Vol. 59 No. 4

April 2007

Dennis Denney, JPT Technology Editor

Scale Treatment

Weatherford Intl. Inc. has introduced its ClearWELL electronic scale-treatment system (Fig. 1). The system prevents scale accumulation on piping walls and can prevent paraffin deposition. The system randomly propagates high-frequency pulses throughout the well system. At supersaturation, the signal promotes carbonate- and sulfate-scale formation in solution allowing it to be carried with the produced fluid rather than depositing on the pipe wall. As paraffin passes through the cloud point it is attracted to the scale that is in solution and also is transported in the produced fluids. The device is attached to the casing or wellhead with a ferrite clamp and emits a 120-kHz signal. The surface equipment and well pipe must be regarded as an open circuit from an electrical point of view. To generate a reasonable flow of electrons in an open-circuit conductor, it is necessary to provide a high-frequency source to a conductor that is long enough to generate a standing-wave voltage over its length. The system-signal quarter wavelength is 624.5 m. The standing-wave voltage will be equal to the source at the quarter wavelength and every half wavelength thereafter. A typical 4000-m wellbore is long enough for the de-vice to establish a standing wave across its whole length.

Fig. 1—Weatherford Intl. Inc.’s ClearWELL scale-treatment system installed on a west Texas oil well.

For additional information, visit www.weatherford.com/clearwell.

Gear Joint

The Moyno 2000 progressing-cavity pump uses a unique gear joint (Fig. 2) that enables handling a wide range of applications from shear-sensitive chemicals to difficult-to-process slurries. The crowned-gear universal-joint drivetrain configuration provides high torque and thrust control. The joint seals protect the gear joints from pumped-fluid contamination. The gear joints are grease-lubricated to run at a temperature of 180°F, much cooler than oil-lubricated joints. The rear gear-joint location in the pump reduces the radial load on the driveshaft and bearing, and results in minimal pump disassembly for servicing.

Fig. 2—Moyno 2000 progressing-cavity
pump gear joint.

For additional information, email literature@tdh-marketing.com.

Wireless Detector

PathFinder provides logging-while-drilling (LWD) measurements with its Slim Density Neutron Standoff Caliper Service as part of a 4 3/4-in. “slim triple combo” multiservice tool string, which includes directional, gamma ray, and resistivity tools. The system has a modular design for placement anywhere in the LWD tool string (Fig. 3). The system uses dynamic (weighted) standoff-based processing, which virtually eliminates standoff effects on density and neutron measurements, thus creating accurate and compensated density, neutron, and photoelectric index data. The system works in borehole sizes from 5 7/8 to 7 7/8 in. with flow rates up to 375 gal/min. The high-temperature/high-pressure tool series has ratings of 350°F and 25,000 psi. The tool provides real-time transmission of computed log data and quality parameters, and advanced petrophysical analysis is available. The spectral-density measurement uses scintillation detectors for formation density and photoelectric index determination. A low-energy californium-252 source is used for neutron porosity, and the tool provides enhanced porosities from three neutron detectors. Two ultrasonic transducers provide redundant standoff and while-rotating caliper measurements.

Fig. 3—PathFinder’s Slim Density Neutron Standoff Caliper Service tools.

For additional information, visit www.pathfinderlwd.com.

Reamer Technology

Security DBS Drill Bits announced that it has added a hole-enlargement product. The XR Reamer tool (Fig. 4) is designed for both conventional and rotary-steerable applications and provides concentric hole-enlargement technology. It is capable of enlarging a pilot hole by more than 40% while drilling. The reamer tool has activation and deactivation capabilities that allow selective enlargement on the basis of existing casing-shoe and well-design parameters. The reamer can be used in the string or in a near-bit application and can be deactivated after enlarging for drilling ahead with the original pilot-hole size and/or full-flow circulation. In one well, the reamer, in combination with the Geo-Pilot and FullDrift bit-matched system, enabled drilling ahead and enlarging a 700-m section of Cretaceous chalk with hard stringers from 12 1/4 to 17 1/2 in. in less than 72 hours. In a Norwegian offshore well, the reamer drilled 4661 m at 80° inclination.

Fig. 4—Security DBS Drill Bits’ hole-enlargement XR Reamer tool.

For additional information, email SecurityDBS@Halliburton.com.

Tomographic Velocity Inversion

Geotrace has developed its MultiScale, MultiParameter Simultaneous Inversion Tomography technology—MuST—to obtain 3D images of geologically complex areas. The subsurface contains many objects of many different sizes and shapes. To represent the Earth inside a computer, it is convenient to use a grid, such as a regular mesh of fixed-sized cells, on which all calculation and equations are solved. The single-cell-size representation of the Earth is a convenient way to do calculations. However, when high resolution is required, small-size cells also are required, and the inversion becomes unstable. High-resolution readings are needed in some places, but not everywhere. This technology uses a multigrid representation of the velocity model. The grids have different cell sizes, which normally are multiples of each other. The multiple velocity models have common gridpoints wherever the grids cross. As long as the velocity models for these different grids agree at the crossing points, the solution is valid. This solution can perform inversions for all the grids simultaneously in a consistent manner. The multigrid approach yields an Earth representation that has different scales in various regions. As shown in Fig. 5, the optimal representation is such that the dominant scale is the natural (red) grid-cell size (Scale 1). At a certain depth, the dominant scale becomes larger (yellow) allowing a coarser representation (Scale 2), but around the fault there is a need for higher resolution, so the dominant scale is reduced to the smaller (white) grid cell (Scale 3). Finer grids are used in areas where the geology is expected to exhibit significant spatial variations, and coarser grid in simpler sedimentary areas.

Fig. 5—In the Geotrace MuST technology, the grids receive different weights depending on the underlying geology.

For additional information, visit www.geotrace.com

High-Temperature Voltage Regulators

CISSOID S.A., a provider of application-specific integrated-circuit and high-temperature electronics for harsh environments, offers its low-dropout and negative-low-dropout voltage regulators for oil and gas applications. The company’s CHT-LDO/LDN family of positive/negative 1-A low-dropout voltage (1 V at 225°C and 400 mA) regulators (Fig. 6) is specified for a temperature range from –40 to 225°C, avoiding screening and high-temperature testing. These circuits are built with silicon-on-insulator semiconductor technology for high temperatures (low leakage and latch-up free). One-die solution and special on-chip (tungsten) interconnections make this circuit reliable for long-term operation at extreme temperatures. These regulators have reached 8,000 hours of continuous operation at 300°C with no drift or failure. The U.S. National Aeronautics and Space Administration Glenn Research Center tested the voltage regulators at temperatures as low as –195°C, demonstrating an operational temperature range from –195 to +300°C. Standard output voltage ranges from 2.5 to 15 V, with custom values possible.

Fig. 6—CISSOID’s high-temperature semiconductors.

For additional information, visit www.cissoid.com.