300-Meter Deep Well Leakage Recurred After Repair: How AML921 Downhole Camera Located a Hidden Borehole Fracture at 220 Meters
Project Location: Guangxi, China
Customer: Manager Liu, a contractor specializing in underground well repair and rehabilitation
Well Depth: Approximately 300 meters
Well Diameter: 10 cm
Core Problem: Water leakage recurred after the well had been repaired and passed acceptance inspection. Three inspections with a conventional downhole camera failed to identify the source of the leakage.
Final Result: The AML921 downhole camera was used for digital borehole imaging and analysis, successfully locating a hidden fracture at approximately 220 meters.
For underground well repair contractors, the most difficult problem is not simply that the well cannot be seen. The real challenge is that a downhole camera may produce an image, but still fail to identify the exact defect responsible for water leakage.
This was exactly what happened in an underground well repair project in Guangxi, China.
Manager Liu’s team was responsible for repairing an approximately 300-meter-deep underground well. After the first repair was completed and the well passed acceptance inspection, water leakage occurred again, requiring rework.
Before starting the rework, the construction team followed its usual inspection procedure and used a conventional downhole camera to inspect the well.
The team lowered the camera into the well three times.
However, no obvious defect could be identified in the footage.
The well wall appeared intact, but the source of the leakage remained unknown.
This made the problem much more difficult. Without knowing where the fracture was located, the repair team could not perform targeted repairs.
Eventually, the team concluded that it would be difficult to locate the fracture by continuing to rely on the existing inspection equipment and manual observation.
1. Why Did the 300-Meter Deep Well Keep Leaking Without an Obvious Fracture?
One of the most difficult aspects of deep-well leakage is that defects can be extremely difficult to detect.
This is particularly true in a small-diameter well of approximately 10 cm. The limited space, insufficient light, and changing water conditions can all affect downhole imaging.
Using a downhole camera does not automatically mean that every defect in the well can be accurately identified.
For a well repair contractor, the real questions are not simply:
“Is there an image of the inside of the well?”
The more important questions are:
“Where exactly is the leakage coming from? At what depth is the fracture located? How large is the fracture? Can the inspection produce reliable evidence for the repair decision?”
This is one of the key differences between a conventional downhole camera and a digital downhole inspection system.
According to the U.S. EPA’s information on borehole video logging, downhole video inspection can be used to observe borehole structures, fractures, casing damage, voids, and groundwater movement. Fractures can also be evaluated based on their location, orientation, and opening characteristics.
For this project, the customer did not simply need a video of the well.
The customer needed to locate the fracture.
2. Why Can Conventional Downhole Cameras Miss Defects in a 10 cm Small-Diameter Well?
After three inspections, the customer found that the problem was not simply the lack of a downhole camera. The existing inspection method had several limitations.
The main limitations involved well diameter, underground environmental conditions, and field of view.
2.1 The 10 cm Well Diameter Limits Downhole Camera Selection
The diameter of this well was only approximately 10 cm.
For small-diameter underground wells, the size of the downhole camera probe directly determines whether the equipment can enter the well and how much of the well wall can be observed after entering.
Traditional equipment often requires different probe sizes for different well diameters. During an inspection, contractors may need to change between two or three probes.
This not only increases inspection time but can also increase the possibility of repeated work and missed sections.
The AML921 used in this project is equipped with a Φ45 mm micro probe, which can enter a 10 cm small-diameter well.
According to AIMOLI’s product information, the 45 mm probe can adapt to approximately 99% of common monitoring well diameters. For special well diameters, actual compatibility should still be confirmed according to the well diameter and internal structure.
For a small-diameter well like the one in this project, this means the construction team does not need to repeatedly change probes with different specifications.
2.2 Deep-Well Conditions Can Make Conventional Downhole Camera Images Difficult to Read
A depth of 300 meters means that the camera must operate under more complex underground conditions.
Insufficient light, turbid water, water mist, and environmental changes at different depths can all affect downhole camera imaging.
If the image itself is not clear enough, even a very small fracture may appear only as a vague line in the footage.
When looking at such an image, the construction team faces an important question:
Is it actually a fracture, or is it water flow, reflection, suspended particles, or image noise?
If the answer depends entirely on experience, it becomes difficult to distinguish between a visible abnormality and a confirmed defect.
2.3 A Single Viewing Angle Can Leave Small Fractures in Blind Spots
A borehole fracture does not necessarily appear directly in front of the camera.
With a single-direction camera, some fractures may be located on the side, behind the camera, or near the edge of the field of view.
Small cracks are particularly easy to overlook when the water is turbid, lighting is limited, or the target is far from the camera.
Therefore, the requirement for this project was not simply to make the image “brighter.”
The inspection needed to solve four problems:
Can the probe enter the well → Can the well wall be observed comprehensively → Can small defects be identified → Can the defect location be determined?
A professional borehole inspection camera can provide more comprehensive visual information about the underground environment.
3. How Did the AML921 Downhole Camera Locate the Hidden Fracture at 220 Meters?
For this approximately 300-meter-deep well, the AML921 inspection approach can be summarized as:
Small probe access + multi-angle imaging + digital analysis + depth positioning.
This transformed a problem that was previously difficult to see into a specific location that could be further investigated and repaired.
This approach is particularly useful for deep groundwater monitoring well repair projects where hidden defects must be identified before repair.
Step 1: The Φ45 mm Micro Probe Entered the 10 cm Small-Diameter Well
The well diameter in this project was approximately 10 cm.
The AML921 uses a probe with a diameter of approximately 45 mm, allowing it to enter this type of small-diameter underground well.
Compared with conventional inspection methods that may require different probes for different well diameters, the small-diameter probe reduces the need for equipment changes and repeated operations.
For underground well repair contractors, the value is not simply that the probe is small.
More importantly:
The equipment can actually reach the area that needs to be inspected. Only then can the subsequent imaging and analysis be meaningful.
Step 2: 360° Circumferential Imaging and Bottom Viewing Expand the Observation Range
The project used multi-angle downhole imaging to inspect the well wall and bottom.
Circumferential imaging expands the observation range around the well wall and reduces blind spots caused by single-direction viewing. The bottom-viewing camera is used to inspect the bottom area.
At the same time, the system uses a 2-megapixel low-light camera and six automatically adjustable shadowless LED lights to improve imaging performance in deep-well conditions.
According to the project test data, clear images could still be obtained under a 50 NTU turbidity condition.
For the construction team, this changed the focus of inspection from:
“Is there an abnormality in the image?”
to:
“Where exactly is the abnormality located?”
This step is critical.
Step 3: Digital Slice Analysis Turned the 220-Meter Fracture From “Invisible” Into a Locatable Defect
This was the most important change in the project.
Traditional downhole camera inspections often require operators to continuously watch the video and manually search for abnormal images.
For a 300-meter-deep well, this method can be time-consuming and highly dependent on the experience of the inspection personnel.
The AML921 uses analysis software to process the well-wall images into digital slices and combines the images with depth markers to identify abnormal locations.
The construction team eventually discovered that:
The hidden fracture responsible for the leakage was located at approximately 220 meters.
In other words, the problem that had not been clearly identified after three inspections with a conventional downhole camera was finally located through digital downhole imaging and analysis.
This changed the next stage of the repair from “continue searching” to:
Focus the repair on the area at approximately 220 meters.
4. Conventional Downhole Camera vs. AML921 Digital Downhole Camera
| Inspection Dimension | Conventional Downhole Camera | AML921 Digital Downhole Camera |
|---|---|---|
| Probe Diameter | Different well diameters may require 2–3 different probes | Φ45 mm micro probe, compatible with approximately 99% of common well diameters |
| Image Quality | Images can become unclear in turbid water or water mist | 2-megapixel low-light camera; project data showed clear imaging at 50 NTU turbidity |
| Field of View | Single-direction camera may create blind spots | 360° circumferential imaging + bottom viewing |
| Resolution | Small fractures can easily be overlooked | 0.1 mm resolution, capable of identifying approximately 0.5 mm-level cracks |
| Deep-Well Transmission | Deep sections may experience signal attenuation or lag | Low-loss coaxial cable maintains 1080P at 500 meters |
| Defect Identification | Mainly depends on manual frame-by-frame observation | Digital slicing + automatic marking + depth measurement |
| Data Archiving | Mainly relies on video and manual judgment | Evaluation data with scale can be digitally stored and transmitted |
| Probe Material | Durability can be a concern in complex environments | 316L stainless steel, 2,000-hour salt spray test, resistant to strong acids |
In one sentence:
A conventional downhole camera solves the problem of “whether you can see inside the well,” while AML921 focuses on “whether you can see clearly, locate the defect, and retain inspection evidence.”
For deep-well leakage repair, the real value is not simply recording another video. It is turning a hidden problem inside the well wall into a specific location that can be identified, analyzed, and repaired.
5. Customer Feedback: “We Used to Have to Guess”
Before using the AML921, Manager Liu’s construction team had already performed three downhole inspections using a conventional downhole camera.
However, because no obvious fracture could be identified, the source of the leakage remained unknown.
After the new inspection, the hidden fracture at approximately 220 meters was located.
Manager Liu described his experience:
“With the downhole camera we used before, sometimes the image was clear, sometimes it was unclear, and sometimes we could only guess. As a result, repair projects depended on luck. But after using AIMOLI’s AML921, these problems were completely solved.”
For contractors who specialize in underground well repair, an accurate well-wall fracture inspection provides value beyond simply “seeing a crack.”
It can help reduce:
- Repeated downhole inspections;
- Unfocused troubleshooting;
- Unnecessary rework;
- Repeated labor and material costs;
- The risk of an entire well being abandoned because the defect cannot be located.
More importantly, the inspection results can provide clearer evidence for subsequent repair work.
6. What Problem Did This Project Actually Solve?
On the surface, this was simply a downhole camera inspection case.
But from the customer’s perspective, AML921 solved a common problem in underground well repair:
Previous inspection process:
Well leakage → Downhole camera inspection → No obvious fracture found → Inspect again → Still unable to confirm the cause → Continue troubleshooting → Higher rework costs
Inspection approach used in this project:
Well leakage → Small-diameter downhole camera enters the well → Multi-angle well-wall imaging → Digital slice analysis → Abnormality marked → Depth identified → Hidden fracture located at approximately 220 meters → Targeted repair
The biggest difference between the two methods is not whether a camera is being used.
It is:
From manually searching for problems to digitally locating problems.
This is also an important value of downhole camera technology in deep-well repair, groundwater well inspection, and well-wall fracture detection.
7. When Should You Use a Downhole Camera for Well Inspection?
For underground wells, monitoring wells, and deep-well repair projects, downhole camera inspection can be considered when the following situations occur:
7.1 Leakage Reappears After Repair
If a well has already been repaired and passed acceptance inspection but develops leakage again, a downhole camera can be used to inspect the well wall, casing, and other visible abnormalities to help identify the source of the problem.
7.2 Repeated Repairs Fail to Identify the Cause
If a well has already been repaired multiple times but the same problem continues to occur, blind rework may increase costs.
In this situation, a downhole imaging inspection can be performed first to determine the actual condition inside the well.
7.3 The Well Wall Needs to Be Inspected in a Deep Well
For underground wells that are hundreds of meters deep, it is impossible for personnel to directly observe the well wall.
A downhole camera can transmit images from inside the well to the surface for inspection.
7.4 A Small-Diameter Well Cannot Accommodate Conventional Equipment
If the well diameter is approximately 10 cm, the probe diameter of the downhole camera should be carefully considered.
In this case, the approximately 45 mm probe of the AML921 was used to inspect the 10 cm small-diameter well.
7.5 Inspection Records Need to Be Preserved
For engineering projects, simply stating that “the well was inspected on site” may not provide sufficient documentation.
Digital downhole images can be stored and transmitted and can become part of the technical analysis and project records.
8. Frequently Asked Questions About Downhole Cameras
FAQ 1: Can a downhole camera really find a fracture in a 300-meter-deep well?
It can be used for visual inspection of the well wall, but actual inspection results depend on factors such as well diameter, well depth, water turbidity, fracture size, equipment configuration, and site conditions.
In this case, the well was approximately 300 meters deep, and the hidden fracture was ultimately located at approximately 220 meters using the AML921.
FAQ 2: Can a downhole camera be used in a 10 cm well?
Yes, but the probe diameter is an important factor.
In this case, the well diameter was approximately 10 cm, and the AML921 used an approximately 45 mm probe that could enter the well.
For other non-standard well diameters, it is recommended to provide the actual well diameter, well depth, and internal structure before purchasing so that equipment compatibility can be confirmed.
FAQ 3: Can a downhole camera still produce clear images if the water is turbid?
Image quality can be affected by turbidity, suspended particles, lighting, and water conditions.
This project used a 2-megapixel low-light camera and automatically adjustable shadowless LED lights. Project test data showed clear imaging under 50 NTU turbidity.
If the actual turbidity is significantly higher, it is recommended to provide the water conditions and underground environment in advance for evaluation.
FAQ 4: Can a downhole camera only record video, or can it also locate the depth of a fracture?
Different systems have different data-processing capabilities.
In this project, AML921 used digital image analysis, image slicing, and depth markers to identify abnormal locations and ultimately locate the fracture at approximately 220 meters.
Therefore, for projects that require defect localization, selecting a downhole camera should not focus only on whether it can record video.
You should also consider field of view, image resolution, depth recording, and data analysis capabilities.
FAQ 5: Why did three inspections with a conventional downhole camera fail to identify the source of the leakage?
Possible factors include well diameter, viewing angle, lighting, water turbidity, fracture size, and the manual inspection method.
Especially in a 10 cm small-diameter, 300-meter-deep well, a small fracture can be extremely difficult to identify from a single-direction video image.
In this case, the first three inspections did not identify an obvious defect. The hidden fracture at approximately 220 meters was subsequently located through digital multi-angle imaging and analysis.
FAQ 6: What information should I provide before purchasing a downhole camera?
It is recommended to provide at least:
- Well diameter;
- Well depth;
- Target inspection depth;
- Water conditions inside the well;
- Well structure;
- Whether casing is present;
- The specific problem that needs to be inspected;
- Whether inspection data or an inspection report needs to be preserved.
This information can help technical personnel determine whether the probe size, inspection depth, and equipment configuration are suitable for the project.
9. Conclusion: The Value of a Downhole Camera Is More Than Transmitting Images to the Surface
This underground well repair project in Guangxi demonstrates that for deep-well repair, the real challenge is often not simply capturing images from inside the well.
The challenge is:
Finding the actual defect responsible for the problem and determining its exact location under complex underground conditions.
In this project:
300-meter well depth
→ 10 cm small-diameter well
→ Three inspections with a conventional downhole camera
→ No obvious fracture identified
→ AML921 entered the small-diameter well
→ Multi-angle well-wall imaging
→ Digital slice analysis
→ Hidden fracture located at approximately 220 meters
This was the most important result of the project.
For underground well repair contractors, choosing a downhole camera should not be based only on whether the image looks clear.
It is also important to consider whether the equipment can reach the target depth, cover the well wall, identify abnormalities, locate defects, and preserve digital inspection data that can support subsequent repair decisions.
Moving from “seeing the well” to “finding the problem” is where a downhole camera delivers real engineering value.
If your project also involves deep-well leakage, well-wall fractures, small-diameter well inspection, recurring leakage after repair, or situations where a conventional downhole camera cannot locate the defect, the appropriate downhole inspection equipment can be selected based on the actual well diameter, well depth, and inspection requirements.
