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

储层酸化是石油工业中一个普遍存在的问题。它的特征是储层中硫化物浓度的增加，随着时间的推移，它会产生液体。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，并给工人带来了安全问题。为了解决这些问题，大大增加了钻井和炼油作业的成本。硫酸盐还原微生物（SRM）被认为是造成酸味的主要原因。SRM“呼吸”硫酸盐，在呼吸过程中将其作为从食物中获得的电子（电子供体）的受体并将其还原为硫化物。由于酸化与SRM的活性有着内在的联系，因此它受到油藏内部条件的严重影响，例如温度、盐度、pH值、营养物质的可用性和电子供体/受体。由于变质给石油工业带来了无数的问题，人们一直在努力了解其潜在机制，并建立准确的预测模型。该项目将侧重于原油成分在确定油藏中观察到的酸化可能性/程度方面的作用。原油是SRM的主要电子供体，一些油中含有对微生物有毒性的烃组分。由于原油在组成上表现出巨大的差异，它们也可能在支持酸化的倾向上表现出显著的差异。这个项目的主要目的是描述油的组成和酸败之间的关系，希望提高预测酸败如何在油藏中发展的能力。这将通过采购大量原油样品，并使用尖端色谱技术对其进行分析，以获得其成分的详细图像来完成。利用实验室微观环境作为油藏的类比物，对这些油的酸化潜力进行评估。使用这些高度控制的实验室系统，可以对成分/酸味关系进行明确的评估，这是单纯通过对油藏的现场观察无法实现的。除了测试每种油的酸化潜力外，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。这将有希望让我们更深入地了解油成分和酸化之间的相互作用，因为可以建立对油所支持的微生物群落的详细视图。最初的调查领域将包括确定非生物降解（轻）油与生物降解（重）油在酸化潜力方面的差异的一般趋势。较少生物降解的油在更小的烃组分中更丰富，更容易被储层微生物用作电子供体的来源，但它们也含有更高浓度的有毒烃组分。一旦确定了总体趋势，就会进一步探讨这种关系的细微差别，因为在现实世界中，含有生物降解水平相似的油的两个油藏可能会表现出截然不同的酸败程度。在这项研究的基础上，可以进一步研究单个油成分或油成分组及其在支持/抑制酸败中的作用。微观模型是在高度受控条件下研究酸化的有用工具，将在该项目中广泛使用，然而，对于它们在多大程度上真正代表复杂的油藏环境，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，以填充生物反应器的形式，更能代表钻井活动期间油藏内的湍流条件。

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.