Vacuum Flask: Instrument, Down hole, Wireline logging, Oilfield and Geothermal

This a limited list of the many downhole tools we have flasked. If you don't see a particular tool listed, please contact us.


Temperature logging is a fundamental production logging measurement. It measures the well bore fluid's temperature gradient primarily to identify fluid flow via fluid production or fluid loss. The temperature sensor is a RTD or thermocouple. Some sensor designs place the sensor in a protective hermetic thermowell while other designs use a sheathed sensor exposed directly to the well bore fluid. RTDs and thermocouples can withstand high well bore temperatures but the associated electronics are thermally protected within a vacuum flask from high well bore temperatures.

A good tool design:

  • maximizes the sensor's exposure to well bore fluid flow (to increase sensitivity to temperature changes) while also mechanically protecting the slender protruding sensor from impact damage within a protective cage.
  • has sufficient distance between the sensor and the tool body's thermal mass. If the sensor is too close it becomes excessively influenced by the tool body's temperature instead of the well bore fluid's temperature. The sensor in part essentially measures the tool's body temperature response to the well bore fluid instead of the well bore fluid itself which reduces the sensor's temperature response time.

Typically, the sensor is at the bottom of the tool although some designs place the sensor mid length in the tool to allow other tools to be connected below the temperature tool section.


Pressure is another fundamental production logging measurement. Pressure logging is also used in steam injection and geothermal wells to differentiate steam and liquid. A relatively new form of pressure logging uses high speed fast sample rate capture during fracturing and perforating operations to capture rebounding pressure return signals from the formation.

The pressure transducer is thermally protected within the flask. Fluid pressure is brought to the transducer via a small diameter buffer tube (oil filled tube). The buffer tube is a conductive heat path into the flask but if the tube is stainless material less heat is transferred than one would think.

Pressure sensor measurements must be temperature compensated and consequently a temperature sensor is required mounted on or near the pressure sensor. Some pressure and temperature logging tools that are not flasked use the well bore temperature sensor's measurement to infer the temperature of the pressure sensor. In order for such a tool to be flasked, the tool requires adding a second temperature sensor (mounted on or near the pressure sensor) since the well bore temperature and internal flask temperature will be drastically different.

Flow (Spinner)

Flow is also a fundamental production logging measurement using a free spinning impeller to infer fluid flow by measuring the impeller's rotational speed using hall effect sensors or reed switches (for geothermal applications). The simplest sensor configuration has the sensors placed outside of the vacuum flask (exposed to well bore temperature) with the associated electronics housed within the vacuum flask (thermally protected from the well bore temperature). Alternatively, the sensors can be protected with the flask along with the associated electronics but requires a novel flask configuration to yield a minimal gap between the sensors and rotating shaft's sensor pickups.

CCL (Casing Collar Locator)

CCL (Casing Collar Locator) tools provide depth correlation in cased wells. They use a set of permanent magnets and a coil assembly that sense the local magnetic field while traveling and detects the brief change in magnetic volume of a casing collar compared to the continuous magnetic volume of a long joint of casing. The magnets and coil assembly have a relatively high temperature rating and depending on the well bore temperature can reside outside of the flask. The CCL is normally already integrated into an existing telemetry/memory assembly so in most cases the CCL's magnet and coil assembly will normally reside in a flask along with the telemetry/memory section for simplicity. When the CCL is within a vacuum flask, the vacuum flask's material is non-magnetic. A CCL has a less stringent non-magnetic requirement compared to more sensitive magnetic sensors such as magnetometers. It is helpful to the field operator to mark a band on the OD of the flask designating the CCL's location to synchronize depth correlation to other tools.

Gamma Ray

Gamma ray, like CCL, also provides depth correlation and a depth reference method to other logs. Unlike the spectral logging tool, gamma ray depth correlation tool is less sensitive to materials for incoming gamma rays. Gamma ray tools are commonly packaged with a CCL sensor as an assembly. It is helpful to the field operator to mark a band on the OD of the flask designating the gamma ray detector's location to synchronize depth correlation to other tools.

Telemetry or Memory

Telemetry tools vary on the amount of heat they dissipate depending on the quantity of power they manage. The top end of the flask terminates in the end user's typical cable head configuration to allow the option of connecting directly to the cable head or using a saver sub between the vacuum flask and cable head. Flasks for mono conductor cable typically terminate at the top end with the industry standard 1-3/8" GO box (1-3/16"-12 thread).

Memory sections by their nature consume and dissipate only a small amount of heat since they are powered by batteries. These tools typically terminate at the top end with the industry standard fishing neck pin thread.

Survey: Magnetic

Magnetic Survey tools measure the Earth's magnetic fields and gravitational forces combined with inclination to establish 3 dimensional points along the well's path to create point to point locations of a well's placement and path. Magnetic survey tools can only survey through non-magnetic material such as non-mag drill collars. The vacuum flask's materials must also be non-magnetic and have a testing method and non-magnetic value reflecting the application.

Survey: Gyro

Like Magnetic Survey tools, Gyro survey tools also establish 3D coordinates along the well's path to create 3D point to point locations of a well's placement and path. Unlike magnetic survey tools, gyro survey tools do not use the Earth's magnetic fields for direction so they are insensitive to magnetic materials which allows gyro survey tools to survey through drill pipe and production tubing and to orient whipstocks.

Mechanical gyros dissipate 15-25 watts and require sufficient heat sink to achieve the target down hole duration. Extremely accurate mechanical gyros have a minimum operating temperature. In deep water offshore applications, the gyro must be thermally insulated from the cold sea bed temperatures encountered in the riser section to maintain the gyro above its minimum operating temperature range.

Other forms of gyro tools such as fiber optic and MEMS have a maximum operating temperature of 50-85C but have been successfully used in many ultra-high temperature geothermal applications while in a vacuum flask.

Motor actuated tools

Motors are used to actuate outward swinging hardware (decentralizing arms, pads, measuring fingers), actuate pull/push rods (set downhole hardware), rotate hardware (pipe cutters, scanning sensors), orient hardware (perforating tools, cameras), pumps (inflatable packers, formation testers), cable head release tools.

Motor systems are comprised of the motor itself and the associated electronic motor controller (motor driver). For high temperature applications, the motor controller and the tool's other electronics are housed within a protective flask. Specifically designed high temperature down hole motors exist which are capable of 200C and a few as high as 225C. The high temperature rating of these motors affords design options as to whether motor is inside or outside of a flask.

Motor controllers dissipate heat during motor operation. The total dissipated heat (total motor cycle time) is a function of the quantity of motor cycles and duration per motor cycle. The flask system design requires that sufficient heat sink is incorporated into the flask system to achieve the target down hole duration and total motor cycle time.

If the motor is housed within the vacuum flask, the motor's heat dissipation can be reduced by utilizing the largest diameter motor possible which decreases the motor's torque load. When the motor is below its torque rating, a typical output is 70% work and 30% heat. If the motor is housed within the flask, the rotary or reciprocating mechanical output shaft is a thermal conductance path into the vacuum flask and is considered in the system's total thermal leakage.

Pulsed Neutron

Pulsed neutron tools are versatile and effective cased hole reservoir characterization tools. A high energy neutron generator emits neutrons into the formation while multiple detectors capture the neutron returns. The neutron generator is powered by a high voltage power supply. The power supply and controlling electronics collectively dissipate 40 watts or more. Since a flask thermally decouples the payload within the flask from the well bore, the 40 watts can not be dissipated to the well bore and are effectively trapped within the flask. Provisions must be made in the flask design to:

  • store the enormous amount of dissipated heat within the flask using heat sink material (thermal mass).
  • transfer the heat from the generator section to the heat sink material.

Since these tools are run through tubing, there is a market premium to minimize the flask's OD. Since the OD must be as small as possible, the additional heat sink material produces a longer length tool compared to the un-flasked version.

The high energy neutrons readily travel through metal and the detectors' response is not decreased by the additional metal that a flask requires over a traditional non-flasked pressure housing.

Detector, Density

Density tools consist of an active radioactive source emitting gamma rays into the formation and multiple detectors capturing the gamma ray returns from the formation. Density tool designs are sensitive to gamma ray attenuation, both high and low attenuation.

Low attenuation for Gamma Rays: The detector response is improved by using low attenuation flask material for incoming gamma rays.

High attenuation for Gamma Rays: The log data quality and accuracy is improved by the strategic implementation of high attenuation flask material for collimating outgoing and incoming gamma rays and shielding the detectors from back scatter.

When an existing density tool is upgrade with a flask, special design effort is required to maintain the original spacing between the source and detectors while not compromising the performance of the high attenuation tungsten shielding. Maintaining the original spacing and optimizing the tungsten shielding avoids the expense and effort of fully recharacterizing the tool's response.

Gamma rays are sensitive to interference from drilling mud. To minimize the drilling mud's effect, the mud is physically displaced from the gamma rays' path by swinging the source and flasked detectors as a unitized pad in an outward direction and pressing the pad against the well bore by motor actuated linkage.

Density tools normally require two vacuum flasks; one for the articulated pad with detectors and one for the associated electronics and motor controller.

Detector, Spectral Gamma Ray

Spectral density tools typically utilize large diameter detectors and photo multiplier assemblies that capture the formations natural gamma ray emissions. In cases, forms of the tool are used with radioactive tracers to analyze fracs and gravel packs. The detectors are delicate and sensitive to damage from temperature shock. The flask provides the additional benefit of protecting the detectors from rapid temperature fluctuations while also protecting the detectors and electronics from an absolute maximum temperature.

Detector, Neutron

Neutron tools consist of an active radioactive source emitting neutrons into the formation and multiple detectors capturing the neutron returns from the formation. Unlike gamma rays, neutrons readily travel through steel and drilling mud which simplifies the tool design. Material selection is less critical, shielding/collimation requirements are simplified and the tool does not require an articulated pad to press the source and detectors against the well bore. Neutron tools require less design effort to upgrade the temperature rating via a flask than a density tool.

Induction and Resistivity

Electric insulation is a design requirement of induction and resistivity tools. The insulation takes place between components in the tools' axial direction (insulating subs) and/or radial direction (insulating sleeves). The vacuum flask design obviously must also incorporate the same form of electric insulation but upgraded to a higher operating temperature.

Some tools incorporate pressure compensated sections that require hermetic bulkhead electrical connectors. The higher temperature design sometimes requires upgrading the temperature rating of the exposed connectors and electrical insulation materials.

Micro imaging tools utilize multiple pads that swing in an outward radial direction by motor actuated linkage to contact the well bore. Each pad has multiple electrodes on its contacting surface. The pad assembly is not flasked which requires that the electrodes' electrical insulation and the hermetic bulkhead electrical connectors are capable of withstanding the well bore temperature.

Most micro imaging tools also incorporate directional sensors such as magnetometers and accelerometers to orient dip and fracture data. The magnetometer section of the tool requires non-magnetic flask material.

Acoustic Imaging

Acoustic imaging utilizes a motor actuated rotating ultrasonic signal to continuously scan the well bore. The transducer's signal is transmitted through the well bore fluid which requires that the transducer or signal reflector is exposed to the full well bore temperature. Most acoustic imaging tools also incorporate directional sensors such as magnetometers and accelerometers to orient fracture data. The magnetometer section of the tool requires non-magnetic flask material.

Magnetic ranging

Magnetic ranging tools are used during drilling for well placement in relation to nearby wells either for collision avoidance of nearby wells or intentional interception of a well. Magnetic ranging uses high resolution magnetic sensors to detect the steel casing of a nearby well. The flask materials must be non-magnetic to avoid interfering with the magnetic sensors. Passive ranging systems are more sensitive to the flask's magnetic properties than active ranging systems. Ranging tools are sometimes run with a gyro survey tool which is typically a separate tool. Although the tools are run together, the tools usually have separate buses which requires extending the lower tool's wires along the length of the upper tool.

Motorized Sidewall coring

The coring operation is motor actuated and requires a fairly complicated mechanical configuration to generate the many mechanical movements to cut the core, break the core and eject/store the core. The tool's mechanical complexity leads to not housing the motor within the vacuum flask and just housing the controller and other electronics within the vacuum flask. Motor controllers dissipate heat during motor operation. The total dissipated heat (total motor cycle time) is a function of the duration per coring operation and the quantity of coring operations. Sufficient heat sink is incorporated into the flask system design to achieve the desired down hole duration and total motor cycle time.

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