In line with the low-carbon strategy, the EU is expected to be climate-neutral by 2050, which would require a significant increase in renewable energy production. Produced biogas is directly used to produce electricity and heat, or it can be upgraded to reach the “renewable natural gas”, i.e., biomethane. This paper reviews the applied production technology and current state of biogas and biomethane production in Europe. Germany, UK, Italy and France are the leaders in biogas production in Europe. Biogas from AD processes is most represented in total biogas production (84%). Germany is deserving for the majority (52%) of AD biogas in the EU, while landfill gas production is well represented in the UK (43%). Biogas from sewage sludge is poorly presented by less than 5% in total biogas quantities produced in the EU. Biomethane facilities will reach a production of 32 TWh in 2020 in Europe. There are currently 18 countries producing biomethane (Germany and France with highest share). Most of the European plants use agricultural substrate (28%), while the second position refers to energy crop feedstock (25%). Sewage sludge facilities participate with 14% in the EU, mostly applied in Sweden. Membrane separation is the most used upgrading technology, applied at around 35% of biomethane plants. High energy prices today, and even higher in the future, give space for the wider acceptance of biomethane use.

Limiting the increase in CO₂ concentrations in the atmosphere, and at the same time, meeting the increased energy demand can be achieved by applying carbon capture, utilization and storage (CCUS) technologies, which hold potential as the bridge for energy and emission-intensive industries to decarbonization goals. At the moment, the only profitable industrial large-scale carbon sequestration projects are large-scale carbon dioxide enhanced oil recovery (CO₂-EOR) projects. This paper gives a general overview of the indirect and direct use of captured CO₂ in CCUS with a special focus on worldwide large-scale CO₂-EOR projects and their lifecycle emissions. On the basis of scientific papers and technical reports, data from 23 contemporary large-scale CO₂-EOR projects in different project stages were aggregated, pointing out all the specificities of the projects. The specificities of individual projects, along with the lack of standardized methodologies specific for estimating the full lifecycle emissions resulting from CO₂-EOR projects, pose a challenge and contribute to uncertainties and wide flexibilities when estimating emissions from CO₂-EOR projects, making the cross-referencing of CO₂-EOR projects and its comparison to other climate-mitigation strategies rather difficult. Pointing out the mentioned project’s differentiations and aggregating data on the basis of an overview of large-scale CO₂-EOR projects gives useful information for future work on the topic of a CO₂-EOR project’s lifecycle emissions.

Drilling fluid represents the most important fluid that must fulfill numerous important assignments during drilling operations. Many commercially available additives for water-based drilling fluid fall into the category of non-degradable and environmentally hazardous materials. Significant development in this area can be made by using biodegradable materials as additives in drilling fluids. The objective of this study was to determine whether mandarin peel powder particle size affects the properties of the drilling fluid. In this paper, mandarin peel was used in the form of a dry powder divided into particle sizes smaller than 0.1 mm, and between 0.1 mm and 0.16 mm. Mandarin peel powder was added to a water-based drilling fluid in four different concentrations (0.5, 1, 1.5, and 2% by volume of water). By increasing the mandarin peel powder concentration, the API filtration reduced up to 42%, PPT filtration significantly decreased up to 61.54%, while the rheological parameters generally increased but remained within acceptable limits. It is determined that the optimal concentration of mandarin peel powder is up to 1.5% by volume of water.

The European Union greenhouse gas emission reduction target can be achieved only by applying efficient technologies, which give reliable results in a very short time. Carbon capture and storage (CCS) into geological formations covers capturing CO2 at the large point sources, its transportation and underground deposition. The CCS technology is applicable to different industries (natural gas processing, power generation, iron and steel production, cement manufacturing, etc.). Due to huge storage capacity and existing infrastructure, depleted hydrocarbon reservoirs are one of the most favourable storage options. In order to give overall cross section through CCS technology, implementation status and other relevant issues, the chapter covers EU regulation, technology overview, large-scale and pilot CCS projects, CO2-enhanced oil recovery (EOR) projects, geological storage components, CO2 storage capacity, potential CO2 migration paths, risk assessment and CO2 injection monitoring. Permanent geological sequestration depends on both natural and technical site performance. Site selection, designing, construction and management must ensure acceptable risk rates of less than 1% over thousands of years.

The sweetness seismic attribute is a very useful tool for proper description of the depositional environment, reservoir quality and lithofacies discrimination. This paper shows that depositional channels and turbidity sandstones deposited during the Upper Pannonian and Lower Pontian in the Sava Depression can be described using porosity–thickness and sweetness seismic attribute maps. Two studied reservoirs are of Neogene stage (“UP” reservoir of Upper Pannonian age and “LP” reservoir of Lower Pontian age) and located in the Sava Depression, Croatia. Both reservoirs contain medium to fine grained sandstones that are intercalated with basinal marls. A comparison of the sweetness seismic attribute and porosity–thickness maps show a good visual match with correlation coefficient of approximately 0.85. A mismatch was observed in areas with small reservoir thickness. This work demonstrates the importance of using porosity–thickness maps for reservoir characterization. The workflow presented in this work has wider applications in frontier areas with poor seismic data or coverage.

The paper provides an analysis of the causes of accidents in oil and gas pipeline systems. As part of a comprehensive overview of the topic, it also presents the historical development of pipeline systems, from the first commercial oil pipelines in the United States to modern infrastructure projects, with a particular focus on the role of regulatory requirements and measures (prevention, detection, and mitigation) to improve transport efficiency and pipeline safety. The research uses historical accident data from various databases to identify the main causes of accidents and analyse trends. The focus is on factors such as corrosion, third-party interference, and natural disasters that can lead to accidents. A comparison of the various accident databases shows that there are different practises and approaches to operation and reporting. As each database differs in terms of inclusion criteria, the categories are divided into five main groups to allow systematic interpretation of the data and cross-comparison of accident causes. Regional differences in the causes of accidents involving oil and gas pipelines in Europe, the USA, and Canada are visible. However, an integrated analysis shows that the number of accidents is declining in almost all categories. The majority of all recorded accidents are in the “Human factors and Operational disruption” and “Corrosion and Material damage” groups. It is recommended to use the database as required, as each category has its own specifics.