Photo: Christian Ove Carlsson

PhD interview: Improving productivity and safety at oil wells through models

Tuesday 26 Mar 19
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The many PhD students at DTU Chemical Engineering contribute to a diverse research environment. This month, we interviewed Diana Carolina Figueroa Murcia about her project “HP/HT Reservoir fluids with focus on scaling and thermodynamic modeling”.

In this edition, you can read about a PhD project by Diana Carolina Figueroa Murcia, who was one of many PhD students that graduated at DTU Chemical Engineering last year.

What is the essence of your PhD project?
The aim of the project was to study the solubility of scaling materials, specifically Zinc Sulphide (ZnS), Iron Sulphide (FeS) and Lead Sulphide (PbS) at conditions that resemble High Pressure High Temperature (HP/HT) oil reservoirs. I designed and built two experimental apparatus at laboratory scale as well as the development of a reliable experimental methodology for measuring the solubility of the scaling minerals. The sulphides studied during the project are particularly sensitive to oxygen and present very low solubility values that made the experiments challenging. Afterwards, the experimental data were used for adjusting the Extended UNIQUAC model to predict the solubility of sulphides by means of thermodynamic calculations.

"The formation of scaling minerals in an oil gas reservoir is a serious threat, as these minerals reduce the productivity of a well by blocking the production tube compromising the safety of the reservoir as well. Therefore, the prediction of the occurrence of the scaling materials in an oil reservoir is a foremost tool for the operator of a well"

What did you discover during your research?
I was able to develop a methodology to accurately measure the solubility of sulphides. Several drawbacks from published solubility methods were addressed in this study: As guaranteeing anoxic conditions from the beginning to the end of the experiments; constant conditions e.g. constant temperature even during the filtration of the samples and so on. From the modelling part, I discovered that the aqueous chemistry of sulphides is not as straight forward as it was thought, especially at elevated temperatures. The inclusion of complexes into the speciation equilibrium model is required to achieve good results.

What are the possible wider implications of your research for society?
The formation of scaling minerals in an oil gas reservoir is a serious threat, as these minerals reduce the productivity of a well by blocking the production tube compromising the safety of the reservoir as well. Therefore, the prediction of the occurrence of the scaling materials in an oil reservoir is a foremost tool for the operator of a well. However, the thermodynamic models rely on experimental data. Therefore, it is of outmost importance to build solid foundations for thermodynamic model by providing sound and reliable experimental data. In this project, we focused on obtaining reliable sulphides solubility data. The solubility data available for ZnS, PbS and FeS in literature is scarce and in some cases ill suited.

What made you apply for a PhD position at DTU Chemical Engineering?
I have a passion for science, so pursuing a PhD degree was an obvious choice for me. When I saw this opportunity at DTU, I thought it fit my profile. I was looking for a PhD that would give me the opportunity to explore, design and work in the laboratory.

What does the future hold for you?
The results of my PhD project brought new insights regarding metal sulphides solubility but at the same time, many questions arose from the results. Currently I am working as a Post-Doctoral fellow at AT-CERE and I continue investigating on the solubility of scaling minerals. This new project will allow us to expand the knowledge of scaling minerals by studying the solubility of Iron Carbonate (FeCO3).