Case Study - Pushing the Minimum Pressure Threshold

As upstream natural gas assets are beginning to age there is a larger need for integrity solutions in this area. The challenge with these assets is they often operate at lower pressures, which can make running a conventional in-line inspection (ILI) tool difficult. Identifying the lowest possible operating pressure is often dependent on the pipe size and the amount of fittings and bends, typically a line that is 8 inches or less in diameter.

Increasing pressure on a pipeline with normal production is not always possible and adding supplemental natural gas or nitrogen is often cost-prohibitive for most operators. This has created a need for conventional ILI tools with more compliant specifications. ROSEN’s solution for this market are our compact low-pressure capable tools with the ability to go as low as 1,800 kPa line pressure. Offering a solution from 6 to 20 inches, the Upstream Diagnostics Service is a new solution for a growing challenge.

The Challenge

The challenging assets addressed in this case are natural gas pipelines with a 6 to 8-inch diameter and standard operating pressure at 2,500 kPa or less. The pipelines are 25 kilometers or less in length and often have multiple areas of heavy wall thickness and tight radius bends. Previous inspections were completed by increasing pressure with supplemental gas or by cutting the line into sections and tethering with a bidirectional tool. Running standard free-swimming inspection tools has resulted in overspeed or stuck tools due to pipeline operating conditions. In most of the lines inspected with 2,500 kPa or less, line pressure will have an effect on velocity as the tool is passing through tight radius bends (3.0D and less). There is not enough head pressure in the pipeline to act as a brake for the ILI tool, resulting in a loss of useable data. The standard MFL-A tool will need to operate at a maximum of 5.0 m/s with an ideal range of less than 3.0 m/s.

The lines could not be taken out of service for a tethered inspection and it was too cost prohibitive to use any supplemental gas flow. Both of the lines in question had multiple locations where 1.5D heavy wall fittings were present and both had multiple above-ground riser locations. Both inspections required the use of a tool combining MFL-A/MD and XYZ technologies. The gas flow of the two pipelines could be manipulated from the launcher side of the pipeline manually. There were no major modifications made to either of the tools before the run to perform the service and no data below has been manipulated.

Case Study 1

An operator in North Western Alberta asked ROSEN to inspect an 8-inch sour natural gas line with a maximum allowable operating pressure of 3,200 kPa. With a length of 24 km, it includes multiple risers with 1.5D 90 degree bends. After a successful gauging survey was completed, the minimum inner diameter of the pipeline was recorded at 190 mm, which is within the acceptable range of the combined tools’ passage capabilities. The pipeline parameters during the inspection would be maximum of 2,000 kPa pressure and a flow rate of 150 e3m3/day, this equates to 2.2 m/s gas velocity.

A combination of MFL-A/XT and XYZ technologies was used for this inspection. The tool was also equipped for an external pressure sensor to verify line parameters of 2,000 kPa were met. As you can see below the pipeline was within range for the duration of the inspection with a maximum line pressure of 2,100 kPa at 15,500 m.

The tool was within its standard 0-5 m/s velocity range for 98 percent of the pipeline with the majority being under 3 m/s. There is an area at roughly 16,000 m that was over the acceptable velocity due to a riser section where the tool needed the increased pressure to pass through. Closer to the end of the inspection the velocity was increasing due to the gas flow controlled from the launcher valve only. Below is a capture of the tool velocity with the red line being the maximum velocity capabilities.

Case Study 2

An operator in North Eastern British Columbia asked ROSEN to inspect a 6-inch sour natural gas line with a maximum allowable operating pressure of 9,650 kPa. This line is 22 km long and includes multiple risers with 1.5D 90 degree bends. After a successful gauging survey was completed, the minimum inner diameter of the pipeline was recorded at 140 mm, which is within the acceptable range of the combination tools’ passage capabilities. The pipeline parameters during the inspection would be maximum of 2,500 kPa pressure and a flow rate of 100 e3m3/day, this equates to 2.1 m/s gas velocity.

For this inspection, we utilized a 6-inch tool combining MFL-A/MD and XYZ technologies which was equipped with an external pressure and temperature sensor used for verification purposes. The ROSEN tool recorded an internal pipeline pressure around the 2,500 kPa mark for the duration of the survey.

During the inspection, the tool was within its standard 0-5 m/s velocity range for 99.7% of the pipeline with the majority being under 3 m/s. The tool behavior was similar for the duration of the line with one exception being a riser near the receiver of the pipeline where it briefly reached over 5.0 m/s.

The tools did not suffer any damage during the inspections and recorded within thresholds. In both cases, the final reports were sent within a 14-day time from of inspection and all findings were verified by the client. After multiple inspections with low operating pressure and a growing database of tool behavior based on various conditions, ROSEN can confidently inspect lines as low at 1,800 kPa with standard in-line inspection tools. Constant improvements to the inspection tools will help push the minimum pressure threshold even lower.

Our Solution

With the growing need for solutions in the upstream gathering market and in addition to the other services offered by ROSEN the Upstream Diagnostics Service is a proactive approach to low pressure inspections. It includes conventional MFL-A, Caliper and XYZ (high-resolution mapping) technologies built into a smaller, more compact form factor with high compliance and less weight. Combining MFL-A/MD and XYZ technologies onto one tool has been used for a number of years in a fast turnaround application with its robust design and small form factor. Coupled with rechargeable batteries and hydrogen sulfide resistance, the combined tools are an ideal fit for this environment. Besides offering full MFL-A, Caliper and XYZ reporting, the tool fleet also fits within the ROSEN toolbox approach, can be used in any medium and meet or exceed the standard ROSEN ILI tool certification.

Your Benefit

Fast reporting
In addition to the tools themselves, reporting timelines have been decreased which is a large focus of the upstream market. Standard reporting timelines are less than 30 days with the majority of reports sent within 14 calendar days.

Meet growing challenges
With the compact low-pressure capable tools with the ability to go as low as 1,800 kPa line pressure, the Upstream Diagnostics Service is a new solution for a growing challenge covering diameters from 6 to 20 inches.