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Nediljka Gaurina-Medjimurec is a Professor at University of Zagreb, Faculty of Mining, Geology and Petroleum Engineering specializing in drilling, drilling fluids, wellbore stability, cementing, and environmental protection in petroleum engineering. She holds a BS and PhD degree in petroleum engineering from the University of Zagreb, and MS degree in petroleum engineering from the University of Belgrade. She is a certified petroleum engineer. She has published over hundred technical and scientific papers. She was head of Petroleum Engineering Department from 1996-1998, and Vice Dean for Finance and Administration of Faculty of Mining, Geology and Petroleum Engineering from 2005-2009. She is a member of Society of Petroleum Engineers (SPE), Croatian Academy of Engineering (HATZ), and Croatian Academy of Science and Art (HAZU) - Scientific Council for Oil.
Hydraulic fracturing operations are performed to enhance well performance and to achieve economic success from improved production rates and the ultimate reserve recovery. To achieve these goals, fracturing fluid is pumped into the well at rates and pressures that result in the creation of a hydraulic fracture. Fracturing fluid selection presents the main requirement for the successful performance of hydraulic fracturing. The selected fracturing fluid should create a fracture with sufficient width and length for proppant placement and should carry the proppant from the surface to the created fracture. To accomplish all those demands, additives are added in fluids to adjust their properties. This paper describes the classification of fracturing fluids, additives for the adjustment of fluid properties and the requirements for fluid selection. Furthermore, laboratory tests of fracturing fluid, fracture stimulation design steps are presented in the paper, as well as a few examples of fracturing fluids used in Croatia with case studies and finally, hydraulic fracturing performance and post-frac well production results. The total gas production was increased by 43% and condensate production by 106% in selected wells including wellhead pressure, which allowed for a longer production well life.
Nediljka Gaurina-Međimurec; Vladislav Brkić; Matko Topolovec; Petar Mijić. Fracturing Fluids and Their Application in the Republic of Croatia. Applied Sciences 2021, 11, 2807 .
AMA StyleNediljka Gaurina-Međimurec, Vladislav Brkić, Matko Topolovec, Petar Mijić. Fracturing Fluids and Their Application in the Republic of Croatia. Applied Sciences. 2021; 11 (6):2807.
Chicago/Turabian StyleNediljka Gaurina-Međimurec; Vladislav Brkić; Matko Topolovec; Petar Mijić. 2021. "Fracturing Fluids and Their Application in the Republic of Croatia." Applied Sciences 11, no. 6: 2807.
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.
Karolina Novak Mavar; Nediljka Gaurina-Međimurec; Lidia Hrnčević. Significance of Enhanced Oil Recovery in Carbon Dioxide Emission Reduction. Sustainability 2021, 13, 1800 .
AMA StyleKarolina Novak Mavar, Nediljka Gaurina-Međimurec, Lidia Hrnčević. Significance of Enhanced Oil Recovery in Carbon Dioxide Emission Reduction. Sustainability. 2021; 13 (4):1800.
Chicago/Turabian StyleKarolina Novak Mavar; Nediljka Gaurina-Međimurec; Lidia Hrnčević. 2021. "Significance of Enhanced Oil Recovery in Carbon Dioxide Emission Reduction." Sustainability 13, no. 4: 1800.
For years, drilling engineers have been faced with the challenge of drilling wells through naturally fractured reservoirs that are present around the world. During drilling, the pressure at the bottomhole of a well is frequently intentionally higher than formation pressure, which can result in the loss of mud in surrounding rocks. During well cementing, the bottomhole pressure is even higher than it is during drilling, because the cement slurry density is higher than the density of the mud. Therefore, if natural or induced fractures in the surrounding rocks are not plugged during drilling, the cement slurry can be lost to them, reducing their permeability which is undesirable in the case of a pay zone. To prevent the loss of circulation and the related consequences, it is necessary to apply good drilling and cementing practices and to use adequate methods and carefully selected materials for plugging the loss zones. The aim of this article is to give an overview of the preventive and corrective methods that can be applied in drilling and cementing through fractured zones as well as improvements in drilling and cementing technology to avoid lost circulation issues (e.g., aerated drilling fluid, casing while drilling, managed pressure drilling, expandable tubulars, lightweight cement slurries, etc.).
Nediljka Gaurina-Međimurec; Borivoje Pašić; Petar Mijić; Igor Medved. Drilling Fluid and Cement Slurry Design for Naturally Fractured Reservoirs. Applied Sciences 2021, 11, 767 .
AMA StyleNediljka Gaurina-Međimurec, Borivoje Pašić, Petar Mijić, Igor Medved. Drilling Fluid and Cement Slurry Design for Naturally Fractured Reservoirs. Applied Sciences. 2021; 11 (2):767.
Chicago/Turabian StyleNediljka Gaurina-Međimurec; Borivoje Pašić; Petar Mijić; Igor Medved. 2021. "Drilling Fluid and Cement Slurry Design for Naturally Fractured Reservoirs." Applied Sciences 11, no. 2: 767.
The drilling of clay-rich formations, such as shale, is an extremely demanding technical and technological process. Shale consists of mixed clay minerals in different ratios and in contact with water from drilling mud. It tends to swell and cause different wellbore instability problems. Usually, the petroleum industry uses various types of salt and/or polymers as shale hydration inhibitors. The aim of this research was to determine whether nanoparticles can be used as shale swelling inhibitors because due to their small size they can enter the shale nanopores, plug them and stop further penetration of mud filtrate into the shale formation. Swelling of bentonite-calcium carbonate pellets after 2 and 24 h in water and drilling mud (water, bentonite, PAC and NaOH) without nanoparticles and with addition of TiO2 (0.5, 1 and 1.5 wt%) and SiO2 (0.5, 1 and 1.5 wt%) nanoparticles was measured using a linear swell meter. Additionally, granulometric analyses of bentonite as well as the zeta potential of tested muds containing nanoparticles were performed. Based on the laboratory research, it can generally be concluded that the addition of SiO2 and TiO2 nanoparticles in water and base drilling mud reduces the swelling of pellets up to 40.06%.
Borivoje Pašić; Nediljka Gaurina-Međimurec; Petar Mijić; Igor Medved. Experimental Research of Shale Pellet Swelling in Nano-Based Drilling Muds. Energies 2020, 13, 6246 .
AMA StyleBorivoje Pašić, Nediljka Gaurina-Međimurec, Petar Mijić, Igor Medved. Experimental Research of Shale Pellet Swelling in Nano-Based Drilling Muds. Energies. 2020; 13 (23):6246.
Chicago/Turabian StyleBorivoje Pašić; Nediljka Gaurina-Međimurec; Petar Mijić; Igor Medved. 2020. "Experimental Research of Shale Pellet Swelling in Nano-Based Drilling Muds." Energies 13, no. 23: 6246.
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.
Nediljka Gaurina-Međimurec; Karolina Novak Mavar. Carbon Capture and Storage (CCS): Geological Sequestration of CO2. CO2 Sequestration and Valorization 2020, 1 .
AMA StyleNediljka Gaurina-Međimurec, Karolina Novak Mavar. Carbon Capture and Storage (CCS): Geological Sequestration of CO2. CO2 Sequestration and Valorization. 2020; ():1.
Chicago/Turabian StyleNediljka Gaurina-Međimurec; Karolina Novak Mavar. 2020. "Carbon Capture and Storage (CCS): Geological Sequestration of CO2." CO2 Sequestration and Valorization , no. : 1.
Degradation of Portland cement under supercritical CO2 conditions (scCO2) is one of the major concern in geological sequestration projects. This paper presents the research on two novel types of binders considered to display a CO2 corrosion resistance potential: (1) Portland cement partially replaced with 20, 30 and 40 w% of zeolite and blended with SBR polymer latex and (2) geopolymer based on lime-slag and lime-pozzolan blends. Specimens were placed in an autoclave, covered with water, heated up to 100 °C and pressurized with 7 MPa CO2 in order to simulate CO2 environment in the Croatian wellbore. On behalf of tests on compressive strength, porosity, permeability and alkalinity, as well as thermogravimetry, X-ray diffraction and SEM microstructural analyses of samples at various penetration depths, carbonation mechanisms were discussed. Portland-Zeolite composites have been argued as potential CO2 resistant cement systems, with an replacement rate below the minimally tested addition of 20 w%, as excessive replacement rates resulted in an increase in porosity and permeability. Geopolymer composites based on lime activation unfortunately haven't exhibited required properties for application in well cementing of CO2 injection wells. Calcium carbonate polymorphs precipitated throughout the whole specimen thickness of all samples, but preferably in mixtures based on Ca-richer raw materials. A re-precipitation of calcium carbonate filled in the porosity preferentially at the 0.5 mm surface layer of PC-based specimens, due to the outward diffusion of calcium at the early stage of carbonation.
Krunoslav Sedić; Neven Ukrainczyk; Vilko Mandić; Nediljka Gaurina-Međimurec; Juraj Šipušić. Carbonation of Portland-Zeolite and geopolymer well-cement composites under geologic CO2 sequestration conditions. Cement and Concrete Composites 2020, 111, 103615 .
AMA StyleKrunoslav Sedić, Neven Ukrainczyk, Vilko Mandić, Nediljka Gaurina-Međimurec, Juraj Šipušić. Carbonation of Portland-Zeolite and geopolymer well-cement composites under geologic CO2 sequestration conditions. Cement and Concrete Composites. 2020; 111 ():103615.
Chicago/Turabian StyleKrunoslav Sedić; Neven Ukrainczyk; Vilko Mandić; Nediljka Gaurina-Međimurec; Juraj Šipušić. 2020. "Carbonation of Portland-Zeolite and geopolymer well-cement composites under geologic CO2 sequestration conditions." Cement and Concrete Composites 111, no. : 103615.
Oil and gas exploration and production activities generate large amounts of waste material, especially during well drilling and completion activities. Waste material from drilling activities to the greatest extent consists of drilled cuttings and used drilling mud with a smaller portion of other materials (wastewater, produced hydrocarbons during well testing, spent stimulation fluid, etc.). Nowadays, growing concerns for environmental protections and new strict regulations encourage companies to improve methods for the reduction of waste material, as well as improve existing and develop new waste disposal methods that are more environmentally friendly and safer from the aspect of human health. The main advantages of the waste injection method into suitable deep geological formations over other waste disposal methods (biodegradation, thermal treatment, etc.) are minimizing potentially harmful impacts on groundwater, reducing the required surface area for waste disposal, reducing the negative impact on the air and long-term risks for the entire environment. This paper gives a comprehensive overview of the underground waste injection technology, criteria for the selection of the injection zone and methods required for process monitoring, as well as a comprehensive literature overview of significant past or ongoing projects from all over the world.
Nediljka Gaurina-Međimurec; Borivoje Pašić; Petar Mijić; Igor Medved. Deep Underground Injection of Waste from Drilling Activities—An Overview. Minerals 2020, 10, 303 .
AMA StyleNediljka Gaurina-Međimurec, Borivoje Pašić, Petar Mijić, Igor Medved. Deep Underground Injection of Waste from Drilling Activities—An Overview. Minerals. 2020; 10 (4):303.
Chicago/Turabian StyleNediljka Gaurina-Međimurec; Borivoje Pašić; Petar Mijić; Igor Medved. 2020. "Deep Underground Injection of Waste from Drilling Activities—An Overview." Minerals 10, no. 4: 303.
During the drilling of a well, differential pressure causes filtration of the mud liquid phase into the surrounding rocks. To reduce the filtrate invasion in the rock, it is necessary to maintain the density of the mud. Also, Wellbore Strengthening Materials (WSM) can be preventively added to the mud to increase the fracture initiation pressure of the drilled formation. The solid particles from the mud create a mud cake on the wellbore wall, which, for conventional drilling, implies the use of bentonite and barite whose particle dimensions range from 0.1 to 100 μm. While drilling shales, rocks which contain pores that have an average pore size of 10 to 30 nm, it is not possible to create a high-quality mud cake, so water passes into the shale and creates wellbore instability problems. To stabilize the shale, the petroleum industry uses oil-based muds, but due to their environmental impact, it is not always possible to implement them. Nanoparticles, because of their small dimensions, can enter into the nanopores and fill this space and strengthen the rock, resulting in decreased filtration. In this paper, a review of previous laboratory research of adding nanoparticles on filtration is shown. Also, the impact of adding nanoparticles on API and HTHP filtration is examined by adding TiO2 and SiO2 nanoparticles in concentrations of 0.5 wt% and 1 wt% to the five water-based muds. The best result was obtained with TiO2 nanoparticles at a concentration of 0.5 wt%.
Petar Mijić; Nediljka Gaurina-Međimurec; Borivoje Pašić; Igor Medved. THE INFLUENCE OF TIO2 AND SIO2 NANOPARTICLES ON FILTRATION PROPERTIES OF DRILLING MUDS. Rudarsko-geološko-naftni zbornik 2019, 34, 67 -77.
AMA StylePetar Mijić, Nediljka Gaurina-Međimurec, Borivoje Pašić, Igor Medved. THE INFLUENCE OF TIO2 AND SIO2 NANOPARTICLES ON FILTRATION PROPERTIES OF DRILLING MUDS. Rudarsko-geološko-naftni zbornik. 2019; 34 (4):67-77.
Chicago/Turabian StylePetar Mijić; Nediljka Gaurina-Međimurec; Borivoje Pašić; Igor Medved. 2019. "THE INFLUENCE OF TIO2 AND SIO2 NANOPARTICLES ON FILTRATION PROPERTIES OF DRILLING MUDS." Rudarsko-geološko-naftni zbornik 34, no. 4: 67-77.