Table of Contents
1 Introduction
Large petroleum pipe systems have been subject to leak sealing since 1922, normally a non-destructive on-site repair method. That year, Clay Furman presented the first pipeline leak-sealing compound to the globe. When referring to maintenance and repair services, the word online denotes that work may be done without interrupting the flow of goods.
Leaks in the valve packing, the substance required to close the gap between the valve stem and body, were first stopped via leak sealing. The procedure entailed adding to or replacing the original packing by injecting the compound into the valve stuffing box, which contained the packing. This method for stopping valve leaks has been in use since it was introduced about 80 years ago. Stopping leaks in piping and other parts and equipment has developed into a similar process that uses packing and sealant.
For seal businesses, the ongoing hunt for stronger seals has been both a blessing and a curse. On the one side, the intense applications push seal businesses to operate more productively and creatively. On the other hand, the aggressive pursuit of improved substances and seal designs has pushed seal manufacturers to their technological and innovative breaking points. To get oil out of the earth, time is of importance. This hurried timeframe puts a burden on resources and prevents lengthy or thorough testing and manufacturing technology.
2 Drill and Tap
A skilled technician uses the drill-and-tap technique to intersect the groove or gasket by drilling and tapping a blind hole between the bolt holes. A blind hole stops short of the other side of the work area; it does not totally penetrate. In the tapped hole is next inserted an injector valve. The technician can regulate any oil flow that could happen during the next stage using this injector valve. The technician will next drill a hole through the injector valve and into the seal region using a drill bit.
A manually operated injection cannon is one of the specialized leak repair tools and equipment that is used to inject sealant for both the drill-and-tap method and the installation of the unique clamps and enclosures. Next, the injector valve is rotated so that it is closed. With more injection sites and valves, the procedure is repeated with the goal of precisely controlling the amount of sealant injected.
Professionals with years of expertise are performing this extremely skilled task. They possess the skills to precisely gauge the best drilling locations, depths, and sealant injection rates. Consider it as though a gasket were being injected from the outside in. The oil does not have to be emptied
with this minimally intrusive procedure. Some of these repairs can be carried out while the machine is powered on, depending on where the leak is located. Lower radiator flanges or the bottom of a tap-changer flange are two examples of typical in-service leak repairs.
The sealant, which is a two-part mixture, first has the viscosity of peanut butter. Using a manually operated pistol with a pressure gauge, it is slowly pumped into each of the valves as they are placed. The cure time of the sealant is around an hour. The injection valves are taken out and Teflon-coated pipe plugs are put in the threaded holes once the sealant has had time to set.
Drill-and-tap repairs are ideal for employing this method because they feature a grooved or recessed region where the O-ring or gasket is situated. There is a channel where the sealant may pass through and form a seal by crossing this grooved region. This method may be used for bushing mounting flanges, cover plates, belly bands, tap-changer handles, tap-changer flanges, and other parts.
Figure 1 Drill and Tap Method
The second form of leak correction uses a specially made clamp or enclosure. Injecting the cavity of that piece of hardware to achieve a seal. This forms a barrier around the leaky component. Through the use of appropriate hardware, leaks can be properly sealed by injecting sealant under pressure.
Two quick interruptions could be necessary for enclosure repairs. For the leak seal expert to accurately measure the enclosure on day one’s morning, there could be a need for a 1-hour outage. The gadget can be created that day and delivered the next day. If necessary, the enclosure is installed during a second outage that lasts between 4 and 6 hours. To stop the leak, the sealant is injected into a channel inside the clamp. The clamp stays in place and is simple to remove when necessary.
There are many unusual leak repair jobs. In addition to the drill-and-tap technique, the custom clamp, or enclosure technique, leaks at the base of radiator fins or cooling rods can occasionally be stopped by fabricating and filling a weir with sealant. Even if the cooling capacity is slightly reduced, this can work as a temporary fix until a replacement is feasible.
Figure 2 Clamp or Enclosure
3 Hot Tapping
Hot tapping is a technique for repairing a leaking joint or making a connection to in-service piping or equipment and drilling or cutting a part of the pipe or equipment within the connected fitting to create an aperture. Forming a new connection to an already pressurized pipe or vessel without halting or emptying that segment of pipe or vessel is known as hot tapping. This implies that a pipeline can keep running while maintenance or repairs are being carried out.
In the hydrocarbon industry, hot tapping is widely used. Due to the delays in product supply to clients and other facilities, shutting down pipelines is typically challenging. A hot tap can be used to connect new links to an already operational pipeline without disrupting the flow. It can also be used in conjunction with line plugging to redirect circulation around a line or piping segment that is being repaired or maintained.[1]
A hot tapping procedure is a high-risk activity that should not be performed on a regular basis. It must only be carried out if a facility closure is not possible – an evaluation that takes into account a variety of factors [2].
Hot tapping entails hot labor, such as welding on operational pipes, piping, or tanks. As a result, a thorough assessment of the hazards of hot work is required. Every hot tapping procedure requires the highest level of safety. Hot tapping should not be done until the safety of the employees and the environment can be assured. In the event of a hot tap failure, the dangers described here include pollution and the discharge of dangerous substances.
The pipes, pipeline, or reservoir to be tapped should be in good working order. To evaluate if the hot tap is safe to operate, the integrity of the machinery or pipes must be carefully examined. It is forbidden to tap equipment or pipes that have degraded beyond a certain point. The system must be configured in such a way that hot tapping may be done without difficulty. For piping layouts and tanks, this is frequently a more important criterion than for pipelines. The hot tap should not be done if accessibility to the lines is restricted. This covers things like soil condition, water tables, and plant overgrowth, among other things.
Hot tapping has a number of operating restrictions, including fluid temperature, pressure, flow velocity, and so on, as will be explained later. To guarantee that hot tapping may be effectively done within these constraints, the system’s operational data must be closely examined. The machine used to execute the hot tap should be capable of effectively completing the task. The choice of equipment is critical since the improper machine can lead to an unsuccessful hot tapping procedure. Temperature, pressure, flow rate, and other operational requirements must all be met by the machine. Hot tapping should not be done if a machine capable of operating efficiently under all defined circumstances is not available.
The hot tap operation’s financial element must be properly assessed. It’s best to avoid situations when the expense of a hot tap is much greater than the expense of shutting down and doing normal maintenance.
Is it possible to safely weld the hot tapping fitting onto the pipeline? Is it possible to weld a pipeline under the working circumstances and with the materials of the container or pipeline? Before executing a hot tap, this must be justified. Before executing any hot tapping operation, all requirements (industry codes, municipal ordinances, etc.) must be thoroughly assessed, and the operation must not continue if the requirements are not satisfied.
Figure 3 Hot Tapping Setup
4 Squeeze Cementing in Oil Wells
Squeeze cementing is frequently employed to fix the annular cement, the casing, or liner, or to halt fluid migration inside a well. This procedure is often carried out when the casing is being run. On the other hand, it can be utilized to fix leaks in the future. Due to the need for well workover and wellbore preparation, squeeze cementing operations can be costly. To maximize the operation’s performance, problem identification, risk assessment, and economic analysis must be done before squeezing activities are started.
Pumping cement slurry via perforations, cracks, or fractures in the casing or the wellbore annular space into a targeted isolated interval, behind the casing, or into the formation is known as squeeze cementing[3]. Wellbore preparation is the first step in squeeze cementing procedures. A stopper below the squeeze interval must be fitted if the slurry needs to be injected bottom-off to stop it from running farther downhole. Drill pipe or coil tubing is used to pump the slurry until the wellbore pressure reaches the desired level. The tube is typically removed from the cement slurry during the setting phase. The following phase is the elimination of extra cement, which is often accomplished by reverse circulation.[4]
Dehydration is a step in the squeeze cementing process. Most of the time, the solid particles in cement slurry are too big to penetrate the formation. While only a liquid filtrate enters a permeable formation, solid particles filter out onto the fracture interface or formation wall in an impermeable formation. The holes are filled with a cement filter cake as a consequence. Cement nodes jut out into the wellbore once the filter cake has accumulated. The filter cake is impermeable and strong enough to handle the increased wellbore pressure even if the cement has not yet been fully set.
According to the bottom hole treatment pressure, squeeze tasks are generally divided into two categories: a) low-pressure squeeze (below the formation fracturing pressure) and b) high-pressure squeeze (above the formation fracturing pressure). Running squeeze and hesitating squeeze, which can be used at low or high pressure, are the two pumping techniques. The Bradenhead squeeze is a fundamental maneuver that may be used with a variety of squeeze instruments and pumping regimens.
Figure 4 Squeeze Cementing
5 Polymer Resins Sealing
Polymer resin systems that are temperature-activated sealants are intended to cure at a certain temperature. This enables placing, pumping, or compression of the resin while it is still in a liquid condition into a chosen space in a well, followed by curing when the resin reaches the proper temperature. For a specific purpose, curing temperature, density, viscosity, and duration may be precisely tuned. In general, polymer resins are compatible with the majority of wellbore fluids and cement and may withstand minor contamination. Reversible treatments using polymer resin systems are possible (milling, acid treatment). The following describes a few instances of commercially available temperature-activated sealants.
A polymer resin system called ThermaSet (WellCem) was created for difficulties including loss of circulation, consolidation of loose formations, channels behind the casing, casing leaks, and plugging generally, but it may also be employed for many other well integrity concerns. ThermaSet has the following qualities: It penetrates porous formation and small channels; it hardens into a robust, flexible plug that can endure heat expansion; and it bonds well to steel and rock.[5]
Wellcem can theoretically stop all leaks. More precisely, leaks in hard-to-reach areas, locations where mechanical seals or other sealing materials are difficult to install, or locations where those other solutions would be prohibitively expensive.
The substance we employ is durable and will endure much beyond the well’s useful life. The sealing material can only be removed mechanically and will withstand all common well fluids. The material is strong and somewhat flexible, allowing it to bear mechanical shock or shock from variations in the well’s temperature or pressure, for example. However, it cannot be used for first-time cementing. It also doesn’t work well for leaks in environments with moving elements that are mechanically dynamic.
A rigid-setting fluid with a controlled right angle set that creates high compressive strength fast is called Thermatek (Halliburton). Consolidation of loose formations, general plugging, annular sealing behind or between casing/liner sections, and repairing casing or packer leaks are a few uses. When exothermic reactions are combined, the setting process is started. As the fluid is pushed downhole, more formation heat quickens the setting process. A retarder can be added to modify the setting time. Controllable right angle set, a quick increase in compressive strength, no shrinkage, no static gel creation, and resistance to invade formation are some of Thermatek’s characteristics.
It is theoretically possible to squeeze-cement and repair annular cement integrity loss using temperature-activated sealants.
6 FFKM and PEEK Sealing
The majority of equipment sealing demands could formerly be met by rubber materials like NBR or FKM and polymers like PPS, but new materials are now needed, such as polyetheretherketone (PEEK) and perfluoro elastomers (FFKM).[6]
The best elastomer sealing material, FFKM, is virtually inert and has a high level of resistance to media and gases. Its polymer construction has been specifically designed for harsh down-hole settings to maximize chemical and heat resistance. A single perfluoro elastomer range comprises a number of substances with various characteristics. For instance, one compound is designed to endure temperatures as high as 608 degrees Fahrenheit, another for steam at 500 degrees Fahrenheit, and a third for general use at 464 degrees Fahrenheit. Even a substance with a tightly packed molecular structure has been developed to lessen the impacts of explosive decompression.
Figure 6FFKM Rings
PEEK is a high modulus, reasonably priced material that works well up to 400 degrees Fahrenheit and is resistant to practically all downhole fluids. PEEK is often employed as a bearing material or seals backup device, but depending on the circumstances, it can also be engineered for use as a sealing element. PEEK is available in a variety of compounds due to the wide range of uses; one range of PEEK comprises an unfilled compound that is suitable for general service up to a filled compound that is suitable for low friction, high load bearing applications.
Figure 7PEKK Ring
Polytetrafluoroethylene (PTFE)-based materials are a good substitute, especially in dynamic settings. They offer excellent friction properties for rotational or reciprocating applications and are suitable with almost all media. If supported appropriately, PTFE can be utilized up to 500 degrees Fahrenheit or greater depending on the circumstances. There are several filled compounds of PTFE that range in filler types from carbon and glass fibers for extrusion resistance to carbon and bronze fillers for wear resistance to no fillers at all. Since PTFE lacks flexibility, an elastomer or metal spring must be used to activate it. To achieve a secure seal, this energizer keeps the PTFE pressed up against the mating hardware or sealing surface.
Some of the most hostile conditions exist in the oil and gas sector. To deliver the performance and dependability required, specific materials are needed. PEEK is one of the materials that performs admirably, therefore in this blog article, we’ll take a closer look at some of the many uses for PEEK in the oil and gas industry.
Couplings, wellhead connections, rotary drill bits, loading swivels, and anti-blowout seals all contain seals manufactured of PEEK materials. Ball valve seats, balancing piston seals, face seals, seal impeller hubs, and seal impeller eyes are further applications for PEEK. It is also used in chokes, valves, and stem packing. Face seals used at the wellhead to hold high-pressure production fluids and gases are one of the most demanding uses for seal assemblies that include PEEK.
The selection of PEEK for so many petrochemical applications is justified (even deepwater drilling and unconventional oil and gas operations). PEEK is extremely resistant to chemicals. One of the few polymers that can withstand exposure to settings with sour gas is this one. Both its specific stiffness and strength are exceptionally high. This implies that components lighter than steel or titanium can yet attain exceptional strength and stiffness. Furthermore, PEEK itself has few adverse effects on the environment. This covers its development, use, and disposal at the end of its useful life. You may solve many of the issues faced in the oil and gas sector by combining low friction, severe temperature performance, and outstanding wear qualities.
7 References
[1] C. Herckis, “Understanding hot tapping and plugging as an effective procedure to facilitate relocation, repair, or modification of water infrastructure when uninterrupted operation is necessary,” in Pipelines 2018: Utility Engineering, Surveying, and Multidisciplinary Topics: American Society of Civil Engineers Reston, VA, 2018, pp. 63-73.
[2] C. Herckis, “Hot Tapping and Plugging in New York City: A Method to Maintain Service and Protect the Marine Environment during Reconstruction of a Major Sewage Pumping Station and Treatment Plant,” in Pipelines 2011: A Sound Conduit for Sharing Solutions, 2011, pp. 372-381.
[3] M. Bellabarba et al., “Ensuring zonal isolation beyond the life of the well,” vol. 20, no. 1, pp. 18-31, 2008.
[4] J.-C. Manceau, D. Hatzignatiou, L. De Lary, N. Jensen, and A. J. I. J. o. G. G. C. Réveillère, “Mitigation and remediation technologies and practices in case of undesired migration of CO2 from a geological storage unit—Current status,” vol. 22, pp. 272-290, 2014.
[5] K. Knudsen, G. A. Leon, A. E. Sanabria, A. Ansari, and R. M. Pino, “First application of thermal activated resin as unconventional LCM in the Middle East,” in International Petroleum Technology Conference, 2014: OnePetro.
[6] J. B. Slay and K. Ferrell, “Proper performance testing to maintain seal integrity in deepwater completions,” in Offshore Technology Conference, 2008: OnePetro.
