MANAGED PRESSURE DRILLING TECHNIQUES AND TOOLS
MANAGED PRESSURE DRILLING TECHNIQUES AND TOOLSA ThesisbyMATTHEW DANIEL MARTINSubmitted to the Office of Graduate Studies ofTexas A&M Universityin partial fulfillment of the requirements for the degree ofMASTER OF SCIENCEMay 2006Major Subject: Petroleum Engineering
MANAGED PRESSURE DRILLING TECHNIQUES AND TOOLSA ThesisbyMATTHEW DANIEL MARTINSubmitted to the Office of Graduate Studies ofTexas A&M Universityin partial fulfillment of the requirements for the degree ofMASTER OF SCIENCEApproved by:Chair of Committee,Committee Members,Head of Department,Hans C. Juvkam-WoldJerome J. SchubertAnn E. JochensStephen A. HolditchMay 2006Major Subject: Petroleum Engineering
iiiABSTRACTManaged Pressure Drilling Techniques and Tools.(May 2006)Matthew Daniel Martin, B.S., Texas A&M UniversityChair of Advisory Committee: Dr. Hans C. Juvkam-WoldThe economics of drilling offshore wells is important as we drill more wellsin deeper water. Drilling-related problems, including stuck pipe, lost circulation,and excessive mud cost, show the need for better drilling technology. If we cansolve these problems, the economics of drilling the wells will improve, thusenabling the industry to drill wells that were previously uneconomical. Managedpressure drilling (MPD) is a new technology that enables a driller to moreprecisely control annular pressures in the wellbore to prevent these drillingrelated problems. This paper traces the history of MPD, showing how differenttechniques can reduce drilling problems.MPD improves the economics of drilling wells by reducing drillingproblems. Further economic studies are necessary to determine exactly howmuch cost savings MPD can provide in certain situation. Furter research is alsonecessary on the various MPD techniques to increase their effectiveness.
ivDEDICATIONThis thesis is dedicated to my parents for all their support and encouragementthroughout the years.
vACKNOWLEDGMENTSI would like to first thank Dr. Hans C. Juvkam-Wold for the chance to dothis research and for all of the advice throughout the years.I would also like to thank Dr. Jerome Schubert and Dr. Ann Jochens forhelping me in completing this thesis and for being on my committee.Thanks also to ConocoPhillips and the Crisman Institute for providingfunding for this project.And last but not least, I would like to thank all my friends at Texas A&MUniversity for their support and encouragement.
viTABLE OF CONTENTSPageABSTRACT. iiiDEDICATION. iiiACKNOWLEDGMENTS . vTABLE OF CONTENTS. viLIST OF TABLES. viiLIST OF FIGURES .viiiINTRODUCTION .1BASICS OF MANAGED PRESSURE DRILLING.2UBD vs. MPD .3Pressure-Gradient Windows.3How Managed Pressure Drilling Works.6The Need for Managed Pressure Drilling .7MANAGED PRESSURE DRILLING TECHNIQUES .13Continuous Circulation System .13ECD Reduction Tool.17Pressurized Mud Cap Drilling .30Controlled Mud Cap System.33Dual-Gradient Drilling Method .41FUTURE OF MANAGED PRESSURE DRILLING REFERENCES .53VITA.56
viiLIST OF TABLESPageTable 1NPT downtime—TVD 15,000 ft. (From Dodson7). .9Table 2NPT cost of 102 wells drilled with TVD 15,000 ft (From Dodson7). 10Table 3NPT downtime—TVD 15,000 ft. (From Dodson7). .11Table 4NPT cost of 549 wells drilled—TVD 15,000 ft (From Dodson7).12Table 5Results of Case 1— Drilling 8-1/2-in. hole to 3800 m (From Jenner3)39Table 6Results of Case 2— Drilling 12-1/4" hole to 3800 m (From Jenner3) .40
viiiLIST OF FIGURESPageFig. 1Pressure-gradient profile (From Juvkam-Wold5). .4Fig. 2Pressure gradient window for tight margins (From Hannegan6).5Fig. 3Report of drilling downtime—TVD 15,000 ft. (From Dodson7).8Fig. 4Report of drilling downtime —TVD 15,000 ft (From Dodson7).11Fig. 5Change in equivalent mud weight during connections(From Jenner6).14Fig. 6Coupler device used in the continuous circulation system(From Jenner8).15Fig. 7Pressure-gradient profile showing effect of ECD reduction tool(From Hannegan6). .20Fig. 8Pressure boost provided by ECD reduction tool vs. flow rate(From Bern10).22Fig. 9Flow rate in well vs pressure boost caused by ECD reduction tool(From Bern10).23Fig. 10Downhole pressure reduction seen as a result of ECD reduction tool(From Bern10).24Fig. 11Additional standpipe pressure needed for pressure boost with ECDreduction tool (From Bern10). .25Fig. 12Surge effect when tripping drillstring with ECD reduction(From Bern10).27Fig. 13Swab effect when tripping drillstring with ECD reduction(From Bern10).28Fig. 14Surge effects as a function of trip time per stand (From Bern10). .29Fig. 15Pressure-gradient profile for pressurized mud cap drilling method(From Hannegan6). .31Fig. 16Controlled mud cap setup (From Juvkam-Wold5).35
ixFig. 17Dual-gradient drilling pressure gradient profile (From Hannegan6) .41Fig. 18Pressure profile for drilling dual gradient without a riser(From Hannegan6). .43Fig. 19Pressure profile for riserless dual gradient drilling with zerodischarge (From Hannegan6).44
1INTRODUCTIONAs current reserves deplete, it is necessary to drill to reservoirs that aredeeper and more complex. Some industry professionals would say that 70% ofthe current hydrocarbon offshore resources are economically undrillable usingconventional drilling methods.1 Managed Pressure Drilling (MPD) is a newtechnology that uses tools similar to those of underbalanced drilling to bettercontrol pressure variations while drilling a well. The aim of MPD is to improve thedrillability of a well by alleviating drilling issues that can arise.MPD can improve economics for any well being drilled by reducing a rig’snonproductive time (NPT). NPT is the time that a rig is not drilling. Many of thedrilling problems in any well can be reduced by using MPD. As with any newtechnology, MPD introduces new techniques that require understanding;becoming confident enough in the technology to use it on a regular basis takestime. With the resources that are currently uneconomical in the offshore marketsand the problems that occur while drilling a well, it is important that industry lookto MPD to improve the drilling ability of the drilling rigs.This literature review summarizes reported successes of MPD over thelast 10 years and shows that additional work is still necessary for the completeevaluation of the technique.This thesis follows the style of SPE Drilling and Completion.
2BASICS OF MANAGED PRESSURE DRILLINGManaged pressure drilling (MPD) is “an adaptive drilling process toprecisely control the annular pressure profile throughout the well.”2 The mainidea is to create a pressure profile in the well to stay within close tolerances andclose to the boundary of the operation envelope defined by the pore pressure,hole stability envelope and fracture pressure.3 MPD uses many tools to mitigatethe risks and costs associated with drilling wells by managing the annularpressure profile. These techniques include controlling backpressure, fluiddensity, fluid rheology, annular fluid level, circulating friction, and hole geometryin any combination.4The International Association of Drilling Contractors (IADC) has definedMPD further by creating two categories.4 Reactive MPD includes drillingprograms that are tooled up with at least a rotating control device (RCD), choke,and perhaps drill string float to safely and efficiently deal with problems that couldoccur downhole. Proactive MPD includes designing a casing, fluids and openholeprogram that precisely manages the wellbore pressure profile. This category ofMPD can offer the greatest benefit to the offshore drilling industry as it can dealwith unforeseen problems before they occur.
3UBD vs. MPDMPD is similar to underbalanced drilling (UBD). It uses many of the sametools that were designed for UBD operations. The difference between themethods is that UBD is used to prevent damage to the reservoir while thepurpose of MPD is to solve drilling problems.4 UBD allows influx of formationfluids by drilling with the pressure of the fluid in the wellbore lower than the porepressure. MPD manages the pressure to remain between the pore pressure andthe fracture pressure of the reservoir. It is set up to handle the influx of fluids thatmay occur while drilling but does not encourage influx. UBD is reservoir-issuerelated while MPD is drilling-issue related.Pressure-Gradient WindowsAs a well is drilled, drilling fluid is circulated in the hole to obtain a specificbottom hole pressure. The density of the fluid is determined by the formation andpore pressure gradients and the wellbore stability.Fig. 1 shows a pressure gradient profile of a well. This profile shows thechange in pressure as the depth increases. The pressure window is the areabetween the pore pressure and the fracture pressure. The goal when drilling awell is to keep the pressure inside this pressure window. In a static well, thepressure is determined by the hydrostatic pressure of the mud. In conventionaldrilling, the only way to adjust the pressure during static conditions is to vary mudweight in the well.
ESSUREFig. 1— Pressure-gradient profile (From Juvkam-Wold5).Fig. 2 shows the problem that can occur when dealing with tight pressuregradient windows. When the well is static, the pressure in the well is less than thepore pressure and the well takes a kick; that is, hydrocarbons flow into the well.6Before drilling can begin again, the kick has to be circulated out. After aconnection, the pumps restart, the BHP (Bottom Hole Pressure) increases, and
5the pressure goes above the fracture-pressure, resulting in lost circulation, orfluid flowing into the formation. The goal of managed pressure drilling is to “walkthe line” of the pressure gradients. Managing the pressure and remaining insidethis pressure gradient window can avoid many drilling problems.CONVENTIONAL CIRCULATION – TIGHT MARGINSNote: In tight margins, well canflow statically, and lose returnswhen circulating.TVDDYNAMICBHP HH(MW) AFPSTATICBHP HH(MW)psiAFPFig. 2— Pressure gradient window for tight margins (From Hannegan6).
6How Managed Pressure Drilling WorksThe basic technique in MPD is to be able to manipulate the BHP and thepressure profile as needed. In conventional drilling, the BHP can be calculated bysumming the mud weight hydrostatic head and the annular friction pressure(AFP). The AFP is the friction pressure that results from the circulation of themud while drilling. ECD is defined as the equivalent circulating density of theBHP. It is basically the BHP while circulating converted into the units of mudweight. During a connection, the pumps turn off and the fluid stops circulating,thus eliminating the annular friction pressure.The starting and stopping ofpumps can greatly affect the pressure profile, causing the pressure to fluctuateout of the pressure-gradient window and thus leading to drilling problems.A conventional drilling system is open to the atmosphere so that thereturns gravity flow away from the rig floor.3 The only way to adjust BHP whiledrilling is by the pumping rate. MPD uses a closed and pressurizable mudsystem. With a closed system the equation for the BHP can be varied to includebackpressure. BHP now can be found by summing the mud hydrostatic and theAFP with the amount of backpressure being applied. Adjusting backpressurewhile drilling can quickly change the BHP.The basic configuration for MPD is to have a rotating control device (RCD)and a choke.4 The RCD diverts the pressurized mud returns from the annulus tothe choke manifold. A seal assembly with the RCD enables the mud returnssystem to remain closed and pressurized and enables the rig to drill ahead. Thechoke with the pressurized mud return system allows the driller to apply
7backpressure to the wellbore. If the pressure starts to climb above the fracturepressure of the formation, the driller can open the choke to reduce backpressureand bring the pressure down. If the driller needs to increase the pressurethroughout the well, closing the choke will increase backpressure. This techniqueis mainly used during connections when the pumps are turned off then on. Whenthe pumps are turned off, the choke is closed to apply backpressure to replacethe lost AFP. As the pumps are turned on and the AFP increases, the choke canbe opened to decrease backpressure. This helps keep pressure profile to remaininside the pressure window throughout the well.In Fig. 2, the pressure profile shows that, in static conditions, the pressurewill fall below the pore pressure and that, while circulating, the pressure willexceed the fracture pressure. By adjusting the mud weight and usingbackpressure, a driller would be able to keep the pressure inside the pressurewindow. The driller can decrease mud weight so that the pressure stays belowthe fracture pressure while circulating. Applying back pressure while notcirculating could keep the pressure above the pore pressure of the formation. Byadjusting the drilling plan, a driller would be able to successfully drill a well thathas tight pressure margins.The Need for Managed Pressure DrillingThe need for MPD is clearly illustrated by current drilling statistics andproblems that currently exist. Fig. 3 shows the results of a database search ofNPT while drilling offshore gas wells.
8Fig. 3— Report of drilling downtime—TVD 15,000 ft. (From Dodson7).MPD can solve a large percentage of the problems the database lists, especiallythose that are caused by wellbore pressure deviating out of the pressure gradientwindow during drilling operations.4 Table 1 shows the NPT from Fig. 3 that couldbe reduced by using MPD.
9Table 1— NPT downtime—TVD 15,000 ft. (From Dodson7).Lost CirculationStuck PipeKickTwist OffShallow Water/GasFlowWellbore InstabilityTotal Downtime12.8%11.1%9.7%4.2%2.0%0.6%40.4%Numerous problems can occur if the wellbore pressure goes below the porepressure gradient. At shallow depths, water or gas can flow into the wellbore. Asnoted above, a kick can occur. With a lower pressure in the wellbore, the holecan also become unstable and start to fall in on the drillpipe. This can lead to thepipe becoming stuck and could cause a twist off, which is breaking the pipe. Themain problem when the pressure exceeds the fracture pressure-gradient is lostcirculation, losing mud into the formation. Reservoir damage can also occur andthe wellbore can become unstable. These problems account for more than 40%of drilling problems in the 10 years this study covers.Table 27 shows the economic impact that these hole problems have ondrilling cost. These hole problems basically cost a company 98 per foot drilled. Ifwe can eliminate the problems with MPD, we could reduce hole costs by about 39 per foot drilled. On wells drilled to 15,000 ft, that can equate to an averagesavings of 585,000 per well.These figures assume that MPD will reduce thedowntime by 40%. MPD will reduce these problems, although other events couldstill occur to prevent solving some of these problems. Even if we assume MPD
10could reduce that 40% to 20%, it could result in a savings of 19.50 per foot, oran average savings of 293,000 per well that is drilled to a depth of 15,000 ft.Table 2— NPT cost of 102 wells drilled with TVD 15,000 ft (From Dodson7).TotalDrill Days7680NPT Time,days1703NPT %22Dry HoleCost/Foot 444Cost/ft Due to NPT 98Fig. 4 shows similar results for offshore wells that were drilled to less than15,000 ft. Table 3 shows the NPT for these wells that could be reduced by usingMPD.
11Fig. 4—Report of drilling downtime —TVD 15,000 ft (From Dodson7).Table 3— NPT downtime—TVD 15,000 ft. (From Dodson7).Lost CirculationStuck PipeKickTwist OffShallow Water/GasFlowWellbore InstabilityTotal Downtime12.7%11.6%8.2%1.7%3.7%0.7%38.6%
12Table 4 shows the economic impact of these problems. If MPD eliminatedthe 38% of drilling problems, the benefit could be 27 per foot.Table 4— NPT cost of 549 wells drilled—TVD 15,000 ft (From Dodson7).Total DrillDays17641NPT Time(days)4264NPT %24Dry HoleCost/Foot 291Cost/ft Due toNPT 71On a 10,000 ft well, a savings of 270,000 can be made. If MPD onlyreduces these problems by half, the benefit of 13.50 per foot would yield anaverage savings of 135,000 per well that is drilled to a depth of 10,000 ft.These statistics show that MPD can help reduce NPT for current drillingoperations with associated excellent economic benefits. These economicbenefits illustrate the need for MPD with current operations to help companiesreduce their drilling costs.
13MANAGED PRESSURE DRILLING TECHNIQUESProjects that have used five of the many different variations of MPD havedemonstrated techniques that are proactive in managing the pressure profile.Continuous Circulation SystemThe continuous circulation system8 (CCS) is a new technology thatenables a driller to make connections without stopping fluid
Drilling-related problems, including stuck pipe, lost circulation, and excessive mud cost, show the need for better drilling technology. If we can solve these problems, the economics of drilling the wells will improve, thus enabling the industry to drill wells that were previously uneconomical. Managed
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 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
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 (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
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.
