The different water shutoff treatments based on in-situ gelation are attractive technologies; however, the field results often fall short of expectation. Reason of unsuccessful treatments might be that the flow resistance against water often develops not in the right time and reservoir space. Therefore, the primary aim of the research project was to develop such chemical systems, which will form the blocking phase triggered by mixing with water. As a novelty, water sensitive petroleum solutions and external microemulsions were developed, which are stable until they are diluted with water forming thus stable water external macroemulsions. Phase inversion of such metastable systems to stable ones in reservoir may radically restrict the water flow through their high viscosity and entrapment of the dispersed particles by the pores. The transformation and structure of phases were analyzed by photon correlation spectrometry, rheometry. The core studies confirmed that all metastable systems reduce the flow of water by 80-90% in water-saturated sandstone. Using chemical-free postflush the flow resistance remains substantial against water; meanwhile the permeability deterioration against gas is negligible.The petroleum microemulsions are in phase of pilot test in two gas wells in the largest Hungarian oil/gas reservoir (Algyő field) with the aim at restricting the substantial water production. The concept and the developed technology is similar to the earlier silicon microemulsion field test, which yielded 3 106 m3 incremental gas production in the same reservoir and measurable decrease in water production. The metastable systems may offer an excellent opportunity for water shutoff in matured gas fields and gas storage facilities. The unique properties of the techniques are that flow resistance may occur only in water saturated reservoir space and in case of technical failure; the flow barrier can be eliminated by oil and gas injection.
The lithological interpretation of well logs is a fundamental task in Earth science that can be accomplished with the application of various machine learning algorithms. The current investigation attempts to evaluate the performance of the K-nearest-neighbour Density Estimate (KNN) and K-means cluster analysis methods for predicting lithology in a dataset of logs measured in the siliciclastic reservoir of the Shushufindi Oilfield of Ecuador. The comparison of lithological interpretation is assembled using classical methods, such as qualitative interpretation and density-neutron cross plot. The lithological interpretation results showed that the supervised method KNN has a higher fitting level with the comparison interpretation data (87.3%, 1145 m predicted of 1311.1 m interpreted) than the results of the K-means method (71.6%, 939.7 m predicted of 1311.1 m interpreted). The geological nature of the reservoir creates a level of a discrepancy because of the near geophysical responses between limestone and intermedia grain size rocks. The possibility of controlling this in the KNN algorithm makes it preferable for usage in these types of reservoir lithological interpretation.
The biopolymers and synthetic polymers are available as concentrated solutions, gels, crushed powders, beads and partially pre-crosslinked solid microgels. All of them are notorious of their poor solubility and jointly with their incompatibility in porous systems often causes serious formation damage hard to cure. Therefore, searching such formulations, which eliminate the mentioned drawbacks, may contribute significantly to improvement of polymer technologies. One of the possible options is the application of "liquid" polymer. The "liquid" polymer is a stabilized suspension of bead-like polymers in organic solvent with active content of 40–45%. The polymer beads are monodispersed and have narrow size distribution (2–4 μm). Usually anionic and nonionic tenside mixtures are used to stabilize the dispersion. The laboratory studies focused on dissolution phenomena, colloid chemical, rheological, and flow properties in porous media (sandstone) of polymer solutions prepared by different "liquid" polymers. Based on the experimental findings, it was found that using "liquid" polymers readily and rapidly dissolve in water, the solutions are free of microgels and mechanical entrapment was minimal in low permeable sandstone cores. In addition, they decrease the surface tension to 30–35 mN/m, the interfacial tension lowering was min. one order of magnitude, and they proved to be compatible with other chemicals (e.g. silicates). In additions, the rheological and flow properties were identical or very similar to those data obtained by conventional solid polymers. The extra beneficial properties of "liquid" polymers may significantly contribute to improvement of polymer-based technologies; meanwhile the surface facilities can be simplified and the chemical cost remains the same. The "liquid" polymer was successfully applied in water shutoff and conformance treatments in oilfields (Oman), but its use is also recommended in smart water flooding and chemical EOR methods.
The primary cause of global warming is the burning of fossil fuels. Therefore, we are looking for alternative solutions for electricity generation, such as the increased use of renewable energies such as solar, wind and hydropower. The main drawback of these energy generation methods is the high degree of weather dependence, highly unbalanced, so the creation of a complex energy storage system is of paramount importance. This system would store the excess energy as a buffer, balancing the periodicity between demand and supply. Hydrogen storage (hydrogen is produced by the electrolysis of water using renewable energy) in the form of clathrate can be one of the possible forms of energy storage. To facilitate hydrogen supply in a future with zero carbon emissions, it is necessary to examine the technical aspects and feasibility of adsorption of hydrogen in high surface area materials. The capturing of molecular hydrogen in a crystalline guest molecule, i.e., water, as a storage method is a relatively new technology. Hydrogen hydrate is a promising medium for hydrogen storage, with advantages such as low production cost, safety, lack of negative environmental effects. The aim of this study is to present the latest developments in hydrogen storage in the form of hydrates and to present the challenges of this research area.
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