The accuracy of fitting the rheological model to the properties of actual drilling fluid minimises the errors of the calculated technological parameters applied while drilling oil wells. This article presents the methodology of selecting the optimum drilling fluid rheological model. Apart from classical rheological models, i.e., the Newtonian, Bingham Plastic, Casson, Ostwald de Waele and Herschel–Bulkley models, it has been proposed to consider the Vom Berg and Hahn-Eyring models, which have not been applied to describe drilling fluids so far. In the process of determining rheological parameters for the Bingham Plastic, Casson, Ostwald de Waele and Newtonian models, it is proposed to use a linear regression method. In the case of the Herschel–Bulkley, Vom Berg and Hahn-Eyring models, it is suggested to use a non-linear regression method. Based on theoretical considerations and mathematical relations developed in the Department of Drilling and Geoengineering, Drilling, Oil and Gas Faculty, at AGH University of Science and Technology, an original computer program called Rheosolution was developed, which enables automation of the process of determining the optimum drilling fluid rheological model. Some examples show the practical application of the method of selecting the optimum drilling fluid rheological model. Taking into account data from actual measurements of drilling fluid properties, it has been proven that the Vom Berg and Hahn-Eyring rheological models are best fitted to the description of drilling fluid rheological parameters.

The search for unconventional energy resources such as coalbed methane (CBM) is on the rise in Poland due to the demand for energy resources and protection of the environment. CBM production has a lower impact on the environment when compared with coal production. Its development is known to be cost effective due to its use of shallow depths with large gas quantities. Sand is one of the by-products (waste) from open-pit mining operations. Conventional disposal of this material is achieved by storage in heaps and its deployment as landfill as well as filling material for mine pits. This paper investigates the potential use of sand (filler) as a proppant for hydraulic fracturing in coalbed methane formations in Poland through crush test measurements in both single and cyclic loadings. The crush test helps to identify proppant strength under various load applications. Test results show that the sand qualifies for the 4 K (maximum allowable stress is 27.58 MPa) and 3 K (maximum allowable stress 20.68 MPa) crush classifications under single and cyclic conditions, respectively. This finding shows the viability and potential of the investigated sand as a proppant for hydraulic fracturing in shallow coalbed methane formations in Poland. Furthermore, its use could help filler-providing companies to maintain their production level and save jobs. Notably, it would contribute to the reduction of environmental problems associated with the management of waste, such as that from open-pit mining operations.

Advances in the field of material engineering, computerization, automation, and equipment miniaturization enable modernization of the existing technologies and development of new solutions for construction, inspection, and renovation of underground pipelines. Underground pipe installations are used in the energy sector, gas industry, telecommunications, water and sewage transport, heating, chemical industry, and environmental engineering. In order to build new pipeline networks, dig and no-dig techniques are used. Horizontal Directional Drilling (HDD) is one of the most popular trenchless technologies. The effectiveness of HDD technology application is mostly determined by its properly designed trajectory. Drilling failures and complications, which often accompany the application of the HDD technology, result from poor design of the well path in relation to the existing geological and drilling conditions. The article presented two concepts of Horizontal Directional Drilling well path trajectory design: Classic sectional, which is a combination of straight and curvilinear sections, and a single-section chain curve trajectory (catenary). Taking into account the advantages and disadvantages of the catenary trajectory relative to the sectional trajectory, the author’s solution was presented, which was the implementation of the sectional trajectory with a maximum shape similarity to the catenary trajectory. The new approach allowed us to take advantage of a chain curve trajectory and was easier to implement using the available technology. The least squares method, based on deviations from a catenary trajectory, was set as the matching criterion. The process of searching for a trajectory, being a combination of straight and curvilinear sections as similar as possible to a catenary-type trajectory, was carried out using two methodologies: State space search and a genetic algorithm. The article shows the pros and cons of both optimization methodologies. Taking into account the technical and technological limitations of HDD drilling devices, a new approach was proposed, combining the methodology of state space search with the genetic algorithm. A calculation example showed the application of the proposed methodology in an engineering design process.

Gas migration through fresh and hardened cement slurry is an ongoing problem in the oil industry. In order to eliminate this unfavourable phenomenon, research is being conducted on new compositions of slurries for gas wells. The article presents the results of research for slurries with low and high resistance to gas migration. The proper selection of the quantity and quality of components makes it possible to design slurry with the required static structural strength values. In addition, the cement sheath of such anti-migration slurry has low porosity and a very low proportion of large pore spaces. Additionally, the mechanical parameters do not decrease during long-term deposition in borehole-like conditions. By obtaining these results, it was possible to design slurry whose cement sheath has high corrosion resistance. The new slurry has a lower water-cement ratio. Additionally, GS anti-migration copolymer, anti-filter additive and latex are used. The presence of n-SiO2 aqueous solution and microcement allows for sealing the microstructure of the hardened cement slurry. Such modifications significantly improve the technological parameters of the cement slurry and the cement coat formed from it.

Drilling boreholes in gas zones and in zones with the possibility of migration or gas exhalation requires a high index of well tightness. An important parameter determining the effectiveness of sealing the annular space is the adhesion of the cement sheath to the rock formation. Low values of adhesion of the cement sheath to the rock formation and to the casing surface result in the formation of uncontrolled gas flows. The lack of adhesion also reduces the stabilization of the pipe column. To obtain the required adhesion, the annular space should be properly cleaned. Thorough removal of filter cake from the drilling fluid increases adhesion and reduces gas migration from the annular space. Therefore, in this work, the authors focus on determining the effect of cleaning the annular space on the adhesion of the cement sheath to the rock formation. The results of the research work allow for further research on the modification of spacers and cement slurries in order to obtain the required increase in adhesion. The article presents the issues related to the preparation of the borehole for cementing by appropriate cleaning of the rock formation from the residue of the mud cake. During the implementation of the works, tests of cleaning the rock surface are performed. The obtained results are correlated with the results of adhesion on the rock–cement sheath cleaned of the wash mud cake contact. When analyzing the obtained test results, a relationship is found between the cleaning of the rock surface and the adhesion of the cement sheath to it.

The exploration and development of new hydrocarbon deposits face increasing challenges, primarily driven by the shift away from hydrocarbons towards renewable energy sources like shallow geothermal deposits, wind farms, and photovoltaics. This shift necessitates finding solutions that minimize environmental impact and enable increased energy extraction from existing or decommissioned fields and wells. This paper explores the possibility of excavating from potentially depleted fields, where a significant portion (up to 85%) of the reservoir’s resources remain unrecoverable due to low reservoir energy. To address this, secondary and tertiary exploitation methods are proposed involving the supply of external energy to increase the pressure in the reservoir layer, thereby enhancing resource exploitation. One of the suggested tertiary methods involves reaming the deposit with multiple small-diameter radial holes using a hydraulic drilling nozzle. The entire process comprises several key components, including the coiled tubing unit (CTU), high-pressure flexible hose, window drilling kit for casing pipe, kit for positioning the exit of the hydraulic drilling head from the casing pipe, anchor, and hydraulic drilling head attached to the end of the high-pressure flexible hose. This method aims to increase the contact between the reservoir layer and the wellbore, potentially leading to an increase in or initiation of exploitation in certain deposit scenarios. The described method presents an environmentally friendly approach, eliminating the need for drilling new boreholes and offering cost-effective access to resources in decommissioned deposits with insufficient reservoir energy for self-exploitation. The applicability of this method to extract methane from coalbed seams is also mentioned in this article. In a separate article, the authors detail the design of a hydraulic drilling nozzle specifically for reaming the reservoir layer.