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Collaborating Authors
Drill pipe selection
Abstract This paper provides an explanation of the concept of the AG-itator, presents field performance results and examines the potential use of the tool in CT (Coiled Tubing) drilling and workover operations. The tool has been widely used as a solution to the major problems associated with slide or oriented drilling. The concept of the tool is based on reducing friction and providing accurate weight transfer to the bit. Typical applications include; sliding with a PDM-PDC combination where previously difficult or impossible; overcoming motor stalling problems; increasing ROP and extending the length of oriented intervals. The technology is to be developed as a CT tool and is expected to be particularly useful, as CT operations are characterised by constant non-rotation and high levels of friction. These two factors ultimately lead to helical buckling which can limit the effective reach of CT drilling or workover operations. The fluid action of the tool creates pressure pulses that generate an axial force of approximately 15,000lb at a frequency of 16Hz (refer to Fig 1). These pulses gently oscillate the bottom hole assembly (BHA), reducing friction and improving weight transfer. In this way, weight is transferred to the bit, continuously and accurately without harsh impact forces. It has been demonstrated that the tools’ fluid action is benign, as it has not damaged the bit, tubulars or more sensitive equipment such as MWD/LWD. Consequently, standard downhole equipment can be used with the tool. It is argued that accurate weight transfer improves drilling performance in several ways (1) PDC bit life can be extended as the bit is prevented from constantly spudding into the formation. Additionally, both roller cone and PDC bits can be run without the risk of damage to bit teeth or bearings; post run bit characteristics have shown that no damage to the bit occurred as a result of impact forces. (2) Higher levels of WOB can be achieved using lower off hook weight. (3) There is reduced drill pipe compression as weight is transferred effectively and not dissipated at points where the BHA or drillstring hangs up. (4) Tool face control is enhanced. (5) Gross rates of penetration are increased. Applications for the technology exist in all modes of drilling but usage appears particularly beneficial in non-rotating drillstrings and BHAs. Such applications are increasingly common as well profiles become more tortuous and the limits of extended reach and directional drilling are reached. Run data shows that the tool is a simple way of extending the reach and capability of conventional steerable assemblies. Accurate weight transfer and exceptional tool face control have been logged using PDC bits, even in significantly depleted formations after large azimuth changes. Intervals have been extended and drilled with higher ROPs while problems associated with setting and maintaining tool face have been minimised. The technology is compatible with MWD systems and is a viable means of extending targets whilst improving ROP, reducing rock bit runs and lowering the risk of differential sticking. Before assessing the use of the technology to extend the reach of CT BHAs, it is worth looking at field performance. Extending the reach of Conventional Steerable Assemblies - A Case History in the Dutch sector of the North Sea The 5 7/8" section of a development well was to be drilled in the Silverpit, Lower Slochteren and Westphalian formations in the Dutch Sector of the North Sea. The drilling objectives for this section were to build inclination from 42° to 84° at the top of the Lower Slochteren, and then to maintain a tangent before dropping angle to TD. The measured depths were recorded as 3,645 and 4,373 metres respectively. Subsequently, a sub-horizontal drain of 85° was to be drilled by a BHA incorporating the AG-itator (Refer to Fig 4). The purpose of using the technology was to provide accurate weight transfer to the bit during slide drilling, thereby minimising motor stalling, the BHA hanging up and to make tool face orientation easier.
- Europe > United Kingdom > North Sea (0.44)
- Europe > Norway > North Sea (0.44)
- Europe > Netherlands > North Sea (0.44)
- (2 more...)
- Europe > Netherlands > North Sea > Dutch Sector > L13 License > Lower Slochteren Formation (0.94)
- Europe > United Kingdom > North Sea > Southern North Sea > Southern Gas Basin > Silver Pit Basin (0.89)
- Europe > Germany > Westphalian Basin (0.89)
- Well Drilling > Drillstring Design > Drill pipe selection (1.00)
- Well Drilling > Drilling Operations > Directional drilling (1.00)
- Well Drilling > Drill Bits > Bit design (1.00)
Abstract A new high-pressure coiled-tubing (CT) drilling system has been developed with support from the DOE that drills 2 to 3 times faster than conventional CT motors. Downhole motors have been developed that utilize diamond thrust bearings, titanium flexshafts, high-pressure rotor/stator sections and other advanced features that allow these motors to operate at high pressures. Laboratory tests have been conducted using the high-pressure system to cut 1 to 2 inch deep helical slots in wellbore walls to remove formation damage (patent pending) and to drill cement out of drillpipe at rates up to 1,400 ft/hr compared to 60 ft/hr for conventional motors. This jet-drilling system can also be used to remove barite scale from tubing, to clean slotted liners, to ream holes at high rates, and to under-ream when drilling with casing. The high-pressure system will be field tested and commercialized during the next phase of this DOE project. Introduction Maurer Engineering Inc. (MEI), under contract to the United States Department of Energy (DOE), has completed laboratory testing of a high-pressure CT drilling system. The system is now ready for field trials. High-pressure (10,000 psi) jet drilling systems have shown they can drill oil and gas well at high rates, but they have not been commercialized due to problems with leaking drill-pipe tool joints. CT is a continuous reel of tubing that contains no connections and therefore eliminates leakage problems associated with drillpipe. This feature offers the opportunity for successful implementation of high-pressure drilling. MEI developed a special high-pressure motor for use with the high-pressure CT drilling system and has successfully completed laboratory tests of critical components. With jet assisted drilling, high-pressure jets cut kerfs into rock ahead of the bit and then mechanical cutters break the rock ledges between the kerfs (Figure 1). Jet assisted drilling has the potential to significantly increase penetration rates in many formations. Figure 2 shows the results of laboratory drilling tests conducted for the Air Force in 19861 where jet-assisted bits drilled at 1000 ft/hr compared to 300 ft/hr for conventional drilling motors and 100 ft/hr for rotary drills. Figure 3 shows the high-pressure CT system. The two critical components of the system are the downhole motor that must operate at 10,000 psi and the CT that must not fatigue at high operating fluid pressures. MEI developed a Moineau motor that operates at 10,000 psi (Figure 4). This motor uses diamond thrust bearings to absorb the high loads caused by the pressure drop across the bit. A proprietary rotor/stator design is used that allows the motor to operate at high pressures. Additional design details on the high-pressure motors are presented in the ASME paper ETCE2000/Drill-10098. Coiled Tubing As coiled tubing (CT) is reeled on and off the reel and over the gooseneck, it yields and eventually fails from fatigue. Fatigue life of the tubing is significantly reduced when CT is operated at high pressures. Grades of CT readily available today will fail after about 50 to 90 cycles when operating at 10,000 psi pressure. Therefore, improved CT had to be developed for use with this high-pressure drilling system. Quantity Tubing worked with MEI to develop QT-1200 CT, which provides much longer fatigue life than conventional grades. The new tubing was extensively tested on the fatigue machine shown in Figure 5. The laboratory tests showed that QT-1200 CT will operate for 240 cycles at 10,000 psi before it fails, compared to 90 cycles for QT-1000 tubing (Figure 6). In addition, other manufacturers have developed composite CT that will operate at 10,000 psi pressure for over 1000 cycles without fatigue failure.
- Geology > Mineral (0.56)
- Geology > Rock Type > Sedimentary Rock (0.30)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > North America Government > United States Government (0.89)
- Well Drilling > Drillstring Design > Drill pipe selection (1.00)
- Well Drilling > Drilling Operations > Coiled tubing drilling (1.00)
- Well Drilling > Drilling Equipment (1.00)
- (2 more...)
Abstract In the past, tubing, casing and drill pipe recovery has been employed where chemical and explosive severing tools could not effectively sever the pipe. A coiled-tubing-conveyed hydromechanical pipe cutting system has proven to be a viable alternative to pipe recovery when conventional severing systems are not effective. The system does not contain or require any hazardous materials, which makes it safer to use than conventional systems. The pipe cutting system incorporates modular stabilizing devices that decrease the risk of the coiled tubing forces and the wellbore deviation from interfering with the cutting operation. The pipe-cutting mechanism uses several unique blade configurations that were designed specifically to address various metallurgical properties and dimensions. The cutting blades contain state-of-the-art cutting inserts, which were previously proved in various metal milling and cutting applications within subterranean wells. A detailed description of the coiled-tubing-conveyed hydromechanical pipe cutting system, its operational function and a variety of case histories are discussed in this paper. Introduction Electrical wireline-conveyed explosive jet and chemical cutters are currently the preferred choices for cutting pipe in slimhole wellbores. Explosive jet cutters are used for severing common sizes of production tubing, drill pipe and casing. The cutting action is produced by a circular-shaped charge. Typically, this type of cutter leaves a flare on the severed pipe string. In order to perform subsequent pipe recovery operations, it is necessary to smooth the top end of the tubing left in the wellbore with an internal mill insert that is usually run with an overshot. Chemical cutters are designed to cut through one string of pipe while not damaging the adjacent string. They produce a flare-free and undistorted cut. The topside of the severed pipe can be engaged with an overshot without dressing with a mill. A wireline-conveyance operation provides several advantages when compared to using coiled tubing and threaded pipe. Wireline equipment can be mobilized and disassembled quickly; the wireline can be run in and out of a hole much faster; and the cost of a wireline operation is usually less than other methods. The success rate can be reduced, however, when wireline-conveyed cutting tools are used for exotic applications such as cutting through plastic coated or corrosion-resistant alloys. High-density wellbore fluids, a greater-than-standard pipe wall thickness and distance between the cutter and the internal wall of the pipe also reduce the effectiveness of the wireline-conveyed systems. Another drawback is that the wireline systems are designed to cut only one string of pipe per operation. Therefore, several trips into the wellbore are required to separate multiple, adjacent strings internally. The limitations of wireline-conveyed cutters can be overcome for the specific applications noted above with a hydromechanical pipe cutting system (HPCS) that takes advantage of proven, downhole metal cutting technology. The HPCS is activated by weight or hydraulic pressure. It can be rotated by a downhole workover motor or from the surface using a rotary rig or power swivel. The HPCS provides the power needed to cleanly cut single or multiple strings of pipe downhole. Such non-distorted pipe cuts are especially beneficial when it is necessary to recover pipe that is stuck in open hole. Time is a critical factor for a successful pipe recovery operation. The quicker the fishing jar assembly can be employed the greater the chances of a successful pipe recovery operation. The clean top of the severed drillpipe left by the HPCS improves efficiency in employing the fishing assembly. History Until the early 1990s, very few pipe-cutting operations were attempted using coiled tubing as a conveyance means.
- Well Drilling > Drillstring Design > Drill pipe selection (1.00)
- Well Completion > Completion Installation and Operations > Coiled tubing operations (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
- Production and Well Operations > Well Intervention (1.00)