AL Khalaf, Hani (2025) Using natural waste fibers and synthetic fibers to develop properties of oil well cement and drilling fluids. PhD thesis, Miskolci Egyetem.
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Text (Dissertation)
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Abstract
Maintaining long-term well integrity is one of the utmost priorities in the oil and gas industry to ensure complete control of fluids flow inside the well during drilling and production operations. The primary cementing operation stands out as one of the most critical operations during well drilling and plays a fundamental role in preserving well integrity. Its primary objective is to isolate the drilled formations by pumping one or more cement slurries into the annular space between the formations and the casing. This primary cementing process serves multiple essential purposes, including safeguarding the casing from corrosion, preventing fluid migration between formations driven by pressure differences, providing effective zonal isolation, minimizing safety risk (well control), and prevent gases from rising to the surface, which could lead to significant environmental issues. In the context of zonal isolation procedures, specifically primary cementing, the standard practice entails the utilization of Portland cement as a key well barrier component. This primary function of Portland cement is to ensure and uphold well integrity by effectively obstructing the inadvertent and uncontrolled movement of fluids situated behind the casing string. Portland cement serves a dual role within the casing system by functioning as an anchoring mechanism and providing protective measures in the face of a potentially corrosive downhole environment. The barrier material assumes a pivotal role in the preservation of well integrity, necessitating the fulfillment of several criteria essential for ensuring safe and reliable operations throughout the entirety of the well's lifecycle. Portland cement is inherently brittle and can’t withstand the wellbore conditions. Consequently, the incorporation of additives becomes necessary to enhance its properties. However, a significant challenge associated with these additives is their tendency to restrict the cement hardening process, leading to a reduction in the formation of calcium silicate hydrates (C-S-H) gel, which is responsible for providing strength to the cement sheath. Moreover, the high costs of these additives, further complicating the cementing process. On the other hand, drilling fluids are used during drilling operations to transfer the drilled cuttings to the surface, cool the drilling bit, suspend the cuttings when the drilling fluid circulation stops, and provide hydrostatic pressure by the drilling fluid column to prevent the gas influx into the well. Similar to cement, drilling fluids necessitate the incorporation of additives to control their different properties like viscosity, density, and fluid loss. The objective of this thesis is to develop high-performance well cement and water-based drilling fluid systems that meet the isolation and operational requirements in oil wells. This will be achieved by using two types of fibers. The first type consists of natural fibers extracted from the pine cones waste, which are prepared in powder form. These fibers are commonly available in nature, environmentally neglected, and inexpensive. The second type comprises synthetic polypropylene fibers (PPFs), commonly used in concrete to enhance mechanical properties. These two types of fibers were added in increasing concentrations to the cement slurries primarily composed of distilled water and Class G Portland cement. Subsequently, a comprehensive experimental investigation was conducted, involving the formulation of cement systems incorporating these two types of fibers. The study aimed to assess the impact of these fibers on the physical properties including (rheological parameters, density, fluid loss, free fluid, sedimentation property, porosity, permeability), chemical properties including (pH), and mechanical properties including (compressive strength, tensile strength, and flexural strength) under ambient temperature and atmospheric pressure conditions. Additionally, a novel laboratory method was developed to measure the bonding strength between cement and casing, offering valuable insights into the adhesive properties on the interface between the casing and the cement sheath. Furthermore, water-based drilling fluid systems were formulated using these two fiber types. Subsequently, the rheological properties, density, and fluid loss characteristics of these drilling fluids were meticulously measured, and the obtained results were subjected to thorough analysis. It was found through experiments that the rheological properties were not significantly affected by incorporation of polypropylene fibers as a well cement additive. However, the permeability and porosity of cement samples increased upon the addition of polypropylene fibers to the cement system. Notably, the mechanical properties of cement samples containing polypropylene fibers measured at different curing times exhibited a significant improvement compared to the reference cement samples up to 0.3 %BWOC. Furthermore, the bonding strength at the casing cement interface showed enhancement with increasing PPFs concentration, reaching an optimum concentration at 0.5 %BWOC. This enhancement reflects positively on the cement's ability to provide effective isolation. The results also showed that adding APCP to the cement samples with increasing concentrations led to an increase in the rheological parameters. Also, it leads to a decrease in fluid loss, free water volume, the sedimentation effect, and density which positively affects the preservation of the original properties of cement slurry. The results also showed a decrease in the permeability of cement samples and the ability to absorb water with increasing concentrations of APCP. The pH values were not significantly affected by the addition of APCP. The addition of APCP also deteriorated the mechanical properties of the cement samples. This can be explained by the results of porosity measurements. The addition of APCP resulted in an increase in the porosity of the samples, making the cement samples more brittle compared to the reference samples due to the formation of a porous structure. This is because the APCP may not fully bond with the cement matrix, leaving void spaces or pores within the material. Furthermore, a significant increase in total weight loss was also observed at high temperatures after APCP was added to cement samples. As a result, the APCP can be regarded as a new filler for well cement, as it possesses the capability to fill the pores within the cement system while simultaneously enhancing certain properties of the well cement, including the density, the free water, the sedimentation effect, and the fluid loss volume. Additionally, an experimental study was conducted on five types of pine cones (Austrian pine cones, Black Hills Spruce, Sitka Spruce, Norway Spruce, and White pine cones) and tested to determine their ability to reduce filtration loss volume and also the effect of those eco-friendly materials on rheological properties and density of the water-based mud. The findings revealed that pine cones powder significantly reduces filtration loss volume, with Norway Spruce cones powder being the most effective type at an optimum concentration of 3 wt.% when compared to other types and concentrations. The results of incorporating polypropylene fibers into water-based mud revealed a notable increase in both apparent viscosity and yield point, especially after adding 0.1 wt.% of PPFs to the bentonite mud. Simultaneously, the filtration loss volume decreased by approximately 7.8 % after adding 0.1 wt.% of PPFs. Based on these findings, it can be concluded that 0.1 wt.% is the optimum concentration of PPFs to reduce the filtration loss volume.
| Item Type: | Thesis (PhD) |
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| Subjects: | Q Science / természettudomány > QE Geology / földtudományok |
| SWORD Depositor: | Software Sword MTMT |
| Depositing User: | Software Sword MTMT |
| Date Deposited: | 05 Jun 2025 08:13 |
| Last Modified: | 05 Jun 2025 08:13 |
| URI: | https://real-phd.mtak.hu/id/eprint/2136 |
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