Anti-Agglomerants Performance in Hydrates Management: Fundamental Insights

Lead Research Organisation: University College London
Department Name: Chemical Engineering


Gas hydrates represent both a possible energy source in the form of methane gas, and could provide a strategy for long-term CO2 repository. Gas hydrates are also a nuisance during the transport of oil and gas via pipelines, where their formation can block and sometimes break the pipeline, causing large environmental damages. The industry, including BP and E-ON, invests ~$500 million per year injecting methanol in pipelines. Unfortunately, methanol, to be effective, needs to be present in amounts exceeding 20% by weight, sometimes up to 50% of the transported fluid.

As the productive oil wells become more and more removed from onshore refining facilities, and as productive oil wells age, leading to increased amount of water produced, new strategies are desperately needed. The present project focuses on alternative chemicals that should be effective (1) at low weight fraction to reduce the amount of fluids transported and pumped through the pipelines; (2) at low temperature and for long time, to be effective through the entire length of the pipelines needed to reach the wells far from shore; and (3) in systems that contain large amounts of water, to allow the exploitation of ageing wells, which produce large amounts of water together with oil and gas.

These chemicals, considered in this project, are known as anti agglomerants (AAs), and they can be effective at concentrations as low as 5% by volume. BASF, Schlumberger, Shell, Champion and Halliburton manufacture and formulate anti-agglomerants. Although it is believed that AAs allow small hydrate particles to form, and then prevent their agglomeration into large plugs, their mechanism of action is not well understood. Consequently, their discovery is based on lengthy trial-and-error protocols conducted on systems representative of the fluids extracted from given oil and gas wells.

To enable the systematic discovery of new effective AAs, the fundamental research proposed here focuses on their molecular mechanism of action. Molecular modelling and massive computer simulations will be implemented, in synergism with detailed micro- and macro-scopic experiments, for a specific class of anti-agglomerants. These compounds contain three hydrophobic tails, and one extended hydrate-philic head that comprises both carboxylic and quaternary ammonium ions. These molecules have been chosen because macroscopic experimental observations show that by changing the length of one of the hydrophobic tails by just 2-6 carbon atoms, while maintaining the rest of the molecule intact, changes their performance from excellent to poor. Our hypothesis is that the molecular structure of a film of AAs formed on a hydrate particle affects the growth mechanism. Two possible mechanisms have been identified by preliminary simulations: (1) aggregation of hydrates, and (2) penetration of water through the AAs film. It is possible that one of the two mechanisms acts as the dominant one at different experimental conditions (e.g., varying salt concentration). The proposed research is designed to first understand and quantify the molecular mechanisms of action of the AAs under various experimental conditions, and then to understand which AAs molecular features can be tuned to maximise their performance.

The fundamental results expected are relevant not only for better understanding hydrates management, but also for better understanding the molecular mechanisms involved in all crystallisation processes. Such processes occur in a number of industries (e.g., pharmaceuticals, specialty chemicals, coatings, foodstuff) that represent the backbone of UK high tech manufacturing. The sectors that will be positively impacted by the proposed research include energy, manufacturing, chemicals and environment.

Planned Impact

While the main impact expected from the proposed research is on the management of hydrates formation in flow assurance problems, industrial sectors that will benefit from the successful completion of the proposed activities include energy, manufacturing the future, chemicals and environmental.

As the proposed research will lead to understanding the mechanisms responsible for the performance of anti-agglomerants, it is likely that guiding principles will be provided for the synthesis of specialty chemicals that could be used as anti-agglomerants. The main beneficiary for these discoveries will be the service industry to the oil and gas industry (e.g., Schlumberger, Halliburton and Innospec). The oil and gas industry will benefit indirectly (e.g., BP, E-ON, Shell, Statoil, Tullow Oil, etc.), as it will be able to produce hydrocarbons from existing wells that are being depleted (as oil wells age, they produce larger amounts of water, which increases the likelihood of formation of hydrates in the pipelines). NOV Flexibles, a company that produces flexible pipelines for the oil and gas industry, will also benefit from the results of this research, as it will be less likely for the hydrates to form and disrupt the pipelines. The chemical process industry (e.g., Process System Enterprise, Ltd) will benefit from a better understanding of the physical processes involved with the formation of hydrates in pipelines. The specialty chemicals industry (BASF) will also benefit because new compounds are likely to be designed based on the proposed research. These chemicals could be manufactured by chemical companies operating in the UK (e.g., Unilever).
Other industries could also benefit from a better understanding of the fundamental mechanisms involved in the growth of crystals form complex systems. These include pharmaceutical companies, as they are interested in both formulating and delivering drugs, specialty chemicals, interested in the synthesis of new materials, coatings and even food industries.

The broad public will benefit from the proposed research from many points of view: it is possible that the proposed research will contribute to lowering the cost of producing fossil fuels from the North Sea, leading to reduced energy prices in the UK, it is possible that new chemicals will be designed using insights from the proposed research, which could lead to new jobs within the UK manufacturing industry, and preventing the formation of hydrates in oil and gas pipelines will reduce the environmental impact of fossil fuels, with benefits for the population at large.

The project will also contribute the development of skilled workforce in the UK, as one PDRA will be directly supported by this project, one post-graduate student is already being trained, possibly another post-graduate student will be trained in the research areas discussed herein, and several MSc/MEng students will be involved in the proposed research.
Description This project sought to understand why some surfactants are able to perform well as anti-agglomerants in flow assurance applications, while others do not.
Four publications have directly resulted from the work. In addition, one is under review, and one patent application has been submitted. The major observations from the five publications are considered as major findings:
1. From the publication in PCCP, we found that when one water droplet approaches one small hydrate particle, both being immersed in hydrocarbons, the agglomeration is irreversible as soon as a molecularly-thin chain of water molecules is able to form across the protective film formed by the surfactant molecules adsorbed on both the water droplet and the hydrate particle. The implication of this observation is that to be effective, surfactants need to provide a mechanically stable film.
2. From the publication in Langmuir, we found that the surfactants that are effective at preventing the formation of large hydrate plugs tend to form well-ordered films when adsorbed on hydrate surfaces at large enough concentrations. On the contrary, the surfactants that are not very effective, yield dis-ordered films. Combined with the observation from the PCCP publication, this reinforces the observation that mechanically stable films are required to prevent the formation of large hydrate plugs. We have now two additional manuscripts that are being reviewed for possible applications. In these manuscripts we further analysed the consequences of our initial observations. Two are the main observations: our simulation results suggest that some surfactants can help grow gas hydrates, and the time scale representative of methane molecule to cross the film of anti-agglomerants at the water-hydrocarbon interface can be of the same order of magnitude of the time scale for hydrate growth. The former result can suggest new applications for surfactants in the field of gas hydrates (perhaps for high-tech applications such as water desalination); the latter proposes a new design criterion that could be used for synthesising new anti-agglomerants.
3. We disclosed in a Langmuir application how it is possible to extract quantitative information regarding how anti-agglomerants could affect the transport of methane from the hydrocarbon mixture to the growing hydrate particle, and we showed that the estimates from our simulations are consistent with experimental observations.
4. in JPC Letters we showed that, perhaps contrary to our expectations, some anti-agglomerants that are effective at preventing hydrate plugs formation in pipelines are actually speeding up the growth of hydrates. We hypothesised that by doing so, these anti-agglomerants remained trapped on the hydrate surface, thus delaying aggregation between different hydrate particles. While this was proposed by others as a possible mechanism, we are the first to report direct evidence for this phenomenon.
5. In an additional publication, currently under review by Nature Scientific reports, we showed how changing the composition of the oil can affect the performance of anti-agglomerants. This has been observed experimentally, and we are the first group to propose a molecular-based explanation, directly observed in our calculations, for the phenomenon.
6. The results just discussed led to the formulation of anti-agglomerants with high performance. Such formulation is the core of a patent application submitted in 2018.

In addition to the above, the project has contributed to several publications in the area of interfacial phenomena.
Exploitation Route Others could test our hypothesis on a number of various surfactants, to see whether our observations have general validity.
It would also be valuable to use the molecular-level results we have obtained so far to produce macroscopic models for hydrates agglomeration and growth.
Our industrial collaborators took advantage of the insights provided by our simulations to design new anti-agglomerant formulations. The results were so good that led to a patent application.
Our collaborators are also synthesising new anti-agglomerants using our simulation results as design criteria.
Sectors Aerospace, Defence and Marine,Chemicals,Energy,Environment

Description The project was in collaboration with Multi Chem, a Halliburton company. The academic work conducted at UCL was instrumental for Halliburton to better understand the possible mechanisms by which surfactants could act as effective anti-agglomerants in flow assurance, one of the applications of the company. In fact, experiments from Halliburton were included in one of the publications resulting from this project. One patent resulted from this work: US patent 11,236,261, published in 2022. The results of the research were presented at the Colorado School of Mines, to the groups of Prof. Koh and Prof. Sloan. This group leads a research consortium on gas hydrates, with a number of industrial sponsors. The appreciation that a mechanism previously not considered could be responsible for the performance of anti-agglomenrants is expected to lead to innovative formulations, which will be tested for performance. Indeed, at a presentation at the 2018 Gordon Research Conference on gas hydrates we learned that this insight has already been included in a model to predict the formation of hydrate plugs. As of 2022, the fundamental hypothesis resulting from the modelling studies is being tested by a combination of stocjastic modeling and experiments. The results have been published in several peer-review journal articles, which are receiving good attention, and, perhaps more importantly from a practical point of view, the results are stimulating the design and synthesis of new anti-agglomerants. New formulations were tested during the project, based on the modeling results, and a patent has been recently issued (US patent 11,236,261). This combination of fundamental insights and practical relevance is attracting attention from academics and practitioners alike.
First Year Of Impact 2016
Sector Chemicals,Energy,Environment
Impact Types Economic

Description Opinion piece in international journal
Geographic Reach Multiple continents/international 
Policy Influence Type Influenced training of practitioners or researchers
Description CBET-EPSRC: Enhancing the CSMHyK fluid dynamics calculations via the inclusion of a stochastic model of hydrate nucleation, agglomeration and growth
Amount £487,425 (GBP)
Funding ID EP/T004282/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 12/2019 
End 11/2022
Description International Exchanges Scheme
Amount £12,000 (GBP)
Funding ID IE160820 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2017 
End 02/2019
Title We have proposed new algorithms for identifying molecular mechanisms responsible for the performance of anti-agglomerants 
Description Using a combination of meta dynamics, umbrella-sampling, and equilibrium molecular dynamics simulations we have demonstrated how it is possible to predict the performance of anti-agglomerants. The approach has been validated via direct comparison to experiments, which led to submission of one patent application. 
Type Of Material Improvements to research infrastructure 
Year Produced 2018 
Provided To Others? Yes  
Impact One patent application has been submitted where we, and our collaborators, disclosed how to enhance the performance of anti-agglomerants. 
Description Center for Hydrates Research - Colorado School of Mines 
Organisation Colorado School of Mines
Country United States 
Sector Academic/University 
PI Contribution The Centre for Hydrates Research at the Colorado School of Mines has been operating for >25 years and has been supported by >$1.5M per year in funding from industry (e.g., BP, Chevron, Shell, Halliburton, StatOil and others) and government (US Department of Energy). This centre conducts cutting-edge experiments for better understanding hydrates, and how to manage them. For example, the centre has developed micro-mechanical force apparatuses for directly sampling the force between two hydrate particles. These type of experiments are at the micro-scale. Macroscopically, the centre has developed flow loops and rocking cells instruments that can be used to quantify the performance of anti-agglomerants. As such, the centre provides an arsenal of experimental capabilities for validating the simulation results achieved within AS' group at UCL.
Collaborator Contribution We have conducted simulation results for a variety of anti-agglomerants. These simulations have been used to steer the experiments conducted at the Colorado School of Mines. We are now developing a joint proposal to bring these initial collaborative studies to fruition.
Impact The proposal EP/T004282/1CBET-EPSRC: Improving CSMHyK via Molecular Modelling and Stochastic Simulations. Funding Agency: EPSRC / NSF. Funding period: three years, just announced. Amount awarded: £ 490,000 (UK) plus ~ $300,000 (US).
Start Year 2020
Description Chevron 
Organisation Chevron Corporation
Department Chevron Energy Technology
Country United States 
Sector Private 
PI Contribution Based on the results achieved during the EPSRC award, we have been able to establish a collaboration with Chevron. Chevorn is collaborating with the CBET-EPSRC project, as we seek to improve the CSMHyK software. In early 2020 Prof. Striolo visited Chevron in Houston, TX, USA, to discuss a new PhD studentship on a topic strictly related to the EPSRC award.
Collaborator Contribution They have provided known how to help identify the best systems to be simulated, and they have helped interpret the simulation results.
Impact One new project under development (Covid has delayed the discussion): PhD Studentship for the simulation of Anti-Agglomerants at the water-hydrate interface. One project is being negotiated related to flow assurance, but focused on asphaltenes. This is a new collaboration, wrth £400,000 over 3 years.
Start Year 2021
Description Institute of Applied Surfactant Research, University of Oklahoma 
Organisation University of Oklahoma
Country United States 
Sector Academic/University 
PI Contribution The modeling results have been presented to this consortium meeting, which brings together 8 companies operating in a varierty of sectors, from the energy to the personal care. The approaciation that simulation insights can be beneficial for formulating new products is stimulating new research ideas.
Collaborator Contribution Ideas are shared, with the possible outcome of including the structure of bio-derived surfactants in future formulations.
Impact A presentation was given at the IASR meeting in November 2021.
Start Year 2020
Description University College Dublin 
Organisation University College Dublin
Country Ireland 
Sector Academic/University 
PI Contribution Our work on hydrates has led us to establish a collaboration wtih Prof. Niall English of UCD. Bilding from a prior EPSRC project, we submitted a collaborative proposal from the EPSRC-SFI platform in 2020. Although well reveiwed, the project was not supported. We are now considering a new project, which will focus on the transport of CO2 using hydrates. We expect to submit the proposal in the summer.
Collaborator Contribution Prof. English will provide insights on hydrates dissociation as well as experimental data to support our results.
Impact Nothing yet, as we are at the discussion stage.
Start Year 2021
Title Polyaromatic Hydrocarbon Additives for Hydrate Inhibition 
Description The following disclosure, "Polyaromatic Hydrocarbon Additives for Hydrate Inhibition", was filed on US Provisional Patent Application No. 62/731,479, 2018. Patent filing records PCT/US2019/047957 on August 23rd, 2019. 
IP Reference PCT/US2019/047957 
Protection Patent application published
Year Protection Granted 2018
Licensed No
Impact This patent identifies some chemicals which, used together with some Anti-Agglomerants, can enhance their effectiveness.
Title Polyaromatic hydrocarbon additives for hydrate inhibition 
Description Methods involving anti-agglomerant hydrate inhibitors and polyaromatic hydrocarbons for hydrate inhibition are provided. In some embodiments, the methods include introducing a hydrate inhibitor composition including an anti-agglomerant hydrate inhibitor into a fluid including (i) water and (ii) one of gas, liquid hydrocarbon, and any combination thereof; and introducing a polyaromatic hydrocarbon into the fluid. 
IP Reference 16549399 
Protection Patent granted
Year Protection Granted 2022
Licensed Commercial In Confidence
Impact it is now possible to enhance the performance of anti-agglomerants
Description Discussion with BP experts on hydrates 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Exchanges ideas on how to use the simulation results obtained so far for enhancing impact
Year(s) Of Engagement Activity 2018
Description Further Discussions with Chevron 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact A discussion took place in Houston, TX, USA, regarding the outcomes of the project, and possible follow ups.
The result was a new collaborative project, which is currently being negotiated.
Year(s) Of Engagement Activity 2019
Description International conference presentation at ICGH2020 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact This is a conference presentation at the upcoming international conference on gas hydrates, to be held in Singapore.
The title of the presentation is:
T. Bui, Q. Lan, L. Vo, S. Bodnar, A. Striolo,* Hydrates Management Using Surfactants: A Molecular Simulation Perspective, 10th International Conference on Gas Hydrates, ICGH10, Singapore, June 21st-26th, 2020.
Year(s) Of Engagement Activity 2020
Description Participation to the Gordon Research Conference on Gas Hydrates 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact the Gordon Research Conference on gas hydrates brings together academia, industry and government to identify new research needs connected with gas hydrates. Much attention is on the production of gas hydrates, but a portion of the conference is also related to flow assurance. The conference was a great venue for connecting with industrial practitioners, in particular some experts from Chevron.
Year(s) Of Engagement Activity 2018
Description Poster presentation to Industrial Advisory Board 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact The Chemical Engineering Department has established an Industrial Advisory Board, IAB. The IAB meets twice a year, once in February and once in September. Since 2017 the meeting in February is focused on students, and the PhD students in the department present their research. Mr Tai Bui has presented the results of his research on anti-agglomerants both in 2017 and in 2018. In fact, in 2018 he won the Best Poster Presentation, voted by the IAB members. The IAB is composed of representatives from 15 international companies. Those most closely related to the research conducted within this project are Halliburton, BP, Innospec, BASF and Unilever. Since 2017, the poster presentation at the IAB meeting in February is also open to alumni from the Chemical Engineering Department. In both years we have ~20 alumni attending the poster presentation. The alumni come to UCL on this occasion because it coincides with the Ramsay Society Dinner, at which all alumni are invited. The alumni who attended the poster presentation are connected to companies such as British Gas, Shell, and a number of consultancies in the general area of energy and chemicals.
Year(s) Of Engagement Activity 2017,2018
Description Presentation at International Conference (PPEPPD 2019) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I have been invited to present the outcomes of this research project at the 2019 PPEPPD conference, in a plenary talk
Year(s) Of Engagement Activity 2018
Description Presentation at UK Colloids 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact This was a oral presentation at a conference. The details of the presentation are reported under the 'publications' section of this report. The presentation made the argument that by understanding at the molecular level the mechanisms by which anti-agglomerants function it might be possible to design new, effective ones.
Year(s) Of Engagement Activity 2017
Description Visit to Chevron to showcase the results 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Visit to Chevron, in Houston, to discuss hydrates and their inhibition. The results from this project were discussed.
Year(s) Of Engagement Activity 2018