CO2-EOR Process and CO2 storage during EOR

Maja Arnaut,

Enhanced Oil Recovery (EOR) methods are used to produce additional oil after the primary production phase (where production is based on natural reservoir energy) or, most often, after waterflooding (secondary phase). Some EOR methods are related to CO2 injection (CO2-EOR), which is attractive since part of injected CO2 retained in the reservoir, enabling a positive effect on storage capacity and cost-effectiveness of CO2 storage. Therefore, these methods are of particular importance due to the emission reduction obligations under European Union international agreements within the climate change domain (Kyoto protocol from the year 1997 and Paris agreement from the year 2015). Carbon Capture Utilization and Storage (CCUS) comes to focus when possibilities of CO2 storage and reduction of storage cost are assessed. Although there are other utilization types such as utilization through beverage production or in agriculture, only the CO2 enhanced oil recovery (CO2-EOR) is implemented at a commercial level on an industrial scale [2]–[4].

By injecting CO2 above the miscibility pressure (or minimum miscibility pressure, MMP), microscopic displacement efficiency is improved due to viscosity reduction, oil swelling, lower interfacial tension and change of density of oil and brine [5]. Regardless of the injection conditions, part of the CO2 is always re-produced so injected CO2 includes recycled CO2 and CO2 that should be brought to complete the total required injected volume (Figure 1)

Research of extreme – explosives

Author: Barbara Štimac, mag.geol.

One of the main aims of the research, as a part of HRZZ project NEIDEMO, is to develop an improved model of nonideal detonation, based on Wood-Kirkwood’s theory and thermochemical code EXPLO5.

Detonation of explosive charge results in a detonation wave through explosive propagating with velocity up to 10 km/s, pressure up to 40 GPa and temperatures up to 6000 K, all in a timeframe of couple of nanoseconds. Due to this extremely short timeframe and high pressure, energy is transmitted from the detonation products to the unreacted part of explosive by motion. There are two generally accepted theories of detonation based on conservation laws and hydrodynamic theory: Chapman-Jouguet (CJ) theory that assumes instantaneous chemical reaction (meaning there is no chemical reaction zone) and Zeldovich-von Neumann-Doering (ZND) theory that takes into account the existence of a chemical reaction zone of defined width and duration (Figure 1). Explosives that behave in according to CJ theory are called “ideal explosives”.

However, detonation parameters of commercial explosives (so-called “nonideal explosives”) cannot be accurately predicted using CJ theory. Theoretically calculated detonation velocity and detonation pressure of commercial explosives are considerably higher than those experimentally obtained, and detonation velocity shows strong dependence on initial radius of explosive charge and confinement (Esen, 2004; Souers et al, 2004; Minchinton, 2015; Sućeska i ostali, 2019).

Determination of the Earth's structure by Local Earthquake Tomography method

Author: Josipa Kapuralić, PhD mag. ing. geol.

Knowledge of the Earth's interior is key to understanding geological structures and their relationships observed on the surface. In the last two decades, many regional studies of the European lithosphere have been carried out, while in the past ten years local geophysical researches have been intensified in the Dinarides. Recent geophysical efforts significantly contributed to the clarification of the crustal and lithospheric geological model in this region. This investigation is a continuation of geophysical studies focused on the Dinarides and its adjacent areas. The study area represents the boundary zone between the African and European plate, i.e. the contact between the Adriatic microplate as part of the African plate and the Pannonian basin as part of the European plate (Figure 1).

Nanoparticle-based drilling muds

Author: Petar Mijić,

The first scientist who pointed out that devices and materials could one day be produced in a size corresponding to the size of an atom was Richard Feynman in 1959. The term "nanotechnology" was first used in 1974 by scientist Norio Taniguchi. Although nanotechnology penetrates all areas of human activity, from the automotive industry, computers and electronics, robotics, medicine to the textile industry, its application in the oil industry has begun a few years ago. Nanotechnology means the use of materials which have very small dimensions, between 1 and 100 nanometers.

Excavator Productivity in Mining of Mineral Raw Materials.

Author: Vjekoslav Herceg, mag. ing. min.

The world mining has been developing rapidly in recent years, following the global trend of economic development. Demand for certain minerals is growing rapidly and natural, technological, law and social conditions can greatly limit capacity. Therefore, one of the biggest challenges of modern mining is to keep up with the times. To achieve this, with quality staff and social support, modern technology is certainly one of the key success factors. Current technological progress in the world is aimed at minimizing the use of fossil fuels with the aim of reducing CO2 emissions into the atmosphere. In the mining industry, the technology is largely related to mobile machines powered dominantly by internal combustion engines. Therefore, the development of technology is based on the highest possible productivity, which directly affects the reduction of energy consumption and CO2 emissions. In the processes of obtaining mineral raw materials, various machines are used, the effect of which is investigated separately.

Teaching-research polygon, Velika Gorica

Autor: Laura Bačani, mag. ing. geol.

Groundwater reserves of the Zagreb unconfined aquifer are defined as a strategic resource of groundwater in Croatia within the Croatian Waters’ Water Management Strategy. They present the only source of potable water for the inhabitants of the City of Zagreb and one part of the Zagreb County. In the past decades, groundwater level declines have been identified in the Zagreb aquifer. Consequently, it became important to identify and quantify every single source of its recharge. In order to observe and measure the processes in the unsaturated zone a teaching-research polygon was constructed (Figure 1) in collaboration between Velika Gorica water supply system (VGV) and Faculty of Mining, Geology and Petroleum Engineering (RGNF), University of Zagreb. Polygon is constructed in 2018. and is located in the southern part of the Zagreb aquifer, at the Velika Gorica well field. The research polygon is designed in order to be suitable for scientific research and educational purposes. The construction design of the pedological pit was prepared by the company HIDROPROJEKT-ING d.o.o. from Zagreb in cooperation with Velika Gorica water supply system and the Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb.

Rockfall susceptibility assessment of the rock slopes above the Town of Omiš

Marin Sečanj,

Rock falls are a common phenomenon on the steep slopes and road cuts in the Dinarides. They are the result of unfavourable characteristics of the rock mass, weathering in combination with heavy rainfall and anthropogenic factor. One of the most endangered places by rockfalls is the Town of Omiš, located just at the toe of the steep Omiška Dinara Mt slopes (fig 1). Comprehensive geotechnical investigation financed by the Town of Omiš identified 22 potential rockfall source areas for which was necessary to design remedial measures to ensure protection of buildings, infrastructure, and citizens (Arbanas et al., 2019). Identification of rockfall source areas was performed by conventional field investigations based on visual inspection of the slopes, without rockfall susceptibility analysis, which should be the first step in rockfall hazard and risk reduction.

Geothermal energy exploitation by revitalizing abandoned oil and gas wells

Author: Marija Macenić,

In the Republic of Croatia hydrocarbon production began back in the end of the 19th century. However, modern oil and gas production began in the mid-20th century and is still continuing today. According to data from INA d.d. group, there are around 4500 exploratory, production and development wells in Croatia (INA d.d., 2018). By the end of the 20th century production decline, higher water cut, and pressure decrease in reservoirs were noticed. This results in abandoning or reassigning production wells in exploratory or monitoring wells. It can be assumed that the number of reassigned wells will increase in the future in Croatia and over the world.

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