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Vol. 231 No. 9 |
Water-based drilling fluids for shale gas
Newpark Drilling Fluids has introduced its Evolution water-based drilling fluids system for Haynesville Shale operators who require a clean, robust alternative to the diesel-based fluids historically required in that area’s harsh drilling environment. In Haynesville Shale applications to date, the new drilling fluid system provided improved penetration rates, wellbore protection and lubricity while standing up to the requirements of temperature, containments and drilled solids. While the new system was originally conceived as a Haynesville-specific drilling fluid, the design concept may provide operational advantages in many other unconventional shale gas applications worldwide. The Evolution system features a clay-free combination of two central components: EvoVis, a polymeric viscosifier; and EvoLube, a high-pressure/high-temperature lubricant that delivers coefficient-of-friction values similar to oil-based mud. Both components, and the system itself, have proven stable to wellbore temperatures of 400°F—even in the presence of CO2, which is common to Haynesville geology. Its thermal stability, contaminant resistance and overall performance differentiate it from other water-based systems. The EvoLube lubricant is credited with penetration rates exceeding those of offset wells where oil-based mud was used.
Extended-life drill motors Mpact Downhole Motors has introduced drilling motors with a stator elastomer material designated Mpact 114 that delivers increased performance, reliability and extended service life. Laboratory testing using a dynamometer, along with field performance under a range of drilling conditions, verified that the Mpact 114 can effectively handle greater differential pressure than standard NBR and HNBR elastomers, developing 62% more horsepower and increasing life expectancy by a factor of four. Drilling motor designs are available for maximum performance in extremely difficult drilling applications.
Fluid additive systems
Schlumberger has released its new OpenFRAC family of hydraulic fracturing fluid additive systems. They can be used for fracturing stimulation treatments, including applications in low-permeability formations such as shale and tight gas sands. The additives are fully functional and disclosable, providing comparable technical performance to conventional systems. Three variants are available, all water-based, viscosified fluids. OpenFRAC SW formulation is used for slickwater fracturing, where drag reduction and less complex fluid systems are desired. OpenFRAC WF is the linear gel variant, offering improved proppant transport characteristics. For crosslinking, OpenFRAC XL offers the characteristics of the other two fluids, while creating wider fractures to enable high proppant concentrations and generate high fracture conductivity.
Tool to melt hydrates The international energy services company Wood Group has launched a new hydrate-liquefying tool to melt ice and paraffin blockages that occur in the production pipes of oil and gas wells. The Thermal Moderator Tool (TMT), designed by Wood Group Logging Services, can be used in pipes with inside diameters as small as 1 in. The tool was developed as a non-chemical solution to eliminate hydrate blockages. It is rated to 15,000 psi, is portable and can be run in coiled tubing, flowlines and other small-channel systems.
Continuous circulation system
The ability to maintain continuous, uninterrupted circulation can be of direct benefit while drilling the pressure-sensitive formations encountered in deepwater wells. The Continuous Circulation System (CCS) was developed for this purpose over the last decade as the result of a joint industry project based in the UK and supported by BG, BP, Eni, Shell UK, Statoil and Total, managed by Maris International, and with the detailed engineering and manufacture carried out by National Oilwell Varco (NOV). The system is rig-floor based, can be deployed on any rig with a top drive and requires no change to the drillstring. It can be introduced at any stage in the well. Once positioned on the rig floor, drilling continues through the main unit, a pressure vessel constructed from three single-ram BOP bodies. With the drill pipe tool joints isolated between two sets of pipe rams, the connection can be safely broken and a new drill pipe added or removed without interrupting circulation to the wellbore. This eliminates the negative and positive pressure surges associated with stop/start circulation when making connections in conventional drilling, which in turn minimizes “wellbore ballooning” and the possibility of flows from, or losses to, the wellbore. Since circulation is continuous, pressure-sensitive formations can be drilled with minimum mud weight—i.e, no static overbalance—using the equivalent circulating density to control the well. The CCS is self contained and computer controlled.
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