chiefobjectives of underbalanced drilling areto protect, characterize and preserve thereservoir, while not compromising thewell’s potential. To accomplish this, influxes are encouraged. Influxes traverseup the hole and are controlled by threemajor surface containment devices: Rotating Control Device (RCD) Drilling Choke Manifold (DCM) Multiphase separator.If the well is producing while drilling, gas is flared, recirculated or sent toa gathering station for sale. If the drillingis land based, produced oil is stored instock tanks.RCDs include surface BOP rigs andsubsea BOPs with marine riser and tophole batch drilling. DCMs are used forbackpressure management and are eithermanual and automatic. These two toolsare used for both underbalanced opera-tions and MPD. Other tools used eitherindividually or in concert with others forMPD include: Continuous circulating system Non-return valves Downhole deployment valves Surface phase separation ECD reduction tools Nitrogen generation Pressure monitoring Hydraulic flow modeling.Some of these MPD-enabling toolsare required; others are optional or notapplicable.MANAGED PRESSURE DRILLINGOn land and in some shallow waterenvironments, a comfortable drillingwindow often exists between the porepressure and fracture-pressure gradientprofiles, through which the hole can bedrilled safely and efficiently, Fig. 2. Froman offshore prospective, MPD was andstill is driven by the very narrow marginsbetween formation pore pressure andformation fracture pressure downhole.Narrow margins are most pronouncedin deepwater drilling, where much of theoverburden is seawater, Fig. 3. In suchcases, it is standard practice to set numerous casing strings at shallow depthsto avoid extensive lost circulation.StaticPBH PHydllingwPoreindowCollapsePAFAnnular frictionpressureFig. 1. Ideally, static and dynamicpressures are within formation-pressureand fracture-pressure reFig. 2. Land-based and shallow-waterdrilling using single-density drilling fluidhave a wide drilling window.March 2007 World Oil%FQUIDynamicPBH PHyd PAFDepthDepthRock formation%FFQXBUFSPWFSCVSEFOOH PMMBQTF XJOEPX'SBDUVSF1PSF1SFTTVSFFig. 3. Deepwater drilling using singledensity drilling fluid has a narrowdrilling window.
SPEcIAL FocUSMANAGED PRESSURE DRILLINGDepth{Depthnon-return valve, and a DCM.The collapse, pore-pressure, fracConstant bottom hole pressure methodVariousmanufacturers produce APIture-pressure and overburden proPBH PAFmonogrammed RCDs that conformfiles often change in more matureto API Specifications 16RCD. APIfields because of production andrecently published API Spec 7NRV,depletion. The drilling window thatSpecifications for Non-Return Valves.was once generous becomes narManual-controlled and microprorower, making it more challengingStaticcessor-controlled chokes are availto “drill within the lines” withoutPBH PHyd PBackable depending on the application.losing circulation or inviting influx.Presuming that the wellbore isUnlike underbalanced drilling,capableof pressure containment,EqualizedMPD does not actively encourageDynamicdrillerscanbetter monitor the wellinflux into the wellbore. The priPBH PHyd PAFbore’s pressure distribution on a realmary objectives of MPD are to mititime basis using MPD. In a closedgate drilling hazards and increasesystem, drillers see pressure changesoperational drilling efficiencies byPressureimmediately. By more precisely condiminishing NPT. The operationaldrilling problems most associated Fig. 4. The constant bottomhole-pressure variation trolling the annular wellbore presof MPD uses lower-density drilling fluid andsure profiles, influx and loss detecwith NPT include:imposes backpressure when static to equalizetion are virtually instantaneous. Rig Lost circulationannular friction pressure.personnel and equipment safety Stuck pipeduring everyday drilling operations Wellbore instabilityis enhanced. Drilling economicsrange of 30–50 psi. One MPD method Well-control incidents.These four categories accounted for does not address all problems and MPD tend to improve through the reduction25–33% of all Gulf of Mexico NPT, pri- is application specific. The drilling en- of mud costs and drilling-related NPT.The constant bottomhole pressureor to Hurricanes Ivan, Katrina and Rita. gineer will have his choice of many opThe Underbalanced Operations and tions to best address the drilling prob- method, the mud-cap method, casingwhile drilling, equivalent circulatingManaged Pressure Drilling Committee lems encountered.While there are some similarities in density reduction and the dual-gradiof the International Association of Drilling Contractors has defined MPD as equipment selection, as well as similar ent method are a few of many proactive“an adaptive drilling process used to pre- training needs for personnel, MPD is not MPD variations used to manipulate thecisely control the annular pressure profile a “poor boy” version of underbalanced wellbore pressure profile to diminishthroughout the wellbore. The objectives drilling. On the contrary, done prop- or eliminate chronic drilling problems.are to ascertain the downhole pressure en- erly, contingencies need to be explored Hydraulics contributes directly to manyvironment limits and to manage the annu- requiring engineering forethought and drilling problems.lar hydraulic pressure profile accordingly.” planning, even though the equipment The MPD process employs a col- footprint is typically not as extensive.DRILLING HYDRAULICSThe vast majority of MPD is praclection of tools and techniques to mitiIn conventional drilling practices, thegate the risks and costs associated with ticed while drilling in a closed vessel, us- hydrostatic pressure (PHyd), created bydrilling wells that have narrow downhole ing an RCD with at least one drillstring the mud column density together withenvironmental limits, by proactivethe circulating annular friction presly managing the annular hydraulicsure (PAF), controls the bottomholeMud Cap Methodpressure profile.pressure (PBH):Static MPD may include control ofPBackDynamicPBH PHyd PAFbackpressure, fluid density, fluidPrheology, annular fluid level, circulating friction, hole geometry orWhen the mud pumps are shutLow densitycombinations thereof.downto make a connection, PAF isHigh density fluiddrilling MPD may allow faster corzero, leaving PBH controlled by the(generally static)fluid, e.g.rective action to deal with observedmud’s hydrostatic column. Shouldseawaterpressure variations. The ability toPBH be greater than the hydrostaticcontrol annular pressures dynamipressure,an influx of hydrocarbonsEquivalent singlecally facilitates drilling of whatcanoccur.The driller must then cirdensity gradientPBmight otherwise be economicallyculate the kick out of the hole withunattainable prospects.kill mud, typically at a slow pump MPD techniques may be usedrate. The slow pump rate minimizesPressureto avoid formation influx. Any flowthe influence of PAF during the killincidental to the operation will be Fig. 5. The pressurized mud-cap method uses aprocedure, while the higher-densitysafely contained using an appropri- lightweight scavenger drilling fluid in the drillpipe. mud increases PHyd, so that after cirate process.culating out the kick, PHyd balancesAfter circulating around the bit, the light-densityThe centerpiece of the definition fluid and cuttings are injected into a weak zonePBH without the influence of the PAF .is “precise control.” The technology uphole. A higher-density fluid remains in theIn MPD applications, theabove the weak zone along with optionalallows drillers to control bottomhole annuluswellboreis closed and able to tolerbackpressure to maintain annular pressure control.pressure from the surface within aate pressure. With this arrangement,March 2007 World Oil
Casing While DrillingDepththe driller can better control PBHwith imposed backpressure (PBack)from an incompressible fluid, in addition to the hydrostatic pressure ofthe mud column and annular friction pressure, Fig. 4:PBH PHyd PAF PBackDrillingPBH PHyd PAF(TD)drillers control influx by imposingbackpressure or by trapping pressure in the wellbore. At the least, anNRV, placed inside the drillstring,stops mud from flowing up thedrillpipe to the surface.MUD-CAP METHODThis method also addresses lostcirculation issues, but by using twodrilling fluids. A heavy, viscous mudis pumped down the backside in theannular space to some height. This“mud cap” serves as an annular barrier, while the driller uses a lighter, lessdamaging and less expensive fluid todrill into the weak zone, Fig. 5.The driller pumps the lightweightscavenger fluid down the drillpipe.After circulating around the bit, thefluid and cuttings are injected intoa weak zone uphole below the lastcasing shoe. The heavy, viscous mudremains in the annulus as a mud capabove the weak zone. The drillercan apply optional backpressure ifneeded to maintain annular pressurecontrol. The lighter drilling fluidimproves ROP because of increasedhydraulic horsepower and less chiphold-down.Depth{REACTIVE VS. PROACTIVEStaticPBH PHyd PAF(Shoe)There are two basic approachesto using MPD—reactive and proactive. Reactive MPD uses MPDPressuremethods and/or equipment as a PAFcontingency to mitigate drillingproblems, as they arise. Typically, Fig. 6. In casing while drilling, pumping managesengineers plan the well conven- friction pressure through the casing drillstring.tionally, and MPD equipment andprocedures are activated during unDual Gradient Methodexpected developments. ProactiveMPD uses MPD methods and/orStaticequipment to control the pressureDynamicprofile actively throughout the exSeawater ornitrified mudposed wellbore. This approach usesthe wide range of tools available toSingle density(a) better control placement of casgradienting seats with fewer casing strings,(b) better control mud density requirements and mud costs, and (c)Dual densityprovide finer pressure control forgradientadvanced warning of potential wellcontrol incidents. All of these leadPressureto more drilling time and less NPTCASING WHILE DRILLINGtime. In short, proactive MPD:Casing while drilling uses casing Drills operationally challenged Fig. 7. The dual-gradient variation uses two densityas the drillstring, so that the well isgradients, a lower density on top and higher densitywellsdrilled and cased simultaneously.on the bottom. Drills economically challengedBecause of the narrow clearance bewellstween the formation wall and casingto block retrograde flow up to the surface. Drills “undrillable” wells.OD, annular friction pressure canUsing an RCD alone does not nec- Options of microprocessor control and be a significant variable in ECD conessarily constitute MPD operations. backpressure pumps can often enhance trol. Flow within the small annular spaceAn RCD is an excellent supplemental the technique commonly referred to as contributes to increased annular frictionsafety device and adjunct to the BOP the constant bottomhole pressure meth- pressure from the shoe to surface, Fig. 6.stack above the annular preventer. Used od. Using the appropriate tools, drillingalone, it is at best a highly effective reac- within the drilling window enables one to DUAL-GRADIENT METHODtionary tool, which can be used to safely “walk the line” between pore pressure andDrillers have used dual-gradient drillmitigate hydrocarbons escaping from the fracture pressure without inviting influx ing successfully, primarily in offshorewellbore to the rig floor. This method is or lose of returns.applications, where water is a significantsometimes described as the Health Safetyportion of the overburden. Since thisEnvironmental Method.liquid overburden is less dense than theCONSTANT BOTTOMHOLEAs additional equipment and know- PRESSURE METHODtypical formation overburden, the drillhow are added, the operation becomesWhile the name Constant Bottomhole ing window is small, because the marginmore and more proactive. The full-time Pressure Method (CBPM) implies con- between pore pressure and fracture presuse of the Rig Choke Manifold (RCM) trol of the bottomhole pressure at the sure is narrow, Fig. 3. Because of weakto control the annular pressure profile, bottom of the hole, its actual objective is formation strength, deepwater conwhile drilling ahead, is not recommend- to control the most troublesome pressure ventional drilling applications usuallyed. The function of the RCM has always anomalies within the exposed wellbore. require multiple casing strings to avoidbeen for well-control incidents. A well- Typically, the drilling fluid is lighter than severe lost circulation at shallow depths,designed and dedicated DCM offers “normal,” so the hydrostatic column is using single-density drilling fluids.functionality and sufficient redundancy statically underbalanced.The intent of the dual-gradient variafor safe MPD operations.During drilling, influx is avoided with tion is to mimic the saltwater overburdenWith rare exceptions, Non-Return the increase in annular friction pressure with a lighter-density fluid. Drillers canValves (NRV) are placed in the drillstring from pumping. During connections, accomplish bottomhole pressure adjustMarch 2007 World Oil
MANAGED PRESSURE DRILLINGto spot a weighted, high-viscositypill to control the well statically. Onthe trip in the hole, the pill can becirculated out.ECD Reduction MethodDynamicPBH PHyd PAF – Ppump PpumpStaticPBH PHydPressure{ment by injecting less-dense media,such as inert gas, plastic pellets orglass beads, into the drilling fluidwithin the marine riser. Anothermethod is to fill the marine riserwith saltwater, while diverting andpumping the mud and cuttings fromthe seabed floor to the surface.Both of these methods alter thefluid density near the mud line.Two different fluids produce theoverall hydrostatic pressure in thewellbore, which avoids exceedingthe fracture gradient and breakingdown the formation. This savesdrilling operations from spendingNPT addressing lost circulation issues and associated costs, Fig. 7.DepthSPEcIAL FocUS PAFFig. 8. To create a reduction in ECD, a downholepump produces a pressure differential thatmodifies the annular pressure profile.EQUIVALENT CIRCULATINGDENSITY REDUCTIONEquivalent Circulating Density (ECD) can be reduced bymodifying the annular pressureprofile directly. Using a singledensity drilling fluid, a downholemotor can add energy to createan abrupt change in the annularpressure profile, Fig. 8.CONNECTIONSWhile making a connection,loss of annular friction pressurecan be directly compensatedby judicious use of imposedbackpressure to control thebottomhole pressure. In severekick–stick–lost circulation scenarios, supplemental backpressure with an incompressible fluidcan complement the low-densitydrilling fluid. Options to controlannular friction pressures withdownhole pumps are readilyavailable, as well.HYDRODYNAMICSVirtually every variation of MPDinvolves manipulation and management of the pressure profile, particularly in the exposed wellbore. Manyfactors affect downhole hydraulics,including: Wellbore geometry Drilling fluid density Drilling fluid rheology Annular backpressure Wellbore strengthening Annular friction pressure.Used singularly or in combination, drillers can manipulate, manage and exploited these factorsto accomplish MPD objectives,decrease NPT and reduce associated expenses.In many cases, where the drilling plan includes a hole sectionthat requires proactive MPD, avery detailed wellbore hydraulicanalysis will foretell the successof various MPD methods. It willalso guide the drilling engineerwhile he contends with the drilling operation’s hydrodynamicsin real time.TRAININGMany drilling operations arealready practicing reactive MPD.Moving from conventional drilling to proactive MPD is a stepchange. The step-change magniFig. 9. A continuous circulating device maintains thetude is roughly equivalent to theequivalent circulating density, while the connection ischange from cable tool to rotarybeing made.drilling. Proactive MPD may require specialized well engineering design and planning. Rigcrews may need additional guidance toCONTINUOUS CIRCULATINGTRIPPINGSYSTEMSince every MPD operation is appli- supplement their well-control training.Another method to control the annu- cation specific, no one tripping proce- They will need to learn how to use tolar pressure profile, while making a con- dure fits all situations. Engineers should day’s tools safely.nection, is to maintain the ECD while discuss the tripping procedure and agreethe connection is being made. Pipe rams upon it during HAZID/HAZOP con- COMPARING RISKSand a blind ram can be configured to ferences. Well control is paramount.The DEA155 joint industry project,effectively maintain circulation, even The annulus may require some filling to A Probabilistic Approach To Risk Assesswhile the drillstring is apart during the compensate for the drillstring’s effective ment Of Managed Pressure Drilling Inconnection. The continuous circulating volume that is removed during tripping. Offshore Drilling Applications, is an atdevice breaks the drillstring connection Backpressure can be applied to com- tempt to better define the risks of usand, through a sequence of operations, pensate for the lack of annular friction ing MPD, compared with conventionaldiverts the fluid flow across the open pressure until the margin encroaches on drilling techniques. Included in thatconnection. The device then makes up the limits defined in the drilling plan. comparison are:the new connection to the appropriate Stripping in or out of the hole with high Expected trouble incident frequencycasing pressures can shorten seal elementtorque and drilling continues, Fig. 9. Incident durationlife. At some point, it may be advisable Consequences (incident cost, includMarch 2007 World Oil
ing direct and indirect safety incidents) Incident detectability.ECONOMICSThe size of the prize is virtually limit less. In one offshore case, after two unsuc cessful sidetracks using conventional drill ing techniques, where most of the timewas spen
DRILLING Managed pressure drilling— What is it anyway? There are many ways to determine the downhole pressure environment limits and manage the annular hydraulic pressure profile. Kenneth P. Malloy, Stress Engineering Services. In the conventional drilling circula-tion flow path, drilling fluid exits the top of the wellbore open to the atmosphere
resources are economically undrillable using conventional drilling methods. Managed Pressure Drilling (MPD) is a new technology that uses tools similar to those of underbalanced drilling to better control pressure variations while drilling a well. The aim of MPD is to improve the drillability of a well by alleviating drilling issues that can arise.
Fundamentals of drilling operations; the drilling rig equipment and their functions; drilling terminologies; drilling processes; planning of drilling operations; logistics, role and responsibilities of service companies including drilling contractor; the functions of drilling fluid, casing, cementing and components of a drill string; the different
Dual Gradient Drilling (DGD) is a variation and a subset of Managed Pressure Drilling (MPD). Managed Pressure Drilling is a drilling tool that is intended to resolve chronic drilling problems contributing to non-productive time. These problems include: Well Stability Stuck Pipe Lost Circulation Well Control Incidents
Drilling (MPD) called Constant Bottom Hole Pressure (CBHP). Managed Pressure Drilling (MPD) is an adaptive drilling process used to precisely control the annular pressure profile throughout wellbore (Vieira P., 2009). This technique enables the drilling operation continued with the bottom-hole pressure is maintained constant whether the fluid .
Casing drilling, otherwise known as drilling with casing (DwC) or casing while drilling (CwD) is an alternative drilling technique to the conventional drilling method. Casing drilling involves the simultaneous drilling and casing of well with a (active-standard) casing string. It is mandatory to note that casing is the same grade and weight as in
and gas industry is faced with complex drilling operations where the pressure limits are narrow. Difficult pressure margins require safe, ef-ficient and precise pressure control. A series of techniques designed for this purpose is known as Managed Pressure Drilling (MPD). The principle of a MPD technique called Constant Bottom Hole Pressure
Drilling Productivity Report (DPR), September 2020. The drilling process is increasingly managed usingmass production operations , such as pad drilling, cube drilling, and multilateral drilling, to achieve higher cost efficiency in both the physical and contractual management of heavy-duty and fully automated drilling rigs.
Annual Day. Since that year, we have raised money to subsidize our conference claims which support many missions of the Christian Methodist Episcopal Church. Among them are our institu- tions of higher learning: Lane College Miles College Paine College Phillips School of Theology Thank you for your continuous support! We are proud to be CME! Sister Patricia McKinney Lewis 17 Sis. Hattie Hicks .
