MANAG MASTER OF IN INDIA

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1 MANAG ED PRESSUREE DRILLING: Experimental and Modeling Based Investigation DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD OF THE DEGREEE OF MASTER OF TECHNOLOGY IN PETROLEUM ENGINEERING By DINESH KUMAR Roll No. 08MT1003 SCHOOL OF PETROLEUM TECHNOLOGY PANDIT DEEND DAYAL PETROLEUM UNIVERSITY GANDHINAGAR, GUJARAT, INDIA 18 th January 2010

2 MANAGED PRESSURE DRILLING: Experimental and Modeling Based Investigation DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD OF THE DEGREE OF MASTER OF TECHNOLOGY IN PETROLEUM ENGINEERING By DINESH KUMAR Roll No. 08MT1003 Under the supervision of Dr. Ajit Kumar Shukla & Dr. Abhay Sharma SCHOOL OF PETROLEUM TECHNOLOGY PANDIT DEENDAYAL PETROLEUM UNIVERSITY GANDHINAGAR, GUJARAT, INDIA 18 th January 2010 i

3 Certificate to be printed on the letterhead of the School Date CERTIFICATE This is to certify that the dissertation entitled Managed Pressure Drilling: Experimental and Modeling based Investigation submitted by Dinesh Kumar (Roll No: 08MT1003) in partial fulfillment of the requirements for the award of the degree of Master of Technology in Petroleum Engineering, from School of Petroleum Technology, Pandit Deendayal Petroleum University, Gandhinagar was carried out under my guidance and supervision. No part of this dissertation has been submitted for the award of any degree or otherwise elsewhere to the best of my knowledge. Signature of the Supervisor 2, if any (Dr. Abhay Sharma) School of Petroleum Technology, Gandhinagar Signature of the Supervisor 1 (Dr. Ajit Kumar N. Shukla) School of Petroleum Technology, Gandhinagar Forwarded by: Signature of the PG Coordinator/Academic Coordinator (Prof. Shrikant Wagh) School of Petroleum Technology, Gandhinagar ii

4 Dedication This thesis is dedicated to my parents and all my family members for all their support and encouragement throughout the years. iii

5 Acknowledgements I would like to sincerely thank Dr. Ajit Kumar N. Shukla and Dr. Abhay Sharma for their valuable guidance, motivation and moral support throughout this project work. I am thankful to them for giving their ideas and proper time for pointing out the right direction for completing this project work. I am also thankful to Mr. V.P. Mahavar (Head of CMT, ONGC) and Mr. Ajay Dixit (Chief Engineer, Drilling, ONGC) for giving me their knowledge and experience in Managed Pressure Drilling. I would like to thank also Drilling fluid lab coordinator Dr. V. K. Srivastava and Fabrication Laboratory Incharge for giving me permission for utilizing their lab Instruments for my Project experimental work. I would like to thanks Mr. S.P.S. Chauhan (Head of Drilling Dept., GSPC) for providing me Drilling fluid material for my Experimental work of project. I would also like to express my sincere thanks to all of the faculty members and my fellow students of School of Petroleum Technology (PDPU) for their support and encouragement. Signature of the Student (Dinesh Kumar) iv

6 Abstract Managed pressure drilling is an innovative technique to precisely manage wellbore pressure. It is particularly applicable for reducing the risk of a kick or lost returns when drilling with a narrow window between pore pressure and fracture pressure. The constant bottomhole pressure method of managed pressure drilling uses annular frictional pressure and choke pressure in addition to mud hydrostatic pressure to achieve precise wellbore pressure control. Managed Pressure Drilling is a new drilling process so research is continuously reported. Experimental and mathematical modeling based investigation in Managed Pressure Drilling could not be revealed and rarely been reported. This dissertation work discussed experimental and modeling based investigation of Managed Pressure Drilling. Experimental and modeling based investigation contains selection of best drilling fluid model, annular flow modeling, annular pressure loss modeling, equivalent circulation density (ECD) calculation and Kinematics Modeling of drilling parameters by dimensional analysis. Annular pressure loss and equivalent circulation density is very important for hydraulics calculation of managed pressure drilling. Bottom hole pressure can be precisely controlled by annular pressure loss, ECD and provided back pressure. The determination of hydraulics is very important for controlling precisely bottomhole pressure. Then experimental and modeling based investigation played an important role in Managed Pressure Drilling. This study presents a simplified and accurate procedure for selecting the rheological model which best fits the rheological properties of a given non-newtonian fluid. The project assumes that the model which gives the lowest absolute average percent error (EAAP) between the measured and calculated shear stresses is the best one for a given non-newtonian fluid. The experimental work presents drilling fluid flow behavior through annulus. This study also presents behavior chart of annular pressure loss and friction factor with respect to Reynolds number of drilling fluid flow through annulus. MPD improves the economics of drilling wells by reducing drilling problems. Further economic studies are necessary to determine exactly how much cost savings MPD can provide in certain situation. Further research is also necessary on the various MPD techniques to increase their effectiveness. v

7 CONTENTS Certificate ii Dedication iii Acknowledgements iv Abstract v List of tables ix List of figures x List of Plates xi Abbreviations Used xii Chapter 1 Introduction Drilling Conventional Drilling Underbalanced Drilling Managed Pressure Drilling Comparison between UBD/MPD Pressure-Gradient Windows Hydraulics of MPD Bottomhole Pressure How Managed Pressure Drilling Works Methods of MPD Reactive MPD Proactive MPD Variations of MPD Constant Bottomhole Pressure Pressurized Mud Cap Method Dual Gradient Method ECD Reduction Method Continuous circulation system Equipments used in MPD Rotating Control Device Non-return Valve vi

8 1.8.3 Drilling Choke Manifold Back pressure pump Coriolis type flowmeter Mud Gas separator Chapter 2 Literature Review Past studies in Managed Pressure Drilling Research publications in MPD Classification of research publications Conclusion of literature review Objective of the research Problem identification Chapter 3 Rheology model Gel Strength Plastic Viscosity Yield Point Drilling Mud Selection of Mud Type Additives Preparation of drilling mud Rheology Data Procedure for selecting the best Rheological models Newtonian Model Bingham Plastic Model Power Law Model Herschel-Bulkley Model Chapter 4 Drilling fluid flow model Newtonian fluid flow model Laminar Pipe Flow Laminar Annular Flow Power Law fluid model Laminar Pipe Flow modeling vii

9 4.2.2 Laminar Annular Flow modeling Experimental Work Description of experimental setup Procedure of the Experiment Experimental reading of fluid flow through annular pipe Pressure Drop Annular pressure loss modeling Friction Factor Equivalent Circulating Density Kinematics modeling of MPD Dimensional analysis Methods of dimensional analysis Development of dimensional analysis model Buckingham s π theorem Chapter 5 Results and Discussion Selection of drilling fluid model Drilling fluid flow modeling Flow Rate vs. Reynolds Number Velocity vs. Reynolds number Annular Pressure Loss vs. Reynolds number Friction factor vs. Reynolds number ECD vs. Reynolds number Parametric Equations for annular flow Kinematics study of MPD Chapter 6 Summary and Conclusion Summary Conclusion Scope of Future work Appendix References viii

10 List of Tables Table 2.1: Flow control matrix of Return Gas Rate Table 2.2: Classification of research publications Table 3.1: Fann-50 Rheometer reading Table 3.2: Rheology data of the drilling mud Table 3.3: Shear Stress Measured in Field Units Table 3.4: Shear Stress Calculated as Function of Viscosity Table 3.5: Shear Stress Calculated as Function of Plastic Viscosity and Yield Point Table 3.6: Shear Stress Calculated as Function of Power Law Parameters Table 3.7: Calculated Shear Stress (τ τ ) Table 3.8: Shear Stress Calculated as Function of Herschel-Bulkley Parameters Table 4.1: Effective Diameter of annular flow of power law fluid Table 4.2: Experimental reading of drilling fluid flow through annulus Table 4.3: Reynolds number of drilling fluid flow through annulus Table 4.4: Annular pressure loss with respect to Reynolds number Table 4.5: Friction factor of the annulus Table 4.6: Equivalent circulating density of annular flow Table 4.7: shows Units and Dimensions of the Drilling Parameters Table 4.8: shows fundamental Dimensions of the Drilling Parameters Table 5.1: Values of absolute average percent error Table 5.2: Parametric equations ix

11 List of Figures Figure 1.1: Comparisons in OBD, UBD and MPD Figure 1.2: Different drilling problems during drilling process Figure 1.3: Narrow margin Drilling Window Figure 1.4: Components of Bottom Hole Pressure in MPD Figure 1.5 Managed Pressure Drilling system Figure 1.6: Constant Bottomhole Pressure Variation of MPD Figure 1.7: Pressurized Mudcap Uses a Lightweight Scavenger Drilling Fluid Figure 1.8: The Dual Gradient Variation Uses Two Density Gradients Figure 1.9: Equivalent Circulating Density method Figure 1.10: Different type of Non Return Valve Figure 2.1: Research publications related survey in MPD Figure 2.2: Classification of Research Paper in terms of Percentage Figure 3.1: Newtonian fluid Rheogram Figure 3.2: Comparison between measured data and calculated data Figure 3.3: Bingham plastic fluid Rheogram Figure 3.4: Comparison between measured data and calculated data Figure 3.5: Power-law fluid Rheogram Figure 3.6: Comparison between measured data and calculated data Figure 3.7: Herschel-Bulkley fluid Rheogram Figure 3.8: Comparison between measured data and calculated data Figure 4.7: Schematic diagram of the experimental setup Figure 5.1: Behavior of annular flow rate with respect to Reynolds number Figure 5.2: Behavior of annular flow Velocity with respect to Reynolds number Figure 5.3: Behavior of annular pressure loss with respect to Reynolds number Figure 5.4: Behavior of annular friction factor with respect to Reynolds number Figure 5.5: Behavior of ECD in annular flow with respect to Reynolds number Figure 5.6: Behavior of ECD in annular flow with respect to annular pressure loss x

12 List of Plates Plate 1.1: Rotating Control Device (RCD) Plate 1.2: Drilling Choke Manifold Plate 1.3: Back pressure pump Plate 1.4: Coriolis type Flowmeter Plate 1.5: Mud Gas Separator Plate 4.1: Experimental setup Plate 4.2: Mud tank of Experimental setup Plate 4.3: Mud Pump of Experimental setup Plate 4.4: Annulus Pipe of Experimental setup Plate 4.5: Gate valve of Experimental setup Plate 4.6: Control panel of Experimental setup xi

13 Abbreviations Used AFP BHP BOP CBHP CMC DDV EAAP ECD ECDRT EMD IADC MCD MFC MPD NPT OBD ROP TVD UBD Annular Friction Pressure Bottom Hole Pressure Blowout Preventer Constant Bottom Hole Pressure Controlled Mud Cap Downhole Deployment Valve Absolute Average Percent Error Equivalent Circulating Density Equivalent Circulating Density Reduction Tool Equivalent Mud Density International Association Drilling Contractor Mud Cap Drilling Micro Flux Control Managed Pressure Drilling Non Productive Time Overbalance Drilling Rate of Penetration Total Vertical Depth Underbalanced Drilling Super script A D F K μ n pp Area of the annular pipe Pipe Diameter Friction factor Consistency factor Length of the annular pipe Shear Viscosity Flow behavior index Pore Pressure Density of Drilling mud Annular Pressure Loss xii

14 Q τ YP Flow Rate the drilling fluid flow Shear Stress Velocity of the drilling fluid flow Shear Rate Yield Point Sub script τ Equivalent diameter Effective Diameter Hydraulic Diameter Inner Diameter of the Annulus Outer Diameter of the Annulus Laminar friction factor Plastic viscosity Effective Viscosity Reynolds Number Mean Shear Stress Maximum Shear Stress Maximum Shear Rate Initial Shear Stress Mean Shear Rate xiii

15 Chapter 1 Introduction Managed Pressure Drilling (MPD) is an innovative Drilling technique which is developed for reducing the various Drilling problems like kick, drilling fluid circulation loss, wellbore instability and formation damage. These Drilling problems generally grow up during the conventional drilling process. So Managed Pressure Drilling is a process which is used for mitigating drilling problems. MPD is used to precisely manage the wellbore pressure when drilling with a narrow window between pore pressure and fracture pressure. It is very useful for mature field because it can be revisited with better well control. Managed Pressure Drilling also reduces the Non Productive Time (NPT) and enhance productivity of the matured or Brownfield. According to the Definition of International Association of Drilling Contractors (IADC) Managed Pressure Drilling is an adaptive drilling process used to control precisely the annular pressure profile throughout the wellbore. The objectives are to ascertain the down hole pressure environment limits and to manage the annular hydraulic pressure profile accordingly. MPD is intended to avoid continuous influx of formation fluids to the surface. Any flow incidental to the operation can be safely contained using an appropriate process. Managed Pressure Drilling process is divided in to two categories Proactive and Reactive. These categories contain three variations of the MPD, like Constant Bottom Hole Pressure (CBHP), Pressurized Mud Cap Drilling (PMCD) and Dual Gradient Drilling (DG). The constant bottom hole pressure method of managed pressure drilling uses annular frictional pressure and choke pressure in addition to mud hydrostatic pressure to achieve precise wellbore pressure control. MPD technology challenges the traditional drilling practice of weighting a mud system while drilling through formations that are over pressured. The technology is an advanced drilling optimization process that applies an advanced well control methodology and specialized equipment to enhance drilling economics and reduce drilling cost uncertainty. 1

16 1.1 Drilling The main objective of drilling process in the oilfield is to make hole. Whether that hole is for exploratory and appraisal purposes or for development of petroleum production. Drilling is the first and very important step for getting petroleum products from the reservoir after doing geological work. Drilling process is very difficult and sensitive also because the recovery of petroleum product depends on the drilling. So to accomplish the chief objective some elements need to be executed along the way: Maintain hole stability Transport cuttings Freedom of drill string to move Control flow in and out of the well Case hole Achieve target bottomhole location Achieve time objective Maintain budget According to the uses of oilfield, generally the drilling process are classified as follows 1. Conventional Drilling 2. Under Balance Drilling 3. Managed Pressure Drilling Conventional Drilling: Conventional drilling has largely been practiced in open field, one that is open to the atmosphere. By the conventional drilling circulation flow path, the drilling fluid inside of the drill pipe through the mud pump and exits the top of the wellbore through a bell nipple and traverses a flow line to mud-gas separation and solids control equipment. Conventional wells are most often drilled overbalanced. Overbalanced is defined as the condition where the pressure exerted in the wellbore is greater than the pore pressure in any part of the exposed formations. 2

17 ... (1.1) Regulatory bodies recommend that the well should be overbalanced under the static condition. For conventional drilling static condition means that the drilling fluid (mud) is not circulating by means of pumps but is at rest in the well. This static column of drilling mud exerts a hydrostatic pressure throughout the wellbore (1.2) While the static overbalanced condition addresses control of the pore pressure, once the mud pumps are engaged the system becomes dynamic. A component, annular friction pressure (P AF ) comes to play (Malloy K. P. 2008)..... (1.3) Figure 1.1: Comparisons in OBD, UBD and MPD Underbalancedd Drilling The origin of Managed Pressuree Drilling (MPD) is found in the utilization of a few specific technologies developed by its forbearer Underbalanced Drilling. Underbalanced Drilling (UBD) is a drilling activity employing appropriate equipment and controls where the pressure exerted in the wellbore is intentionally less than the pore pressure in any part of the exposed formations with the intention of bringing formation fluids to the surface, p Hyd is less than p B H. (Malloy K. P. 2008). 3

18 .. (1.4) or... (1.5) Underbalanced Operations (UBO) is a well construction or maintenance activity employing appropriate equipment and controls where the pressure exerted in the wellbore is intentionally less than the pore pressure in any part of the exposed formations with the intention of bringing formation fluids to the surface. In addition to improved rate of penetration, the chief objectives of UBD are to protect, characterize, and preserve the reservoir while drilling so that well potential is not compromised. To accomplish this objective, influxes are encouraged. The influxes are allowed to traverse up the hole and are suitably controlled by three major surface containment devices. (Malloy K. P. 2008). Rotating Control Device Drilling Choke Manifold Multiple Phase Separator Managed Pressure Drilling Unlike Underbalanced Drilling, Managed Pressure Drilling (MPD) does not actively encourage influx into the wellbore. Managed Pressure Drilling applications are driven by the very narrow drilling margins between formation pore pressure and formation fracture pressure downhole. The narrow margins are most pronounced in deepwater applications where much of the overburden is actually seawater. In such cases, it is usual to set numerous casing strings at shallow depths to avoid extensive lost circulation. More mature fields also offer the challenges of depleted zones and pressure reversals that are technically difficult to drill. The primary objectives of MPD are to mitigate drilling hazards and increase drilling operations efficiencies by diminishing Non-Productive Time (NPT). The operational drilling problems most associated with non-productive time include are: (Malloy K. P. 2008) 1. Lost Circulation 2. Stuck Pipe 3. Wellbore Instability 4. Well Control Incidents 4

19 Figure 1.2 Different drilling problems during drilling process (Malloy K. P. 2008) 1.2 Comparison between UBD & MPD MPD is similar to underbalanced drilling (UBD). It uses many of the same tools that were designed for UBD operations. The difference between the methods is that UBD is used to prevent damage to the reservoir while the purpose of MPD is to solve drilling problems. UBD allows influx of formation fluids by drilling with the pressure of the fluid in the wellbore lower than the pore pressure. MPD manages the pressure to remain between the pore pressure and the fracture pressure of the reservoir. It is set up to handle the influx of fluids that may occur while drilling but does not encourage influx. UBD is reservoir-issue related while MPD is drilling-issue related. These points are suggested by Malloy K. P and required to get confirmation through the field experience. 1.3 Pressure-Gradient Windows As a well is drilled, drilling fluid is circulated in the hole to obtain a specific bottom hole pressure. The density of the fluid is determined by the formation and pore pressure gradients and the wellbore stability. Below Figure 2.1 shows a pressure gradient profile of a typical well. This profile shows the change in pressure as the depth increases. The drilling window is the area between the pore pressure and the fracture pressure. The goal while drilling a well is to keep the pressure inside this pressure window. In a static well, the pressure is determined by the hydrostatic pressure 5

20 of the mud. In conventional drilling, the only way to adjust the pressure conditions is to vary mud weight in the well (Martin M. D. 2006). during static Figure 1.3 Narrow Margin Drilling Window 1.4 Hydraulics of MPD In MPD applications, the wellbore is closed and able to tolerate pressure. With this arrangement, p BH can be better controlled with imposed backpressure (pback) from an incompressible fluid in addition to the hydrostatic pressure of the mud column and annular friction pressure Bottomhole Pressure The Bottomhole Pressure (BHP) has three components: hydrostatic pressure, annulus frictional pressure (AFP) and choke pressure in a closed circulating system. The Constant Bottomhole Pressuree (CBHP) technique is intended to utilize the combination of these three pressure components for precisee wellbore pressure management at all times during drilling. Figure illustrates these three components of BHP and the variables that affect the magnitude of these pressure components. The variables such as mud flow rate which controls the AFP and choke pressure which controls the back pressure can be manipulated in real time during drilling allowing relatively quick changes in the wellbore pressure. Conversely, changing the magnitude of the mud properties, such as mud weight and viscosity, has a more delayed impact. 6

21 (1.6) Figure 1.4 Components of Bottom Hole Pressure in Managed Pressure Drilling 1.5 How Managed Pressure Drilling Works The basic technique in MPD is ability to manipulate the BHP and the pressure profile as needed. In conventional drilling, the BHP can be calculated by summing the mud weight hydrostatic head and the annular friction pressure (AFP). The AFP is the friction pressure that results from the circulation of the mud while drilling. Equivalent Circulating Density (ECD) is the equivalent circulating density constituting the BHP. It is basically the BHP while circulating converted into the units of mud weight. During a connection, the pumps turn off and the fluid stops circulating, thus eliminating the annular friction pressure. The starting and stopping of pumps can greatly affect the pressure profile, causing the pressure to fluctuate out of the pressure-gradient window and thus leading to drilling problems. The basic configuration for MPD is to have a rotating control device (RCD) and a choke. The RCD diverts the pressurized mud returns from the annulus to the choke manifold. A seal assembly with the RCD enables the mud returns system to remain closed and pressurized and enables the rig to drill ahead. The choke with the pressurized mud return system allows the driller to apply backpressure to the wellbore. If the pressure starts to climb above the fracture pressure of the formation, the driller can open the choke to reduce backpressure and bring the pressure down. If the driller needs to increase the pressure throughout the well, closing the choke will increase backpressure. This technique is mainly used during connections when the pumps are turned off then on. When the pumps are turned off, the choke is closed to apply backpressure 7

22 to replace the lost AFP. As the pumps are turned on and the AFP increases, the choke can be opened to decrease backpressure. This helps keep pressure profile to remain inside the pressure window throughout the well. The pressure profile shows that, in static conditions, the pressure will fall below the pore pressure and that, while circulating, the pressure will exceed the fracture pressure. By adjusting the mud weight and using backpressure, a driller would be able to keep the pressure inside the pressure window. The driller can decrease mud weight so that the pressure stays below the fracture pressure while circulating. Applying back pressure while not circulating could keep the pressure above the pore pressure of the formation. By adjusting the drilling plan, a driller would be able to successfully drill a well that has tight pressure margins as shown figure 1.3. (Martin M. D. 2006). Figure 1.5: Managed Pressure Drilling system ( 1.6 Methods of Managed Pressure Drilling There are two basic approaches to utilize MPD Reactive and Proactive. Reactive MPD uses Managed Pressure Drilling methods and/or equipment as a contingency to mitigate drilling problems as they arise. Managed Pressure Drilling is accordingly classified in two categories (Malloy K. P. 2008). 1. Reactive MPD 2. Proactive MPD 8