Pipelines carrying crude oil, especially those of small bore, not infrequently become at least partially blocked. Even if complete blockage is avoided, the loss of throughput due to flow resistance caused by the buildup of accretions on the walls of the pipeline can greatly degrade the maximum flow capacity of the line. These accretions usually result from the build-up of paraffin waxes and other high-melting point components of the crude stream (some of which can easily separate out, especially in cold weather) on the pipeline wall, together with scaling of the inner surface of the pipe due to corrosion.
Small-bore pipelines can best be treated while in normal flow mode - no shutdown is necessary, although there may be a slight advantage if a pipeline is already out of use. Smaller-bore lines such as those typically used for oilfield collection systems can also be treated in longer segments (e.g., between pumping stations) and when flowing oil.
Large-bore pipelines (e.g., 1 meter diameter) in effect, should be treated as a horizontal, cylindrical tank. Large-bore lines may need some post-treatment mechanical cleaning (which will now be much more effective due to loosened deposits), e.g., using a motorized mechanical "pig", but the OSS treatment alone is usually sufficient.
The OSS concentrate must be used diluted 1:10 in water (e.g., 100 gallons of SWR to 1000 gallons water) in a holding tank and then heated to 170-200 OF (77-93 OC). For this purpose, a mobile heater truck is recommended (readily available in the US). The line to be treated, if of large diameter, should be closed off in segments and treated as if it were a tank. It is important that the hot OSS solution fill the entire segment being treated and that it be circulated as vigorously as possible to ensure maximum turbulence.
For smaller-bore pipelines and, in some cases, larger ones, it has proven possible to clean pipelines on-line (while they are flowing oil) by simply injecting OSS at ambient or higher temperature (the higher the better) into the flow stream for a period, preferably at multiple points around the pipe. The mixture of oil and OSS solution must then be pumped into one or more large holding tanks at the end of the pipeline (as would normally happen anyway) to allow good separation of the water solution of SWR and debris (such as scale) from the pipe.
Scale and other solid material falls to the bottom of the holding tank provided that flow in the line is sufficient to transport them that far. The supernatant oil is of pipeline quality (i.e., contains less than 1% water), separates sharply from the residual OSS solution after a fairly short holding period and is easily pumped off, preferably into a storage tank. The OSS-water bottom layer can be re-used or disposed of, with proper dilution, into waterways.
It is fully degradable and is non-toxic.
OSS aggressively promotes the separation of the hydrocarbon phases from the cleaning solution, resulting in a hydrocarbon-free cleaning solution for recovery and recycling and a water-free hydrocarbon phase which, absent any other contamination (e.g., from non-SWR cleaning systems) can be re-blended with the crude stream or used elsewhere. The amount of oil recovered is typically 1-20 bbl per 1,000 U.S. gallons of SWR-water solution used.
There are no other products known to or tested by OSS that offer the performance and ease of use of OSS. Hydrocarbon-based systems, solvent-based systems and even those based on natural oils are often environmentally unfriendly and result in contamination of the recovered crude and paraffins. Neither these systems nor any other water-based system known to OSS offers the same combination of low cost, ease of use and environmental friendliness that is available with OSS.
Most competing products must be used in undiluted or only slightly diluted form while OSS is used at 1:10 dilution (slightly more concentrated solutions, but never more concentrated than 1:5, may be needed for removal of very severe deposits).
OSS not only prevents oil/water emulsion formation but also destabilizes any existing emulsions. It also leaves a film on cleaned metal surfaces, that helps to prevent erosion formation and can also be painted, if needed.
Sludge Pit Petroleum Recovery and Cleanup
Sludge pits typically contain a semi-emulsified mixture of crude oil, water and miscellaneous solids (together with whatever else has been dumped in them - they are often used as unofficial and unauthorized waste disposal sites. Cleanup of a sludge pit requires as a minimum, efficient separation of oil, water and solids. The oil phase is then recombined with the crude stream. The water should be sufficiently clean (and especially hydrocarbon-free) to dispose of after proper dilution. The solids residue, after additional washing with OSS or any biological treatment that may be necessary, (depending on the origin and composition of the solids) should be clean enough to be used as land fill.
Addition of OSS to sludge pits has shown itself in field trials to be extremely effective in achieving all of these objectives although each application may require minimal experimentation on a small scale to define the optimum use conditions. OSS affords excellent separation of the oil and water components of sludge into two layers that can then be separated by mechanical skimming and promotes settling of solids to the bottom of the pit. From there, the solids can easily be removed after the supernatants liquid have been pumped off and easily stripped of any residual contaminants by re-washing with OSS. The OSS solution can be recycled until it is no longer effective with addition of replacement OSS, depending on the water level in the untreated sludge, since this creates a product dilution. Or, it can be disposed of. More OSS than the usual 1:10 formulation should be used in cases where the sludge has unusually high water content (>25%). Even at these higher concentrations, the effluent OSSsolution is not harmful to aquatic species with proper dilution.
The best approach is to circulate the sludge* using a suitable pump and holding tanks during which time it is blended with the appropriate amount of OSS. In most cases a heater and two tanks are needed. One tank to contained the separated (typically skimmed) oil and the second to separate solids from the OSSsolution, a third, smaller tank in which the solids can be washed and if necessary treated biologically. Even more efficient separation of solids can be achieved by centrifuging, but this type of equipment is seldom readily available.
*If it will flow - some sludge contains too much solid material that can vary from spent catalyst to sand and scale.
The contents of the sludge pit should be circulated continuously. OSS is injected into the circulating stream at a rate sufficient to provide a total dosage of 2 bbl (about 110 U.S. gallons) of OSS to 1,000 bbl (56,000 US Gallons) of sludge. Heating may be desirable to reduce the viscosity of the sludge, which is often high due to suspended solids, especially in cold climates. The receiving tank should be set up to permit continuous skimming of the oil layer, which rises to the top and is transferred to the second receiving tank. The first tank provides both space and time for the solids to settle while the third permits washing of the solids before disposal in a landfill.
About 90-95% of the oil or crude in the sludge pit will be recovered. Typically, 1,000 bbl of sludge will contain about 50% of crude or crude equivalent. Thus, 450-500 bbl of this should be recoverable. At current world crude prices, this is a substantial saving.
OSS is not aware of any equally effective or equivalent product value on the market. Several products from suppliers claim to facilitate sludge pit cleanup but are reportedly much less effective, much more costly and less environmentally friendly. Most allow only minimal recovery of usable hydrocarbons from the sludge.