Vacuum Flasks & HPHT Solutions in Louisiana

In Louisiana, the Haynesville Shale covers more than 9,000 mi2 (14,484 km2) and is considered one of the largest unconventional gas plays in the U.S. with wells ranging from 10,000 ft to 14,500 ft (3,048 to 4,267 m). The formation experiences higher pressures and temperatures (HPHT) than most other unconventional plays in the U.S which can cause significant technical challenges for wireline tools. The formation can see pressures in excess of 13,000PSI and temperatures ranging from 300°F (149°C) to over 380°F (193°C).

Even with today's high temp electronics that have been developed, quality and reliability remain a significant issue in HPHT environments. It is common that high temp electronics start to degrade above 300°F (149°C) with the chance of failure increasing significantly above 350°F (177°C). The cost of electronics above 300°F (149°C) is significant, and it is important to protect this investment. National K Works has been an industry leader in HPHT wireline conditions offering thermal flasks and pressure housings which help signification reduce the risk of failure. With over 600 different designs, NKW provides customized thermal flasks and pressure housings for the majority of commonly used wireline tools today. If you have a question about your tool's ability to be flasked or want to know more about our flasking capabilities, contact us online here.

Vacuum Flask: Overview

Vacuum Flask Diagram

Vacuum Flask Synonyms

Dewar, Dewar Flask, Vacuum Bottle, Heat Shield, ThermoFlask, ThermoHousing

Contact National K Works for Vacuum Flask Manufacturing for HPHT Solutions

If you're looking for expertly engineered and manufactured vacuum flasks for the oil & gas industry, geothermal industry, data logging, or any other application, don't hesitate to contact us today to see how we can help with your next project. We work with clients in Louisiana (and across the United States).

Vacuum Flask: Instrument, Downhole, Wireline Logging, Oilfield and Geothermal

If you need a vacuum flask high pressure, high temperature solutions for any of the tools listed here (or anything not listed), don't hesitate to contact us today! We specialize in vacuum flask engineering and production for a wide range of downhole tools, wireline tools, oilfield logging tools, geothermal logging tools, downhole logging tools, wireline logging tools, and more.

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

Downhole & Wireline Tools We Have Flasked:

Temperature Logging Tools

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 an 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 Logging Tools

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. 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 require 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 cannot 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.

Contact National K Works for High Temperature, High Pressure Vacuum Flask Solutions for Downhole, Wireline, Oilfield & Geothermal Tools in Louisiana

If you need a vacuum flask high pressure, high temperature solutions for any of the tools listed here (or anything not listed), don't hesitate to contact us today! We specialize in vacuum flask engineering and production for a wide range of downhole tools, wireline tools, oilfield logging tools, geothermal logging tools, downhole logging tools, wireline logging tools, and more.

Overview of Vacuum Flasks

Dewar Flasks & Vacuums
Small vacuum flask for AAA battery assembly in 0.75" (19mm) OD high temperature downhole production logging tool. Stainless material.

Vacuum flasks are thermally insulated double wall vessels. The narrow space between the two walls is evacuated which dramatically reduces thermal transfer. The near absence of air molecules minimizes thermal transfer by convection. Reflective surfaces in the vacuum space minimize radiant thermal transfer and the separation between the inner and outer wall minimizes thermal transfer by conductance. In summary, a vacuum flask thermally decouples a flask's payload from the external environment. The most common application of vacuum flasks is the storage or transmission of cryogenic fluids such as liquid nitrogen or liquid natural gas which can be maintained at extremely very low temperatures for extended durations. National K Works specializes in designing and manufacturing vacuum flasks exclusively for thermally insulating instruments from hostile temperature environments.

Vacuum flasks provide very effective thermal insulation. The insulation is passive and the largest portion of thermal transfer into the vacuum flask occurs by conductance through the neck of the inner wall and by the electrical wiring or mechanical feed through entering the vacuum flask (thermal leakage). The small amount of conductance eventually raises the inner temperature within the vacuum flask which limits the payload's duration within hostile high temperature environments to a finite duration.

An additional form of heat gain in the vacuum flask is the heat generated by the electronics within the vacuum flask. Since the vacuum flask thermally decouples the contents of the flask from the external environment, the heat dissipated by the electronics cannot escape from the vacuum flask and consequently increases the inner temperature within the vacuum flask which also limits the payload's duration within hostile high temperature environments.

The duration can be extended by increasing the specific heat (thermal mass) within the vacuum flask in the form of separate heat sink material or by increasing the payload assembly's total specific heat (changing materials and/or quantity of material). Typical application durations are 1 to 24 hours. The duration is a function of the ratio of heat gain (by thermal leakage plus heat dissipated from the electronics) to specific heat (thermal mass) within the vacuum flask. In other words, the duration can be extended by increasing the amount of specific heat within the flask. Unlimited durations can be achieved by actively cooling the flask and removing the small amount of thermal leakage into the flask plus the heat dissipated by the electronics.

External flask temperature applications can exceed 1,000C (1,832F).

Common payloads protected within a flask are electronic assemblies, detectors, sensors, batteries, motors, cameras, explosives and temperature sensitive chemicals.

High temperature vacuum flask applications include insulating instruments within industrial processing ovens (glass, metal, electronics, paint, cement), food processing, pharmaceutical sterilization, oil and gas wells, geothermal wells, and power generation (nuclear reactors, boilers, steam lines).

If you're looking for vacuum flasks for the oil & gas industry, geothermal industry, data logging, or any other application, don't hesitate to contact us today to see how we can help with your next project.

Flask vs. high temperature electronics

For cost and time savings, many of our customers prefer to use standard temperature rated electronics housed within a vacuum flask instead of sourcing or developing special high temperature electronics without a vacuum flask. Benefits of standard temperature electronics over special high temperature electronics are:

  • Standard temperature electronics are drastically less expensive.
  • Standard temperature electronics offer electrical engineers a wider selection of components permitting more design options and access to the newest technology.
  • Standard temperature electronics decrease project development time which allow projects to come to market sooner (more revenue) and consequently decrease engineering costs.
  • Standard temperature electronics allow less expensive future upgrades and easier future evolution paths.

Contact us for vacuum flask solutions for your standard temperature electronics so they can withstand high pressure and high temperature environments.

The Vacuum Flask's Thermal Insulator

The thermal insulator's function is to thermally seal the opening of the vacuum flask, displace air to reduce thermal transfer by convection, provide a feed through passage for inputs into the flask, mechanically secure the payload within the flask, and provide a method to extract the payload from the flask.

The insulator's material should have low thermal conductivity properties, sufficient mechanical properties to support the payload's weight within the flask, and sufficient temperature rating to withstand the external environment's temperature. Common materials are Teflon, PEEK and Ceramic.

The Vacuum Flask's Heat Sink

The heat sink's function is to reduce the rate of temperature rise within the flask by absorbing and storing the thermal energy leaking into the flask and the thermal energy dissipated by the payload within the flask. Increasing the quantity of heat sink within the flask; increases the duration.

The heat sink's material should have a high volumetric heat capacity (J/cm3°K). In other words, the material should have high specific heat (J/K) for its volume (cm3).

In some applications, it is beneficial for the heat sink material to have low a thermal conductivity property because it reduces the rate of thermal transfer within the flask environment while in other applications, it is beneficial for the heat sink material to have a high thermal conductivity property such as when a localized component is dissipating heat within the flask. High thermal conductivity allows heat to be rapidly pulled away from the heat dissipating component and stored within the heatsink. In this case, the high thermal conductivity property of the heat sink prevents concentrated "hot spots" within the flask's environment.

Common heat sink materials are aluminum, stainless, brass, copper, Teflon, PEEK. Phase change alloys are also used because the latent heat provides significant thermal absorption but these alloys have a lower volumetric heat capacity than conventional heat sink materials.

Shapes and Sizes

Vacuum Flask Shapes

Shapes are limited by the practicality of manufacturing. Round is the least expensive shape because round tubes are commercially available and, if not available, are readily manufactured to necessary sizes.

Sizes are limitless and lengths can exceed 9 meters. Long lengths require supports to centralize the inner tube within the outer tube.

Optional Openings on Both Ends of Vacuum Flasks

Vacuum Flask Openings

There is the option to have openings on both ends of the flask. The through passage opening incorporates an expansion joint to compensate for the differential in thermal expansion between the outer and inner walls while maintaining the vacuum integrity.

Vacuum Flask Materials & Characteristics

Thermal conductivity

The inner tube is a path for thermal conductance along its length, consequently the inner tube's material should have low thermal conductance.

  • Stainless, nickel alloys and titanium have low thermal conductivity and are the most common materials.
  • Aluminum and copper have high thermal conductivity and are poor material choices for a vacuum flask.


Some instruments such as magnetometers are sensitive to interference from magnetic materials. The term "non-magnetic" is not specific enough and too general for design purposes. The application must be defined early in the flask design stage to select the appropriate vacuum flask materials and magnetic testing specifications to match the application. Various applications for non-magnetic materials are:

  • Absolute magnetic measurement
  • Relative magnetic measurement (quantifying magnetic change in an environment)
  • Electromagnetic induction triggers

Magnetic Shielding

Some photomultiplier applications are sensitive to magnetic fields and mu-metal is used in the flask to improve performance by optimizing magnetic shielding while minimizing overall size.

Low Attenuation for Gamma Rays

Some detector applications are sensitive to the flask materials' gamma ray attenuation properties. Materials with lower gamma ray attenuation properties improve the detector's response by affording increased count levels and count qualities. Titanium has a low atomic number which reduces its gamma ray attenuation and consequently improves detector responses. In this case, the entire flask must be titanium material because of the difficulties of joining titanium to other materials such as stainless.

High Attenuation for Gamma Rays

Tungsten has a high atomic number and very high gamma ray attenuation properties. It is used to selectively shield detectors from gamma rays and also collimate gamma rays to the detectors. Tungsten is built directly into the flask to minimize the overall size, maximize the quantity of shielding and optimize the source to detector spacing.

Optical window

We design and manufacture flasks with transparent windows for cameras and optical sensors in high temperature environments. Applications include high temperature protection for video cameras, proximity sensors, bar code readers and lasers.

Trust National K Works for Your Vacuum Flasks & High Pressure, High Temperature Solutions in Louisiana

If you're looking for vacuum flasks, dewar flasks, vacuum bottles, heat shields, ThermoFlasks, or ThermoHousings you've come to the right place! As mentioned above, those terms all refer to the same apparatus, and we specialize in vacuum flask engineering and manufacturing. We customize our high pressure, high temperature solutions to your specific needs. We work with clients and projects in Louisiana.

Don't hesitate to contact us today to learn more about our capabilities and share more about your particular high pressure, high temperature needs.

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