Height Of Zone Research Articles

Dimenzioniranje armiranobetonskih pravokutnih presjeka prema drugoj generaciji Eurokoda

This paper describes the design procedure for reinforced concrete rectangular cross-sections according to the standard FprEN 1992-1-1 (second generation of Eurocode 2). Design was carried out in two ways: using design tables for reinforced concrete rectangular sections and using a direct analytical procedure. The stress-strain diagram in the form of a parabola-rectangle was used for concrete, while for the reinforcing steel a bilinear stress-strain diagram with a horizontal post-elastic branch without strain limit was applied. For this reason, when designing the reinforced concrete cross-section, it is necessary to limit the strain in the compression zone of the concrete. Tables for the design of reinforced concrete rectangular sections were obtained using a new procedure in which the mechanical reinforcement ratio is varied. A direct analytical procedure was used for comparison, which can be used for the design of reinforced concrete rectangular sections without the need to use tables. The limit values of the coefficient of the height of the compression zone for pure bending were calculated according to the standard FprEN 1992-1-1.

Experimental studies of a continuous catalytic distillation column from startup to steady state for the production of methyl acetate

Abstract Esterification of acetic acid with methanol to produce methyl acetate and water has been studied in a continuous packed bed catalytic reactive distillation. The key challenge is the startup method of the experiments fora continuous reactive distillation as well as reactive zone height selection. In the present study, the effect of various operating conditions on the methyl acetate composition (mole fraction) is studied. Indion 180 ion-exchange resin solid catalyst is used in the reactive zone. The catalyst is immobilized by using a novel equivalent Katapak-S in the reactive section. Experiments were performed under different operating conditions to find the high purity methyl acetate product in the distillation. The experiments were performed for various conditions like total feed flow rate, reboiler temperature, reflux ratio, methanol to acetic acid mole ratio and catalyst loading with the time. The experiments were carried out till the system reaches to the steady state under different conditions. The maximum methyl acetate concentration is obtained at 80 °C reboiler temperature, 2.01 reflux ratio, 16.3 g/min flow rate, 60 g catalyst loading and 1 mol ratio of methanol to acetic acid. The highest purity of methyl acetate obtained under optimal condition is 95 % by mole.

Determination of the Caving Zone and Fracture Zone Heights by Using the LK-Means Algorithm

The caving zone and fracture zone frequently appear after coal excavation. However, the caving zone and fracture zone can hardly be obtained with an empirical equation. Therefore, identifying a proper method to determine the caving zone and fracture zone is critically important to engineering practice. In this paper, Universal Distinct Element Code numerical simulations were conducted. Furthermore, the LK-means algorithm was used to determine the caving zone and fracture zone heights. To verify the validity of the proposed method, two engineering case studies were used. It could be found that the height calculated by the proposed method agrees well with that determined in engineering tests. Hence, the proposed method can be used in engineering practice.

Research on Subsidence Prediction Method of Water-Conducting Fracture Zone of Overlying Strata in Coal Mine Based on Grey Theory Model

The development height and settlement prediction of water-conducting fracture zones caused by coal seam mining play an important role in the stability of overburden aquifers and the safety of roadways. Based on the engineering geological data of the J60 borehole in the Daliuta Coal Mine and the mining conditions of the 2−2 coal seam, China, this study established a similar material test model of mining overburden. The deformation characteristics of overlying strata in the mining process of coal seam were studied by using distributed optical fiber sensing technology, and the development height of water flowing fractured zone was determined. According to the equidistant sampling characteristics of Brillouin optical time domain reflection technology and the principle of the grey theory model, the settlement prediction model of the water-conducting fracture zone was established. By analyzing and comparing the prediction accuracy of the GM (1, 1) model, grey progressive model, and metabolic model, the optimal method for settlement prediction of the water-conducting fracture zone was discussed. The results show that, for the metabolic model, with the increase in the number of test sets and the decrease in the number of prediction sets, the mean square error ratio c and the small error probability p of the prediction accuracy evaluation parameters display a downward trend. The accuracy is related to the sudden change in the settlement of the water-conducting fracture zone caused by the breaking of the key stratum of the overlying rock. The optimal time of test sets selected for the best settlement prediction model is 7~8, and that of prediction sets selected is 5~6. For the GM (1, 1) model and the grey progressive model, the prediction accuracy of mining overburden subsidence is grade 4, which is not suitable for settlement prediction of water-flowing fractured zones.

Machine-learning-based investigation of the variables affecting summertime lightning occurrence over the Southern Great Plains

Abstract. Lightning is affected by many factors, many of which are not routinely measured, well understood, or accounted for in physical models. Several commonly used machine learning (ML) models have been applied to analyze the relationship between Atmospheric Radiation Measurement (ARM) data and lightning data from the Earth Networks Total Lightning Network (ENTLN) in order to identify important variables affecting lightning occurrence in the vicinity of the Southern Great Plains (SGP) ARM site during the summer months (June, July, August and September) of 2012 to 2020. Testing various ML models, we found that the random forest model is the best predictor among common classifiers. When convective clouds were detected, it predicts lightning occurrence with an accuracy of 76.9 % and an area under the curve (AUC) of 0.850. Using this model, we further ranked the variables in terms of their effectiveness in nowcasting lightning and identified geometric cloud thickness, rain rate and convective available potential energy (CAPE) as the most effective predictors. The contrast in meteorological variables between no-lightning and frequent-lightning periods was examined for hours with CAPE values conducive to thunderstorm formation. Besides the variables considered for the ML models, surface variables and mid-altitude variables (e.g., equivalent potential temperature and minimum equivalent potential temperature, respectively) have statistically significant contrasts between no-lightning and frequent-lightning hours. For example, the minimum equivalent potential temperature from 700 to 500 hPa is significantly lower during frequent-lightning hours compared with no-lightning hours. Finally, a notable positive relationship between the intracloud (IC) flash fraction and the square root of CAPE (CAPE) was found, suggesting that stronger updrafts increase the height of the electrification zone, resulting in fewer flashes reaching the surface and consequently a greater IC flash fraction.

Evolution mechanism of flip-fold removal behaviour through crossed scratching of glass-ceramics

In this study, a novel flip-fold removal model was established to reveal the ductile–brittle mixed removal phenomenon in the grinding process of glass-ceramics. This flip-fold model proposed for the ductile–brittle mixed removal mode differs from conventional brittle or ductile removal mechanisms. Using the theoretical exploration method, a theoretical model of flip-fold removal is established based on the analysis of different scenarios of the relationship between the depth of the stagnation region and pile-up height of the interference zone. Through an experimental verification method, the approach of crossing double scratches with a continuously variable scratch distance is proposed to observe the evolution progression and verify the flip-fold removal model. Using the analytical analysis method, the amplitude and direction cosine distributions of the interference stress field were analysed to reveal the internal mechanism of the flip-fold removal model. The results of the three scientific research methods were in good agreement with those of the proposed model. The flip-fold material removal model supports the comprehension of the ductile–brittle mixed removal mode during the grinding of hard-brittle materials. This model provides an approach to controlling the material removal mode from the perspective of regulating the flip-fold behaviour by adjusting the scratch distance.

Development of technology for ingots production using electroslag remelting at direct current with consumable electrode rotation

The paper describes the problem of increasing the productivity of electroslag remelting (ESR) furnaces. The remelting technology on direct current is proposed as the most effective method. The description of the technology touches upon positive and negative effects affecting the specific productivity of smelting, energy consumption, and quality of the obtained ingots in terms of their physical and mechanical properties and chemical purity. The authors proposed the electroslag remelting method with rotation of the consumable electrode as a new technology, and realized a brief comparison with the external magnetic field application technology. The schemes that clearly demonstrate the principle of controlling the crystallization front shape and the thermal center localization in the slag bath are considered. A stationary numerical model for the slag bath of the operating semi-industrial furnace ESR A-550 on direct current with polarity reversing ability was developed. The mathematical apparatus consisting of electrothermal, hydrodynamic and convective parts was constructed. The authors designed the mesh domain for a slag bath located between the consumable electrode and the water-cooled crystallizer with diameters of 60 and 90 mm, respectively. The height of the sub-electrode zone is 10 mm. The current limit is 800 A and the voltage is 46 V. Numerical fields of current density and temperature distribution in the slag bath volume are obtained. The range of temperature values is located in the range from 1400 to 2200 °C at the peripheral and subelectrode zones of the slag bath, respectively. The scheme of the ESR furnace modernization is given in terms of mechanical part automation and transferring to direct current.

A Comparative Case Study on Stress Redistribution due to Extraction of Conventional and Split-Level Longwall Panels in Deep Inclined Coal Seams

Through field observations, theoretical analysis, and a calibrated numerical model, a study of stress redistribution due to the extraction of longwall panels at depths ranging from 580 to 660 m with a 30° dip angle at Tangshan coal mine is presented in this paper. Conventional and new split-level longwall layouts are compared regarding their stress redistributions. The height of the caved zone is 21.7 m; angles of break of 55.6° on the left and 54.2° on the right side of the gob are observed using cross-measure boreholes. Structural models as well as numerical models are constructed based on the above field data to make the geometry of the gobs closer to the in situ situation and more realistic. Compared with the conventional layout, the theoretical analysis shows that the overall influence of the elevated split-level longwall gob on the lowest intact stratum increases by more than 5.07%, meaning that the split-level longwall layout is more likely to maintain the stability of the overlying strata. This is also corroborated by numerical modeling. Conventional longwall panels and split-level longwall panels with and without considering the gob are all simulated using FLAC3D. Instead of only backfilling the height of the coal seam or the height of the coal seam and the immediate roof, as in many numerical modeling studies in the past, in this study, the whole caved zone is backfilled with “double-yield” material. It is found that along the floor, the split-level longwall gob assumes 23.4% more load than the conventional longwall gob, and the split-level longwall abutment bears 6.2% less load than the conventional longwall abutment; stress arches are developed within the gob; concave-down stress beddings are more evident at higher locations of the gob; a self-supporting structure develops within the gob and surrounding rock mass around the lower end of the gob, forming a protective localized intact destressed zone around the location where the split-level tailgate is situated; the yield zone in the floor of the curved section tends to extends toward the center of the curved part, where the curvature is the maximum; the upper stress concentration zone is within the coal seam, while the lower one is above the coal seam; the upper one is more concentrated.

Stability of tunnel face in unsaturated sand possessing apparent cohesion: A micro-macro analytical approach

Although the stability of tunnel face in the dry and saturated sandy ground is widely studied, the unsaturated sandy ground which possesses apparent cohesion is more common in engineering. For remedying this deficiency, the theoretical association between apparent cohesion and the saturation degree is firstly established in microscopic prospective. Then, the formation mechanism of the self-stabilized arch and the limit support pressure (LSP) of the tunnel face are derived by incorporating apparent cohesion into the macroscopic limit equilibrium analysis of the multi-arches model. Subsequently, the validities of the proposed approach in estimating apparent cohesion, loosening zone height and LSP are well confirmed (the average error rates of LSP are within 12 %) via comparisons with direct shear tests, model tests and other existing methods. Finally, as revealed by the parametric discussion, under the effect of apparent cohesion, LSP is negatively correlated with compactness, internal friction angle, and contact angle while decreases firstly (to a minimum value of 0.09γD ∼ 0.15γD) and then increase with the rise of saturation degree. Besides, the LSP has a parabolic distribution along the depth with its peak value emerges between 0.3D and 0.45D.

Analyses of International Standard Problem ISP-47 TOSQAN experiment with containmentFOAM

The ISP-47 TOSQAN experiment was analyzed with containmentFOAM which is an open-source CFD code based on OpenFOAM. The containment phenomena taking place during the experiment are gas mixing, stratification and wall condensation in a mixture composed of steam and non-condensable gas. The k-ω SST turbulence model was adopted with buoyancy turbulence models. The wall condensation model used is based on the diffusion layer approach. We have simulated the full TOSQAN experiment which had a duration 20000 s. Sensitivity studies were conducted for the buoyancy turbulence models with SGDH and GGDH and there were not significant differences. All the main features of the experiments namely pressure history, temperature, velocity and gas species evolution were well predicted by containemntFOAM. The simulation results confirmed the formation of two large flow stream circulations and a mixing zone resulting by the combined effects of the condensation flow and natural convection flow. It was found that the natural convection in lower region of the vessel devotes to maintain two large circulations and to be varied the height of the mixing zone as result of sensitivity analysis of non-condensing wall temperature. The computational results obtained with the 2D mesh grid approach were comparable to the experimental results.

A truss-arch model-based method for calculating shear walls with small shear span ratio

In this paper, based on the equivalent diagonal web truss-arch (EDWT) model and considering different failure modes and deformation coordination conditions, a method for calculating the shear capacity of shear walls with small shear-to-span ratio is proposed. The method considers the effects of both horizontal and vertical reinforcements in the web on the shear capacity of the member through the stress equivalence principle in the truss action, and an empirical formula to calculate the height of the compression zone for determining the section height of the concrete diagonal compression truss are also proposed. The test data of 359 small shear-span ratio shear walls were collected, and their shear capacity was calculated using the method proposed in this paper, and compared with the Chinese, American, European and Japanese codes. The results show that: except for the Japanese AIJ code, the calculation of shear capacity of small shear span ratio shear wall is conservative, while the AIJ code overestimates the height of the arch bar, which makes its calculation results unconservative; while the proposed formula can calculate the shear bearing capacity of small shear span ratio shear wall more accurately.

Evaluation of Implant Placement Risk Levels in Partially Edentulous Patients Using Cone Beam Computed Tomography.

This study aimed to evaluate the implant placement risk levels in partially edentulous patients using cone beam computed tomography (CBCT) and implant planning software. A total of 101 CBCT scans of partially edentulous patients were included. Evaluations of jawbone anatomy, vital structures' proximity, and the risk of inferior alveolar nerve injury with esthetic considerations were done on CBCT images using implant surgery software (BlueSkyPlan4;BlueSkyBio, Grayslake, IL). A total of 101 patients with 106 edentulous sites were examined. The mean ridge height of the non-esthetic zone was 10 mm and 14.4 mm in the maxilla and mandible, respectively. The period of edentulousness significantly affected the risk of placing implants in the non-esthetic zone (P<.05). The relation between gender and mandibular canal identification was significant (P<.01). A higher risk of implant placement is associated with a more extended period of edentulousness. The preoperative assessment revealed that the mandibular canal could be identified more easily in females than males; thus, nerve injury could be avoided. However, age hadno associated effect. Age has no associated effect on the implant placement risk levels for partially edentulous patients during dental implant planning. A higher risk of implant placement is associated with a more extended period of edentulousness. Mandibular canal identification during virtual preoperative assessment was higher in females.

Experimental investigation on stress distribution and migration of the overburden during the mining process in deep coal seam mining

Coal mining has a significant impact on the movement of the overburden, leading to potential safety hazards in the working face. In this paper, a similarity simulation experiment was conducted to investigate the migration of overburden during the mining process of a specific working face in the Liuzhuang Coal Mine located in southern China. Sand and gravel were used to simulate the geological environment of each rock stratum. The deformation of the stratum was monitored using strain gauges, the fracture and displacement changes of the overburden stratum were recorded using cameras, and the characteristics of roof collapse was monitored using infrared thermal imager. The experimental model fully simulated the situation of the working face, and the actual working face size was obtained by enlarging the model by 100 times. The experiment found that during the initial stage of mining, there was no significant subsidence of the roof. In the course of the advancement of the working face, the primary roof intermittently fractured behind the working face, with subsequent propagation of upper cracks in an upward direction. The overburden rock layer above the goaf experienced continuous compaction, leading to the gradual closure of the separation layer. Simultaneously, new cracks constantly emerged in front of the working face, resulting in the progressive stabilization of the height of the crack zone. The stress measurements at each point exhibit a pattern of initial increased, followed by decrease, and ultimately stabilization. By considering the stress variation law of the overburden rock, the stress changes in key layers of the bedrock during mining could be categorized into four zones: the stress stable zone, stress increasing zone, stress reducing zone, and compaction stable zone. During the initial phase of coal seam mining, the presence of rock layers provided support, resulting in minimal subsidence of the overburden rock. However, as the mining operation progressed, the disturbance force and collapse of the overburden rock leaded to further downward subsidence. When the working face reached the stop line, the collapsed overburden rock gradually consolidates, resulting in a deceleration of energy release and the formation of a pressure relief zone. Consequently, the overburden rock above the working face underwent a slight additional subsidence, reaching its maximum level. A short cantilever rock beam structure was formed in the experiment. This study will provide valuable reference for future coal mining and serve as a vital theoretical basis for roof control in deep coal seam mining.

Research on Dust Migration and Dust Deposition Rules of Breathing Zone in Fully Mechanized Mining Face.

The dust in the breathing zone of the fully mechanized mining face poses a serious threat to the lives and health of the workers, and clarifying the distribution and settlement pattern of the dust in the breathing zone is an important foundation for reducing dust concentrations in the breathing zone and improving the workers' working environment. The dust concentration distribution at the mining face and the settlement results of different dust particle sizes along the breathing zone were analyzed in detail using a combination of computational fluid dynamics simulation and downhole measurements by establishing a highly simulated 3D solid model of the 2302 fully mechanized mining face at the Xinqiao coal mine. The study's findings reveal that dust from advanced support and coal-cutting processes converge within 20-60 m of the coal mining region, generating a high-concentration pollution zone at the height of the sidewalk breathing zone. The particle size of dust in the breathing zone is primarily concentrated between 1 and 40 μm, and the fully mechanized mining face is split into a rapid settling area, a medium settling area, and a slow settling area based on particle size settling speed. Eddy currents in the return airway lead to an increase in dust particles of 20-40 μm in the breathing zone area. The results of the study can provide a theoretical basis for dust management at the fully mechanized mining face for the breathing zone area.

Bending performance of Y-shaped joints of subway station built by enlarging two parallel shield tunnels

Based on the characteristics of the Y-shaped joint of a subway station built by enlarging two parallel shield tunnels, a bending mechanical model of the segmental joint was proposed. The model was used to characterize the cracking and crushing of concrete, the yielding of the bolt, and the damage of the segmental joint. Theoretical equations were derived for the bending stiffness of the joint under various forms of joint opening. Bending experiments were conducted on full-scale models of the joints under different structural configurations. The results demonstrated that the nonlinear properties of the joint structure were evident under loading and that the bending stiffness of the joint initially increased and then decreased. The computed values were in good agreement with the experimental results for the pre-embedded connector joint when lc was 0.5 times the height of the compression zone, where lc was the effect depth of the compressive deformation of the outer edge of the concrete. The axial force had a great influence on the bending stiffness. The mechanical performance of the joint was influenced not only by the change in the stress–strain curve of the concrete from the rising stage to the descending stage but also by the structural morphology of the rotational angle of the joint.

Maternal-fetal safety evaluation of an aqueous extract of Casearia sylvestris leaves in rats.

This study evaluated the maternal, embryotoxic, and teratogenic effects of the aqueous extract of Casearia sylvestris (AECS), a species listed in the Unique Health System of Brazil, and widely used for treating several conditions, such as diarrhea, wounds, pain, and ulcers. Pregnant rats were daily treated orally with 0, 175, 350, or 700 mg/kg/body weight of AECS, from gestational day (GD) 6 to 15 (organogenesis period). On GD 20, the pregnant rats were euthanized, and the litters submitted to an assessment of fetal development. No clinical signs of toxicity were observed in the dams during the treatment. In the embryo-fetal development study, a significant increase in the basal zone height of the placenta was observed in the intermediate dose group. Furthermore, there was a significant increase in the relative anogenital distance measurement of female fetuses in the lowest and intermediate dose groups. Although no visceral abnormalities were observed in the treated-fetuses, skeletal anomalies evidenced by changes in the ossification of the sternum and the presence of supernumerary ribs were found in the intermediate and high dose groups. In conclusion, the treatment with AECS during organogenesis at this dose level had detrimental effects on the normal development of fetuses.

Domination and effect of multi-parameters in direct chill casting based on establishment of thermo model by numerical simulation and experiment

In this paper, a mathematical model validated by in-situ temperature measurement data of the direct chill (DC) casting process has been established in order to study the domination and effect of multi-parameters including secondary cooling water flow rate (Q), casting speed (V), condition of primary cooling, and spraying water temperature (Tw) on DC casting index of sump depth (dsump), maximum and minimum temperature gradient (Tg,max and Tg,min) at mushy zone and shape of solidus line. Further, the height of impingement zone (Hip) is systematic quantitative analysis by a novel designed test (Hip=1.08865Q`+0.06272V−4.75597). The calculated temperature using the numerical simulation exhibits a good match with the actual temperature measurement data. The results of multi-factors on index by the designed orthogonal test indicate that V dominates the dsump (dsump=0.033+27.74V) and Tg,min (Tg,min=2569.15−766342.20V) at mushy zone, Q dominates the Tg,max (Tg,max=9195.12+2344770Q−27.83Tw) by analysing the range (R), variance (S) and significance (F). Likewise, by discussing the combination of R, S, F and microstructure observation, the priority influencing the shape of solidus line at center part was V. The Q dominates the shape of solidus line at the position between the center and edge part.

Research on the Distribution of Overlying Rock Fractures Caused by Mining in Ultra-Thick Coal Seams and Its Impact on the Near-Surface Aquifer

Near-surface water is the foundation for maintaining the ecological environment, and coal remains an important energy source in today’s world as we face a shortage of green energy. Achieving near-surface-water protection while safely mining coal is an important way to ensure social and ecological health and sustainability. The key lies in whether the fracture height of the mining overlying strata affects the aquifer. This article compiles the coupling finite element and discrete element method (CFE-DEM) and established mechanical constitutive models such as the interaction between rock blocks on both sides of the penetrated fracture, rock mass fracture process, and the plastic deformation law of rocks based on the results of mining-induced overlying rock failure. On this basis, a numerical calculation model is established based on the engineering geological conditions of the Beixinyao Coal Mine. The numerical simulation results indicate that the theory and the CFE-DEM method can numerically simulate the distribution and evolution of mining-induced overlying rock fractures. The water-conducting fractures in the overlying strata of extra-thick coal seams extend to the front of the working face in a trapezoidal shape, and the angle formed between them and the advancing direction ranges from 62° to 75°. Combined with the in situ measurement results, the height of the water-conducting fracture zone of the extra-thick coal seam is between 209 m and 230 m; the fractures were not found to have affected the aquifer at a vertical distance of 252 m from the coal seam. This means that the impact of ultra-thick coal seam mining on the aquifer is very limited. The research is of great significance for ensuring coal mining and surface ecological sustainability in ultra-thick coal seam areas.

Optimization of design parameters of the vibration protection system of a motor grader seat with quasi-zero stiffness

BACKGROUND: Vibrations occurring during operation of land transport-technological machines deteriorate the quality of control, reduce the productivity of the work performed, adversely affect the health of machine operators. In order to reduce the impact of vibrations on the operators, vibration protection systems of the cab and seat are used.&#x0D; AIMS: For practical application of the developed design of the passive vibration protection system of the motor grader operators seat on the basis of a parallelogram mechanism, tensile spring, cable and rollers, it is necessary to develop an algorithm for optimizing the values of design parameters.&#x0D; METHODS: The mean square value of seat acceleration in a stationary reference frame, determined as a result of simulation of the motor grader motion over a set of stochastic microprofiles of the support surface with various characteristics and velocities, was used as an optimization criterion. Comprehensive simulation mathematical model of a motor grader with cabin vibration protection supports and vibration protection system of a seat was used. All parameters of the optimization algorithm and model were divided into fixed, random and varying ones. The latter include a number of dimensions of the parallelogram mechanism of the seat vibration protection system, the coefficient of viscous friction of the mechanisms shock absorber, the height of the quasi-zero stiffness zone. The dependence of the criterion on the design parameters of the seat vibration protection mechanism, which has an implicit pattern and is determined by means of a simulation mathematical model, served as the target function. Boundary conditions were imposed on a number of parameters to ensure the operability of the mechanism, manufacturability of its parts as well as ergonomic considerations. Optimization of the values of the varying parameters was performed with the simplex method. At the same time, a part of the parameters unambiguously influencing the value of the target function was preliminarily maximized or minimized within the boundary ranges.&#x0D; RESULTS: An algorithm for assignment and optimization of design parameters of the vibration protection system of a motor grader seat with quasi-zero stiffness is developed, one of the key features of which is the possibility to adjust the vibration protection system of the seat to the weight of the current operator. Examples of algorithm application are given.&#x0D; CONCLUSIONS: The algorithm makes it possible to determine the optimal values of design parameters of the seat vibration protection system based on a parallelogram mechanism such as: the dimensions of the parallelogram mechanism, including the attachment points of rollers and cable, the coefficient of tensile spring stiffness, the coefficient of viscous friction of a shock absorber, the parameter of adjusting the mechanism to the weight of the current operator. The key feature of the developed vibration protection system and the optimization algorithm of its design parameters is the possibility of adjustment to the weight of the current operator.

An estimation of gas volume in the water-saturated part of Cenomanian gas reservoirs: a case study of the Medvezhye oil and gas condensate field

The amount of remaining recoverable natural gas reserves is affected by the pinching of gas reserves by infiltrating water and degassing of formation water in the Cenomanian water-pressure complex. It is necessary to reliably determine the volume of gas-saturated water in order to estimate the volume of gas dissolved in produced water. The area of the gas-oil contact is determined by known methods, but the height of the reservoir zone, represented by gas-saturated water (transition zone), must be specified.The fluid distribution and the structure of the transition zone depend on gravitational and capillary forces. These forces depend on the physical and chemical properties of the gas and formation water, as well as the composition and filtration properties of the reservoir. To calculate the thickness of the reservoir in which the process of gas dissolution in water takes place, it is proposed to consider it from the point of view of molecular diffusion processes.The authors of the article propose an adapted VNIIGAZ method for determining the transition zone and the volume of water in which gas from underground gas storages is dissolved (a case study of the Medvezhye oil and gas condensate field). The proposed method for calculating the volume of gas dissolved in formation waters of Cenomanian gas deposits, taking into account diffusion, showed an acceptable result. The proposed method for calculating the volume of gas dissolved in formation waters of Cenomanian gas deposits, taking into account diffusion, gave an acceptable result.