The role of flow remediation in optimizing production

LEONARD HAMILL, Pipetech 

Throughout the E&P stages, operators face all manner of challenges, with production disrupted—or even halted—by several limitations.  The environmental obstacles common within isolated or extreme oil fields, and even external political or social pressures can restrict production and therefore profits, depleting reserves. Combined with the competition for resources, with the growth of renewable energies (technologies, funding and investment, and the workforce), there is very little margin for error or waste. These factors make it critical to ensure optimal production of existing and emerging reserves and oil fields.  

While many of these challenges are outside an operator's control, several elements remain firmly within their authority. Waxes, hard scales and corrosion, while frequent inhibitors within oil production, can easily be monitored and mitigated by operators equipped with the right solutions. The capacity to tackle waxes, hard scale and corrosion makes it even more important to understand their causes and the methods available to limit their impact.  

For over 20 years, Pipetech has established a reputation for providing innovative cleaning solutions and patented technologies to resolve flow and blockage issues, including innovative methods in line with evolving industry and production requirements.   

WAX DEPOSITION 

Common to operators globally, wax deposition, also known as paraffin deposition, is a persistent flow assurance trial within the field. When the crude oil extracted from the reserve cools down in the pipeline, wax deposition, mixed with inorganic solids, can form and subsequently crystallize throughout the system. With consistency ranging from a fine paste to harder and more fragile matter, wax deposition can be diverse, but the consequences of its buildup are all too familiar.  

The accumulation of wax deposits will severely limit the flow of the pipeline, reducing productivity. Additionally, the quality of the produced oil is likely to be affected because of any buildup, along with the risk of unwanted sediment being carried through the flow. Materials, such as gums, fine sands, clays, salt and water, are all commonplace in deposits. Removal of wax deposits is imperative to maintain optimal flow and quality, but it does come at the expense of downtime and increased operating costs. Still, short term pain is a better option than risking the long-term viability of the production field.  

HARD SCALE 

Carbonate, sulfide and sulfate. These are among the most common types of hard scale found within oilfield applications that can cause issues in production. Caused by temperature and pressure fluctuations within the pipeline, the mixing process itself, the flow of water and the prevalence of naturally occurring minerals, hard scales are unavoidable throughout production, whether in the pipeline, at the surface or within the disposal well.  

Instead, regular maintenance, the use of descalers, and an effective cleaning strategy are all essential in avoiding the reduced flowrates, asset damage, or in extreme cases, the well shut-ins that are caused by the proliferation of hard scales.  

CORROSION 

Fig. 1. Wax, corrosion, and scale contribute to a “billion-dollar problem” within the oil and gas industry.

In the subsurface and far-reaching environments of oil exploration, exposure to harsh chemicals is inevitable. The result is naturally occurring corrosion—both sweet corrosion (caused by carbon dioxide and carbonic acid) and sour corrosion (caused by high concentrations of hydrogen sulfide). The pervasiveness of acids and salts—alongside carbon dioxide and hydrogen sulfide—within production only adds to the acceleration of corrosion within pipeline systems and wellbores. Corrosion and its impact are incredibly well documented (Fig. 1), commonly resulting in leaks and their various consequences to operations, assets and the surrounding environment. Just like hard scales and waxes, corrosion can be mitigated with proactive measures. 

IMPACT 

The widespread formation of wax deposits, hard scales and corrosive elements leaves behind substantial environmental, operational and financial consequences.  

Avoiding a proactive asset integrity and maintenance plan will only lead to the spread of any—or all—of the aforementioned issues, increasing the potential for leaks and breakages. Although common, leaks and spills can be disastrous for your reputation and the environment. With a spotlight on the environmental durability of the E&P sector, avoidable leaks, and the pollution they cause, are a quickfire way to increase pressure on the entire industry. Water pollution, oil spills, increased greenhouse gas emissions, and habitat destruction or impediment can all progress from leaks and breakages. Not to mention the increased costs and emissions from trying to rectify mistakes and patch up the system.  

The financial and operational impacts of wax, scale and corrosion are often intertwined. A 2022 report from the University of Lisbon pointed to wax deposition, alone, as being a “billion-dollar problem” within the oil and gas industry, with the annual economic impact being as high as $330 billion. Reduced flowrates and productivity, the cost to repair or replace equipment, and the increased operational costs of extensive maintenance all contribute to this astronomical figure. Additionally, the risk of causing environmental damage will only lead to further fines, regulation breaches and reputational damage for the company. 

To avoid any of these issues, it's important for operators to know the options available. 

TACKLING WAX, HARD SCALES AND CORROSION 

Rather than a single fix-all solution for tackling wax, hard scales and corrosion, a varied and in-depth strategy can help combat the consequences of each variation of production inhibitor.  

The injection of hot oil or steam; Electrical Trace Heating (ETH) to control the temperature within the well; and the application of insulation materials are all thermal-based techniques that have a history of preventing or removing wax, hard scales and corrosion. Injecting hot oil, known as hot oiling, is a particularly popular method for wax removal. Thermal techniques such as these rely on maintaining the well at a set temperature to prevent crystallization and deposit formation, or dissolving deposits that have already formed. 

The success of these methods, however, depends on a variety of factors. The severity of the deposit within the well, the integrity and condition of the system, and the properties of the oil all contribute to the method's effectiveness. While thermal techniques provide quick results, are relatively cost-effective in the short term, and are an easier process, they can be limited in their application against difficult-to-break-down materials. Additionally, the fluids used can often contain harmful contaminants that can damage the asset or accelerate corrosion. 

Chemical inhibitors, like polyphosphates, acrylic acid polymers and sulfonated polymers, rely on organic and inorganic chemicals to maintain flow and disperse depositions. By and large, chemical inhibitors succeed by reshaping wax crystal structures as a preventative measure against aggregation, or, in a best-case scenario, going one further and preventing scale crystals from forming at the outset. 

Like thermal techniques, chemical inhibitors are cost-effective and help to maintain a steady flow. They also can help to combat deposits from building up and reduce the need for later—and more severe—intervention. Unfortunately, once again, chemical inhibitors have limited application against more challenging materials, while the correct dosage can be difficult to pinpoint with complete accuracy. Because inhibitors require specialist chemicals and toxins to be effective against deposits, when applied in the field, and particularly for large dosages, the environmental impact can be severe, leaving behind a trail of pollution that is difficult to compensate for. 

Through the application of sheer force along the pipeline or wellbore wall, mechanical cleaning methods, such as pigging or scrapers, can break down and subsequently remove wax and scale. By propelling pig or scraper technology through a system, any buildup of material can be cut away to optimize flow and maintain efficiency. Mechanical cleaning techniques rely on force, propelled by compressed air or water, so they have a greater track record against a wider variety of materials than chemical inhibitors or thermal techniques. 

Mechanical cleaning is also a quick and more environmentally conscious process that can reduce downtime. However, mechanical cleaning solutions do pose a risk to the integrity of the pipeline or well, due to a reliance on force. Any tools used must be meticulously designed to avoid causing any severe damage to the asset, while, generally, they are not applicable in deepwater systems because of the reach required. For many offshore operators, this rules out mechanical cleaning. 

CLEANING & FLOW ASSURANCE 

Cleanliness is non-negotiable within the oil and gas industry. While various options are available to maintain the integrity of wellbores and pipelines, each with their own benefits and limitations, the problem of scale, wax and corrosion could be partially mitigated, if a clear and consistent cleaning strategy is in action.  

Regular cleaning procedures are essential to maintaining continuous flow and production, while preventing and inhibiting the spread of harmful foulants is much more cost-effective than the removal and repair process. Not to mention that proactive steps to prohibit flow assurance problems, such as effective cleaning methods, can help to extend the lifespan of a pipeline or wellbore. Additionally, cleaning procedures aren’t an opt-in option, with several regulatory frameworks and compliance standards acting as a requirement across the industry. 

Fig. 2. Innovative cleaning solutions are needed to meet evolving industry requirements.

Unfortunately, that doesn't always mean that these standards are adhered to. A lack of awareness of pipeline and wellbore maintenance expectations and the options available to support optimal flow assurance may prevent expert intervention. So, too, may a lack of awareness on the long-term benefits of cleaning strategies (financial, operational and environmental), especially when compared to the short-term focus of a production cycle.  

Concentrating on the immediate profitability and productivity of an oil field, many could see cleaning as a disruptive process that hinders the initial investment of the field while also reducing the time spent actively producing. While cleaning and maintenance provide long-term benefits, in the context of short-term gains and intensive production demands, a prolonged perspective can be difficult to come by.  

Flow assurance and cleaning is a specialist service that will likely require external support. Knowing the options available and who to turn to are key to a sustainable cleaning strategy, Fig. 2. 

TRADITIONAL CLEANING METHODS 

Retro-jetting is a common process used to tackle issues of scales, wax and corrosion. Widely used to target small and large deposits within pipe systems, retro-jetting (also known as hydro-jetting or hydro-milling) is a trusted technique throughout the oil and gas industry, as well as within the utilities industries.  

Traditionally, retro-jetting equipment has a PSI (pound-force per square inch) of anywhere between 10,000 and 40,000. This has established retro-jetting as a flexible option, suitable for a range of requirements, depending on the application needing cleaning and the debris or foulant that is causing blockages. The environmental impact of retro-jetting can also be measured through its usage of less water than other methods, as well as the ability to recycle the water used.  

The utilization of high-pressure water jets is what has set retro-jetting apart as a superior cleaning solution. Running down a wellbore or through a simple pipeline/system, retro-jetting delivers a highly pressurized stream of water that acts aggressively to remove the buildup of deposits in both directions. By forcibly dislodging and then removing debris throughout a system, retro-jetting can help to restore productivity and reduce the risk of long-term damage within an asset. Compared to many other cleaning methods, retro-jetting can often exceed cleaning standards while reducing the cost of downtime, and waste and water disposal.  

However, retro-jetting does have its limitations around the varying diameters in which it can clean and the ability to negotiate bends. Additionally, like mechanical cleaning methods pigging and scrapping, retro-jetting is typically delivered on a centralized mechanism that can limit results against various types of difficult foulants inside pipelines and wellbores. Like all methods and techniques, consistent innovation is required to address existing limitations and propose new solutions that advance the industry as a whole. 

PIPETECH 

Throughout 20+ years of operating, Pipetech has established a reputation for removing difficult waxes, hard scales, corrosion and other foulants that the industry struggles with. Specializing in pipe and process cleaning, inspection and flow remediation solutions, Pipetech utilizes patented technologies to resolve flow and blockage issues across topside, subsea and downhole oil and gas assets. Among these solutions is the Aqua Milling® technology.  

The natural evolution of retro-jetting and other traditional systems, Aqua Milling^® is an efficient innovation that doesn't cause any damage to the system it is deployed within, thanks to its rotating hose design. In comparison to retro-jetting, Aqua Milling^® can clean back to bare metal while navigating more bends, including more complex systems, at a greater distance—all from a single-entry point to minimize disruption. 

Fig. 3. Pipetech's Aqua Milling® technology helps remove waxes, hard scales, corrosion, and other foulants.

Developed by Aqua Drill International, some key features of the Aqua Milling^® technology include: 

• Access to 12-mm to 3-m diameter pipes;  
• The ability to negotiate multiple diameter changes; 
• A 600-m continuous reach; 
• Up to 20 directional changes; 
• Up to 2,000 nozzle configurations. 

Used by operators worldwide to support flow assurance and help optimize production, Aqua Milling® (Fig. 3) has removed diverse materials, including sulphur, calcium, pulp, asphalt, barium sulphate and corrosion, among many more. To date, across its track record within the industry, there has yet to be a naturally forming material that Aqua Milling^® hasn't effectively targeted. 

CASE STUDY: IN-HOUSE PIPELINE CLEANING 

The effectiveness of Aqua Milling^® is regularly displayed in the projects that Pipetech is involved in.  

Working with one of the oil and gas industry’s leading mechanical engineering firms, Pipetech delivered urgent support to counter the growing impact of corrosion on a series of 12x reducer spools. Through its Aqua Milling® technology and its facilities located in Aberdeenshire, Scotland, Pipetech’s intervention ensured the client’s system was clean and debris-free, ready for reinstallation on site, and verified that no loose sediment would be found within the system. 

Within the pipeline system, the client was rapidly experiencing the negative consequences of loose product sentiment caused by corrosion. The impact was directly affecting the reducer spools within the pipeline. Initially aiming to handle the spread of corrosion internally, the client tried several cleaning procedures including retro-jetting. 

Unfortunately, because of retro-jetting's lower water flow and inability to access diverse diameters, these initial attempts were unsuccessful. Each of the 12 spools affected by corrosion had varying diameters that needed a specialist solution.  

Relocating the client’s system to its Aberdeenshire facilities, Pipetech assembled a team of three highly experienced personnel and its Aqua Milling^® technology to work on cleaning the spools. Ensuring no water from the use of Aqua Milling^® was wasted or disposed of in drains, Pipetech self-contained each spool with all waste and water from the cleaning operation sent to a local processing facility for safe reuse.  

Alongside Aqua Milling^®, a camera inspection both pre- and post-cleaning was delivered to the client to compare results, followed by an end of project report. The camera inspection was pivotal to showcase the results of Pipetech’s intervention in which its team provided the highest level of cleanliness. Additionally, Pipetech’s ability to transport the system to its in-house facilities helped to minimize disruption at the client’s site. 

Since this project, Pipetech has continued to deliver regular cleaning and maintenance work to the client, including additional parts of the same system. The work completed has contributed to Pipetech’s 20+ year track record of using innovative cleaning and maintenance solutions to promote the importance of flow assurance techniques in optimizing production globally. 

LEONARD HAMILL,  

Pipetech’s very first employee, has over 15 years of experience in managing and directing complex manufacturing and development projects within the oil and gas, energy and utilities industries. In 11 years at Pipetech, Mr. Hamill has helped establish the company as the ‘go-to’ solutions provider for flow remediation within the North Sea and Norwegian Continental Shelf. As Operations director, he has led the widespread implementation of the Aqua Milling® technology and has also been fundamental in the development of Pipetech’s patented Downhole Scale Remediation (DSR) solution.