Author: Igor Medved, PhD
In recent period, researchers have started conducting laboratory research to determine whether different types of biodegradable food waste can be used as additives in water-based drilling mud. Correctly designed composition of the mud is extremely important for the successful construction of the wellbore, since mud is complex fluid whose composition and properties affect the efficiency of drilling process (Gaurina-Međimurec et al., 2000). Therefore, any new type of additive must be researched in detail in relation to all the necessary properties that must be obtained during drilling operations. Wasted drilling mud and associated waste generated during drilling operations represents second largest volume of waste generated during exploration and production projects in oil and gas industry, so this kind of research can have considerably positive results for the environment (Haut et al., 2007; Gaurina-Međimurec et al., 2020). Along with environmental protection, the disposal of generated waste presents a significant cost, which leads to a logical conclusion that reducing the amount of hazardous waste to the lowest possible value must be a priority. Since many commercially available water-based mud additives fall into the category of non-degradable and environmentally hazardous materials (Zheng et al., 2020), there is a need to find and create new environmentally friendly additives that ensure the achievement of all the necessary mud properties at the level of current commercial additives, but with a minimal impact on the environment. Therefore, many researchers are actively conducted on the use of food waste (Haider et al., 2019) and other types of biodegradable waste as additives that could be used for this purpose. Among the analyzed types of biodegradable waste, there is some data on the use of mandarin peel for these purposes, and due to the considerable annual production of this type of fruit in Croatia along with contradictory results of previously published results, it was decided that detailed laboratory research will be carried out on this type of biodegradable waste.
By adding dried, grinded and sieved mandarin peel powder, in the water-based drilling mud, it was tested how this additive affects the mud filtration properties, rheological properties and the wellbore stability. Drilling muds that have a certain concentration of mandarin peel powder in their composition (Figure 1) were compared with base mud which consists of water, bentonite and sodium hydroxide (NaOH). In addition to studying the influence of the concentration of mandarin peel powder, the influence of different particle sizes divided into two groups, particles smaller than 0.1 mm and particles between 0.10 mm and 0.16 mm in size, was also researched. The selected concentrations in the mud samples varied from 0.5% to 2% by the volume of water, since it was concluded during preliminary laboratory test phase that a concentration higher than 2% leads to a significant increase in plastic viscosity of the tested muds.
Figure 1 Drilling mud with added mandarin peel powder in its composition
On the basis of the conducted laboratory tests and the analysis of the results, useful insights were obtained on the effect of mandarin peel on the observed mud properties. Results show that mandarin peel has positive effect on mud filtration, since every mud sample with added mandarin peel powder showed decrease of filtrate volume in room conditions. Even better results were recorded in conditions of elevated temperature and differential pressure on PPT device (Figure 2).
Figure 2 Permeability Plugging Tester
An exceptionally positive influence of mandarin peel powder was also observed in data obtained after swelling of pellets that have a clay component in their composition (Figure 3), when pellet is in contact with mud to which this eco-friendly additive is added. Laboratory tests showed significant swelling reduction, and this correlates well with results of filtration measurements which is essential to prove the improvement of the wellbore stability.
Figure 3 Artificial rock samples (pellets) before and after swelling test
The rheological properties of mud samples that are containing mandarin peel were not decreased but also did not significantly increase observed properties. Rheological parameters show increase and remain within acceptable limits up to concentration of 1.5% of mandarin peel powder by volume of water. Because of this data set, the recommended concentration of this additive should be kept in the range of 1.0% to 1.5%, and at those concentrations observed additive has a significant positive effect on the filtration properties and wellbore stability as well as maintaining stable rheological properties at the same time. Considering the particle size used for laboratory research of mentioned mud properties, it can be concluded that slightly better results were obtained with larger particles between 0.10 mm and 0.16 mm but both sizes provide satisfactory water-based drilling mud properties. Also, by conducting laboratory tests of temperature stability, it can be concluded that water-based drilling mud with added mandarin peel powder is stable even after exposing the water-based drilling mud to temperatures up to 133 °C.
Ecotoxicity measurements showed that toxicity of water-based drilling mud that has mandarin peel powder in its composition is reduced, compared to conventionally used commercial additives. This test confirmed the ecological component of using this type of material, and whole research confirmed the applicability of the circular economy concept in drilling technology.
References:
Gaurina-Međimurec N., Simon K., Matanović D. (2000): Drill-In Fluids Design Criteria. Nafta (Spec. Issue), 27–32.
Gaurina-Međimurec N., Pašić B., Mijić P., Medved I. (2020): Deep underground injection of waste from drilling activities—An overview. Minerals, 10, 303.
Haider S., Messaoud-Boureghda M.Z., Aknouche H., Akkouche A., Hammadi L., Safi, B. (2019): An ecological water-based drilling mud (WBM) with low cost: Substitution of polymers by wood wastes. J. Pet. Explor. Prod. Technol., 9, 307–313.
Haut R.C., Rogers J.D., McDole B.W., Burnett D., Olatubi O. (2007): Minimizing Waste during Drilling Operations. In Proceedings of the AADE National Technical Conference and Exhibition, Houston, TX, USA, 10–12.
Zheng Y., Amiri A., Polycarpou, A.A. (2020): Enhancements in the tribological performance of environmentally friendly water-based drilling fluids using additives. Applied Surface Science, 527, 146822.
Igor Medved, PhD is a senior assistant at the Department of Petroleum and Gas Engineering and Energy, Faculty of Mining, Geology and Petroleum Engineering at University of Zagreb. He successfully defended his doctoral dissertation on April 11th, 2023 entitled Influence of Mandarin Peel on Water-Based Mud Properties and Wellbore Stability.
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