Condensate Field Research Articles

HYDRODYNAMIC STUDIES OF WELL 32 OF THE SOUTHERN SECTION IN THE CHINAREVSKOYE FIELD OF THE WEST KAZAKHSTAN REGION

The paper analyzes the factors influencing the development of high-quality and cost-effective oil and gas reserves in the region (assessment, design). In order to operate wells, directions for calculating the size of reserves have been found. The scientific and technical trends of their (wells) development are considered. A comprehensive analysis of complex surveys was carried out at well No32 of the Chinarevskoye oil and gas condensate field, located in the southern section of the region. Hydrodynamic studies were carried out by interpreting the pressure recovery curve (PRC) to determine reservoir pressure, reservoir properties and the state of the bottomhole zone. These studies confirmed the low porosity properties of the reservoir: permeability - 0.004 mkm2 , conductivity - 0.056 mkm2 *m, hydraulic conductivity - 0.055 mkm2 *m/MPa*s. The skin factor varied in the range from - 0.92 to 18.4, which indicates a deterioration in the state of the bottomhole formation zone. Reservoir pressure dynamics (reduced to WOC) according to hydrodynamic studies showed that in the deposit, as the reservoir is withdrawn, there is a decrease in reservoir pressure. As of October 2019, according to the pressure build-up data, the formation pressure in well 32 (at the VNK level) is 38 MPa. Well 32 during the analyzed period (5 months) worked in three modes (from July to September 2019 with a washer with a diameter of 6 mm, from the end of September with a washer with a diameter of 8 mm, in October - 10 mm). At the same time, with an increase in the washer diameter to 8 and 10 mm, the downhole working pressure sharply decreased from 25 to 11 MPa and the static bottomhole pressure from 37.5 to 29.7 MPa. During the analyzed period, the well worked with a bottomhole pressure below the saturation pressure of oil with gas. The average gas-oil ratio was 757 m3/m3.

飽和蒸気と空気の混合気体の流れにおける温度と蒸気質量分率の分布

Wall functions are generally used in a numerical simulation of turbulent flows with computational fluid dynamics (CFD) codes. The logarithmic law is widely adopted for the wall functions, but its validity has not been confirmed for dimensionless profiles of temperature and steam mass fraction in condensation fields due to lack of data. In this study, we evaluated dimensionless profiles of temperature and steam mass fraction in flows of saturated steam and air mixtures in a vertical pipe with the diameter of 49.5 mm. The local Nusselt number Nuy and Sherwood number Shy (which were proposed in our previous study) were used for defining the dimensionless temperature T+ and steam mass fraction Ys+, respectively, because physical properties in computation cells in contact with the condensation surface are generally used in a CFD analysis. The T+ and Ys+ values obtained from the measured temperature profiles were smaller than the existing logarithmic law due to condensation in the turbulent boundary layer (i.e. mist generation), and correlations for T+ and Ys+ were obtained by using the least square method. The standard deviation of the correlations were 3.8 % and 0.75 ℃ for the steam mass fraction of Xs = 0.05-0.63 and the mixture temperature of Tg = 63-97 ℃, respectively.

Development of a hydrocarbon completion system for wells with low bottomhole temperatures for conditions of oil and gas fields in Eastern Siberia

The paper presents the results of investigations on the influence of low bottomhole temperatures in the intervals of productive formations on the technological properties of solutions used for drilling and completion of wells in order to determine the possibility of increasing gas recovery coefficient at the field of the “Sila Sibiri” gas pipeline. The analysis of technological measures determining the quality of the productive horizon drilling-in was carried out. It was found out that the dispersion of bridging agent in the composition of the hydrocarbon-based drilling mud selected from the existing methods does not have significant influence on the change in the depth of filtrate penetration into the formation in conditions of low bottomhole temperatures. The main reason for the decrease in the near-bottomhole zone permeability was found out – the increase in plastic viscosity of the dispersion medium of the hydrocarbon-based drilling mud under the influence of low bottomhole temperatures. A destructor solution for efficient wellbore cleaning from hydrocarbon-based solution components in conditions of low bottomhole temperatures was developed. The paper presents the results of laboratory investigations of hydrocarbon-based drilling mud and the developed destructor solution, as well as its pilot field tests. The mechanism of interaction between the destructor solution and the filter cake of the hydrocarbon-based drilling mud ensuring the reduction of the skin factor in the conditions of the geological and hydrodynamic structure of Botuobinsky, Khamakinsky and Talakhsky horizons of the Chayandinskoye oil and gas condensate field has been scientifically substantiated.

The relationship of the oil and gas fields of the Forecarpathian region with the regional faults system and deep structure

The oil and gas fields of Forecarpathian oil and gas region are compared with the structure of earth’s crust and regional faults. Most of the oil and gas condensate fields are localized in Borislav-Pokutia nappe over Precarpathian Fault zone. The majority of gas fields are located in under thrusting zone of the Sambir fault, which is a gently dipping detachment connected with the Forecarpathian fault and other faults of autochthonous basement. The regional gravity low of Carpathian Foredeep is also limited from northeast by the Sambir fault and from the southwest by the Uzhok fault. The Forecarpathian fault tends to the central part of gravity low. Transverse Tyachev-Nadvorna fault displaces the gravity low and delimits the oil and gas condensate fields. Velocity model along the wide-angle reflection and refraction PANCAKE profile shows a deep (25 km) sedimentary trough under the Carpathian Orogen. The Forecarpathian fault coincides with a jump of the Moho under the trough. Along the RomUkrSeis profile under Carpathian Orogen there were revealed a sedimentary trough as deep as 15 km and a low-velocity domain under the trough. From northeast, the trough is limited by the Forecarpathian fault, which goes up to the keel structure of the Moho discontinuity. Structure of the trough under Carpathian Orogen reflects development of East European Platform margin. The earliest stage of the formation of Baltica paleocontinent passive margin is seen in the structure of the trough’s lower part. Autochthonous basement under Borislav-Pokutsky and Skiba nappes includes a Riphean Massif limited by the Krakovets, Forecarpathian and Uzhok faults. The oil and gas condensate fields are located above the Riphean Massif.
 The purpose of this article is to analyze the fault system and the structure of the earth’s crust in the Forecarpathian oil and gas region, as well as their relationship with the distribution of oil and gas deposits, taking into account new WARR profiles and other geological and geophysical data.

Specific features of the multiphase fluid subsea pipeline operation at the liquid accumulation mode

The operation modes of an extensional subsea pipeline of multiphase fluid at the initial stage of the offshore gas condensate field development under the conditions of liquid accumulation are studied. By means of the dynamic simulation of the slug flow mode, the frequency and volume of liquid plugs removed from the pipeline are analyzed as a function of the gas flow rate. It is demonstrated that with a decrease of the gas flow rate, the steadystate hydraulic calculations predict significantly lower values of the liquid volume flow rate at the pipeline outlet compared to the results of the dynamic simulation. The dynamics of the liquid removal from the pipeline with an increase of the gas flow rate is studied. It is shown that the surge liquid volume increases sharply at a rapid growth of the gas flow rate, which leads to restrictions on the increase in the well flow rate. Keywords: subsea pipeline; natural gas; multiphase fluid; liquid accumulation; slug flow.

Increasing hydrocarbon recovery of Hadiach field by means of CO2 injection as a part of the decarbonization process of the energy sector in Ukraine

Purpose is studying the efficiency of a carbon dioxide injection technology to control a water flooding process of the reservoir of the horizon V-16 of Hadiach oil and gas condensate field and displace the residual gas reserves trapped by the formation water involving numerical modelling. Methods. A technology of carbon dioxide injection into the reservoir of the horizon V-16 of Hadiach oil and gas condensate field was tested in terms of numerical reservoir model with the use of basic modelling instruments. Findings. The modelling results makes it possible to calculate the main technological indices of the development of the reservoir of the horizon V-16 of Hadiach oil and gas condensate field in terms of carbon dioxide injection and while developing for depletion. According to the results of the performed calculations, it is identified that there is considerable influence of the number of injection wells on the efficiency of the analyzed technology as for control of a water flooding process in the productive formation. It should be noted that while increasing the number of injection wells, more complete coverage of the gas-bearing area with carbon dioxide is provided; owing to that, the efficiency of blocking the formation water inflow into the production wells turns to be much higher. The implementation of the technology under study makes it possible to increase the final hydrocarbon recovery factors. In case of using wells ## 52, 101, 201, 202 for carbon dioxide injection, the highest final hydrocarbon recovery factors are provided. The predictive gas recovery factor grows by 2.95% and the condensate recovery factor increases by 1.24% comparing to the field development for depletion. Originality. Basing on the research results, technological efficiency of the implementation of a carbon dioxide injection technology in terms of the reservoir of the horizon V-16of Hadiach oil and gas condensate field is determined; that is aimed at increasing the hydrocarbon recovery within the field by controlling a water flooding process in the productive formations and production wells. Practical implications. Application of the research results helps improve the current system of the development of productive formations of Hadiach oil and gas condensate field in terms of water drive. Implementation of such technologies stipulates the increase in final hydrocarbon recovery of the depleted fields and allows developing optimal ways of utilization of technogenic carbon dioxide in terms of the whole decarbonization process of the energy sector in Ukraine.

Automation of the storage of operational information of the collector-beam system for collecting products for its control

Within the framework of this work, a model for storing operational information of a collector-beam system for collecting products from the Orenburg gas condensate field for its management is proposed. A feature of the proposed model is its presentation as a graphic-dynamic system with the ability to store the performance characteristics of the wells included in it, and the history of upgrades of the main structural elements. The use of a single model to describe the operational information of various acquisition systems allows minimizing the likelihood of errors in operational data due to the limitations defined by the model and increasing the speed of their processing. All of the above implements the possibility of synthesizing effective management decisions in the operation of gathering systems, the consequence of which is to extend the life of the field and minimize operating costs. Also, the proposed model can be used in the implementation of a decision support system for collector-beam systems for collecting products.

Обоснование альтернативной конструкции скважин (на примере Среднеботуобинского нефтегазоконденсатного месторождения)

The circulation loss in well construction is one of the most frequent troubles at the Srednebotuobinsky oil and gas condensate field (SBOGCF). Such problems occur in the two basic intervals of the geological section, trapp intrusion and the Botuobinsky productive horizon. The intervals of salts, endogenic fracturing spread in the intrusive sheet, and gas-bearing collectors with abnormally high formation pressure, available in the SBOGCF, are currently considered incompatible drilling conditions. The emergency time, spent for fighting these issues within the trap intrusion interval, may reach 42 days per well. However, the loss of working time is not the only trouble; costs of drill fluids and cement grouts as well as of concomitant emergencies (striking of the drill column bottom arrangements) result in the increasing costs of well construction as well as to the lost advantage due to the late launching of the well. One of the ways to decrease the well construction cycle is reconsidering the existing design and adapting a brand new approach to drilling and well construction, which would permit to use the alternative well design for solving the abovementioned problems.

ON THE ANALYSİS OF OPERATİNG PRACTİCES OF LİQUEFİED GAS PİPELİNES

ON THE ANALYSİS OF OPERATİNG PRACTİCES OF LİQUEFİED GAS PİPELİNES

ABOUT SKIN EFFECTS OF OBLITERATION AND COMPRESSION

There should be factual information on the skin-effect on each well that reduces oil and gas production for operational work, as well as for the calculation of oil and gas deposits or for the design of field development. Well development and operation experience shows that contamination of the bottomhole zone and deterioration of leakage properties may be associated not only with collution, but also with events such as obliteration and rock compaction. Thus, during the operation of wells, events such as shrinkage and retention of microcatches and capillaries in fractured-porous formations over time are inevitable. The impact of this factor must also be taken into account, as the method of impact on the bottomhole zone and the compression of formations under the influence of overburden pressure. Such events should be attributed to the factors that increase the resistance of the bottomhole zone and should be studied as an object of research. The discovery of deep hydrocarbon deposits and their development experience show that failure to take into account the deformation of the porous medium as a result of a drop in formation pressure during development reduces the reliability of development parameters. The commissioning of deeper oil, gas and gas condensate fields requires the interpretation of mining data and the development of methods for hydrodynamic research of wells, taking into account the density of layers. Compression of stratified formations with significant deformation during development and the impact of this effect on the development process significantly improves the theory of filtration, taking into account the compression of formations in gas-hydrodynamic modeling, interpretation of mining data and other issues. In order to study and assess the skin effect associated with obliteration and compression, it is necessary to analyze real well data during the operation of productive oil layers. Three of them used the concepts of "normal" production, productivity, as well as the lowest production and productivity of the oil well in operation, and analyzed the performance of the well for several years. This analysis is based on the fact that production changes from depression to exponential law. The article puts forward a version of the existence of obliteration and compression skin effects along with colmatation in a practical example, and a methodology has been developed and tested to determine them. It has been found that during real depressions for collectors, these skin effects (So-c) may be greater than the colmatation skin effect (Scol). However, in practice, the value of the Scol is not accurately determined by one measurement based on the pressure build-up curve. The skin effect of obliteration and compression (So-c) is simply often negligible. In order to assess the skin-effect of colmotion and obliteration-compression in the reduction of well production, calculations were made at the values of the contour radius Rk = 150 m and well radius rq = 0.1 m. As a result, it was determined that the production of wells can be reduced by 64% due to the obliteration-compression effect. This is about 10 times more than skin effect of colmotation. It was determined that the skin-effect of obliteration and compression had a greater effect on productivity should be taken into consideration when forecasting well production. Keywords: obliteration, skin effect, collector, productivity, production, pressure

Construction of a gas condensate field development model

Abstract This article has developed and verified a mathematical aggregated approximate model of developing a gas condensate field using a cyclic process. The essence of the cyclic process is to pump the drained gas into the productive formation to reduce the pressure drop into the deposit. This process allows for increased condensate recovery in the future. The model discussed in this article is a continuous dynamic system with control parameters. It is a modification of the dynamic aggregated model of a purely gas field, designed for planning for a sufficiently long period with limited information about the state of the reservoir (the initial flow rate of wells, the initial recoverable gas reserves, the initial reservoir pressure, the dependence of potential condensate content per unit volume of fatty gas on the reservoir pressure). A non-standard approach underlies the model construction. Logical simplifications and a priori assumptions about the processes occurring in the field during its development are at its core. The instruments in the model are the increase in production and injection wells and the proportion of injection wells involved in the production. The purpose of the article is to calculate various variants of the dynamics of the fundamental indicators of the development of a gas condensate field for a sufficiently long-term period at the stage of preliminary design.

ADJUSTMENT OF THRUSTING STRUCTURE IN THE KOVYKTA-KHANDINSKAYA REFLECTED FOLDING ZONE

The Kovykta-Khandinskaya zone, which includes the Kovykta gas condensate field, is a giant located in the junction zone of the Angara-Lena stage with the craton edge – the Cis-Baikal trough. Here, according to the results of long-term geological exploration, the Verkhnelenskoe uplift was identified, the northern part of which is reflected on tectonic maps as the Kovykta ledge. At the same time, the geological model of the field today is based on the standard two-member model, which includes a slightly disturbed sedimentary cover and basement. However, new geophysical studies revealed that the sedimentary cover of the eastern part of the zone is intensely deformed and has a two-tiered nodular-thrust structure (the lower layer is autochthon, the upper layer is allochthon). The main object for gas exploration within the Kovykta gas condensate field is the Vendian formation. The middle (halogen-carbonate) section has been studied fragmentarily, mainly as an object of geological geohazards when drilling deep wells. The involvement of new data from 3D seismic and 3D transient electromagnetic methods made it possible to clarify the Kovykta gas condensate field tectonic structure to assess the potential of secondary carbonate reservoirs characterized by intense fluid (natural gas, brines) inflows.

Gas reserves calculation based on the results of reservoir pressure distribution modeling

The object of this study is the gas-bearing layer B-26 of the Zakhidne-Radchenkivsʹke gas condensate field (Ukraine). A bottleneck in the process of exploration and experimental and industrial operation of the Zakhidne-Radchenkivsʹke gas condensate field was the ambiguous data on extractive reserves (values that were calculated by different authors range from 14 thousand to 424 million m3). At present, the field is mothballed, which is why the use of a new approach to calculating the initial gas reserves could be useful for deciding to start developing a single productive layer B-26. During the study, such theoretical research methods were used as the system analysis of the information used, numerical modeling based on the combined finite-element-difference method, the methods of visual representation of the information received, as well as analytical methods. The method of calculating gas reserves proposed in this work combines a volumetric method and the simulation of filtration processes using a combined finite-element-difference method. The latter makes it possible to take into consideration the structure of the reservoir, which is heterogeneous in terms of permeability, and to adequately, at the quantitative level, to describe the distribution of non-stationary reservoir pressure around the extractive well. By applying an analytical formula based on the values of average reservoir and downhole pressures, the radii of the well's feed circuit at different stages of the reservoir development have been calculated. Thus, the active area (and volume) of the reservoir can be determined, according to which the extractive reserves of the deposit are calculated. The mining reserves of the Zakhidne-Radchenkivsʹke field, estimated in this way, amount to 174 million m3 of gas. The method for calculating reserves proposed in this study could prove useful for deciding on the further development of the Zakhidne-Radchenkivsʹke gas condensate field. Combining the volumetric method with the results of modeling filtration processes is an operational method for calculating the reserves of the reservoir, opened by one mining well. In this case, the application of the combined finite-element-difference method makes it possible to take into consideration the complex heterogeneous structure of the reservoir and predict the distribution of reservoir nonstationary pressures around the extractive well. The current study that used the Zakhidne-Radchenkivsʹke gas condensate field in Ukraine as an example is interesting when calculating the reserves of layers of complex structure all over the world, whereby the productive reservoir is opened by a single mining well.

Inhomogeneities in the two-flavor chiral Gross-Neveu model

We investigate the finite-temperature and -density chiral Gross-Neveu model with an axial U$_A$(1) symmetry in $1+1$ dimensions on the lattice. In the limit where the number of flavors $N_\mathrm{f}$ tends to infinity the continuum model has been solved analytically and shows two phases: a symmetric high-temperature phase with a vanishing condensate and a low-temperature phase in which the complex condensate forms a chiral spiral which breaks translation invariance. In the lattice simulations we employ chiral SLAC fermions with exact axial symmetry. Similarly to $N_\mathrm{f}\to\infty$, we find for $8$ flavors, where quantum and thermal fluctuations are suppressed, two distinct regimes in the $(T,\mu)$ phase diagram, characterized by qualitatively different behavior of the two-point functions of the condensate fields. More surprisingly, at $N_\mathrm{f}=2$, where fluctuations are no longer suppressed, the model still behaves similarly to the $N_\mathrm{f}\to\infty$ model and we conclude that the chiral spiral leaves its footprints even on systems with a small number of flavors. For example, at low temperature the two-point functions are still dominated by chiral spirals with pitches proportional to the inverse chemical potential, although in contrast to large-$N_\mathrm{f}$ their amplitudes decrease with distance. We argue that these results should not be interpreted as the spontaneous breaking of a continuous symmetry, which is forbidden in two dimensions. Finally, using Dyson-Schwinger equations we calculate the decay of the U$_A$(1)-invariant fermion four-point function in search for a BKT phase at zero temperature.

On the questions of supply of active gas raw materials in central Yakutia

The article deals with the problem of the reliability of the balance gas reserves of the Vilyui oil and gas region calculated by the volumetric method. Based on the analysis of the development of gas and gas condensate fields of the Predverkhoyansk and Vilyui oil and gas bearing regions, the low production capabilities of the depleted fields of the region are shown. It is concluded that the most reliable in the conditions of a complex geological structure of deposits is the assessment of gas reserves by the pressure drop method. The idea is formulated that for the fields of the Vilyui oil and gas bearing area, which have productive horizons with low initial gas saturation of reservoirs, the final gas recovery factors can be estimated at 0.55. The expediency of considering the issue of the special status of the Srednevilyui gas condensate field as a field with strategic gas reserves is noted.

Modelling the Development of the Achimov Natural Gas Deposits

Currently, the Russian Federation is one of the largest natural gas producers in the world, second only to the United States in production. The world’s largest proven gas reserves are located in Russia. Despite the colossal initial volumes of gas, many unique Russian fields have been operating in a declining production mode for a long time (for many years) and are steadily approaching the transition to the mode of fields with low-pressure gas, which is currently economically unprofitable to compress for supply to main gas pipelines for transportation to consumers. New gas and oil and gas condensate fields of the Russian Federation are located in new undeveloped regions of Russia. These areas are distinguished by a harsh climate, lack of transport infrastructure, are located far from existing gas pipelines and are characterized, as a rule, by a complex geological structure and multicomponent gas composition, which inevitably entails a further increase in the already considerable capital and operating costs, time lag, which, accordingly, reduces economic attractiveness of their development for gas producers. In this regard, additional exploration and production of gas from the Achimov deposit - formations lying below the developed Valanginian deposits of large gas fields, close to the transition to closure, is of great interest. The production of gas from the Achimov deposit at fields with a built infrastructure, where there is a connection to the main gas pipelines, can significantly reduce costs - both production and capital. The article is devoted to the issues of modelling gas production of the Achimov deposit.

Forecasting Formation Losses of Hydrocarbons in the Process of Development of Oil and Gas Condensate Deposits

One of the important tasks in forecasting and monitoring the development of oil and gas condensate fields is taking into account the current losses of condensate in the reservoir. In this case, it is necessary to use several versions of models that differ in the formation of parameters and thermodynamic properties of hydrocarbon phases. Models are considered in which either the liquid phase dissolves in the gas phase, or it is assumed that heavy fractions are absent in the gas phase. Models of this type are used more often when predicting the development of deposits in the natural depletion mode. Experimental and computational models of equilibrium phase transitions make it possible to improve the prediction of condensate losses in the reservoir. The complexity and laboriousness of the PVT experiment, along with the introduction of new technologies, create a lack of information on the thermodynamic properties of hydrocarbon systems. In order to take into account reservoir losses of hydrocarbons for the development conditions of the Vostochno-Urengoyskoye field, the forecast of the balance of condensate production for the current and final periods of operation was carried out. The model considered in the work allows for adjusting the forecast indicators of condensate production at the current moment of reservoir operation [1,2,3].

Calculation of the Optimal Gas Flow Rate Under Conditions of Sand Plug Formation

The development and operation of gas and gas condensate fields in Western Siberia is associated with a number of serious problems associated with the aging of the fields. One of these problems is the formation of sand plugs at the bottom of the well, which leads to a halt in production and the need for repairs. To solve this problem, it is necessary to correctly calculate the optimal well flow rate, taking into account the filtration resistance and pressure losses along the wellbore. The construction of an adequate mathematical model of fluid filtration in the conditions of sand plug formation will make it possible to correctly regulate the flow rate of the well and avoid complications in its operation.

Estimation of the Influence of Oil Flows on the Formation Losses of Condensate During the Development of Multi-Layer Deposits

During the development of multilayer oil and gas condensate fields, the production of condensate is influenced by the associated oil. Analysis of field data showed that the cause of oil flows is the outstripping decrease in reservoir pressure in the gas condensate section in comparison with oil zones. Thus, incoming heavy oil fractions into a gas condensate reservoir have a negative impact on reservoir losses of hydrocarbons, including the final condensate recovery factor. Many years of experience in the development of such fields showed that the bulk of the presence of associated oil in well production is explained by the following reasons: the relationship between the reservoirs through lithological windows, the residual oil saturation of the reservoirs, and the presence of lenticular layers. Determination of the quantitative content of oil in the reservoir mixture was determined by infrared spectrometry using a Perkin-Elmer Fourier transform spectrometer, which makes it possible to assess changes in the component composition of gas condensate systems. In the course of the research, selected samples of the gas and liquid phases were analyzed directly from the production facilities of the development. The analysis of IR spectrometry showed that in most of the samples of gas condensates, the effect of displacement is recorded, which is characteristic of fluids with the manifestation of oil impurities.The purpose of these studies is to study the influence of the produced oil on the dynamics of hydrocarbon production and the final condensate recovery factor.

Localization of oil and gas deposits depending on the types of new structures on the territory of the West Siberian plate

The division of deposits by types of hydrocarbons on the territory of the West Siberian Plate allowed us to identify three areas: Yamalo-Gydan, where gas and gas condensate fields are concentrated, Nadym-Taz with a mixed type of deposits and the Latitudinal Ob region, where oil fields predominate. These areas are confined to certain neotectonics areas. Comparison of the location of hydrocarbon deposits with the latest structures allowed us to establish signs of their localization both within each of the regions and in general for the territory of the West Siberian Plate. It is recorded that oil and gas fields are confined mainly to the areas of the newest regional inherited depressions, faults with a shear component of the northwestern and northeastern strike, areas with high (66–100%) and low (0–33%) lineament density, depressions-valleys separating the newest regional and local structures and the boundaries of local uplifts and depressions.