How to Measure Groundwater Flow Velocity and Direction in a 1,500 m Geothermal Deep Well? A Real Customization Case
For conventional groundwater monitoring wells, measuring groundwater flow velocity and direction is not particularly difficult.
However, when the well depth reaches 1,500 meters and the well is located in a geothermal environment, the situation becomes completely different.
This was the challenge faced by Mr. Wang.
Mr. Wang is the owner of a geothermal project in northwestern China. He needed to measure groundwater flow velocity and direction in a 1,500-meter-deep well.
Before contacting us, he had reached out to several groundwater flow velocity and direction instrument manufacturers. The response was almost always the same: no one was willing to take the project directly.
Even manufacturers offering imported equipment generally gave similar responses:
Non-conventional working conditions. Customization is required.
However, customization means a longer R&D cycle, more complicated technical evaluation, and uncertainty regarding both pricing and delivery time.
Why would a 1,500-meter geothermal well make so many conventional groundwater flow velocity and direction instrument manufacturers reluctant to take the project?
The real reason is not simply the number “1,500 meters.”
1. Why Is a 1,500 m Geothermal Deep Well So Difficult to Measure?
From an equipment perspective, a 1,500-meter deep well + geothermal environment is a typical non-conventional measurement condition.
The main challenges are concentrated in three areas:
Pressure, temperature, and water quality.
When these three conditions occur simultaneously, the operating range of conventional groundwater flow velocity and direction instruments may be exceeded.
1. Pressure: 1,000 m and 1,500 m Are Not Simply 500 m Apart
For the groundwater flow velocity and direction instruments we manufacture, the conventional mature working depth is 1,000 meters.
This depth represents a relatively mature range in which the equipment has been widely used and configurations are relatively well established.
Once the depth exceeds 1,000 meters, it enters the customization range.
We have currently completed customization for depths of up to 2,000 meters, so 1,500 meters is not simply a matter of taking a 1,000-meter instrument and lowering it another 500 meters. Instead, the instrument needs to be redesigned and verified according to the specific well conditions.
According to a hydrostatic pressure estimate, the static water pressure increases by approximately 0.1 MPa for every 10 meters of water depth.
Therefore:
- At 1,000 meters: approximately 10 MPa
- At 1,500 meters: approximately 15 MPa
Although the depth increases by only 500 meters, the corresponding static water pressure increases by approximately 5 MPa.
This additional 5 MPa cannot be ignored.
The probe dimensions, pressure-resistant structure, seals, and internal components all need to be reevaluated.
2. Temperature: Geothermal Well Temperatures Can Exceed the Operating Range of Many Conventional Instruments
Another issue caused by increasing depth is temperature.
Publicly available well-logging data shows:
- The measured well temperature at 1,600 meters was 60.6°C
- The temperature in the 1,170–1,500 meter section was 50–57°C
Meanwhile, the publicly stated operating temperature of many similar instruments is generally around -10 to 45°C.
In other words, in this type of geothermal deep well, the actual well temperature may already exceed the operating temperature range of some conventional instruments.
Therefore, a 1,500-meter geothermal well is not simply a matter of solving the pressure-resistance problem.
The equipment must also deal with issues such as:
- Stability of electronic components
- Sealing performance
- Probe structure
- Imaging quality
- Signal stability
under high-temperature conditions.
3. Water Quality: High Mineralization Places Higher Demands on Materials and Sealing
The water quality of geothermal deep wells is also different from that of conventional shallow monitoring wells.
In highly mineralized environments, factors such as chloride ions and sulfides may increase the corrosion risk of metal materials.
Therefore, in addition to withstanding higher pressure and temperature, the equipment’s material selection and sealing design must also take into account long-term exposure to complex water conditions.
In other words:
The real difficulty of a 1,500-meter geothermal deep well is not one single parameter, but the simultaneous presence of pressure, temperature, and water-quality challenges.
Key Differences Between a 1,500 m Geothermal Well and a Conventional Deep Well
| Comparison Item | Conventional Deep Well (≤1,000 m) | This Geothermal Project (1,500 m) | Basis / Explanation |
|---|---|---|---|
| Static water pressure | Approx. 10 MPa | Approx. 15 MPa | Approx. 0.1 MPa per 10 m of water column (hydrostatic estimate) |
| Well temperature | Relatively low | Significantly higher | Public well-logging data: 60.6°C at 1,600 m; 50–57°C at 1,170–1,500 m |
| Water quality | Conventional | Highly mineralized and highly corrosive | Publicly available geothermal well water-quality data |
| Conventional measurement method | Wind vane + mechanical fan can be used | Cannot be used under high-temperature conditions | CN115128298A background technology |
Therefore, the combination of pressure, temperature, and water quality is an important reason why conventional groundwater flow velocity and direction instrument manufacturers are reluctant to directly take on this type of project.
2. Above 1,000 m Is Not Simply a Matter of “Making the Equipment Longer”
When people see this project, their first reaction may be:
“If the equipment can measure 1,000 meters, can’t it simply be lowered another 500 meters to reach 1,500 meters?”
In reality, it is not that simple.
The working depth of a groundwater flow velocity and direction instrument is not something that can be solved simply by using a longer cable.
When the working depth increases from 1,000 meters to 1,500 meters, the equipment faces completely different pressure conditions. If the environment is also geothermal, higher temperatures and complex water quality must be considered as well.
Therefore, we did not simply take our mature 1,000-meter model and lower it into the well.
1,000 meters is the mature operating range, while 1,500 meters is a customized working condition.
We have currently completed customization for depths of up to 2,000 meters, but this does not mean that every 2,000-meter working condition can be directly replicated.
The following factors need to be reevaluated according to each individual well:
- Working pressure
- Well temperature
- Water quality
- Cable configuration
- Probe structure
- Sealing requirements
3. The Customer Found Us: This Time, We Decided to Take the Project
When Mr. Wang contacted us, we had a technical basis for evaluating the project.
However, we did not immediately promise that “it would definitely work.”
The reason was simple:
1,000 meters is a mature product range, while 1,500 meters is a customized working condition.
Even though we had previously worked on deeper wells, we could not simply assume that the same solution could be directly applied to this 1,500-meter geothermal well.
We explained the situation clearly to Mr. Wang:
This project can be done, but it requires customized development.
We also made it clear that the project would require R&D time, repeated testing, and debugging.
Mr. Wang had previously contacted larger manufacturers as well.
Some manufacturers considered the project too small and were unwilling to take it. Others were willing to do it but eventually quoted extremely high prices.
In the end, both parties signed a customization contract.
This project also reinforced one point for us:
For groundwater flow velocity and direction measurement projects deeper than 1,000 meters, customers should ask not only about the price, but first whether the manufacturer has actually completed similar projects and whether it can provide customized development based on specific well conditions.
4. Three Months of R&D: Complete Data Obtained on the First Deployment into the 1,500 m Geothermal Well
After signing the contract, we spent 3 months on R&D.
The development focused on the actual working conditions of the 1,500-meter deep well. We addressed factors including pressure, high temperature in the geothermal environment, and corrosive water conditions, while also solving several technical issues related to structure, sealing, and signal transmission.
Last week, our engineers brought the AML920 groundwater flow velocity and direction instrument to the project site.
Before the first deployment, to be honest, we were also under some pressure.
This was not a conventional 1,000-meter working condition, but:
1,500-meter depth + geothermal environment + high temperature + high pressure + complex water quality.
The final result was:
Complete data was obtained during the first deployment.
Mr. Wang was satisfied with the data obtained.
This also means that the customized development carried out for this 1,500-meter geothermal deep well successfully passed actual field verification.
5. How Does the AML920 Measure Groundwater Flow Velocity and Direction?
The AML920 uses a particle-tracking measurement principle.
The instrument captures the movement trajectories of particles in the water through microscopic magnification and CCD imaging inside the well, and then combines this information with an internal geomagnetic electronic compass and a three-dimensional vector algorithm to analyze groundwater movement.
The final output is:
A three-dimensional groundwater flow velocity vector that includes the vertical component.
This method does not require tracer injection into the well and does not actively disturb the in-situ flow field.
For projects that need to understand groundwater flow velocity, flow direction, and well conditions simultaneously, multiple types of data can be obtained during a single deployment.
AML920 Standard Measurement Parameters
| Measurement Parameter | Description |
|---|---|
| Flow velocity | Water flow velocity inside the well |
| Flow direction | Geographic flow direction (corrected by the built-in geomagnetic electronic compass) |
| Water temperature | Well water temperature at the measured depth interval |
| Water level | Water level inside the well |
| Top-view well condition | Top-view imaging for observing conditions inside the well |
| 360° panoramic well condition | 360° panoramic imaging for observing the circumferential condition of the well wall |
The above are our published product parameters. Procurement shall be subject to the technical agreement.
The standard configuration currently includes 6 measurement parameters, with the capability to expand to more than 10 parameters.
This means that a single deployment can simultaneously obtain:
- Groundwater flow velocity
- Groundwater flow direction
- Water temperature
- Water level
- Top-view well conditions
- 360° panoramic well conditions
Among these, groundwater flow velocity and direction can be output as a three-dimensional vector that includes the vertical component.
6. What Is the Difference Between the AML920 and Common Groundwater Flow Velocity and Direction Instruments?
If we simply compare the names of the instruments, groundwater flow velocity and direction instruments on the market may appear similar.
However, once they are used in deep-well projects, differences in measurement dimensions, working depth, and applicable conditions become much more apparent.
| Comparison Item | Similar Groundwater Flow Velocity and Direction Instruments (Public Information) | Our AML920 (This Project) | Basis / Explanation |
|---|---|---|---|
| Data dimension | Mostly two-dimensional horizontal vectors | Three-dimensional vector (3D flow vector), including the vertical component | Our published product parameters |
| Particle images | Single grayscale image | Can distinguish and display the colors of individual particles | Our published product parameters |
| Rated working depth | Commonly around 300 m | 1,000 m standard; customized up to 2,000 m | Public technical parameters of similar instruments / our product capabilities |
| Applicable conditions | Conventional monitoring wells | High-temperature, highly mineralized geothermal deep wells | Actual working conditions of this project |
One of the most direct differences is whether three-dimensional flow velocity data, including the vertical component, can be obtained from the same well.
Some common instruments mainly provide information about horizontal flow direction, while the AML920 used in this project outputs a three-dimensional flow velocity vector that includes the vertical component.
For projects that need to determine the actual movement direction of groundwater inside a well, this difference in data dimensions is particularly important.
7. What Can This Instrument Not Do?
Every measurement instrument has clearly defined application boundaries.
To avoid creating inaccurate expectations about groundwater flow velocity and direction instruments, it is also important to clarify what the AML920 cannot replace.
1. It Cannot Replace Water Quality Testing
The AML920 is primarily used to measure groundwater flow velocity, flow direction, and related downhole parameters.
Water chemistry indicators, contaminants, and other parameters require separate water sampling and laboratory testing.
2. Downhole Flow Velocity Is Not the Same as Actual Groundwater Flow Velocity in the Aquifer
The instrument measures the water flow velocity inside the well.
If the actual groundwater flow velocity in the aquifer needs to be calculated, factors such as effective porosity and well-structure correction coefficients must also be considered. In many cases, relevant pumping-test data and other information are also required.
Likewise, well yield and permeability coefficient cannot be obtained solely through a groundwater flow velocity and direction instrument; methods such as pumping tests are required.
3. The Wellbore Must Meet Certain Conditions
The instrument must be capable of being lowered into the well, and a continuous water column must be present inside the well.
The following conditions require careful evaluation:
- Dry wells
- Uncased wells
- Wells with severe deformation
Whether the instrument is suitable must be evaluated according to the specific well conditions.
4. Above 1,000 m Is Not a Standard Configuration
Depths above 1,000 meters are customized working conditions.
The specific customization depth cannot be determined by depth alone. It must be evaluated according to the individual well’s:
- Depth
- Temperature
- Pressure
- Water quality
- Well structure
- Cable configuration
The equipment must then be individually evaluated and tested.
8. FAQ: 1,500 m Geothermal Deep-Well Groundwater Flow Velocity and Direction Measurement
Q1: How deep can a groundwater flow velocity and direction instrument measure?
It depends on the specific model, configuration, and actual well conditions.
The publicly stated maximum working depth of similar instruments is commonly around the 300-meter range.
The conventional mature working depth of our AML920 is 1,000 meters, and it has been customized for depths of up to 2,000 meters.
For projects deeper than 1,000 meters, customization is required based on the specific well conditions. The final procurement depth shall be subject to the technical agreement.
Q2: What is the biggest challenge when measuring groundwater flow velocity and direction in a 1,500 m geothermal deep well?
The main challenges are pressure, temperature, and water quality.
A depth of 1,500 meters means significantly higher hydrostatic pressure. The geothermal environment also brings higher well temperatures, while highly mineralized water may increase the corrosion risk to materials and seals.
In addition, traditional measurement methods relying on a wind vane and mechanical fan have limitations under high-temperature conditions.
Therefore, a 1,500-meter geothermal well cannot be solved simply by increasing the deployment depth of conventional deep-well equipment.
Q3: What data can the AML920 obtain during a single deployment?
The AML920 has 6 standard measurement parameters:
- Flow velocity
- Flow direction
- Water temperature
- Water level
- Top-view well condition
- 360° panoramic well condition
The system can also be expanded to more than 10 parameters.
Groundwater flow velocity and direction can be output as a three-dimensional vector that includes the vertical component.
Q4: Why are imported instruments also reluctant to directly handle 1,500 m geothermal wells?
This situation can be understood from the perspective of the manufacturer’s product line and business model.
A 1,500-meter application is a non-conventional working condition that exceeds the standard product range of many manufacturers.
If structural components, materials, seals, and other systems need to be redeveloped for a single project, both the R&D cycle and cost will increase.
Therefore, this does not mean that “imported equipment definitely cannot do it.” Rather, these 1,500-meter geothermal deep-well projects often exceed the applicable range of standard products and require separate technical evaluation and customized development.
Q5: If an instrument has a rated depth of 2,000 meters, can it automatically be used in a 1,500-meter deep well?
No.
The “maximum working depth” alone cannot determine whether an instrument is suitable for a particular well.
Even if an instrument has previously been used at 2,000 meters, the actual pressure, temperature, water quality, well structure, and other working conditions must still be reconfirmed for the specific project.
Meeting the required working depth is only one condition for project evaluation, not the entire evaluation.
Q6: Why did this project require 3 months of R&D?
Because this project was not a standard 1,000-meter working condition.
The 1,500-meter geothermal deep well involved higher pressure, high temperature, and complex water quality. Customized development and testing were therefore required for the structure, sealing, signal transmission, and other aspects of the equipment.
The project adopted a customized development approach and, after 3 months of R&D, completed the first field deployment and verification.
9. What Does This 1,500 m Geothermal Deep-Well Case Demonstrate?
The real value of this project is not simply proving that “a certain instrument can measure at 1,500 meters.”
More importantly, it demonstrates a practical point:
Groundwater flow velocity and direction measurement cannot be evaluated based solely on the instrument’s rated depth. The actual well conditions must also be considered to determine whether the instrument is truly suitable.
For conventional monitoring wells, depths within 1,000 meters are generally within a mature application range.
Once a project exceeds 1,000 meters, especially when high temperatures and highly mineralized water are also present in a geothermal well, the equipment needs to move from a standard product approach to customized development for the specific project.
This project started with the customer’s requirement for measurement in a 1,500-meter geothermal deep well, followed by the signing of a customized development contract. After 3 months of R&D, our engineers brought the AML920 to the site and successfully obtained complete data during the first deployment.
This was also the most important consideration for us when deciding to take on the project:
Instead of simply telling the customer that it could be done, we evaluated the specific working conditions, determined how it could be done, and ultimately used field verification to demonstrate whether the solution was actually feasible.
For projects requiring groundwater flow velocity and direction measurement in 1,500-meter or deeper wells, 1,000-meter-plus deep wells, geothermal well flow velocity and direction measurement, or other non-conventional deep-well measurements, the final solution should still be determined according to the actual well conditions and the technical agreement between both parties.
