Brimstone and Treacle: Understanding Oil-Driven Microbial Souring In Petroleum Reservoirs

储层酸化是石油工业中普遍存在的问题。它的特点是随着时间的推移，储层内硫化物浓度的增加，以及它产生的流体。这降低了原油质量，从而降低了其市场价值，导致基础设施腐蚀，并为工人带来安全问题。对这些问题的重视大大增加了钻井和炼油作业的成本。硫酸盐还原微生物（SRM）被认为是造成大多数酸化的原因。SRM“呼吸”硫酸盐，在呼吸过程中使用它作为从食物中获得的电子的受体（电子供体），并将其还原为硫化物。由于酸化与SRM的活性有内在联系，因此它受到油藏内条件的严重影响，如温度、盐度、pH值、营养素和电子供体/受体的可用性。由于酸化给石油工业带来了无数的问题，人们一直在共同努力了解其潜在的机制，并建立准确的预测模型。本项目将侧重于原油成分在确定储油层内观察到的酸化可能性/程度方面的作用。原油是SRM的电子供体的主要提供者，并且一些油含有对微生物显示出毒性的烃馏分。由于原油的成分变化很大，因此它们支持酸化的倾向也可能变化很大。该项目的主要目的是描述石油成分和酸化之间的关系，以期提高预测油藏内酸化可能如何发展的能力。这将通过采购各种原油样品，并使用最先进的色谱技术对其进行分析，以获得其成分的详细图片来完成。将使用实验室微观世界模拟油藏，评估这些油的酸化潜力。使用这些高度受控的实验室系统将允许对成分/酸化关系进行明确的评估，这是仅仅通过油藏的现场观察无法实现的。除了测试每种石油的酸化潜力外，还将使用宏基因组学对它们所支持的微生物群落进行详细分析。这将有希望使石油成分和酸化之间的相互作用有更深入的了解，因为可以建立由石油支持的微生物群落的详细视图。最初的调查领域将涉及确定非生物降解（轻质）油类与生物降解程度较高（较重）油类之间酸化潜力差异的总体趋势。生物降解程度较低的油在较小的烃馏分中更丰富，这些馏分更容易被储层微生物用作电子供体的来源，然而它们也含有较高浓度的有毒烃馏分。一旦确定了总体趋势，将进一步探讨这种关系的细微差别，因为在真实的世界中，两个含有生物降解程度相似的石油的油藏可能显示出截然不同的酸化程度。根据这项研究，可能会对单个油成分或油成分组及其在支持/抑制酸败方面的责任进行进一步研究。微观世界提供了一种在高度受控条件下调查酸化的有用工具，并将在本项目中广泛使用，但对于它们如何真正代表复杂的储层环境，肯定存在批评。因此，该项目的后期阶段将涉及使用基于平流的系统来研究酸化，其形式为填充生物反应器，更能代表钻井活动期间储油层内的湍流条件。

Reservoir souring is a widespread problem within the petroleum industry. It is characterised by an increase in sulfide concentrations within a reservoir, and it's produced fluids, over time. This reduces crude oil quality and consequently its market value, drives corrosion of infrastructure, and presents safety concerns for workers. Accommodating for these issues significantly inflates the cost of drilling and refining operations. Sulfate reducing microorganisms (SRM) are thought to be responsible for the majority of souring. SRM "breathe" sulfate, using it during respiration as an acceptor of electrons obtained from food (electron donors) and reducing it to sulfide. As souring is intrinsically linked to the activity of SRM, it is heavily influenced by conditions within an oil reservoir, such as temperature, salinity, pH, availability of nutrients and electron donors/acceptors. Due to the myriad of problems souring poses to the petroleum industry, there has been a concerted effort to understand its underlying mechanisms and produce accurate predictive models. This project will focus on the role of crude oil composition in determining the likelihood/extent of souring observed within a petroleum reservoir. Crude oil is the main provider of electron donors for SRM, and some oils contain hydrocarbon fractions that have displayed toxicity to microbes. As crude oils show massive variations in their composition, they may also display significant variation in their propensity to support souring. The key aim of this project is to describe the relationship between oil composition and souring, in the hopes of improving the ability to predict how souring may develop within an oil reservoir. This will be done by sourcing a wide array of crude oil samples, and analysing them using cutting edge chromatography techniques to gain a detailed picture of their composition. Using laboratory microcosms as analogues to oil reservoirs, the souring potentials of these oils will be assessed. Using these highly controlled laboratory systems will allow for a definitive assessment of composition/souring relationships, unachievable simply by in situ observations of oil reservoirs. In addition to testing the souring potential of each oil, detailed analysis of the microbial communities they support will be undertaken using metagenomics. This will hopefully allow for a deeper understanding of the interactions between oil composition and souring, as a detailed view of the microbial communities supported by an oil can be established. Initial areas of investigation will involve establishing general trends between the differences in souring potential of non-biodegraded (light) oils compared to more biodegraded (heavier) oils. Less biodegraded oils are more abundant in smaller hydrocarbon fractions that are more easily used as a source of electron donors by reservoir microbes, however they also contain the higher concentrations of toxic hydrocarbon fractions. Once a general trend is established there will be further probing into the nuances of this relationship, as in the real world two oil reservoirs containing oils with similar levels of bio-degradation can display vastly different levels of souring. Subject to this research, further study into individual oil components, or groups of oils components and their culpability in supporting/inhibiting souring may be undertaken. Microcosms present a useful tool to investigate souring under highly controlled conditions and will be used extensively during this project, however there are certainly criticisms as to how well they truly represent a complex reservoir environment. Later stages of the project will therefore involve the use of advection based systems to study souring, in the form of packed bioreactors which are more representative of the turbulent conditions within an oil reservoir during drilling activities.