From its installation in 2007, this subsea pipeline in the Gulf of Mexico experienced recurring paraffin and tar deposition problems that completely blocked flow. After acquiring the completely blocked line in 2013, the current operator used a high-pressure, low-rate pump to unplug the line and achieve partial flow. The line subsequently required complex, costly, and frequent remediations including hot-tap flushes, coiled tubing, chemicals, and biocides. The operator was forced to batch-flow the product, which proved uneconomical. The line was scheduled for abandonment.
INSTALLATION HISTORY
Line was installed in September 2006 from EI 275K to within 237 feet of EI 259C as S-15620.
Final 237 feet to EI 259C was installed in June 2007.
Line was renamed S-18045 in June 2007.
Line was laid/bundled with S-15619, which runs 19,644 feet from EI 275K to EI 259SSTI.
IDEAL'S RESPONSE
Ideal recommended PipeRenew® treatment, the only non-hazardous, environmentally responsible remediation solution that effectively removes paraffin and asphaltenes. PipeRenew® treatment reacts with the portion of oil that contributes to the acid value, to make a simple soap. This breaks up the paraffin and allows it to be pumped out.
Based on extensive experience with similar challenges, Ideal experts thought the line contained numerous plugs, which was evidenced by the frequency of significant pressure drops. But the main problem was a 2,664-ft plug, along with 39.28 bbl of N-Scrub gel (remaining from a previous service company’s attempt at cleanup), between the leading edge of the paraffin blockage and one end of the line.
PROJECT CHRONOLOGY
Day 1
M/V Harvey Wave arrived in the field
8:50 a.m. - EI 259C reported 1,180 psi on the pipeline
9:50 a.m. - Installed pressure gauge at EI 275K and recorded pipeline pressure of 1,010 psi.
2:45 p.m. - Drainer riser at EI 275K and received fluid with traces of hydrocarbons. Pressure bled down to 0 psi in approximately 10 minutes.
3:45 p.m. - Departed EI 275K for EI 259C.
5:00 p.m. - Arrived at EI 259C and recorded a pipeline pressure of 1,010 psi.
7:00 p.m. - Departed EI 259C to install pressure gauge on the riser at EI 275K.
8:10 p.m. - Installed gauge at EI 275K and recorded pressure of 360 psi.
Day 2
The team boarded EI 259C to begin the equipment rig-up process:
7:00 a.m. - Recorded a pipeline pressure of 950 psi on the riser.
10:45 a.m. - Installed hot tap below the boarding valve and rigged up hose to drain the riser.
11:50 a.m. - M/V Harvey Heat arrived at EI 275K and recorded a pipeline pressure of 560 psi.
12:00 noon - Opened riser at EI 259C to bleed the line. Some small paraffin solids were observed in the returns.
After comparing the time required to bleed the pipeline at each end, we were able to confirm the main blockage was located closer to EI 275K, which was consistent with the 2011 remediation history that showed the blockage between 3,000-6,000 feet from the EI 275K platform.
Day 3
Pumping operation began from M/V Harvey Wave at EI 259C. The purpose of the first attempt was to see if there was communication from EI 259C to EI 275K.
4:05 p.m. - Started pumping from EI 259C at low pressure. Initially, the pressure dropped rapidly when pumping stopped.
4:50 p.m. - Injected 2 bbls of PipeRenew® solution in 45 minutes
5:10 p.m. - Pressure holding at 600psi.
Not wanting to push too hard until we knew if it was possible to pump from EI 275K to EI 259C, the decision was made to stop pumping when the pressure stabilized at 550 psi.
Day 4
The M/V Harvey Heat opened up the riser at EI 275K and received hydrocarbons.
1:50 p.m.- The crew started pumping from EI 275K to EI 259C.
2:22 p.m. - Maintaining 600 psi on the pipeline.
3:20 p.m. - Pressure was up to 1,000 psi and bleeding slowly when the pump was disengaged.
7:02 p.m. - Limited communication was established. M/V Harvey Wave received some interesting materials in the returns (see picture below).
A total of 1.5 bbls of PipeRenew® solution were injected from EI 275K
Approximately 10 gallons of a heavy, grease-like substance were recovered in the 250 bbl tank on the M/V Harvey Wave at EI 259C
Day 5
A total of 3 bbls of PipeRenew® solution was injected into the riser at EI 275K.
8:10 a.m. - Began pumping from EI 275K to EI 259C.
2:15 p.m. - M/V Harvey Wave had received limited returns over the past 6 hours. IES personnel made the decision to inject/displace fluids at EI 259C to get PipeRenew® solution into the line.
4:32 p.m. - We discovered we could not pump through the hot tap back to the vessel due to an object in the riser. It is likely this object restricted returns during the pumping operations from EI275 to EI259C
In an attempt to remove the object, the riser connection was disassembled and checked, but the object was no longer atop the riser. We suspected the object retreated down the riser when pressure was bled off.
Since we were unable to remove the object and it would not flow through the 2-inch "hard 90" connection installed on the riser at EI 259C, we removed the 4-inch x 3-inch spool connection at EI 275K and installed it at EI 259C. In addition to its larger diameter, the 4x3 spool had a smooth radial transition.
Day 6
The M/V Harvey Wave set up to pump from EI 275K to EI 259C. The M/V Harvey Heat crew checked the riser at EI 259C and reported there was no sign of the unidentified object.
11:20 a.m. - Began pumping from EI 275K and were able to maintain lower pressure.
12:00 noon - A total of 3 bbls of PipeRenew® solution were injected over a 40-minute period.
A total of 9.2 bbls of PipeRenew® solution were injected from EI 275K on August 27, 2015.
After the valves were shut in, the line was pressured up to 1,400 psi from EI 259C a total of six times. During this period, the pressure dropped from 1,200 psi almost immediately. After the sixth attempt, the line was shut in at 200 psi.
Day 7
The pressure had bled down to 50 psi. At that time, the decision was made to pump from EI 259C to EI 275K to confirm the system would hold pressure.
After injecting 3 bbls of PipeRenew® solution into the line, the pressure eventually stabilized around 700 psi.
It is likely that numerous voids in S-18045 were penetrated and the pressure was dispersed across those sections.
After pumping operations were halted at EI 259C, the pressure was bled off slowly to allow the PipeRenew® solution adequate time to migrate down the line.
Prior to starting pumping operations on the M/V Harvey Wave at EI 275K, the crew displaced fluids in the riser and received approximately 10 gallons of paraffin.
1:20 p.m. - M/V Harvey Wave began pumping from EI 275K. The injection rate was consistent initially, but pressure started to bleed more slowly.
When this trend continued for some time, M/V Harvey Wave contacted M/V Harvey Heat and asked them to inject product into the hot tap and circulate back to the 500 bbl tanks. Soon thereafter, M/V Harvey Heat confirmed their pressure had increased, which indicated a blockage in the line.
... Day 9
A hot tap was installed on the +10 at EI 259C. The purpose was to push the unidentified object to the top of the riser and close the 4-inch ball value to trap it. Unfortunately, we were not able to push the object back up the riser after installing the hot tap.
Volume of solids recovered from the riser at EI 275K increased substantially over this 3-day period.
Day 10
Day 10, Ideal was confident the leading edge of the main paraffin blockage was approximately 3,000 feet from the EI 275K platform. To estimate the volume of PipeRenew® and time required to reach the blockage, we used the following assumptions:
Assuming 50% paraffin deposition from EI 275K to the leading edge of the blockage, a total of 21.5 bbls of PipeRenew® solution would be required to reach the affected areas.
20.4 bbls of PipeRenew® were then injected from EI 275K, being an estimated 147 feet from the leading edge of the blockage.
8:15 a.m. - Began pumping from EI 275K. The line pressured up immediately and held at 1,375 psi.
10:00 a.m. - Began pumping from EI 259C to see if we could insert PipeRenew® into the line.
10:45 a.m. - 1.85 bbls of PipeRenew® injected from EI 259C.
11:00 a.m. - Pressure at EI 259C was holding at 1,400 psi.
11:10 a.m. - Pressured up to 1,375 psi at EI 275K and bled down rapidly to surge the line.
6:25 p.m. - EI 259C reported oil in the returns.
8:15 p.m. - Pressured up to 1,375 psi at EI 275K and bled down rapidly to surge the line.
10:00 p.m. - Rigged down. Pressure at EI 275K was 1,375 psi.
Day 11
Operations were delayed due to a crew change.
11:40 a.m. - M/V Harvey Heat reported 0 psi on the pipeline at EI 259C.
11:45 a.m. - Pipeline pressure at EI 275K was 100 psi (a drop of 1,275 psi overnight). Because the suspected blockage was more than 3.5 miles from the EI 259C platform, we did not expect to see pressure when the plug was penetrated.
12:00 noon - Drained riser at EI 275K and received a significant amount of paraffin solids.
12:25 p.m. - Pressured up to 1,400 psi at EI 275K and EI 259C reported immediate returns.
12:55 p.m. - Pressure was holding steady, so we released it quickly to surge the line.
3:23 p.m. - EI 259C reported receipt of periodic oil spurts.
5:50 p.m. - Bled pressure at EI 275K to allow the line to relax.
6:20 p.m. - Pressured up to 1,350 psi at EI 275K.
8:20 p.m. - M/V Harvey Heat at EI 259C had received 8 gallons of oil in approximately two hours.
9:45 p.m. - Pressured up to 1,375 psi and shut in.
HIGH PERFORMANCE RESULTS
Ideal established limited communication after only five hours of pumping. Full communication was established after 75 hours of pumping.
A portion of available oxygen in the PipeRenew solution attacked the backbone of the gel, allowing penetration of the 2,664-ft plug. While reduction in oxygen may have increased the contact time required, it conclusively shows the adaptability of PipeRenew treatment to penetrate through various fluids and solid materials.
Approximately 50 bbl of paraffin was removed from the line, and 118 bbl of gel and solvent was recovered. The project was completed on time, on budget, and incident free, and the line was returned to full service.
For more information about how non-hazardous, environmentally responsible PipeRenew® remediation treatment can cost-effectively remove paraffin and asphaltenes from your pipeline, contact your Ideal Energy Solutions representative today.
