Applying Biochemistry Concepts to the Analysis of Oilfield Produced Fluids

摘要

Oilfield produced fluids are complex mixtures with hydrophobic, hydrophilic and solid entities: as such, sensitive and specific analysis is a challenge, particularly in the field. Biological systems are also complex and can be difficult to analyse. Inspiration can be taken from biological systems to solve detection problems for oilfield produced fluids. For example, by exploiting nature’s highly specific chemical recognition systems, analysis of these mixtures can be simplified. We have conducted a study to investigate whether biochemical concepts such as the use of lipophilic and hydrophilic markers, bioassays and small biomolecular tags can be applied to the analysis of oilfield additives. Currently pursued applications of these concepts include oil in water or water in oil monitoring; analysis of methanol in crude oil and produced water; non-radioactive tracers for characterization and monitoring of oilfield fluids; tagging difficult to detect polymers such as sulfonated scale inhibitors and monitoring treatment chemicals (e.g. minimum inhibitor concentrations). Our study tested these concepts and found that a marker could be used to detect the presence of dispersed oil in produced water at concentrations less than 5 (parts per million) ppm. We also found that a bioassay could be used to analyse crude oil for the presence of methanol, with a limit of detection (LOD) of 1 ppm. A biomolecule was also investigated for its suitability as a “tag” for scale inhibitors. The tagged inhibitor could be detected to 1 ppm and detection was resilient to various field conditions such as in produced water and the presence of crude oil. This study shows that biochemistry concepts and techniques can be used to analyse oilfield chemicals. Advantages of biochemistry-based techniques include the use of simple spectrophotometric measurements, often using inexpensive equipment, and the absence of complicated separation procedures. Furthermore, since the analysis methods involve addition of reagent to samples, background readings can be taken beforehand to remove potential interferences. The assays therefore involve ‘latent detection’. These attributes lend themselves to the development of simple, highly sensitive, quick detection assays that can be used on-site; providing near real-time information to Operators and allowing them to make timely, informed decisions, especially where time is critical and delays in instigating treatment regimes risk well closure and loss of revenue. Monitoring of oil, produced water and chemical additives is essential for flow assurance and maintaining regulatory compliance. The ability to analyse these fluids on-site, quickly and frequently, enables Operators to detect flow assurance, asset integrity and process problems early enabling them to take preventative action to minimize the risks of production loss. Operators also need to ensure that they are meeting environmental regulations and crude quality standards set out by refineries, otherwise they risk fines or discounts. However, the inherently multifarious nature of crude, with its hydrophilic, hydrophobic and solid components, complicates and poses significant challenges to the detection and monitoring of the diverse range of chemical species present, often resulting in Operators waiting days or weeks for results.