Opoka: polymorphic composition, genesis, problems of study

P.V. Smirnov1

1Institute of the Earth's Cryosphere SB RAS, Tyumen, Russia

Abstract. This paper is a comprehensive review devoted to topical issues in the study of opoka - marine sedimentary siliceous rocks of the Cretaceous-Paleogene age. For almost two hundred years of studying these sedimentary formations, the term “opoka” itself has not received due recognition globally due to the lack of a detailed mineralogical definition and the general imperfection of the systematics of siliceous rocks. A distinctive feature of the opoka is the presence of opal-CT lepispheres, which form a recognizable framework of siliceous rock or form an obscure lepispheric/cryptocrystalline mass. The article discusses various aspects of opoka – history of study, nomenclature, mineralogical composition, microtexture, the distribution of Cretaceous-Paleogene opoka, etc. The etymology of the genesis of the opoka and models of its origin at the early and late stages of diagenesis are critically discussed. In this review, attention is focused on recent studies, that provide detailed information about silica polymorphic forms distributed in the opoka, as well as its typical microtexture types. A model of the genesis of opoka and the relationship with global biogeochemical cycle of silica, is presented. Differences recorded in opoka of different ages, geological and tectonic positions, indicate both the predetermination of many parameters of the mineral composition from the very genesis, and the disproportionate contribution of individual factors to the evolution of opoka rocks, namely the source of silicic acid, the role of siliceous bios in the mobilization of dissolved silica, the nature and volume of terrigenous influx from the adjacent landmass, secondary changes and mineral formation, etc.

Keywords: opoka, silicites, opal-ST, opal, cristobalite, silicic rocks, silica cycle, Trans-Urals

Age, conditions and sources of igneous rocks of Gora Rudnaya (southern Yakutia)

V.E. Guzev*, V.I. Leontiev, B.V. Belyatsky, A.V. Terekhov, A.V. Molchanov

A. P. Karpinsky Russian Geological Research Institute, Saint Petersburg, Russia

Abstract. The paper presents the results of a complex petrogeochemical and isotope-geochemical (Rb-Sr and Sm-Nd systems) study of alkaline syenites and ore-bearing metasomatites (beresites) of the Gora Rudnaya, as well as a comparative comparison with compositionally similar massifs of the Aldan Mesozoic igneous province. The Gora Rudnaya, together with the recently discovered Morozkinskoye deposit, is located within the Central Aldan ore region. The massif is composed predominantly of alkaline syenites with a minor amount of alkaline porphyritic syenites, which are intruded by later dikes and sills of alkaline syenite porphyries and calc-alkaline lamprophyres. Industrial gold mineralization is confined to beresitization zones (Qz–Ser–Ank–Py) in areas of intense metasomatic reworking of rocks along steeply dipping fault structures within the intrusion. The obtained Rb-Sr age values for ore-bearing metasomatites (132±1 Ma) indicate subsynchronism of the ore process and crystallization of alkaline syenites, which corresponds to the time of manifestation of the main stage of magmatism in the Aldan Mesozoic igneous province (150-115 Ma). The rocks of the Gora Rudnaya do not differ in petrogeochemical and isotope-geochemical characteristics from rocks of similar composition from other massifs of the Aldan Mesozoic igneous province, indicating a wide lateral distribution of enriched EM I type mantle beneath the studied region. Variations in the initial isotopic composition of neodymium ((143Nd/144Nd)0: from 0.511375 to 0.511636) in the studied samples are probably due to the heterogeneity of the source composition. At the same time, the calculated model ages indicate that the enriched mantle source was formed no later than 2.0-2.5 Ga.

Keywords: Mesozoic magmatism, Aldan Mesozoic igneous province, Central Aldan ore region, Gora Rudnaya, Morozkinskoye deposit, Sr-Nd isotope composition, Rb-Sr isotope system

The formation conditions of the Volga Basin oil shales in relation to their metallogeny on rhenium and other valuable elements

V.S. Ilyasov1, V.N. Staroverov 2, V.N. Ilyasov 3

1LLC "Gazprom Neft Yamal" Tyumen, Russia

2JSC "NVNIIGG" Saratov, Russia

3LLC "Perelyubskaya Mining Company" Saratov, Russia

Abstract. The Volga oil shales are located on the Russian platform and represent a potential non-traditional and promising source of rhenium and other valuable metals. Concentrations of rhenium at the level of industrial types of ores have been identified at the Perelyubskoe and Kotsebinskoe deposits. The complex of lithological and geochemical studies suggests that the metallogeny of the Volga oil shales is associated with the influence of volcanism and anoxic conditions during the sedimentation period. The main criteria have been identified by which high concentrations of rhenium in the Volga oil shales can be predicted: the content of organic carbon, molybdenum, and the DOPR indicator. Based on the analyzed data, promising layers have been identified for the Perelyubskoe and Kotsebinskoe deposits to detect industrial concentrations of rhenium.

Keywords: oil shales, Volgian basin, metal content, volcanism, rhenium, anoxic event

Features of distribution of rare-earth elements in coals of the Far East

V.I. Vyalov1,2, A.V. Nastavkin2, E.P. Shishov1*, A.A. Chernyshev1

1A.P. Karpinsky Russian Geological Research Institute, Saint-Petersburg, Russia

 2Southern Federal University, Rostov-on-Don, Russia

Abstract. For the first time, the distribution of REE has been studied in detail for a number of coal facilities (30 deposits, 650 samples of coal and 210 samples of carbonaceous rocks). The ubiquitous presence of elevated concentrations of rare earth elements (REE) in coals has been noted. The REE mineral cluster in coals includes the association: ash content of coals – SiO2 – K2O – Al2O3 – TiO2 – Sc – Y – Dy – Ho – Er – Tm – Yb – Lu, and the association La – Ce – Pr – Nd – Sm – Eu – Gd – Tb. The presence of these elements of the mineral part of the coals is preferably in the composition of phosphate minerals – monazite and apatite (according to electron microscopy with microanalysis, the correlation of REE with P2O5). The content of individual REE in humic acids isolated from coals and fractions of coals of different densities has been studied. The specific role of organic matter(s) in the concentration of REE, their presence in the humus component of S and in low-ash coals is shown. Selective accumulation (fractionation) of heavy REE by organic matter has been experimentally established for the first time. Two genetic types of REE mineralization have been identified in coals: mainly terrigenous (hydrogenic) and tufogenic. The increased concentrations of REE in coals are due to the influence of the petrofund. The deposits were ranked according to the degree of prospects for REE based on an assessment of the resource potential of associated REE in the coals of the studied brown coal deposits. REE raw materials (lanthanides in coal ash) differ significantly from traditional types of rare earths ores by an incomparably large relative amount of heavy REE (on average 3-4 times), sometimes reaching 46% of the total REE content. Thus, coal ash is a unique non–traditional source of heavy lanthanides – more rare, valuable and expensive. The coals of the studied deposits should be considered as associated raw materials for rare earths.

Keywords: brown coal, hard coal, rare-earth elements, metalliferous, Russian Far East, mass-spectrometry, electron microscopy, ash content, coal ash

Hydrogeological modeling of groundwater treatment from dissolved hydrocarbons using biotechnological solutions

N.G. Maksimovich1, A.D. Demenev1*, V.T. Khmurchik1, O.A. Berezina1, A.V. Mukhametdinov2

1 Perm state national research university, Perm, Russian Federation

2 LLC «Spb-Giproshakht», St. Petersburg, Russian Federation

Abstract. The development of the oil industry is accompanied by a technogenic impact on the environment. According to various estimates, annual losses of hydrocarbons can reach 15% of the produced volumes at the transportation stage alone. These losses are accompanied by the formation of more than 510 million tons of contaminated soil. Emergency situations, which are difficult to predict, may arise at oil production and oil refining enterprises. That situations also lead to environmental pollution. The remediation of groundwater from dissolved petroleum products is one of the difficult tasks. There are two main approaches to remediation of oil pollution: ex situ, i.e. at special sites, and in situ, i.e. at the site of contamination. Using in situ techniques can be significantly cheaper and more effective. The applying of in situ techniques should be based on a well-developed strategy for implementing environmental protection measures. Mathematical modeling allows one to reliably determine and justify hydrogeological studies and to obtain parameters for the development of designed solutions. This article studies the possibility of mathematical modeling methods applying for the biotechnological process of groundwater remediation used a dosed supply of oxygen into a contaminated aquifer. The results of field observations and model data were compared. During the research, it was established that the developed geomigration model, which uses a package of instantaneous aerobic degradation of hydrocarbons, adequately describes the dynamics of pollutant reduction in groundwater when compared with field measurements. To assess the effectiveness of the measures taken, forecast calculations were additionally performed on the model with different numbers of treatment wells and the distance between them. The data obtained allowed us to conclude that the development of mathematical modeling at the preliminary stage makes it possible to select the most optimal scheme for groundwater treatment even before the construction of the technological complex, which can significantly reduce costs when implementing such projects.

Keywords

Groundwater remediation; water-dissolved oil products; hydrogeological modeling; biotechnology; environmental measures

Experimental and statistical study of the influence of geological and technological parameters on the result of acid treatments in carbonate reservoirs

V.A. Novikov, D.A. Martyushev*

Perm National Research Polytechnic University, Perm, Russian Federation

Abstract. To date, acid treatment technology has become widespread in the development of carbonate layers in oil fields. Virtually every well in the history of its production has been acid treated downhole, ultimately providing millions of tons of incremental oil production globally. Despite the considerable amount of theoretical and practical research devoted to this technology, the problem of controlling the efficiency of acid treatments remains topical. In this connection, the purpose of this paper is to study the influence of known and available in field conditions geological and technological parameters on the efficiency of acid stimulation in carbonate reservoirs. Laboratory studies (in free volume, filtration and X-ray tomography tests) using two hydrochloric acid compositions and carbonate rock samples of the same geologic age from oil fields of Perm krai to determine the dependencies were performed. Acid treatments were modeled by varying technological parameters (volume, rate and pressure of injection of acid compositions, reaction time of acid with rock) under thermodynamic conditions corresponding to reservoir properties. Statistical processing of empirically obtained data allowed us to note the predominant role of technological parameters to achieve a successful result of acid stimulation. Multivariate statistical models describing the process of formation of acid treatment efficiency in carbonate reservoirs have been developed. It was found that the reservoir stimulation efficiency varies in direct proportion to the increase in the injection pressure of the acid composition and the volume of agent used due to the development of wormholes. The efficiency of acid treatment at dolomite content in the rock is significantly lower, which requires increasing the rate of composition injection and reaction time to achieve the highest stimulation result. Thus, the paper provides a basis for further development of the process of controlling the effectiveness of acid treatments in carbonate reservoirs of oil fields.

Keywords: acid treatment, carbonate reservoir, laboratory studies, wormhole, acid injection rate, correlation analysis, step-by-step regression analysis.

ON THE RELATIONSHIP OF POISSON’S RATIO WITH GEOPHYSICAL CHARACTERISTICS OF ROCKS

D. V. Shustov, Yu. A. Kashnikov, A E. Kukhtinskii, A. A. Efimov,

Perm National Research Polytechnic University (PNRPU), Perm, Russia

Abstract. Currently, there are no reliable universal dependencies of the Poisson's ratio on the geomechanical and geophysical characteristics of productive objects. This study aims to investigate the influence of geophysical parameters on the Poisson’s ratio for oilfield productive objects using machine learning methods. The analysis is based on data from several oil and gas fields, presenting results of dependencies between the Poisson's ratio and parameters such as natural radioactivity of rocks and P-wave velocity. The elastic parameters were identified through triaxial tests of rock samples under reservoir conditions conducted on the PIK-UIDK/PL triaxial system at Perm National Research Polytechnic University. A brief overview of existing standards for conducting triaxial tests is also provided. The importance of standardizing methods for determining the Poisson's ratio and other elastic parameters of rocks is emphasized to ensure comparability of research results from different fields and their applicability in various geological conditions. The proposed data analysis method relies on linear regression and machine learning methods to establish stable relationships between the Poisson’s ratio and geophysical parameters obtained from various well logging studies. These dependencies allow for more accurate estimation of the Poisson’s ratio for different types of rocks and fields, representing a significant step in developing methods for assessing elastic properties of rocks in oil fields. The obtained results can be used for more precise modeling and forecasting of oil field development processes, contributing to increased efficiency in hydrocarbon extraction and optimization of production processes in the oil industry.

Keywords: Poisson’s ratio, geomechanics, triaxial tests, machine learning

Improving the technology for inflow profile evaluation in horizontal wells by temperature changes due to calorimetric mixing

Kremenetskiy M. I.1*, Bakinova E.V.2, Nikonorova N.N2., Solov'eva V.V2,

1 Gazpromneft Scientific and Technical Center.

2 National University of Oil and Gas «Gubkin University»

Abstract

The paper is devoted to the problem of increasing the effectiveness of temperature logging quantitative interpretation for the inflow profile evaluation in horizontal production wells draining heterogeneous reservoirs with low permeability. Such wells are characterized by an extremely uneven distribution of inflow along the length of the wellbore. One of the ways if quantitative interpretation of temperature logging is based on the effect of calorimetric mixing. It’s widely used to quantify the share of local producing interval in the total flow rate.

The low accuracy of interpretation, as a rule, is associated with the lack of reliable information about the temperature of the fluid flowing into the wellbore. The authors propose an estimate of this parameter based on the similarity of the behavior of the temperature field vs time in the near-wellbore zone of a reservoir during periods of stable production and the periods of the well shut-in.

This relationship is confirmed by the results of modeling the temperature field of the "well-reservoir" system, taking into account changes in a wide range of reservoir permeability and thermal properties of the reservoir, the geometry of hydraulic fractures in the reservoir, the flowing fluids, as well as the parameters of the well production targets.

The logging technology recommended by the authors involves the registration of several temperature profiles along the length of the wellbore at the beginning of the well production with the maximum rate and drawdown and during the well shut-in.

Their integrated analysis based on the behavior of the temperature field features in time identified on the basis of modeling makes it possible to evaluate with a high degree of certainty the dynamics of the temperature of the gas-liquid mixture coming from reservoirs to the wellbore during production periods. This provides the required accuracy in the quantitative assessment of the inflow profile from mixing anomalies.

The proposed approaches to the interpretation of thermograms are applicable in the analysis of the results of non-stationary temperature logging results in horizontal wells during the production from heterogeneous reservoirs both through perforation and multi-stage hydraulic fracturing.

Key words: oil and gas reservoir development surveillance by production logging, horizontal wells production logging, temperature logging, calorimetric mixing effect, inflow profile evaluation.

Modeling of hydrogeochemical processes of carbon dioxide interaction with formation water and rock minerals during enhanced oil recovery and underground storage

Klimov D.S.1*, Indrupskiy I.M.1, Garifullina Ch.A.2, Ibragimov I.I.2, Lutfullin A.A.3, Zakiev B.F.3, Akhmetzyanov F.M.3

1 Oil and Gas Research Institute of Russian Academy of Sciences (OGRI RAS), Moscow, 119333, Russia

2 Almetyevsk State Technological Universiti «Petroleum High School», Almetyevsk, 423462, Russia

3PJSC Tatneft named after V.D. Shashin, Almetyevsk, 423450, Russia

Abstract

Application of hydrogeochemical modeling using PHREEQC software to study interaction of formation water, carbon dioxide and reservoir rock minerals during CO2 injection for enhanced oil recovery or underground storage is discussed. Hydrogeochemical modeling is a powerful tool to evaluate the physicochemical processes occurring in the “gas phase - aqueous solution - solid phases” system depending on initial parameters such as temperature, pressure and reactant concentrations. The use of hydrogeochemical simulators provides a wide range of opportunities to analyze the processes of dissolution and precipitation of minerals, changes in the ionic composition and pH of the solution, which can affect the efficiency of CO2 injection, fluid flow, well and equipment operation. A step-by-step method for modeling interactions in the “formation water - CO2 - rock” system using the PHREEQC hydrogeochemical simulator provides good reproducing accuracy for the results of laboratory experiments and analysis of their correspondence to the processes occurring under different conditions. The obtained results are useful for optimization of oil and gas production processes involving carbon dioxide, planning and stability assessment of underground carbon dioxide storage facilities and other geological applications.

Keywords: hydrogeochemical modeling, PHREEQC, formation water, carbon dioxide, carbonic acid, carbonized water, minerals, underground storage, injection into the reservoir.

On the method of temperature measurements in borehole using precision thermometers

Demezhko D.Yu., Khatskevich B.D., Fakaeva N.R, Gornostaeva A.A.

Bulashevich Institute of Geophysics, Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia

Abstract

Precise autonomous borehole thermometers (loggers) allow measuring temperature anomalies of small amplitude (up to 1 mK). It significantly expands the range of problems that borehole thermometry can solve in exploration geophysics, hydrogeology, engineering geology, and geoecology. However, thermal logging techniques remain outdated that hinders the effective implementation of the capabilities of these devices. The paper discusses methodological issues of precision temperature measurements in water-filled boreholes. Experimental studies with an autonomous thermometer RBRsolo³ T (RBR Ltd., Canada) showed that the device’s response to changes in ambient temperature (relaxation) is complex. Within a few seconds after the immersing of device in a borehole, it registers a temperature close to the fluid temperature. However, this temporary “window” closes soon, and after 15–20 seconds the measured temperature begins to deviate more and more from the undisturbed temperature. Next time measured temperature returns to the undisturbed temperature after 1000–6000 sec. In addition, the temperature response in the interval of 20–600 sec is complicated by non-periodic fluctuations with an amplitude of 0.02–0.05 K associated with thermal convection. The presence of a time “window” on the relaxation curve makes it possible to measure fluid temperature quickly and accurately in stop-and-go mode. The design parameters of thermometers determining the width of the “window” were assessed using mathematical modeling. Recommendations for conducting precision temperature logging of boreholes in both continuous and stop-and-go modes have been provided.

Keywords: geothermy, borehole temperature logging, RBRsolo³ T logger, precise temperature measurements, free thermal convection.