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Vol. 59 No. 2
February 2007
Dennis Denney, JPT Technology Editor
Self-Sharpening PDC Bit
Varel Intl. 7 7/8-in.
matrix-bodied WISE bit.
Current drilling activity continues to extend polycrystalline-diamond-compact (PDC) -bit activity into deeper, harder, and more-abrasive drilling environments. As a result and to reduce operational costs, there is a need for PDC bits that drill faster and last longer in these applications. Varel Intl. is launching its WISE-technology PDC bits developed with high-abrasion-resistance cutters, which help delay the wear-initiation process. To improve PDC drilling performance, bit development focused on development of high-performance PDC cutters, formation-drillability analysis, bit-behavior and performance-prediction tools, and computational-fluid-dynamics modeling. However, and as is the case in hard and/or abrasive formations, wear always occurs. These bits incorporate a unique cutting structure (cutter layout) that establishes a self-sharpening effect on the PDC cutters. In this regard, the cutters gain aggressiveness with depth, as formations get harder and more abrasive. Therefore, the bits are able to shear deeper harder formations effectively with minimal weight-on-bit requirements.
For additional information, visit www.varelintl.com.
Openhole and Cased-Hole Solid Expandables
Weatherford is introducing its new-generation MetalSkin openhole and cased-hole solid-expandable systems. These systems incorporate an improved design with more running clearance to avoid equivalent-circulation-density problems and differential sticking. Other key system components include retrievable collapsible/expandable cones for contingent recovery, fully qualified premium metal-to-metal expandable connectors, and elastomeric sealing elements that enhance pressure containment. Also, each system includes a hydraulically assisted backup expansion system, which provides an important operational contingency. The systems use a positive seal with a circulation valve for more-reliable pressure containment than conventional dart seals. These systems can provide single-trip efficiency. Four distinct solutions have been developed. The openhole-clad and openhole-liner systems help mitigate drilling hazards. The monobore system is an 11 3/4 x 13 3/8-in. openhole liner system that can extend a 13 3/8- or 13 5/8-in. casing and maintain a 12 1/4-in. drift of the expanded casing. The cased-hole-liner system is designed for casing repair. In mature fields, corroded or parted casing requires long-term repair. Cement squeezes often break down or require multiple efforts. Elastomer bands around the liner provide multiple seals to stop wellbore leaks. The openhole-liner system maximizes hole size during hole deepening and sidetracking operations by providing an added casing string while minimizing hole-size reduction.
Fig. 2—A pre-expanded openhole-clad system can easily be passed through a
previously installed openhole-clad system and expanded again to remediate the
subsequent drilling hazard.
For additional information, visit www.weatherford.com/metalskin.
Lower Operating Temperature of Downhole Motors
Duoline’s Thermoline thermal
lining system with proprietary grout
used in tandem with composite liners.
Duoline Technologies enabled an independent producer to lower the operating temperature of electrical submersible pumps (ESPs) by installing a Thermoline production string, a concentric tube with a special-grout system that provides a highly effective insulating layer between produced fluids and the surrounding environment. The annulus between the production tubing and the glass-reinforced-epoxy inner liner is filled with a grout containing glass beads. The shrouded ESP motors were overheating and scaling up, even though the static bottomhole temperature was a relatively mild 130°F. It was suspected that as fluid rose in the tubing, waste heat was transferred to the cooler, falling annular fluids through the tubing wall above the pumps, and that this adverse heat-cycle buildup exceeded the motor’s thermal rating and caused scale precipitation. In one project, a total of 1,500 ft of insulated pipe was installed in three wells, approximately 500 ft above each pump and across the perforated interval. The operating temperature of the ESP motors immediately dropped by 50°F.
For additional information, e-mail pjay@duoline.com.
Green Polymer Slurries
Benchmark Energy Products has introduced its GreensKeeper line of environmentally friendly polymer slurries for well stimulation and other treatment applications. The polymer solutions include guar, guar derivatives, and other polymer concentrates that are stable for extended periods at temperatures higher than 100°F and can be pumped and poured at subzero (°F) conditions. These solutions are compatible with the boron, titanium, and zirconium crosslinkers used to formulate crosslinked fracturing fluids. The solutions are nonflammable, are not regulated regarding transportation, and are compliant with the U.S. Safe Drinking Water Act of 1974. The polymers are coalbed-methane compatible, have 1% phase separation, and do not form sludge. The polymer’s flashpoint is 200°F and the specific-gravity range is 0.75 to 0.82, with a pour point of -10 to -30°F. The benzene concentration is 5 parts per billion, with total aromatics less than 0.5 wt% and polynuclear aromatics less than 0.001 wt%.
For additional information, visit www.benchmark-research.com.
Vertical Pump
Moyno
Vertical Pump
The Moyno Vertical Pump is designed for use at depths to 20 ft (Fig. 4). The pump has an extra-long intermediate shaft supported by a flange bearing with replaceable bushings. Its inlet is submerged and set to pull fluid from the bottom of a sump, pit, or other underground storage vessel and discharge the fluid at the surface for further processing downstream. An optional suction strainer prevents debris from entering the pump. The pump is a progressing-cavity pump. A single-helical rotor rolls eccentrically inside the double-helical stator, creating the pumping action. The rotor, in conjunction with the stator, forms a series of sealed cavities 180° apart. As the rotor turns, the cavities progress from the suction to the discharge end of the pump. As one cavity volume diminishes, the opposing cavity volume increases at exactly the same rate. Thus, the sum of the two discharges is a constant volume, and the result is a pulsation-free positive-displacement flow that does not use valves. The abrasive-handling characteristics and low-shear flow make the pump useful for transferring heavy crude oil and shear-sensitive fluid. The pump can be flange mounted to closed tanks or affixed to mounting beams above open tanks.
For additional information, e-mail literature@tdh-marketing.com
Liner Drilling
Baker Oil Tools and Hughes Christensen developed the EZLine liner drilling system to place casing across problematic zones. The system reduces occurrences of stuck pipe, lost circulation, and lost hole sections. The EZCase casing bit uses standard PDC cutting structures and is designed specifically to drill new hole. The cutters are mounted on a composite-steel body that is strong enough to drill through problematic formations, yet it is drillable with a milled-tooth or custom-PDC bit to drill the next hole section. The system outside diameter is smaller than conventional liner hangers, which increases the annular area for cuttings removal and keeps debris from packing off around the top of the liner. A tieback extension is used on top of the liner if an isolation packer is required as a secondary pressure barrier or if problems occur with the primary cement job. An increased torque requirement when drilling or reaming down is accommodated through special casing connections. The hydraulic efficiency of the bit has been op-timized through computational-fluid-dynamics analysis on the frame of the bit to maximize cooling, cleaning, and cuttings ejection. A lift nipple enables picking up the liner assembly with the elevators and set slips. A junk cover keeps cuttings and debris from falling inside of the tieback sleeve, which ensures that the liner will release from the setting tool. A polished-bore-receptical packoff provides a way to pack off and seal the work string to the liner and acts as a secondary debris barrier. The liner-setting tool provides a way to run the liner into the hole and transfer high torque from the work string to the liner.
For additional information, visit www.bakeroiltools.com.
