New impact technology could revolutionize wireline logging

Impact sensors can determine if a sliding sleeve is open or closed and can read the inclination of the tool string at depth. They also measure temperature and pressure.

“Using pressure and temperature sensors and the ability to log with jarring, the system can be used when retrieving devices that can have differential trapped behind them. Sensors also can be used when shifting SSDs and can monitor U tube effects of fluid at depth,” McLaughlin says

Evaluating the challenges

The primary reason for deploying impact sensors is to produce digital data. “The data can be shown on charts that display the actual forces being applied to a given toolstring configuration at depth. Toolstring configurations differ greatly, and there can be hundreds if not thousands of ways to configure a toolstring assembly for a given installation or retrieval,” McLaughlin says. “Completion geometry also differs from field to field, and toolstring dimensions must change to accommodate this.”

Another consideration is horizontal completion technology, which greatly accelerates production, but greatly reduces functionality of slickline deployed equipment, McLaughlin explains. “Wellbore deviation causes friction on toolstrings, which reduces the functionality of the impact jars. Reduced jar functionality ultimately impedes the operation, sometimes to the point that the operation cannot be completed successfully.”

While the application of impact sensor technology benefits both the service provider and the operator, it does not eliminate the need for a surface weight indicator or load cell, McLaughlin says. “To function properly, the technology requires the application of three critical components; the impact sensor, the load cell, and the skill of the slickline engineer.”

Applying the technology

Impact sensor technology has been used with slickline toolstrings in over 100 applications since its launch in September 2005, says McLaughlin. The technology had been applied by electric line, coiled tubing, drilling, and reservoir analysis groups as well as others in the industry, but it was applied less than two years ago to the slickline intervention business.

“The primary reason impact technology was not applied to slickline operations sooner,” McLaughlin explains, “was a reluctance resulting from the perceived risk associated with deploying slickline into the well bore where an unknown event could cause irreparable damage to the completion system or at the very least, a costly exercise in equipment recovery.”

In fact, using impact sensors with the slickline toolstring eliminates many unknown risk factors by supplying the operator with known parameters being applied at depth.

Using impact sensors with downhole equipment

McLaughlin says the design of the impact sensor is in line with today’s slickline toolstring geometry. “The system comprises a single modular structure that emulates slickline weight bars in terms of dimension and physical properties. The modular design permits implementation of the system below the mechanical impact jarring tool.”

The impact sensor is placed below the jarring tool.

The location of the sensor is critical to its reliability. “When placed below the mechanical impact jar, the sensor only sees impact forces when it is in one of two positions: latched onto a device in preparation for impacting downwards with the mechanical jar and latched onto a device in preparation to upwardly impact with the mechanical jar,” McLaughlin explains.

Positioning determines the ability to accelerate the impact sensor prior to impact and protects the electronics packaged within the tool from damage resulting from the massive deceleration process after the mechanical jars impact.

McLaughlin says the physical properties of the impact sensor must meet or exceed that of the toolstring to which it is attached and must be able to withstand impact forces of varying degrees of severity. “Where smaller diameter toolstrings are used, impact forces are generally reduced; so a calibrated impact sensor would be supplied for that application.”

Material selection is also critical. “The sensor must be of at least the level of the material composition to which it is mated,” McLaughlin says. “Compatibility aids in the sensor’s force recognition capability because the sensor does not have to determine different material yields from one toolstring to another, a factor that can cause differences in acquired impact data.”

Jarring tools

The system is design to operate with the minimum of human interface but does have the ability to be programmed with various cycles for alternate toolstring configurations, McLaughlin says. The system incorporates timing sequences that permit the operator to increase or decrease record intervals during impact events that are occurring downhole:

• Where mechanical jars are to be used, the operator may only require a five-second record time during each impact event and prior to re-setting the jars for the next impact event
• Where hydraulic jars are to be used, the operator, may require a longer record interval due to low temperatures to ensure the hydraulic jar impact event is captured. When a hydraulic jar is activated in a low temperature well, firing times for the jars can extend to several minutes.

The impact event itself is critically important, McLaughlin says, and can vary in length and force as a result of several factors, including:

• Acceleration
• Deceleration
• Toolstring weight
• Toolstring deviation
• Tubing size
• Wellbore fluid
• Winch speed
• Wire size
• Wellhead/lubricator pressure.

Duration is also a factor. Two impact events of the same force can be applied to the same device with different results, McLaughlin explains. This happens when the length of the impact event changes as follows:

• 9.072 kg (20,000 lb) impact force with a duration of 20 ms.
• 9,072 kg (20,000 lb) impact force with a duration of 200 ms.

While both impacts are of the same force, the time the force was applied to the device changes by a factor of 10. This type of impact event frequently is seen in toolstrings, and the results can cause enormous variations in the ability to install or retrieve a specific device. The problem, McLaughlin explains, is that impact duration is not generally measured.

“It is clear that the ability to understand the impact duration for a specific toolstring assembly can greatly enhance the success of a particular intervention,” McLaughlin says.

Impact jars are complex pieces of equipment, but the point at which the stored energy is released to create an impact event is by far the most dynamic consideration. “The variety and variability of conditions that jars are exposed too is so diverse that no amount of testing can ensure that the jar will function as required in various conditions every time,” McLaughlin says.

Impact testing theory, application

“From testing to application,” McLaughlin says, “impact sensors have shown that while some of the theory that was believed to be true was indeed valid, other accepted theories do not match up to best practices.”

Testing jars using impact sensors reveals that jars manufactured to release a calculated force do not perform the same on the test bed at surface as they do downhole, McLaughlin says.

While this observation itself is not startling, McLaughlin says, what is surprising is that the loss of force discovered during testing and in live well applications is far greater than expected. “In some cases during live well application at depth with moderate, 40o deviation, the impact sensors are showing that the loss from the jars at depth can exceed 40%.”

When the multitude of toolstring configurations a single jar design can be impacted by is taken into account, it is evident that there are many open questions regarding what is really happening at depth, McLaughin says. “Is the result of miss-runs in the field due more to jar performance, or are well conditions to blame?” he asks.

Impact sensor calibration

For an impact sensor to be used as an accurate method of analyzing impact force, the unit has to be calibrated to a known standard so a true measurement can be determined.

Many of the output forces a device generates are based on mathematical calculations that can give an indication of the expected force in a perfect environment, but adding variables such as fluid, scale, angle, pressure, and temperature, can affect the true output value, McLaughlin says.

“One example is wireline jars,” McLaughlin says. “Jars are designed to initiate an output force once manipulated. Based on recent verification testing using impact sensors, we have seen that once environmental variables are introduced, values can change dramatically, which means the desired output may not be achieved.”

Wireline Jars are generally tested on a service provider’s test bed. Without a known, accurately calibrated standard, it is not possible to determine the true output force from the test bed and from the device being tested, McLaughlin says. “Service providers generally manufacture their test beds to their own internal standards, so it is likely that there is a variance between the test beds of one company and another.”

One method of ensuring consistency is to calibrate the test bed to a known standard. Standard ASTM-E-4-03 is defined by the American Society for Testing and Materials. The standard incorporates the guidelines for force verification by means of a calibration device.

In order to satisfy ASTM-E-4, the impact sensor can be calibrated in line with a load cell and a precise loading force. “Once calibrated, the impact sensor was capable of measuring the applied force within a tolerance of +/- 0.03%,” McLaughlin said.

A calibrated impact sensor can be made up to the bottom of a jar either on a test bed or downhole environment and can be used to determine the true output force with reference to a known industry standard.

Surface equipment interface

An impact sensor is a memory-based system that has to be programmed prior to installation. The USB serial interface of the device IGS has designed couples both the surface PC and the impact sensor via a USB cable and interface box, McLaughlin explains. A probe attached at the interface box is inserted into the impact sensor receptacle on the female thread end of the tool to be programmed.

“Programming in this manner eliminates the need for breaking down or unscrewing modular assemblies,” McLaughlin says, “so it simplifies programming and saves a lot of time.” It also maintains sensor integrity. An isolation plug is inserted into the female threaded portion after the tool is programmed to ensure no hydrocarbons enter the assembly.

“The surface interface allows the operator to program the system with a one-touch, one-button operation, which reduces the possibility of programmable human error,” McLaughlin says.

The surface PC operating system walks the operator through the programming process and informs the operator what can and cannot be accommodated during programming.

Old vs. new

Slickline engineers have always known that when jarring at shallow depth - less than 305 m (1,000 ft) - the preferred method for applying a significant force is to jar by hand, holding the wire and manipulating it by pulling and releasing it.

Using a wireline winch at shallow depths is not ideal, McLaughlin explains, because the winch is generally hydraulically operated and cannot react quickly enough at shallow depths for efficient jar action to be applied. “Whilst the theory is widely accepted, until now, it has never been proven other than in consistent and successful hand jarring application,” McLaughlin says.

Applying impacts at depth with the wireline winch at 131 m (430 ft) enabled a maximum impact force of 3,050 lb (1,383 kg). When the impact was carried out by hand, however, the results were drastically improved and showed a maximum impact force of 4,200 lb (1,905 kg).

This theory is now proven through the impact sensor’s ability to supply accurate and consistent data, McLaughlin says.

Applications where impact sensor technology is being used

• Heavy duty fishing operations
• Plug setting
• Plug retrieval
• Sliding side doors (SSD) manipulation
• Side Pocket Mandrels (SPM) manipulation
• Safety valve change-out
• Bridge plug retrieval
• Tubing Conveyed Perforating (TCP) gun firing force recognition
• High-deviation device installation/retrieval
• Formation isolation valve (FIV) manipulation
• Crown plug installation/retrieval
• Tubing patch retrieval
• Pressure and temperature logging (long/short term)
• Differential pressure analysis (plug retrieval)
• Pressure test confirmation at depth (plug setting)
• Drift with bottomhole survey
• Day-to-day operations with pressure/temperature survey
• Gradient surveys
• Static surveys

All of these application can be performed in combination with the onboard sensors built into the impact sensor module. The ability for the system to withstand impact forces of 110,000 lb (48,895 kg) for a 1.75-in. (44.5 mm) diameter tool negates the need for separate drift runs or alternate interventions to take place.

The ability of the impact sensor’s gauges to withstand these forces allows the sensors to be deployed in any toolstring wellbore application, including heavy duty fishing operations, without the need to first make a drift run.