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Open Hole Services

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Gamma Ray (MCG) Tool

gamma ray (MCG) tool combines gamma ray, temperature, and casing-collar locator (CCL) logs with power conversion and surface communications for all other measurements in a Compact tool string. It is always the top tool in the string. The auxiliary gamma sub (MGS) is shorter and can be placed anywhere in the string, enabling gamma radiation and temperature to be recorded close to the bottom of the well. An integral power conditioner in the MCG tool automatically converts a wide range of cablehead voltages to a standard value for all tools in the Compact string. This feature adds to the system’s flexibility and reliability by eliminating the need to match surface power to particular logging cables. The MCG tool also processes data from the following auxiliary measurements: spontaneous potential originating from the array induction (MAI) and dual laterolog (MDL) tools; tension from the tension cablehead (MCB-A and MCC); tension and compression from the tension compression sub (TCS); external temperature; and CCL.


Determining the volume of shale content in simple lithologies, such as shaly sand

 Correlating well-to-well details in open and cased hole

 Providing primary log for depth correlation of other logging tools in the same well

Features, Advantages and Benefits

The NaI detector is rugged, reliable, and sensitive, providing a full range of accurate data for quantitative analysis and repeatability.

The tool’s 2- to 3-ft (0.61- to 0.91-m) depth of investigation enables the detection of gamma rays through several strings of casing.

The tool’s 3-ft (0.91-m) vertical resolution enables accurate identification of formation contacts and is widely used for well-to-well correlation and between log runs.

Spectral Gamma Ray (SGR) Tool

spectral gamma ray (SGR) tool provides superior clay type and volume analysis by measuring gamma ray energy from the naturally occurring radioactive elements potassium, uranium and thorium. The SGR tool measures naturally occurring radioactive elements in formations to provide clay type and volume analysis. The tool contains a large scintillation crystal which provides higher detection efficiency and sensitivity. The result is a detailed spectrum of 256 discrete data channels. Surface processing uses five energy windows to “strip” relative concentrations of potassium, uranium and thorium from the raw spectra. The resulting log displays potassium content as a percentage of uranium and thorium contents in ppm. A total gamma curve equivalent to a regular natural gamma ray is also displayed, along with a uranium-free gamma ray curve. The tool is almost always run in combination with the Spectral Pe Density (SPeD) and Compensated Neutron Tool (CNT). These tools also can be combined with other services.


Quantitative measurement of actual radiation and separation into its three predominant components: potassium, uranium and thorium

 Determination of clay and shale volumes

 Clay typing

 Heavy mineral identification

 Input for complex lithology analysis

 Differentiation between radioactive pay zones and shales 

Identification of fractured and highly permeable zones where high uranium concentrations are present

 Detailed well-to-well correlation

Features, Advantages and Benefits

The highly sensitive NaI detector provides accurate spectral analysis of natural gamma ray energies.

 Detailed spectrum determines Potassium, Uranium, and Thorium weight concentrations in the formation.

Compensated dual neutron

A compensated neutron log is useful for identifying zones of interest and determining perforating depths, tracking gas cap movement and gas encroachment under shale layers, as a correlation between open and cased hole where a gamma ray is not indicative, and to measure overall porosity of the well.

 Density/photo electric effect (PE)/Caliper

The photoelectric effect, or Pe, measures a formation's ability to absorb gamma rays. The absorptive abilities of formations vary with lithology. The photoelectric absorption is recorded as a supplementary measurement to the formation density measurement, using common detectors and radioactive sources. Since this measurement is part of the density measurement, the tool is a pad contact tool and is subject to borehole wall rugosity. The measurement is not valid in muds weighted with barite. The recording can be used both for correlation of formations between wells and for determining lithology.

Array Induction (MAI) Tool

Weatherford’s Compact array induction (MAI) tool acquires and records data that can be used to determine true formation resistivity (Rt ) in openhole environments. The MAI tool provides raw data from multiple subarrays, which are integrated vertically and radially with environment-dependent processing to produce five depths of investigation. This data is provided in a broad range of borehole environments. When the MAI tool is run with a high vertical-resolution-proximity device, such as the shallow-focused electric (MFE) tool—a mandrel-type tool—or with the flushed-zone resistivity (MMR) tool—a standard pad-type tool—the advanced processing includes true formation resistivity and enhances vertical resolution to 4 in. (10.00 cm).


Determining formation conductivity  Determining water saturation (Sw)  Providing well-to-well correlation  Identifying moveable fluids  

Identifying fluid contacts

 Creating an invasion profile

 Providing thin-bed analysis

Features, Advantages and Benefits

The enhanced vertical resolution and radial profiling improve accuracy in Rt determination, resulting in more accurate reserve estimates.

 The unique profile of the tool facilitates flexible deployment, in wireline or memory mode, to mitigate the risk of bridging events and reduce nonproductive time.

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Focused electric (shallow resistivity)

Laterlog (salt system resistivity)

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Spontaneous potential (sp)

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Borehole Navigation (surveys in open hole only)

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Micro imager(borehole image which requires processing via       Weatherford or other)

Micro log (mud cakes, or mud logs)

Compensated sonic (monopole sonic)

Dipole sonic

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Cross dipole (dipole + navigation for orientation.

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Geochemical Spectroscopy instrument (elemental or minerology)

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High resolution temperature

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Two arm caliper

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Formation Tester (fort worth specialty - pressure and flow rate)

 Dual Laterolog (MDL) Tool

laterolog (MDL) tool is the resistivity tool of choice in wells drilled in high-contrast, true formation resistivities (Rt ) / mud resistivities (Rm) environments. The MDL tool provides individually optimized deep- and shallowpenetration curves that share a common 2-ft (0.6-m) vertical resolution. Optimizedelectrode geometry and digital-measurement sequence control give the tool excellent environmental performance over a wide range of Rm and hole sizes and virtually eliminate electrode-polarization effects. The voltage reference and simultaneous SP electrodes are incorporated into a stiff bridle at the top of the tool string to optimize reliability. The cableless logging variant enables the MDL to be run without a wireline. The Groningen curve is used with the deep measurement to detect anomalous responses as the tool approaches nonconductive formations, such as salt caps. The MDL tool is normally run with the microlaterolog (MMR) or microlog (MML) tool to determine the invaded-zone resistivity


Determining formation resistivity in conductive-mud environments  Determining water saturation (Sw) Providing well-to-well correlation  Identifying moveable fluids  Identifying fluid contacts  Creating an invasion profile to indicate permeability, when used with the flushed-zone resistivity (Rxo) MMR tool

Features, Advantages and Benefits

The arrangement of the electrodes on the MDL tool detects the Groningen effect for quality control to provide accurate, real-time, deep-resistivity readings.  The MDL can be run in combination with the microresistivity (MMR/MML) tool to obtain an independent, shallower measurement for improved accuracy in determining Rxo and Rt in complex invasion profiles.

 Data from the microresistivity (MMR) or the shallow-focoused electric (MFE) tool can be used to significantly enhance the vertical resolution of the MDL to less than 1 ft (0.3 m) for improved thin-bed analysis and reserve estimates.  The small diameter of the tool facilitates flexible deployment in wireline or memory mode to mitigate the risk of bridging events and reduce nonproductive time.

 Photodensity (MPD) Tool

photodensity (MPD) tool provides bulk density, caliper, and photoelectric (Pe ) factor for porosity and lithology determination in conventional and slim wells. The unique profile of the tool enables it to pass through restrictions as small as 2.5 in. (57 mm). The density and Pe detection and processing system are contained in an articulated shoe, which maintains closer contact with the formation over caved intervals, eliminating the gross errors typical of mandrel tools in similar conditions. The highly optimized shoe has smaller borehole size corrections than many conventional tools. A connector at the bottom of the tool can be rotated 180° to provide 0.5 in. (13 mm) of standoff to tools below. It is normally used to eccentralize the induction (MAI) tool and eliminates the need for an intersonde crank.


Determining formation porosity and lithology 

Logging through-drillpipe past severe hole conditions

 Determining fluid density (in combination with other measurements)  Identifying formation gas

 Identifying mineral properties  Providing input to advanced formation-evaluation programs  Providing input to determine mechanical properties of rock  Providing input to seismic programs  Providing detailed well-to-well correlation

Delineating the reservoir

Features, Advantages and Benefits

 The MPD uses an articulated shoe that reduces the effects of borehole size and rugosity and provides a high-quality density measurement.

 The unique profile of the tool facilitates flexible deployment, in wireline or memory mode, to mitigate the risk of bridging events and reduce nonproductive time.

Dual Neutron (MDN) Tool

 dual neutron (MDN) tool provides a boreholecompensated porosity measurement. The MDN is fully characterized for air and mud-filled environments in both open- and cased-hole wells. The tool design minimizes sensitivity to environmental effects; for example, borehole size corrections are smaller than those for conventionally sized tools. Full environmental corrections are applied automatically during data acquisition. Porosity is recorded simultaneously in apparent limestone, sandstone, and dolomite porosity units. Enhanced resolution processing is available when acquiring data at a high sample rate. The MDN tool is usually run with a V-bow spring, which forces the tool against the borehole wall for maximum porosity sensitivity. In oval boreholes, this doublespring eccentralizer can keep the photodensity (MPD) tool, which is normally placed below the MDN, aligned along the short axis.


Determining porosity and lithology Gas identification (with density porosity)

Determining shale volume  Providing input for water-saturation calculations

 Providing detailed well-to-well correlation 

Delineating the reservoir  Determining porosity in open- and cased-hole environments

Features, Advantages and Benefits

The MDN tool is designed with the latest advances in modeling and detector technologies to deliver excellent porosity sensitivity and a 65 percent reduction in radioactive source activity for safer operation and simpler transportation.

 The tool’s small diameter enables flexible deployment.

 The tool is characterized for air- and mud-filled environments.

Cross-Dipole Sonic (CXD)

cross-dipole sonic (CXD) tool combines monopole and cross-dipole sonic technology, providing acoustic data for a wide variety of geophysical, petrophysical, and geomechanical applications. The data obtained by the CXD tool assists in improving reservoir characterization and ultimately maximizes well and reservoir productivity. The tool incorporates three high-powered transmitters—one monopole and two wideband, low-frequency, dipole transmitters perpendicular to each other. The receiver section has an array of eight receiver stations. Each receiver station consists of four gain-matched, piezoelectric hydrophones that are aligned with the dipole transmitters. Ninety-six, high-fidelity, wideband waveforms are recorded, ensuring excellent quality control. Patented isolator technology prevents direct flexural wave transmission to the receivers through the tool body and provides a rugged tool for flexible conveyance. Anisotropic orientation data is produced by combining the CXD with either the Compact borehole navigation (MBN) tool or the Compact microimager (CMI) tool.


Geophysics – Velocity calibration, time/depth conversion – Amplitude variation with offset (AVO) calibration


– Porosity estimation and lithology

– Gas identification  Geomechanical – Anisotropic presence, magnitude, and orientation

– Elastic properties

– Hydraulic-fracture design

– Sanding potential

Features, Advantages and Benefits

Propriety transmitter and receiver design produces high-data quality over a broad range of environmental conditions.

The small diameter and length of the tool facilitate flexible deployment, in wireline or memory mode, to mitigate the risk of bridging events and reduce nonproductive time.

The CXD records all waveform data into flash memory, independently from the data communicated by wireline, for data assurance.

Sonic Sonde (MSS)

sonic sonde (MSS) measures formation compressional slowness (inverse velocity) at five spacings with 1- and 2-ft (0.30- and 0.61-m) vertical resolution. In cement bond log (CBL)/variable density log (VDL) mode, the MSS tool records a waveform (normally from the 5-ft [1.52-m] receiver) and up to four first-arrival amplitude logs. The ratio of two amplitude curves defines an attenuation log that is sensitive to cement bond quality. Data quality is maintained at high levels over a broad range of environmental conditions from a combination of high transmitter output, real-time despiking, and cycle-stretch compensation. Cycle-stretch compensation gives improved accuracy and consistency by adjusting transit times based on information about waveform shapes close to the first arrivals.


Determining secondary porosity and lithology

Providing formation mechanical properties

Providing fracture detection Providing gas detection Integrating seismic, time-to-depth corrections

Providing a synthetic seismogram (when used with the MPD tool) Providing a CBL

Features, Advantages and Benefits

Unlike traditional 3- to 5-ft (0.91- to 1.52-m) sonic tools, the MSS uses a single-sided array with depth-derived, cave compensation and tilt correction. This feature, together with a short electronics package, makes the tool unusually short and light.

The MSS passes through restrictions as small as 2.5 in. (63 mm), enabling throughdrillpipe logging for increased operational efficiency

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