Anti-Agglomerants Performance in Hydrates Management: Fundamental Insights

天然气水合物既代表了甲烷气体形式的一种可能的能源，也可以提供长期CO2储存的策略。天然气水合物在通过管道运输石油和天然气期间也是一个麻烦，在管道中，它们的形成可能堵塞甚至有时会破坏管道，造成巨大的环境破坏。包括BP和E-ON在内的该行业每年投资约5亿美元在管道中注入甲醇。不幸的是，为了有效，甲醇需要以超过20重量%的量存在，有时高达输送流体的50%。随着产油威尔斯越来越多地从陆上精炼设施中移出，并且随着产油威尔斯老化，导致产生的水量增加，迫切需要新的策略。本项目的重点是替代化学品，这些化学品应：（1）在低重量分数下有效减少通过管道输送和泵送的流体量;（2）在低温和长时间下有效贯穿到达远离海岸的威尔斯井所需的整个管道长度;以及（3）在含有大量水的系统中，允许开采老化的威尔斯井，这些井产生大量水以及石油和天然气。在本项目中考虑的这些化学品被称为防聚剂（AA），并且它们可以在低至5体积%的浓度下有效。巴斯夫、斯伦贝谢、壳牌、Champion和Halliburton生产和配制防聚剂。虽然据信AA允许小的水合物颗粒形成，然后防止它们聚集成大的堵塞物，但它们的作用机制还没有很好地理解。因此，他们的发现是基于漫长的试错协议进行系统的代表性的流体从给定的石油和天然气威尔斯wells.To使新的有效的AA的系统发现，基础研究建议集中在他们的分子作用机制。分子建模和大量的计算机模拟将实施，在协同详细的微观和宏观实验，为一类特定的防聚剂。这些化合物含有三个疏水性尾部，和一个包括羧酸和季铵离子的扩展的亲水性头部。选择这些分子是因为宏观实验观察表明，通过改变其中一个疏水尾部的长度仅2-6个碳原子，同时保持分子的其余部分完整，将它们的性能从优异变为较差。我们的假设是，在水合物颗粒上形成的AAs膜的分子结构影响生长机制。通过初步模拟，确定了两种可能的机制：（1）水合物的聚集，和（2）水通过AAs膜的渗透。在不同的实验条件下，两种机制中的一种可能起主导作用（例如，改变盐浓度）。该研究旨在首先了解和量化各种实验条件下AAs的分子作用机制，然后了解可以调整哪些AAs分子特征以最大限度地发挥其性能，预期的基本结果不仅与更好地理解水合物管理有关，而且还有助于更好地理解所有结晶过程中涉及的分子机制。这样的过程发生在许多工业中（例如，制药、特种化学品、涂料、食品），是英国高科技制造业的支柱。将受到拟议研究积极影响的部门包括能源、制造业、化学品和环境。

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.