Production Chemicals Trilogy (Part 2)
Selecting the right Production Chemicals. There is a bit more to it than you think!
In Part 1 of the Production Chemicals Trilogy, Pontem Analytics gave an overview of what Production Chemicals are all about. The aim was to provide an introduction into the application of chemicals in the oil and gas industry.
Now, in Part 2 we want to provide you with the information required to test and select the chemicals needed to keep the oil and gas flowing. But even with this it is still a complex problem to solve. Ultimately you may have the jigsaw pieces but Pontem Analytics is here to help you put them all together.
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What are the chemicals needing tested?
First things first, as mentioned in our previous post, there are a wide range of chemicals that may need to be injected into a process system to keep it functioning. The extremely complex nature of the chemistry of oil systems and the higher oil and water production rates means that more often than not, oil systems use a wider variety of chemicals and larger volumes of these chemicals compared to gas systems.
Why is this you ask? The answer is actually quite straightforward because oil systems produce lots more oil and water and when the chemicals’ dose rates are based on the volume of oil and water being produced, you use more chemicals. Whereas the liquid volumes produced in gas systems are relatively low. Additionally, production of multi-phase fluids introduces an enormous variety of hydrocarbon species and inorganic, aqueous chemical components which require a more robust chemical program to operate the system.
With that in mind, let’s review what chemicals Operations are likely to need. There may be chemicals required to prevent lines from blocking, stop corrosion of the carbon steel pipelines, vessels and equipment, aid in the separation of the oil from the water, stop bacteria from growing and remove contaminants from the oil, water and gas phases. It is also worth mentioning that when selecting the chemicals to use, the system the chemicals will be injected into along with the fluid composition, drive the chemical selection process. Consequently, having a solid understanding of the system’s fluid flow dynamics and the chemical composition of the fluids will greatly aid in creating a higher performing chemical program.
Here is what you need to inject chemicals - A Chemical Injection Skid
Taking all of the above into account, here are some commonly used production chemicals:
Demulsifiers – These are used to aid the separation of the oil, gas and water phases and are one of the more significant production chemicals from a usage perspective. They are also known as “emulsion breakers”.
Corrosion inhibitors - Required all along the process stream where free water and carbon steel is present to prevent corrosion of the pipelines, vessels and equipment used in the oil and gas production process.
Paraffin treatment chemicals – These are injected to prevent the deposition of paraffin and prevent gelling of the crude oil. There are a variety of chemical classes employed, which include paraffin dispersants, paraffin inhibitors and pour point depressants. We’ll come back to this as the selection will depend on the system, as well as the fluid characterization.
Scale inhibitors – These chemicals prevent / reduce inorganic solids deposition.
Asphaltene inhibitors - To prevent the deposition of asphaltenes, which are a class of polycyclic aromatic molecules.
Hydrate Inhibitors – Some of the highest usage chemicals are hydrate inhibitors and they are needed to prevent the formation of hydrates which are ice like solids that block oil and gas production systems. Current technology requires dose rates much higher than other production chemicals, and historically operators have treated hydrates as a zero-risk flow assurance issue because failures are catastrophic for production uptime and hydrate blockages can occur in a matter of minutes.
Naphthenate Inhibitors – These are acid-based chemicals that prevent the formation of calcium naphthenate solids and naphthenate stabilised emulsions.
Biocides - Prevent biological contamination throughout the oil and gas production process by killing the bacteria that grow in oil and gas production and water injection systems. While there is some variability in product selection, these chemicals are regulated and as such, registered products are required for the treatment of microbial species in the oilfield.
Water clarifiers / Deoilers / Reverse Emulsion Breakers – These chemicals are injected to ensure that the water separated from the crude oil is sufficiently free of hydrocarbon before water is reinjected or discharged to the environment. Typically, injected in conjunction with demulsifiers, these chemicals provide a secondary separation benefit and are effective at cleaning water to pristine levels for overboard disposal.
Solids Flocculents / Filter aids – To help meet oil and water specifications these chemicals are used to aid in the removal of solids from both the oil and water phases.
Antifoam – These chemicals are added to the process stream to prevent foaming in the oil and gas processing facilities.
Drag Reducers / Flow improvers – Reduce pressure drops across the pipeline systems oil and water are transported in to increase the volume of fluid that can be transported through the pipeline.
H2S and O2 scavengers – Scavengers are used to remove impurities from the oil, gas and water phases to ensure oil and gas specifications are met and to minimise corrosion in the case of the O2 scavengers.
Other notable chemical types that are used during the production of oil and gas are:
Stimulation chemicals – This can be a wide range of chemicals that include surfactants and acids. These chemicals help remove blockages in the reservoir rock allowing more oil and gas to be produced through the rock to the well.
EOR (Enhanced Oil Recovery) / Water Shut-off chemicals – Here chemicals such as surfactants and polymers are injected into the formation rock to increase the amount of crude oil which can be extracted from an oilfield or to reduce the amount of water that gets produced along with the oil.
Analysing the oil, gas and water from new wells, that’s easy right?
Unfortunately not, there are a lot of pitfalls along the way.
Everything begins by analyzing the oil, gas and water samples that are taken from the well during the drilling process or when the system is in production. The results of this analysis will tell you what the problems may be once oil, gas and water production starts from the field. But don’t forget to combine this knowledge with a thorough understanding of the system design: such as number of wells, production rates, flowline diameters and lengths, pressures, temperatures, bathymetry, etc. While not the focus of this post, it is an important consideration as some chemical formulations are specifically designed to account for these variables.
One of the problems you may come across when doing the initial fluid analysis is the limited volume of oil and water that may be available for analysis. The cost of taking samples from deepwater wells can be significant as you are looking at drilling rig day rates of anywhere between $250,000 and $750,000 / day depending on how sophisticated the drillship is and how difficult the environment is to drill in. The deeper the water and the nastier the weather usually means the more costly the drill rig. Yes, it is recognized that onshore wells are much cheaper to drill but budgets are also likely to be a lot less, so the problems are usually similar.
Consequently, even for onshore wells, time is money and when the sampling process can last for days depending on how deep the well is, how many samples you take and how they are taken, this can hinder the total volume that is taken. On many occasions only a small volume of oil may have been sampled due to the size of the sample containers (<1 litre) so you have to make sure any analysis is done at a lab you can trust because you might not get a second chance to do it. And when $billion developments rely on getting this right, there is a lot of pressure to make sure it is done correctly. The irony and magnitude is not lost on Pontem that such heavy and impactful decisions on a field designed to produce millions of barrels over the life of the field is relying on …one…litre of product.
Why is this important? Well, without fully understanding the fluid chemistry of the produced oil, water and gas, you cannot properly identify what the challenges may be when production starts and without that you don’t know what production chemicals to use. So, you need to focus on getting this right and until you do that you shouldn’t start looking at what chemicals to use. To start-up production first and then decide what chemicals to apply is asking for a very short production life cycle. We have seen a field producing > 2 MMscf/d shut-in after 12 HOURS because an inappropriate chemical application caused catastrophic processing issues.
Identifying the Chemicals to use
Once you know what you are dealing with from an oil, water and gas perspective, the chemical screening process can start. The objective of that process is to determine the effectiveness of chemical treatment methods in mitigating the various flow assurance and production chemistry challenges that the fluid analyses have identified.
In many cases, the flow assurance challenges that are mitigated by injecting chemicals are:
There can be other issues that need chemical treatment such as H2S removal, Calcium Naphthenate deposition, bacterial growth, etc. These can be tested on an “as needed” basis. To identify all the potential issues, you really need to work with a trusted partner with a recognized track record in this area.
Once we know what needs to be tested, the next thing is to identify a lab to do the chemical testing for you. There are lots of labs out there that can do the testing but that doesn’t mean that you want them to do it. They may have the right equipment and a shiny lab but without the right people doing the testing, you may end up spending a lot of money for little payback.
For example, a lab may be tasked with testing wax properties and chemical performance, however if they do not understand how to properly precondition the oil, they may inadvertently allow significant wax to fall out even before the first test is run!
As previously discussed, there may not be a lot of oil to do the testing with. Therefore knowing what you need to test up front to get your critical answers will allow what sample you have to go a long way and will help keep chemical qualification costs down. So, you need to be smart with how you use the oil you have. Pontem have spent years perfecting this so can help you get the most out of your limited volume of sample. The table below gives you at starting point of what may be needed.
Chemical Inhibitor Test/Volume Requirements
When it comes to performing the chemical test program, one of the most common mistakes that is made is that there is too much focus on the primary function of the chemical being tested i.e. does the pour point inhibitor reduce the gel strength of the oil, can the corrosion inhibitor prevent corrosion, etc. This on many occasions leads to unexpected problems elsewhere in the system, especially when there are a number of different chemical products being injected into the same system. Consequently, for whatever production chemical that has been proposed, there needs to be a whole suite of tests looking at how the chemicals may impact the overall system and to ensure it is compatible with the other chemicals being injected, the materials it comes into contact with and the fluids it is being added to.
Problems that have been identified previously are:
Loss of performance when various different chemicals are added to the same system at once. Some chemicals can adversely affect the performance of other chemicals.
When injected at high temperatures, into high salinity brines, into “dry” gas and near other chemicals, the chemicals can “gunk out” causing solids to form and cause blockages.
If the chemical is acidic and it is injected into a carbon steel system this can cause excessive corrosion at the point of injection. This can often lead to a leak.
Some chemicals in the oil and gas industry can aggressively attack elastomer and plastic materials so it is important to make sure that any proposed chemical is compatible with the materials that the system is made from.
Some production chemicals are highly surface active therefore they can cause very stable emulsions. Emulsion tests should be performed to make sure any recommended production chemical does not make oil and water separation more difficult.
Check that if a chemical is added to stop one problem it does not make another problem worse. For example, if a pour point depressant (PPD) is utilized to reduce the pour point and/or viscosity of the fluid, testing should be completed to ensure that the PPD does not adversely affect the wax deposition rates (as wax deposition rates are inversely proportional to viscosity).
Furthermore, any chemical tested will have to meet Health, Safety and Environmental requirements. This may mean that the best performing chemical may have to be removed from the chemical selection process if it cannot meet the project’s environmental, health or safety requirements. The hazard symbol for chemicals that are harmful to the environment can be found below. It looks quite gruesome, but it is like that for a reason.
When it comes to the health and safety implications of chemicals, you do not want to use carcinogenic chemicals or chemicals that affect fertility for instance unless you really have to. The same goes for flammable and corrosive chemicals. Being exposed to these chemicals due to chemical spills can result in significant injuries so it is always better to avoid them when possible.
As you can see there are lots of different things to think about even before you need to decide who is going to do the testing for you. With respect to that there are a couple of options. For new assets the most common approach is to obtain chemicals from multiple chemical vendors and get those chemicals’ performance validated at an independent laboratory. The outcome of this analysis can be used to select the preferred chemical vendor for the new asset. The other option that is often used is that the Operator uses their preferred chemical vendor who already supplies chemicals to their other oil and gas fields. Both approaches have their positives and negatives, and it will probably come down to things such as the cost of the testing, how much oil is available to do the testing, what your company’s corporate policy is, your geographic location, etc.
It's all about the Money!!
When managing the testing programs, it is obviously important to make sure the chosen chemical meets its required performance and environmental targets but that is not all you need to keep an eye on. When it comes down to it, the best performing chemical may not be the one that gets chosen because if the 2nd best performing chemical meets the required performance target but the cost to treat a barrel of oil is significantly cheaper, then that would be the one to choose. Conversely it is important not to focus on the unit cost of the chemical. Just because one chemical may be so much cheaper from a per litre perspective doesn’t mean it is the chemical to use. For example, a more expensive chemical may be effective at a much lower dosage, making the overall cost of the chemical program less. Ultimately it is usually way cheaper for a reason and that is probably due to it being mainly solvent and very little active ingredient. An example of this was when we were asked to evaluate an incumbent chemical and when it arrived, the sample bottle had leaked. There was nothing remaining, not even residual, and it was obvious the entire sample was virtually all solvent. It was no wonder the chemical wasn’t working as advertised in the field!
In those instances you will probably need to add significantly more to get the performance you need. If you don’t get this right, you end up doing this.
Therefore, to prevent you wasting your money we have come up with some expected dose rates for the chemicals you are likely to use as a go by. This can then be used against what you might be initially told that is required. Remember most people / chemical companies err on the side of caution here so the first dose rates you get given are likely to be on the high side. This is why you do the testing so you can identify the optimum dose rates for the chemicals you plan to use.
The table below summarizes ‘typical’ inhibitor properties and dosage rates, taken from various projects. Physical properties of individual chemicals (e.g. viscosity) can change, depending on pressure and formulation. It is required to get confirmation of the final properties from the chemical vendor, but the values in the table below can be used as a guide to help determine whether the chemical is going to be pumpable over the distances that are required.
Chemical Inhibitor Properties
Ideally, to minimize transportation and storage costs you want to have a product as active as possible to reduce the total volume of chemical that needs to be transported. But as with most things there is a drawback and that is the increased viscosity of the product. The more active it is the more viscous it is likely to be, bringing some additional challenges.
Oh no something else to worry about! Why does the viscosity of the chemical matter?
One of the primary concerns related to chemical injection is the viscosity of the chemical being injected. This is because with high viscosity products, the pressure you need to inject them may not be achievable due to it being greater than the design pressure of the system. There is probably going to be a cost penalty as well since high pressure pumps usually cost more. This issue becomes a real problem in many subsea developments due to the lower ambient sea temperatures that may be experienced causing viscosities to increase. One recent project in deepwater Gulf of Mexico had a challenging issue related to delivery of wax inhibitor downhole, due in large part to the actual viscosity of the chemical.
Wax inhibitors are high molecular weight polymers. When dissolved in solvent they uncoil and extend out in the fluid. When the formulated product is put under pressure the molecules are forced closer together, so they begin to interact. The higher the pressure the more the interaction which causes the viscosity to increase more than it would at ambient pressure. To counteract this, you can use lower molecular weight polymers but there is a limit to how low in molecular weight you can go before the products no longer perform as wax inhibitors. To achieve the required viscosity, the resulting product will be considerably less concentrated than the original.
The figure below illustrates an example of pressure impacts on viscosity, for a wax inhibitor and for a LDHI. It should be noted that any chemical’s viscosity can show a sensitivity to pressure, but wax inhibitors and LDHI are well known for exhibiting this problem. Taking all of this into account every chemical should be screened early on to ensure that it is possible to deliver the required volumes to the desired injection locations through the proposed chemical injection lines. Most Deepwater systems are pressure rated to anywhere between 5,000 psi to 15,000 psi and above, so knowing viscosity values at typical operating pressures, as well as design limits is an important consideration.
As part of confirming the suitability of chemicals to be injected through a lengthy chemical injection line it is also important to know where each chemical will likely have to be injected. If there is a limited space topsides for chemical pumps and storage tanks and chemical injection lines and injection points combined products are used. These are single production chemicals with dual functionality. Some of the more common types of these chemicals are combined scale / corrosion inhibitors, hydrate / corrosion inhibitors and wax inhibitors / demulsifiers.
When creating combined products, it is important to be aware of the solubility of the active products. Solubility of the active ingredients is important when trying to combine them together because it can be very difficult to combine a water-soluble product with an oil-soluble product and vice versa. It can be done but it normally requires a very good understanding of solvent chemical properties. In some instances, exotic co-solvents may be required, which drives up the cost of the combined product. These products may also have limited product stability at the temperature extremes they may experience when stored and injected.
The table below provides an illustration of some typical chemical configurations that are possible. These are not hard and fast rules but should give you an idea of what is possible.
Typical arrangements of chemicals applied in production systems
Once the preferred injection points have been selected, it is important to understand how the chemical will be injected and at what location in the pipe circumference the chemical will be added (i.e. in the top, bottom or side of the pipe). Some chemicals only require a basic injection point as they are easily dispersed through the liquid allowing them to start working in the required time frame. However, some chemicals due to their corrosivity or the need to maximise performance to reduce chemical costs may require specialised injection quills so that they are injected as an aerosol. This maximises mixing and thus chemical effectiveness. It will also minimise the corrosiveness of the neat chemical as it quickly gets diluted in the stream. In some extreme cases where corrosion or mixing of the chemical needs to be confirmed the use of corrosion resistant alloy static mixer may be required.
When do you need to do the lab testing and what needs to be done?
In the previous sections we gave you information on:
The chemicals to be tested
How to determine what the problems you can get from the oil, water and gas that is produced
What tests you may need to do and how much oil you need to do the tests,
What to look out for when doing the Chemical testing
Some of the issues involved when injecting chemicals
So what is next to be shared? Well, that will be when you should start the testing, what needs to be done and the total volume of oil for the tests. With that in mind the sections below highlight the “typical” fluid testing required for each stage of the project process.
The output of this work should confirm which flow assurance and production chemistry issues need to be managed when producing oil, water and gas. In turn, this will help decide what chemical types are required but it is highly unlikely to confirm the exact chemicals that will be used. This usually occurs in the Execute phase of the project when you are deciding what chemical vendor to work with. So the skill is knowing what the physical properties and the required dose rates of the chemicals are before knowing exactly what chemicals are going to be selected for use because this information is usually needed in Front End of the project before it even reaches the Execute phase.
The purpose of this section is to give you a go by of what needs to be done from fluid and chemical testing perspective during each stage of the project process.
NOTE: Specific projects may require additional (or fewer) testing, depending on the specific nature of the fluid properties.
A lot of the above work will be dependent on how much oil you have. So when you have a limited amount of oil, be prepared to be unable to do a lot of the testing that is recommended. How you deal with that is where experience and knowledge help.
Where do we go from here?
From all the information supplied there is a lot to take on board but without a good grasp of the issues there are a lot of holes to fall in if you are not careful.
This is where partnering with a company like Pontem Analytics can assist with avoiding these typical (and atypical) pitfalls. Our team comes from a diverse background, with many spending time with operators, chemical companies, engineering firms, and often “all of the above.”
We know a thing or two…
We have been doings this successfully for over 30 years so we know what to do and more importantly we know what not to do and consequently where things can go wrong.
We have no skin in the game here. We are the perfect Nerds to partner with, as we treat all our projects as if the assets were our own. We are constantly looking for improved efficiencies, proper applications, maximizing the production and life cycle, and minimizing costs.
As part of this journey through the use of production chemicals in the oil and gas industry we have one final post to share in this Production Chemical Trilogy and that will involve taking you through the tricky technical and commercial process of selecting the best chemical vendor to work with for your oil and gas asset.
I realise the suspense will be killing you but don’t worry you won’t have long to wait for the next exciting episode.
Please reach out to email@example.com to discuss how we can help solve your business’s most important problems!
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