Lesson 15 Special Considerations - PETE 689 - UBD Lesson 15...

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Unformatted text preview: PETE 689 - UBD Lesson 15 Special Considerations Read: UDM - Chapter 6 Harold Vance Department of Petroleum Engineering Special Considerations Safety in UBD Regulatory Requirements Environmental Issues Directional Drilling Harold Vance Department of Petroleum Engineering Special Considerations Percussion Drilling Cementing High Pressure Drilling Formation Evaluation Harold Vance Department of Petroleum Engineering Safety in UBD Since significantly greater volumes of oil and gas are produced in underbalanced drilling (compared to overbalanced drilling), and because these products are highly combustible, considerable attention must be paid to safety procedures. Produced fluids must be handled safely. Harold Vance Department of Petroleum Engineering Hydrogen Sulfide Provide necessary notice of the proposed operations and hazards. Provide adequate training. Special Safety equipment, such as sensors, warning alarms, wind socks, concentration measuring devices, portable and fixed air breathing respirators. Harold Vance Department of Petroleum Engineering Hydrogen Sulfide An H2S emergency contingency plan with the site specific information and detailed procedures. Hydrogen sulfide resistant materials and training. Pressure surface separation vessels and auxiliary vacuum degassing equipment to isolate all personnel from possible exposure to this poisonous gas. Harold Vance Department of Petroleum Engineering Flaring Gas Adequate sized flare lines, leading to properly positioned flare stacks, equipped with automatic flame igniters, are essential. Take wind direction into consideration. Height may need adjustment. Flare lines must be properly anchored. Harold Vance Department of Petroleum Engineering Separation and Storage Liquid hydrocarbon separation and storage facilities must be: positioned remotely provide adequate storage volume proper manifolding for transfer to sales. Harold Vance Department of Petroleum Engineering Training Personnel training must be provided. Written procedures must be provided. Redundancy in critical man power must be provided. Redundancy in choke manifold. Emergency ingress and egress must be provided. Harold Vance Department of Petroleum Engineering Downhole Fires Air drilling can lead to downhole fires and corrosion. Harold Vance Department of Petroleum Engineering Drilling with Natural Gas Surface fires can be a problem. Prepare for proper handling of hydrocarbon gasses at the surface. Guidelines can be found in: API RP 500B National Fire Protection Association (NFPA) 70 NFPAA 496 Harold Vance Department of Petroleum Engineering Backflow Drillstrings need floats to prevent flow back up the drillstring. Placement of drillstring floats is important for operational and safety reasons. Harold Vance Department of Petroleum Engineering Well Control No standards for testing of RH and RBOP has been developed. Harold Vance Department of Petroleum Engineering Equipment Operational and equipment testing procedures must be established. Operations should not continue if pressures exceed the maximum limits established. In flowdrilling, emphasis is placed on monitoring pressure while drilling, tripping, and stripping, in addition to early kick detection. Harold Vance Department of Petroleum Engineering Equipment To develop testing procedures, prepare a detailed BOP and manifolding flow diagrams that show stepbystep testing for system parts. Test BOPs when installed, each time they are reinstalled, once each week, and following repairs. Harold Vance Department of Petroleum Engineering Equipment Regularly inspect and monitor surface equipment. Stop flowdrilling when H2S is detected. Inspect mud/gas separators at least daily. Inspect diverter rubber elements several times a day. Check diverter alignment with the rotary. Develop contingency plans. Harold Vance Department of Petroleum Engineering Regulatory Requirements In planning an UB well, always check with local, state, or federal agency governing the well's location for the latest regulations. Harold Vance Department of Petroleum Engineering Canada Interim Directive ID 943, from the Energy Resources Conservation Board provides the most detailed regulations in North America. Mandates strict enforcement of: BOP system configuration. Tripping procedures. Well control certification of key personnel. Harold Vance Department of Petroleum Engineering United Kingdom The Department of Trade and Industry sets specific requirements and regulations pertinent to the drilling and completion of underbalanced wells. Authority has be delegated to the Health and Safety Executive to review operators plans, and to grant or deny permits for proposed work. Harold Vance Department of Petroleum Engineering United States In the United States, a survey of the primary oil and gas producing states indicated that there were no special regulations written specifically for UBD. In most cases, the existing regulations could be broadly interpreted to cover UBD. Harold Vance Department of Petroleum Engineering Issues to Consider Be certain that the BOP stack, with a diverter System: permits drilling to proceed while controlling annular pressure. allows connections to be made either with the well flowing or shutin. allows tripping of the drillstring under pressure to change bits or bottomhole assemblies. Harold Vance Department of Petroleum Engineering Issues to Consider provides for backup annular control in case of failure of the diverter. provides for a choke manifold arrangement which allows annular pressure to be varied so that it will not exceed related working pressure of the equipment. Provides a mean to bleedoff pressure or to kill the well, independent of the diverter system. Provides a means to quickly and safely shutin the well. Harold Vance Department of Petroleum Engineering Issues to Consider Use string float(s) and fire float(s), if air is used. If sour gas is present, drillpipe protection and blind shear rams are needed. Kill fluid is needed. Casing integrity needs to be guaranteed and full length cementing should be implemented as regulated. Surface equipment spacing needs to adhere to appropriate regulations. Harold Vance Department of Petroleum Engineering Issues to Consider Flaring must follow appropriate regulations. Appropriate separator equipment should be used, as required. Provide adequate provision for storage of produced fluids. Crews need to be appropriately certified and trained. Monitoring and alarms are essential for H2S environments. Adhere to all safety regulations. Harold Vance Department of Petroleum Engineering Environmental Issues Regulations vary significantly from state tostate, and countrytocountry. Check applicable regulations carefully. Harold Vance Department of Petroleum Engineering Land and Water Pollution UBD provides some environmental benefits (closed loop systems, less drilling mud, etc), but produces more formation fluids than conventional. Oil coated cuttings must be disposed of properly. Harold Vance Department of Petroleum Engineering Air Pollution Considerations Burning hydrocarbons during drilling can become an environmental concern. Know regulations on air pollution. Dust during air drilling can be a problem. Harold Vance Department of Petroleum Engineering Produced Water Disposal Produced water must be disposed of. Disposal operations can include: Disposal into surface water drainage systems. Reinjection. Approved land disposal Overboard offshore disposal Reserve pits Harold Vance Department of Petroleum Engineering Directional Drilling There is no reason why directional wells cannot be undertaken with UBD. However, compressible fluids can complicate directional drilling. Harold Vance Department of Petroleum Engineering Directional Drilling (Complications) Conventional downhole motor life is shorter, and conventional motors are not as efficient. Conventional MWD systems do not work with compressible fluids. Hole cleaning can be a problem with angles >50 deg Harold Vance Department of Petroleum Engineering Directional Drilling (Complications) The horizontal section length is reduced due to increased drag. Not all formations and lithologies are suitable for drilling with dry gas, moist or foam. Harold Vance Department of Petroleum Engineering Bottomhole Assemblies Main issues for directional drilling underbalanced are similar to those for conventional directional drilling: Directional control. Surveying. Hole cleaning. Drillstring friction. Harold Vance Department of Petroleum Engineering Bottomhole Assemblies BHA is designed to control direction and angle. The deviation tendency is a function of the stiffness of the assembly. Harold Vance Department of Petroleum Engineering Three Types of BHAs Building assemblies Holding assemblies Dropping assemblies Harold Vance Department of Petroleum Engineering Building Assemblies Harold Vance Department of Petroleum Engineering Dropping Assemblies Harold Vance Department of Petroleum Engineering Holding Assemblies Harold Vance Department of Petroleum Engineering Downhole Motors Conventional mud motors can be run with compressible fluids, but there are disadvantages. Harold Vance Department of Petroleum Engineering Conventional Mud Motors Disadvantages Designed to run with low volumetric flow rates and high pressure drops. Leads to high inlet pressures and low efficiency with compressible fluids. Compressible fluids can lead to motor stall. High inlet pressure results in high energy stored in the drillstring above the motor. Harold Vance Department of Petroleum Engineering Conventional Mud Motors Disadvantages Volume to clean the hole with air drilling is three times greater than the recommended flow rate for the conventional mud motor. Mud motors are hydrostatic, they can use only the displacement work, and not the expansion work of the compressed air. Harold Vance Department of Petroleum Engineering Mud Motors Mud motors have been developed for use with compressible fluids. Advantages: Boosters are not needed. Efficiency is improved. Motors do not stall as easily. Overspeed is less likely. Can be used with compressible and slightly compressible fluids. Harold Vance Department of Petroleum Engineering Surveying Conventional MWD signals cannot be sent up compressible fluids. Electromagnetic MWD (EMWD) tools are being developed. Steering tools are still available. Harold Vance Department of Petroleum Engineering Hole Cleaning Hole cleaning is more difficult in highly deviated wells. A ruleofthumb is that for adequate hole cleaning in horizontal wells, a volumetric rate of 2.5 times greater than a vertical well is necessary. Harold Vance Department of Petroleum Engineering Torque and Drag Friction coefficient in an airdrilled hole can be three to four times than expected in mudfilled hole. Harold Vance Department of Petroleum Engineering Horizontal Section Length Additional torque and drag can lessen the achievable horizontal displacement of high angle and horizontal wells. Harold Vance Department of Petroleum Engineering Lithology and Target Constraints Lithologies that can be drilled with air are limited. Younger less consolidated rocks are usually not good candidates for air. Directional wells sometimes must be drilled overbalanced to prevent wellbore collapse. Harold Vance Department of Petroleum Engineering Percussion Drilling In percussion drilling, rock is broken by causing the bit to repeatedly strike the workfront, without imparting any significant shearing component to its action. A hammer tool is used in the BHA. Normally only used with dry gas, mist, and foam drilling. Harold Vance Department of Petroleum Engineering Background ROP for three different percussion tools with 8 to 8inch solidhead bits in Sierra White Granite, For a WOB of 5,000 lbf. The flow rate was between 600 and 1,100 scfm for each hammer (after Finger, 1984 26) Harold Vance Department of Petroleum Engineering Approximation of ROP Assume that the MSE = Co Determine the hammer manufacturer's power output value. The penetration rate is related to the rock's unconfined compressive strength, the hammer power output and the hole area by: Harold Vance Department of Petroleum Engineering Approximation of ROP ROP = 2.52*10 6 * [ / (Co Dh2)] ROP Co Dh rate of penetration (ft/hr) hammer power output (hp) unconfined compressive strength, (psi) hole diameter (inches) Harold Vance Department of Petroleum Engineering Equipment Flatbottom bits, used in conjunction with an air percussion hammer (anon) Harold Vance Department of Petroleum Engineering Equipment Internally ported hammer and a flatbottom bit (anon) Harold Vance Department of Petroleum Engineering Equipment Components of an externally ported hammer (anon) Harold Vance Department of Petroleum Engineering FPB/HT (flatbottomed percussion bit/hammer tool) tandem recommended WOB Versus hole size (after Whiteley and England, 1986 30) Recommended Weight on Bit (lbf) Bit Diameter (inches) Harold Vance Department of Petroleum Engineering Hole Cleaning Pratt modified velocity by: Angel's minimum Using a revised air prediction module inside the drillstring where the friction factor was calibrated from actual measurements. Exit boundary conditions were modified as an input parameter and exit chip velocity was fixed at zero. The influence of the BHA and changing hole size were incorporated. Chip size change was built into the model. Harold Vance Department of Petroleum Engineering Gauge Wear DiamondEnhanced Insert (after Reinsvold, et al., 1988 31) Harold Vance Department of Petroleum Engineering Smooth Hole? Spiral hole drilled with an industrial hammer and a flatbottomed bit (after Pratt, 1989 29) Harold Vance Department of Petroleum Engineering Smooth Hole? Ledges drilled with an industrial hammer and a flatbottomed bit (after Pratt, 1989 29) Harold Vance Department of Petroleum Engineering Summary Maintain proper WOB. Rotate as slowly. Provide an air bypass. Deep the threads clean and use recommended lubricants. Dope the pins only. Never run on junk. Harold Vance Department of Petroleum Engineering Summary When changing out bits, make sure that the new bit is no more than 0.25 in larger than the old. Stabilize as required. Monitor compressors. Blow the hole clean. Harold Vance Department of Petroleum Engineering High Pressure Drilling Special attention should be given to high surface pressures because of the additional force required to trip pipe. Stringent safety considerations are required. Harold Vance Department of Petroleum Engineering Flowdrilling in High Pressured Formations The use of CT drilling is increasing with high pressure flowdrilling. Surface well control equipment must be rated based on maximum anticipated conditions. RBOPs should replace rotating heads. Harold Vance Department of Petroleum Engineering Coiled Tubing Drilling Design Criteria 1. Select the CT size, hole size, drilling fluid, and BHA. 2. Calculate the reel weight and size. 3. Calculate the tubing forces and stresses. Do not let them exceed 80% of the yield strength, and the minimum WOB can be provided at TD. Harold Vance Department of Petroleum Engineering 4. In vertical wells. Dmax Wdf y Coiled Tubing Drilling Design Criteria maximum depth (feet) drilling fluid weight (ppg) yield stress (psi) Dmax = (y) / ( 4.245 0.06493Wdf ) 5. In Deviated wells. Ensure that the injector can supply the necessary push/pull. Harold Vance Department of Petroleum Engineering 5. In Deviated wells. Coiled Tubing Drilling Design Criteria Ensure that the injector can supply the necessary push/pull. Calculate the drilling fluid pressure drop in the CT, BHA and annulus at 100 % motor flow capacity and determine the absolute pressure in the CT during drilling. Asses torsional limitations. The downhole motorstall torque should not be longer than the maximum working torque for the CT. Harold Vance Department of Petroleum Engineering Coiled Tubing Drilling Design Criteria 5. In Deviated wells. Calculate the fatigue life of the pipe. Asses any hydraulic limits . Consider hole cleaning in vertical, inclined , and horizontal wellbores. Be sure that directional control is possible. Harold Vance Department of Petroleum Engineering Cementing Extremely light cement can be used to: Provide primary cementing in formations with low fracture pressures. Cure lost circulation in cavernous vugs. Squeeze depleted zones. Zonal isolation. Heat Insulation. Harold Vance Department of Petroleum Engineering Properties of Foamed Cement Will the strength be adequate and will the sheath be destroyed by perforating? Compressive strength of foamed cement is generally higher than a comparable non foamed cement of the same density. Will there be gas migration through the cement itself? Will the bond be different than for conventional cements? Harold Vance Department of Petroleum Engineering Systems with Low Density Particulate Matter Cement companies have additive in which the HSP of the cement can be reduced. Example is hollow glass micro spheres. Harold Vance Department of Petroleum Engineering Design Considerations Foam quality. PVT behavior. Free water. Cement system. Backpressure. Permeability. Fluid Loss. Compressive strength. Harold Vance Department of Petroleum Engineering Formation Evaluation Harold Vance Department of Petroleum Engineering Evaluation of Formation Fluids While Drilling Evaluation of formation fluids during UBD is more accurate than conventional. Qualitative and Quantitative information can be obtained or inferred. Harold Vance Department of Petroleum Engineering Evaluation with Logging Tools Gamma Ray. For formation or bed definition (e.g. distinguishing sands from shales). Spectra Gamma ray. Quantitative definition of the gamma ray spectrum; to define clay content, clay and mineral type, and to aid in fracture detection. Epithermal Neutron. To identify porosity of liquidfilled zones. Induction Resistivity. To help distinguish hydrocarbons from saline formation water and to help quantify the water saturation. Harold Vance Department of Petroleum Engineering Evaluation with Logging Tools High Resolution Density. To quantify porosity. Temperature. To indicate liquid level in the borehole and to delineate zones where fluids are actually being produced. Production. Production logs, such as borehole spinners, cam help to quantify the relative amount of production from each interval. Nuclear Magnetic Resonance. To help quantify the permeability of formations. Harold Vance Department of Petroleum Engineering MWD If a compressible fluid is used, conventional mud pulse telemetry tools cannot be used. Electromagnetic devices can. Harold Vance Department of Petroleum Engineering Coring Underbalanced Reducing coring fluid invasion allows for careful determinations of formation properties where wettability alteration has been minimized. Harold Vance Department of Petroleum Engineering Permeability and Deliverability Assessments Effective monitoring of production rates permits realtime decisions regarding changes in drilling depth, wellbore orientation, and overall section length. Harold Vance Department of Petroleum Engineering THE END Harold Vance Department of Petroleum Engineering ...
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