Downhole Pressure Gauge Comparison: Quartz vs Piezo
posted on 11 June 2019 7:27 PM by James Wright ( CEO )
Quick Downhole Shut In Tool Overview
posted on 16 January 2019 5:21 PM by James Wright ( CEO )
- Patented Instant Close Valve (US#7823633)
- Multiple Cycles
- 10,000 psi differential pressure
- 150°C and 177°C Drive Options
- 2-3/8” to 2-7/8” Valve = 1.135 square inch flow
- 3-1/2” and larger = 2.50 square inch flow
A downhole shut in tool’s purpose is to enable the well-bore to be shut in downhole rather than at surface. The process of shutting in a well downhole eliminates the “well bore storage effects”. Well bore storage effects are the result of long lengths of production tubing that need to be pressurized before the buildup can be recorded. The benefit of using a downhole shut in tool is to allow for a quicker well build up and better pressure data quality. This saves operators money on down time, and gives reservoir engineers better data for their calculations.
Instant Close DataCan has a unique valve design that closes instantaneously giving the production engineer the best available pressure build up data.
Multi Cycle DataCan’s valve has the ability to re-open and close multiple times, this is necessary when reservoir engineers are performing three or four point isochronal pressure tests. DataCan’s production and injection valve designs are patented in the United States and Canada.
High Temperature Use Our motor and controls circuit has recently operated in a production 151°C gas condensate well. This well is the highest field temperature DataCan has seen and is a milestone for shut in tool operations. DataCan can confidently rate its drive section to 150°C. Further engineering is in progress to raise the operating temperature of the downhole shut in tool to 165°C and higher.
Shock resistance The DataCan instant close / multi-cycle downhole shut in tool is highly durable. Shut in tools are often mounted below locks or plugs. As such, it is necessary that our valve and drive section are capable of withstanding the most physical of downhole conditions.
Drawdown and build-up tests are often performed on production and injection wells at regular intervals to monitor the performance of the producing formations in the well. A typical test setup usually includes a downhole valve (shut in tool) which is placed in the well and manipulated by slick line.
There is usually a pressure recording device below the valve which records the pressure response of the formation being tested as the valve is opened or closed. The formation is allowed to flow for a sufficient length of time to ensure that it is drawn down to a desired level. After this draw down period is complete, the shut in valve is used to shut in the well. The formation pressure is allowed to build up for a sufficient period of time to allow it to reach a desired level, before another draw down period is started. The entire process is then sometimes repeated immediately to acquire more pressure data from another drawdown/build-up test.
There are two common sizes of valves, a 1.75” OD valve used for 2-3/8” and 2-7/8” tubing and a 2.5” OD valve for 3-1/2” and larger tubing. An important aspect of the downhole assembly, is the connection from the valve to the lock mandrel assembly.
The lock mandrel is set inside the lock, below the lock mandrel is a crossover, below the crossover is the DataCan valve, below the valve is a set of memory pressure gauges. The connection from the valve to the lock mandrel assembly is typically performed with a mechanical equalizing sub. There are two common types of mechanical equalizing subs, a sliding sleeve or a Kobe knockout type. DataCan recommends using the Kobe knockout type.
In any case, it is important to know the exact size and type of lock mandrel that is going to run downhole. The mechanical equalizing crossover is customized to attach to each specific type and size of lock mandrel. There are two common types of lock mandrels, the Otis type, and the Baker type. In each type, there are a variety of common sizes, each size is determined by the OD of the mechanical equalizing sub. Typical sizes are (in inches of diameter): 1.781, 1.875, 2.125, 2.188, 2.313, 2.56, 2.75, 2.813, 3.66, 3.81.
DataCan is able to manufacture a custom equalizing sub that wil integrate directly into the top of the valve housing. The DataCan mechanical equalizing solution means that your crossover solution will have at least one less potential leak path. DataCan highly recommends using an integrated mechanical equalizing sub to connect the downhole shut in tool to the lock mandrel.
In Depth O-Ring Overview
posted on 16 January 2019 4:55 PM by James Wright ( CEO )
If your job is critical, DataCan recommends using an Aflas 7182B® material. This material is great for H2S, CO2, and high pressure conditions. The cost of a failure due to a poor o-ring selection is too great.
For an o-ring to seal properly, it must have chemical and mechanical strength. The material must be chemically compatible with the sealing fluid. The gland and o-ring must be tough enough to maintain the seal during high pressures and high temperatures.
Chemical strength means matching the material to the environment. DataCan has a simplified o-ring selection guide that helps operators choose the correct material. In general, Viton 90 o-rings work most of the time. For critical wells, long term surveys, and unknown environments, DataCan recommends using Aflas 7182B® seals.
The physical strength of a seal is dependent on the o-ring strength and the gland design. Commonly, an o-ring will have an extrusion failure at high pressures and temperatures. This is because the high pressure squeezes the o-ring through the gap in the seal joint. An easy solution to this problem is to reduce the gap size. The smaller the gap, the higher pressure the seal can withstand before extruding. However, it becomes difficult to machine small gaps. Another solution, is to use a high strength back-up, such as a PEEK® back-up. The back-up must extrude through the seal gap. Since the back-up material is stronger than the o-ring, higher pressures can be withstood. The final solution is to use a face seal joint design, as seen in DataCan’s super seal. In the super seal design, a metal to metal face seal behind the o-ring gland prevents the o-ring from extrusion failures.
The premature failure of an o-ring can usually be attributed to a combination of causes and not merely a single failure mode. It is important to maximize sealing life and reliability by reducing the probability of seal failure at the onset with proper compound selection, installation and continued education of personnel.
|O-Ring Failures and Examples|
The seal exhibits a flat-sided cross-section, the flat sides correspond to the mating seal surfaces. Excessive pressure and temperature, excessive volume swell in chemical, and specific elastomers with high compression set lead to this failure mode.
Once an o-ring has compression set, it is no longer elastic and will not form a seal.
The seal may exhibit many signs of degradation including blisters, cracks, voids or discoloration. In some cases, the degradation is observable only by measurement of physical properties.
The selection of a more chemically resilient elastomer such as Aflas 7182B will prevent degradation.
The seal exhibits blisters, pits, or pockets on its surface. Absorption of gas at high pressure and the subsequent rapid decrease in pressure results in gas that was once trapped inside the elastomer to explosively decompress and exit the seal. The absorbed gas blisters and ruptures the surface as the pressure is rapidly removed.
High modulus or a harder elastomer, as well as a slower decompression rate will prevent this mode of failure. Aflas 7182B is explosion decompression resistant. It is an effective seal material for high CO2 gas wells.
The seal develops ragged edges (generally on the low pressure side) which appear tattered. Excessive seal clearances, excessive pressure, low modulus or hardness elastomers, or improper sizing will lead to an extruded seal.
Decreasing gland clearances, use of a high strength back-up ring, or DataCan’s metal to metal super seal will prevent extrusion.
Surface Logging Suite
posted on 16 January 2019 10:25 AM by James Wright ( CEO )
DataCan’s surface logging suite is built around our surface pressure or temperature transmitter. The transmitters are fully welded designs that have been calibrated. The transmitters (or smart sensors) can be packaged into a variety of different configurations to meet specific customer needs. DataCan offers a: Digital Chart Recorder, Wellhead Logger, and a new Multi-Channel Surface Logger.
Any pressure or temperature transmitter can be turned into a digital chart recorder. Chart recorder software is loaded onto a laptop, and a special USB cable is attached directly to the transmitter. The Cable can be up to 100 feet long, and is oil resistant. The chart recorder software is very easy to use. One button for stop and one for go. You can toggle between the classic spiral and a standard x-y graph. The laptop continuously stores data to a user determined text file which can be e-mailed or viewed at any time. This digital chart recorder solution is great for customers who do not want to store and file physical Barton charts. Multiple transmitters can be operating and running at one time.
If you can’t have a laptop on location, but you want to record data and have a display. Then we suggest using our Wellhead Logger. This product is the combination of a pressure or temperature transmitter, a digital display, memory, and a large “2 x D” battery pack, all packaged in an explosion proof housing. The wellhead logger is a classic product that is easy to use. Like all surface products, the smart sensor is fully welded. A single button is used to turn the device on and off. A lemo connection allows operators to program and download the wellhead logger using our standard DataCan gauge software. The wellhead logger can come with an antenna, which will send data to a laptop via radio frequency.
The Surface Logger is the second generation wellhead logger. The surface logger gives users much more flexibility when designing a surface testing suite. The surface logger has all of the features of the wellhead logger, but you can now add multiple transmitters to one data logger. The enclosure was redesigned to meet our specific packaging needs. Up to 3 additional wired, and 4 additional wireless transmitters can be connected to the device at a single time.
Lithium Metal Battery Pack Information
posted on 16 January 2019 9:07 AM by James Wright ( CEO )
Battery packs provide power to downhole devices, an understanding of battery technology is critical in maintaining a high level of success.
DataCan’s high temperature battery packs use Lithium Sulfuryl Chloride or Lithium Thionyl Chloride cells. There are numerous battery sizes, temperature ratings, and rate capacities. In most cases, the customer tool type and maximum downhole temperature will dictate the battery pack required. Refer to DataCan’s battery brochure page to match your tool with its correct battery pack.
Battery pack life is critical. Measuring the voltage of a lithium battery pack will not help you determine its remaining life. The voltage discharge curve of a Lithium cell is very flat. Hence, when you measure the voltage of a lithium battery pack, you are not confident in knowing how much life remains in the battery cells.
The voltage of a lithium battery pack will be "acceptable" until the very end of its life. At the end of its life, a lithium battery cell suddenly loses its available energy.
The battery tester is used to:
- Depassify the battery cell.
- Check to make sure the battery pack fuse has not blown
- Check to make sure the battery pack is wired correctly
- Check to make sure the battery pack is working correctly
The most common question DataCan receives is, “How long will the battery pack last downhole?” To correctly answer this question you need to know the following:
What battery pack are you using, or more specifically, how much energy do you have available? Different battery packs have different amounts of available energy. All of DataCan’s new battery packs have their available energy printed on the label (highlighted in yellow below).
For used battery packs, the customer must manually record how much energy has been used during previous jobs. Alternatively, DataCan has a “Smart Battery” pack design which saves its own energy usage and its remaining energy can be downloaded by the customer.
What type of tool? Different tools use different amounts of energy as they sleep and sample.
What sample rate? DataCan’s tools use more battery energy while they are recording samples. In the case of the downhole shut in tool, relatively no energy is being used unless the motor is on.
What is the expected downhole temperature? This is critical as battery packs have significant levels of self discharge at temperature.
Once the above criteria are known, users can input this information in DataCan’s “Battery Calculator”. The Battery Calculator program can be found in DataCan’s program and download software under the "Utilities" tab.
It is important for users to also understand the concept of battery pack passivation. Battery cells contain two main chemicals: the anode, and the cathode. To increase shelf life, a thin layer of corrosion builds up between the anode and cathode. This thin layer is called the “passivation” layer. The passivation layer prevents the anode and cathode from reacting prematurely.
However, in some cases (especially in higher temperature cells) the passivation layer grows too large and can prevent the battery from operating correctly. The passivation can restrict the chemical reaction between the anode and cathode to the point where the cells appears to be dead. The solution is to depassivate the cell (remove the passivation layer). To depassivate the cell you can:
- Put a large current draw on the battery. A large current draw will act to erode the passivation layer.
- Vibrate the cell. Physical shock will help to displace the passivation layer.
- Heating the cell will also help to melt the passivation layer (heat is a common catalyst to any reaction).
Geothermal Measurement Tool Overview
posted on 15 January 2019 10:32 PM by James Wright ( CEO )
• Up to 300°C for 8 hours
• Thermally insulates your downhole electronics
• External fast response temperature sensor
• Internal pressure measurement
• Can be expanded to measure flow and add a casing collar locator
A geothermal tool has a large Dewar flask housing that insulates the internal, temperature sensitive components. As well as the insulating housing, the tool assembly has a large internal heat sink assembly. The insulation, and the internal heat sink work together to prevent and absorb heat energy. This allows the internal electronics to stay below their critical operating temperatures.
The following graph illustrates the geothermal tools performance at different external temperatures.
Downhole Quartz Gauge Overview
posted on 15 January 2019 9:45 PM by James Wright ( CEO )
- Downhole pressure and temperature measurement
- Pressure up to 30,000 psi maximum
- Accuracy of up to +/- 0.020% full scale
- Resolution of 0.00006% full scale
- Temperature up to 200 °C maximum
- Accuracy of +/-0.25 °C
- Resolution 0.005 °C
- 2 million data sets of memory
- 1 second to once a day sampling
Quartz tools are more stable and have less drift than a Piezo tool. Typically you can go 2 years or more between calibrations with a quartz tool. Quartz tools are preferred for long term high temperature jobs.
All of DataCan’s quartz tools use hybrid oscillating circuits. Hybrid circuits are 100 times more reliable than standard surface mount (soldered) electronics.
Hybrids, like the one above, have no plastic parts. The raw die is mounted onto a ceramic substrate. The resulting structure is much smaller, and will work reliably to higher temperatures (up to 225°C).
A modular memory cartage means that DataCan’s quartz tools can be upgraded in the field. At any time, a DataCan customer can change the memory module out for a surface readout module.
DataCan’s mechanical package uses electron beam welding to reduce leak paths. DataCan has one tool joint, the competitions’ tools have up to three. As well as reducing the number of potential leak paths, DataCan has improved their seal joint. A common seal failure is extrusion. DataCan’s seal design uses a metal to metal beveled seal to eliminate the extrusion gap.
High Speed Memory Pressure Gauge - Burst
posted on 15 January 2019 3:51 PM by James Wright ( CEO )
An ultra fast sampling memory tool called the Burst Tool is now available for sale or rental. This pressure gauge will capture a perforation event, at a rate of 32,000 samples per second.
There are 3 sampling speeds:
• Slow Speed = As fast as 1 sample / second
• Intermediate Speed = 10,000 samples / second
• Fast Speed = User Selectable 32,000 or 16,000 samples / second
Like all DataCan products, the Burst Tool operates using the same simple and easy to use program and download software as all other DataCan products. A change in sample rate can be initiated in three ways:
• Normal = Change sample rates at pre-programmed time intervals
• Absolute Pressure Trigger = Change rate at a pre-programmed absolute pressure set point
• Delta Pressure Trigger = Change rate after a pre-programmed change in pressure over time
The gauge has non-volatile memory, so the data will not be lost when you disconnect the battery pack.
The Burst Tool can store up to 8 high speed sampling events. One high speed event will capture 500,000 samples, or ~15 seconds of data at the Fast Speed. The Burst Tool can also store up to 1 million Slow Speed data samples.
The current Burst Tool works at temperatures up to 150°C.
Downhole Piezo Gauge Overview
posted on 15 January 2019 3:21 PM by James Wright ( CEO )
- Downhole pressure and temperature measurement
- Pressure up to 25,000 psi maximum
- Accuracy of up to +/- 0.022% full scale (Typically 0.03%)
- Resolution of 0.0003% full scale
- Temperature up to 177 °C
- Accuracy of +/-0.25 °C
- Resolution 0.005 °C
- 1 million data sets of memory
- 1 second to once a day sampling
- Special gauges can sample 10 times a second, or even up to
- 32,000 times a second
- Pressure triggers are available
- Accelerometer sensors can be added to the board to measure vibrations
- External fast response temperature sensors can be added
Piezo, refers to the “piezoresistive” effect of the silicon sensor. A piezoresistive semi-conductor will see a change in resistivity due to a change in mechanical stress. Hence, a change in pressure or temperature results in a change in resistance.
Some people call these tools “sapphire” or “strain” gauges. In every case, the same piezoresistive silicon sensor is used.
Piezo is less expensive - Less than half the price of a quartz pressure gauge.
Piezo is small – Which means it responds quickly to changes in pressure and temperature. This makes piezo gauges suitable for gradients.
Piezo is fast – We have piezo circuits which can sample up to 32,000 times per second. Perforating events can be captured with this high data acquisition rate.
The piezo resistive sensor is a small Silicon drum (shown below on top of a pencil) that uses changes in resistance to measure pressures and temperatures.
Looking closely at the chip above you can see a pattern that has been created on the top of the silicon. That pattern is a diffusion layer in the silicon that has been etched away. The diffusion layer is a semiconductor which has piezoresistive properties. This means that forces applied to the semi-conductor will result in a change in resistance of the material. There is a cavity in the middle of the silicon/glass sandwich and like a balloon, the die collapses under pressure, and the resistance values of the semi-conductor change.
DataCan’s piezo tools are offered in a variety of packages and with different options. It is important to understand each design. Critical mechanical package elements include: Outer Diameter and Battery Pack Size, Sensor Seal (O-Ring or Welded), Carrier Fitting (O-Ring or Metal to Metal), Battery Housing Seal. As well, each having different packages, DataCan offers custom boards which include: Pressure Trigger, Fast Sampling (10 samples per second), Accelerometer Sensor (to measure vibrations downhole), RTD Sensor (for fast temperature sensing), Smart Battery Technology (you can connect a smart battery to our download cable and measure its remaining life).
Outer Diameter – Options include 0.50”, 0.75”, 1.25”, and 1.375” OD.
The 0.50” size is a relatively new design and is great for applications with extreme space restraints. AAA battery packs are used in the 0.50” OD tool, which means the tool can only be run for a short period of time of 1 week or less.
The 0.75” size is our most economical package and works well for gauge carrier, coiled tubing, and DST operations. AA battery packs are used in the 0.75” OD tools, which limits the duration the tool can be “on” downhole, typically no more than 2 to 3 months.
DataCan now offers four different 0.75” OD packages. The 0.75” classic gauge is characterized by its o-ring sealed sensor; a very simple and reliable design. When additional memory is required, the 0.75” gauge with 4 million sample capacity is also available. It has expanded memory which allows for a high sample rate for an extended period of time.
The 0.75” welded piezo is characterized by its electron beam welded sensor and high pressure rating. And lastly, the 0.75” piezo with accelerometer is also available. Similar to the classic gauge but with an accelerometer sensor to measure any vibrations downhole.
The 1.25” gauge has a larger diameter barrel which allows for a large enough battery to run the gauge for a long duration job. DataCan offers four different 1.25” OD packages. The 1.25” classic gauge is characterized by its o-ring sealed sensor. The battery pack and housing for this tool is considered a standard or basic; a good economy tool.
The Welded III design is very similar to the 1.25” classic design, but in this case, the sensor is welded. Over time, DataCan will phase out the original 1.25” and replace it with the Welded III package. The 1.25” Welded Piezo RTD design has a RTD sensor for fast temperature sensing. It has a higher reliability with its shock mounted electronics and electron beam welded pressure sensor.
The 1.375” Welded Piezo IV is our flagship piezo tool. This tool is rugged and robust. It has all of the best design characteristics in mind. The sensor is welded and available for easy maintenance. The board is shock mounted for vibration and drops. The “C” sized battery pack is locking and large enough for long duration jobs. And the three o-rings and metal to metal seal prevent leaks from entering. This is DataCan’s most robust piezo pressure gauge.