Final Recovery Research Articles

Huff and Puff by Flue Gas for Tight Oil Recovery to Achieve Sustainable Energy Future

Due to its distribution and reserve characteristics, tight oil has become one of the main targets for future oil and gas exploration. The use of waste flue gas for oil displacement can not only reduce carbon emissions but also enhance oil recovery, which is a technology with great prospects nowadays. In this paper, the pore structure of the tight reservoir core was first characterized by scanning electron microscopy and casting thin section test. Based on these foundations, the displacement experiment was carried out on the tight oil recovery modelling platform, and the pressure distribution and recovery percent of reserves by flue gas huff and puff were innovatively characterized. Study shows that the formation pressure can be maintained in a good level by this technology and the final recovery can be improved a lot than depletion exploitation method. Therefore, the flue gas huff and puff is an effective and advanced technology for tight oil recovery. In the end, specific suggestions are also provided concerning future studies on the field application of flue gas flooding for enhanced oil recovery.

The Impact of Froth Launders Design in an Industrial Flotation Bank Using Novel Metallurgical and Hydrodynamic Models

In flotation cells, especially in large flotation units, froth management is a crucial variable that should be considered during the design phase or optimized to improve the performance of existing flotation circuits. This paper presents a simulation evaluation of the effect of launder design on the metallurgical performance of an industrial flotation circuit consisting of five TankCell® e630 (630 m3) cells in a Cu rougher duty. This analysis was carried out using a new industrial simulator that includes novel metallurgical and hydrodynamic models, developed from a wide database collected from many industrial concentrators. This tool is currently incorporated into HSC Chemistry® software and allows evaluating the effect of launder design on mineral froth recovery, water recovery, entrainment, and other variables. The industrial flotation circuit was evaluated under different launder design scenarios, considering an actual flotation circuit that includes TankCell® e630 cells for calibration and as a reference (baseline). Firstly, two different designs were evaluated in the full circuit: a standard launder design and a new launder technology. It was found that the new launder technology enabled improvement of the mineral recovery along the circuit, mainly for coarse particles, due to the improvement in froth mineral recovery. Next, a partial upgrade of the launder design along the circuit was analysed. Thus, the new launder technology was evaluated in the first and the last two cells of the bank. The results showed that upgrading the launders in different cells along the circuit delivered an increase in the final recovery with respect to the baseline, with a partial impact on the concentrate grade. However, these changes are less than those when evaluating the full upgrade scenario. A partial launder upgrade either in the first or last two cells of the bank showed similar final recoveries, but the latter enabled a slightly higher concentrate grade (about 1% higher) to be achieved. Finally, the evaluation of launder design using the industrial simulator made it possible to estimate its effect on variables that are not commonly obtained from plant surveys, including superficial gas rates at the froth surface level, froth recovery per particle size, collection recovery per particle size and liberation, gangue entrainment, and bubble loading grade.

Technology for increasing the oil recovery factor by reservoir stimulation by thermochemical methods

Background: In the presented article, a composition is proposed that leads to the intensification and increase in oil production with an increase in temperature in the reservoir, as well as in the bottomhole zone.
 Aim: To study the improvement of methods for influencing deposits and bottom-hole zones of both production and injection wells, which allow completely displacing oil from the reservoir, as well as increasing oil production in general, thereby contributing to an increase in the final oil recovery factor of the reservoirs.
 Materials and methods: Based on laboratory studies, a new technology has been developed and a composition has been proposed, which includes a strong oxidizing agent, lower alcohols and trihydric alcohol, surfactants, etc.
 Results: The composition proposed for influencing the reservoir acts as follows: when the components of the composition interact, an exothermic reaction occurs, as a result of which a large amount of heat and gas is released in the bottomhole zone. Due to the released heat, heavy oil components are melted, deposited on the pore channels of the rock near the bottomhole zone and worsening the permeability of the bottomhole rock zone and reservoir injectivity. As a result of the impact of the composition, the permeability of the bottomhole zone and the injectivity of the injection well increase. Such an impact is also effective in that there is no loss of generated heat as a result of the exothermic reaction, and it directly affects the restoration of the permeability of the bottomhole formation zone and improves the rheological properties of oil.
 Conclusion: Conducted experiments have shown that, due to the effect of the proposed composition on clay rocks, clays do not swell, but, on the contrary, hydrophobization of the rock surface occurs due to clay compression, which prevents the subsequent negative impact of water on clay rocks. The reason for this incident is the acidic nature of the proposed composition. These properties of the proposed composition are a guarantee that its use in any formations (sandy, clayey, carbonate, dolomites, etc.) will be effective. Key words: bottomhole formation zone, permeability, strong oxidizing agent, lower alcohols, trihydric alcohol, surfactants.

Feasibility and Mechanism of Deep Heavy Oil Recovery by CO2-Energized Fracturing Following N2 Stimulation

There are large, heavy oil reserves in Block X of the Xinjiang oilfields, China. Due to its large burial depth (1300 m) and low permeability (26.0 mD), the traditional steam-injection technology cannot be used to obtain effective development benefits. This paper conducts experimental and simulation research on the feasibility and mechanism of CO2-energized fracturing of horizontal wells and N2 foam huff-n-puff in deep heavy oil reservoirs with low permeability in order to further explore the appropriate production technology. The foaming volume of the foaming agent at different concentrations and the oil displacement effect of N2 foam at different gas/liquid ratios were compared by the experiments. The results show that a high concentration of foaming agent mixed with crude oil is more conducive to increasing the foaming volume and extending the half-life, and the best foaming agent concentration is 3.0∼4.0%. The 2D micro-scale visualization experiment results show that N2 foam has a good selective blocking effect, which increases the sweep area. The number of bubbles per unit area increases as the gas/liquid ratio increases, with 3.0∼5.0 being the optimal gas/liquid ratio. Numerical simulation results show that, when CO2-energized fracturing technology takes into account the advantages of fracturing and crude oil viscosity reduction by CO2 dissolution, the phased oil recovery factor in the primary production period can reach approximately 13.7%. A solvent pre-slug with N2 foam huff-n-puff technology is applied to improve oil recovery factor following primary production for 5∼6 years, and the final oil recovery factor can reach approximately 35.0%. The methodology formulated in this study is particularly significant for the effective development of this oil reservoir with deeply buried depth and low permeability, and would also guide the recovery of similar oil deposits.

Red mud recycling by Fe and Al recovery through the hydrometallurgy method: a collaborative strategy for aluminum and iron industry.

In this work, a collaborative strategy for the aluminum and iron industry based on red mud recycling through the hydrometallurgy method was proposed. In this method, Fe3+ and Al3+ were firstly separated from the red mud by using H2SO4 as a leaching agent, which was by-produced from the sintering process of an iron and steel industry. Multiple influence factors on the leaching process were investigated, with the H2SO4 addition amount showing the strongest influence on the leaching rates of Al and Fe. The main components of the filter residue were CaSO4, TiO2, and SiO2, which could be reused as additives in the building materials. Subsequently, the final Fe recovery product was obtained through the co-precipitation, Fe/Al separation, and Fe(OH)3 calcination. In the final product, the content of Fe2O3 reached 82.87%, and the iron grade was 58.01%, meeting the requirement being raw materials for sinter production.

A new and efficient procedure to load bioactive molecules within the human heavy-chain ferritin nanocage.

For their easy and high-yield recombinant production, their high stability in a wide range of physico-chemical conditions and their characteristic hollow structure, ferritins (Fts) are considered useful scaffolds to encapsulate bioactive molecules. Notably, for the absence of immunogenicity and the selective interaction with tumor cells, the nanocages constituted by the heavy chain of the human variant of ferritin (hHFt) are optimal candidates for the delivery of anti-cancer drugs. hHFt nanocages can be disassembled and reassembled in vitro to allow the loading of cargo molecules, however the currently available protocols present some relevant drawbacks. Indeed, protein disassembly is achieved by exposure to extreme pH (either acidic or alkaline), followed by incubation at neutral pH to allow reassembly, but the final protein recovery and homogeneity are not satisfactory. Moreover, the exposure to extreme pH may affect the structure of the molecule to be loaded. In this paper, we report an alternative, efficient and reproducible procedure to reversibly disassemble hHFt under mild pH conditions. We demonstrate that a small amount of sodium dodecyl sulfate (SDS) is sufficient to disassemble the nanocage, which quantitatively reassembles upon SDS removal. Electron microscopy and X-ray crystallography show that the reassembled protein is identical to the untreated one. The newly developed procedure was used to encapsulate two small molecules. When compared to the existing disassembly/reassembly procedures, our approach can be applied in a wide range of pH values and temperatures, is compatible with a larger number of cargos and allows a higher protein recovery.

Studies of natural gas production prediction and risk assessment for tight gas in Sichuan Basin

After a new round of tight gas geological evaluation was launched in 2018, a new chapter of tight gas exploration and development has been opened in the Sichuan Basin. In order to make better planning work, it is very important to study the variation rule and risk assessment of tight gas production. In this paper, the peak production is predicted by Ward model. Based on the prediction results, Hubbert and Gauss models were established to study the variation law of tight gas production, and the accuracy and prediction results of the models were determined by the degree of fitting and correlation coefficient. By studying the relationship between URR and production, it is concluded that the production increases in a step, and the future production of tight gas is simulated from the perspective of realization probability. Finally, the risk assessment matrix is established to study the difficulty degree of achieving the production target. The results are as follows: 1) Hubbert model has higher accuracy in predicting tight gas production change. The peak year of tight gas is 2042, the peak production is (86−106)×108m3/a, and the final URR recovery degree is about 60%. 2) The realization probability of production is calculated, and the possibility of reaching the target value is evaluated from the perspective of risk, so as to guide the production of tight gas, and finally promote the formulation of tight gas development planning in the Sichuan Basin.

Expression and characterization of a maltogenic amylase from Lactobacillus plantarum in Escherichia coli and its application in extending bread shelf life

A Lactobacillus sp. was screened from various cereal sourdoughs and was designated as Lactobacillus plantarum YXY418 based on the 16S rRNA gene analysis. A putative Lactobacillus plantarum maltogenic amylase, LpMA, was discovered based on computer-aided analysis. Then, its encoding gene (lpma) was expressed in E. coli BL21(DE3). The expressed recombinant LpMA (reLpMA) was efficiently purified to 12.2-fold using the one-step nickel-nitrilotriacetic acid (Ni–NTA) affinity chromatography. The final recovery yield and specific activity of the purified reLpMA were 61% and 36.4 U/mg towards soluble starch, respectively. The purified reLpMA exhibited optimal amylolytic activity towards soluble starch at 45 °C and pH 6.0, with a good pH stability ranging from pH 5.0 to 8.0. Besides, the reLpMA also hydrolyzed soluble starch, β-CD and pullulan to maltose with specific activity of 96.4 SU/mL, 78.2 CU/mL and 2.0 PU/mL, respectively. The reLpMA hydrolytic activity was increased in the presence of metal ions especially Ca2+ and Zn2+, which could be applied to different processing processes. Baking test indicated after 7-day storage, the reLpMA at a dosage of 2000 U/300 g could significantly reduce hardness and chewiness by 29.5% and 26.4%, respectively, compared with the control. Adding reLpMA improved bread quality, increased bread volume and decreased hardness during storage, thus extending its shelf life.

Study on Microscopic Pore Structure Classification for EOR of Low Permeability Conglomerate Reservoirs in Mahu Sag

The microscopic pore structure controls the fluid seepage characteristics, which in turn affect the final recovery of the reservoir. The pore structures of different reservoirs vary greatly; therefore, the scientific classification of microscopic pore structures is the prerequisite for enhancing the overall oil recovery. For the low permeability conglomerate reservoir in Mahu Sag, due to the differences in the sedimentary environment and late diagenesis, various reservoir types have developed in different regions, so it is very difficult to develop the reservoir using an integrated method. To effectively solve the problem of microscopic pore structure classification, the low permeability conglomerate of the Baikouquan Formation in Well Block Ma18, Well Block Ma131, and Well Block Aihu2 are selected as the research objects. The CTS, HPMI, CMI, NMR, and digital cores are used to systematically analyze the reservoir micro pore structure characteristics, identify the differences between different reservoir types, and optimize the corresponding micro pore structure characteristic parameters for reservoir classification. The results show that the pore types of the low permeability conglomerate reservoir in the Baikouquan Formation of the Mahu Sag are mainly intragranular dissolved pores and residual intergranular pores, accounting for 93.54%, microfractures and shrinkage pores that are locally developed, accounting for 5.63%, and other pore types that are less developed, accounting for only 0.83%. On the basis of clear pore types, the conglomerate reservoir of the Baikouquan Formation is divided into four types based on the physical properties and microscopic pore structure parameters. Different reservoir types have good matching relationships with lithologies. Sandy-grain-supported conglomerate, gravelly coarse sandstone, sandy-gravelly matrix-supported conglomerate, and argillaceous-supported conglomerate correspond to type I, II, III, and IV reservoirs, respectively. From type I to type IV, the corresponding microscopic pore structure parameters show regular change characteristics, among which, porosity and permeability gradually decrease, displacement pressure and median pressure increase, maximum pore throat radius, median radius, and average capillary radius decrease, and pore structure becomes worse overall. Apparently, determining the reservoir type, clarifying its fluid migration rule, and formulating a reasonable development plan can substantially enhance the oil recovery rate of low permeability conglomerate reservoirs.

Natural Fracture Occurrence Model Based on FMI Imaging Logging.

Natural fractures are crucial for connecting with reservoir matrix pores and influencing the fluid velocity in the matrix during unconventional oil and gas development. The development of natural fractures has significant impact on the effectiveness of extraction and even the final recovery factor. The development stage of natural fractures in reservoirs is characterized by fracture density and fracture occurrence, which are the key characteristics. The probabilistic models of fracture occurrence and density that are now available, however, still have several drawbacks. Therefore, a fracture occurrence model that may reflect both inclination and dip angles is proposed in a three-dimensional scenario in this study based on formation micro-imager imaging logging and the elliptic Fisher model. The findings demonstrate the accuracy and clarity of the proposed 3D fracture occurrence model in reflecting the fracture density and occurrence, as well as the superiority of data simulation. The algorithm described in this study is shown to be very close to the real distribution law. The results enable visualization of the fracture density and occurrence, which is crucial for directing engineering practice and assessing the sensitivity of directional data in other domains.

Исследование пластового флюида при разработке месторождений на шельфе Kарского моря

Introduction. With the expansion of offshore drilling and the distance of fields from the coastline, the number of production wells located in difficult underwater geological conditions is increasing, which complicates research. For example, the Yurkharovskoye field is located in a strip along the Tazovsky Peninsula under the waters of the Kara Sea. At the same time, the data obtained from the results of research are necessary when calculating reserves and designing the development of hydrocarbon deposits. Materials and research methods. Modeling of the operating conditions of the field under various thermodynamic conditions was carried out in order to determine the effect of water vapor and oil fractions on condensate losses during the development of the deposit [6–9]. The experiments were carried out to determine the amount of condensate in the reservoir gas, the physicochemical properties of hydrocarbons, and the effect of heavy oil fractions on condensate recovery [5, 10]. Prediction of condensate losses in the reservoir depending on the influence of negative factors must be taken into account when calculating hydrocarbon reserves and drawing up a field development project [11, 13]. Research results and their discussion. In the studied part of the section of the Yurkharovskoye field, located on the shelf of the Taz Bay, gas deposits were identified in the Aptian-Albian-Cenomanian complex and gas condensate deposits with oil rims in the Neocomian complex. The selection of development objects was based on a set of geological and geophysical data, the main of which are the presence of reservoirs and seals in the section and a single hypsometric position of the GWC or WOC in the case of an oil and gas condensate deposit. Correlation of well sections and identification of productive formations was based on the choice of benchmarks, the similarity of well logs, taking into account the nature of reservoir saturation and well test results. As a result of experimental PVT studies, the influence of water vapor and oil fractions as an integral part of the hydrocarbon system on the reservoir losses in the deposit was determined. The analysis of the performed studies confirmed that multicomponent hydrocarbon systems consist of a mixture of gas, condensate and water vapor, as well as oil fractions, which significantly changes the properties of the system and the dynamics of its phase processes during the development of the Yurkharovskoye field. Conclusions. The conducted PVT-experiments in order to identify the effect of water vapor and oil components that are part of natural gas showed that the predicted current and final condensate recovery factors are overestimated. An analysis of the research results revealed a different effect of water vapor on reservoir losses of hydrocarbons in the deposit due to an increase in partial pressure. In the presence of formation water in the gas condensate system, the CFC value decreased to 4-5%. Thus, the reason for the increase in reservoir losses of condensate in the deposit during the development of oil and gas condensate fields on the shelf of the Kara Sea was determined.

Degradation of Alkaline Lignin in the Lactic Acid-Choline Chloride System under Mild Conditions

Lignin is a natural polymer, second only to cellulose in natural reserves. Degradation is one of the ways to achieve the high-value transformation of lignin. Deep eutectic solvent (DES) thermal degradation of lignin can be used as an excellent green degradation method. This paper introduces the degradation mechanism and effect of the lactic acid-choline chloride DES system in dissolving and degrading alkaline lignin, and the final solvent recovery. It can also be found from the scanning electron microscope (SEM) images that the surface of the degraded solid product is transformed from smooth to disordered. Fourier transform infrared (FTIR) spectroscopy and 1 H-NMR spectroscopy were used to characterize the changes in lignin functional groups during DES treatment. The results showed that the content of phenolic hydroxyl groups increased after degradation, indicating that the β-O-4 ether bond was broken. The molecular weight of the degraded lignin was observed by gel permeation chromatography (GPC), and the lignin residue with low molecular weight and narrow polydispersity index was obtained. The lowest average molecular weight (Mw) reached 2512 g/mol. The ratio of oxygen to carbon atoms in lignin increased substantially during degradation as measured by X-ray photoelectron spectroscopy (XPS), probably because DES treatment was accompanied by many oxidation reactions, which led to significant structural changes in lignin and a large number of ether bond breakage reactions during the reaction. The main final degradation products are aromatic monomers, vanillin, butyrovanillone, etc.

Value of Direct Decompression of Lumbosacral Roots in Sacral Fractures with Neurologic Deficit: Is It Mandatory?

The value of direct decompression of neural structures to treat lumbosacral plexus injury associated with sacral fractures is still debatable. Direct decompression allows decompression of nerve roots by sacral laminectomy and removal of bone fragments in the spinal canal. In contrast, indirect decompression may offer similar neurological outcomes if good fracture reduction and correction of sacral kyphosis are achieved. In this comparative retrospective study, we analyzed differences between direct and indirect neurological decompression in terms of neurological recovery, complications, and functional outcome. This study included 33 cases with spinopelvic dissociation with variable degrees of lumbosacral plexus injury. All cases were managed by spinopelvic fixation. Eighteen patients (group 1) had direct decompression of lumbosacral nerve roots while 15 patients (group 2) had indirect decompression. Initial sacral kyphosis, quality of fracture reduction, and postoperative residual kyphosis were the main factors that significantly affected functional and neurological outcome in both groups. The final neurological improvement was similar in both groups. No significant difference was observed between both groups in the residual Gibbons' score recorded in the last visit (p = 0.206). The final Majeed score also showed no significant difference between the two groups (p = 0.869). Indirect decompression of sacral fractures showed similar final functional outcome and neurological recovery compared to direct decompression. Restoration of lumbosacropelvic stability and anatomic reduction seem to be the cornerstone for better functional outcome and neurological recovery rather than direct decompression of neural elements.

Clay minerals influence on the process of oil displacement by water in Jurassic reservoirs

Investigations of mineralogical composition of clay fraction of rock samples, injection of different water into Jurassic sediments at different fields are considered. It was found that the final oil recovery of reservoirs at reservoir pressure maintenance by water injection is significantly affected by swelling of clay minerals.

Spatial and temporal distribution of hydrocarbon production on the UK continental shelf

AbstractHydrocarbon production from oil and gas fields is controlled by a variety of interconnected factors with a hierarchy of significance that is, for the most part, difficult to untangle. This article documents and investigates the spatial and temporal distribution of key hydrocarbon field parameters on the UK Continental Shelf. Data have been compiled from publicly available sources for 424 fields. Variables are considered as “descriptive parameters,” “control parameters” and “outcomes”. Descriptive parameters are metadata such as field name, location, etc. Control Parameters include depositional environment, present depth of burial, porosity, permeability, reservoir formation pressure, reservoir temperature, average net‐to‐gross, number of fault populations, hydrocarbon API, field area, bulk rock volume, well density, number of wells (production and injection), well spacing, gas oil ratio, reservoir thickness, fluid saturation, compartmentalization (quantitated by number of observable non‐communicating fault compartments), structural complexity (scaled from 0 to 5), field production strategy, trap type and stratigraphic heterogeneity. Outcomes are used to assess field performance and include final recovery factor (estimated), maximum production rate, and cumulative monthly production. Analysis of the database illustrates a number of empirical observations regarding hydrocarbon production on the UKCS. The Jurassic plays have been the most successful in the region in terms of total volumes produced while the Permian reservoirs of the SNS account for the majority of the gas. Most of the UKCS reservoirs record top depths between 2000 and 4500 m with good reservoir quality. The best reservoir quality is observed in reservoirs that were deposited within deep marine systems. The largest hydrocarbon reserves are found in the Northern North Sea basin in these deep marine (as well as paralic and shallow marine) reservoirs. Using the data from this article and affiliated data, potential exists for extracting insight beyond spatio‐temporal distributions.

Comprehensive treatment strategy for high water cut stage of medium and low permeability reservoir

Maintaining good conditions for petroleum exploitation is an important basis for achieving better exploitation results. At present, the main reservoir conditions of our main oil fields are relatively good, and have entered high water cut, middle and late development. Due to long-term exploitation, the reservoir has suffered a certain degree of destruction, resulting in the rapid rise of aquifers and sharp reduction of production. It has certain influence on the output of oil and well and the final recovery efficiency of oil field. In order to alleviate the contradiction of rapid reduction of oil production pressure and output in high water cut stage of medium and low permeability reservoir, the development efficiency of reservoir can be improved. By analyzing the high water cut stage of medium and low permeability reservoir, this paper puts forward the comprehensive treatment measures, which provides the idea for realizing the increase of production.

Experimental Investigation on the Imbibition Behavior of Nanofluids in the Tight Oil and Gas Reservoir through the Application of Nuclear Magnetic Resonance Method

Tight oil and gas resources are widely distributed and play an important role in the petroleum industry. Due to its nanoscale pore-throat characteristics, the capillary effect is remarkable, and spontaneous imbibition is very beneficial to the development of low-permeability reservoirs. In this study, the imbibition experiments of 2D nano blackcard, nanoemulsion, and water were carried out, respectively. The pore-throat fluid distribution characteristics before and after core imbibition were analyzed with nuclear magnetic resonance technology, and the enhanced oil recovery effects of 2D nano blackcard nanoemulsion, and water were comprehensively evaluated. The results show that the final recovery factors of cores soaked in 2D nano blackcard (0.005 ωt%) and nanoemulsion (0.02 ωt%) or imbibed in water are 32.29%, 26.05%, and 7.19%, respectively. It can be found that 2D nano blackcard is the fluid with the best imbibition effect. In this work, a new type of 2D nano blackcard was proposed and identified as a functional imbibition fluid for enhanced oil recovery in tight reservoirs, providing a practical reference for the effective development of tight, low-permeability oil and gas reservoirs.

DOES PERTURBATION-BASED BALANCE TRAINING ON COMMERCIAL TREADMILLS IMPROVE BALANCE RECOVERY IN OLDER ADULTS?

Abstract Background Perturbation-based training (PBT) is a balance training method that causes a trip like event requiring a rapid step response to regain balance. There are numerous examples in the literature demonstrating the effectiveness of PBT but the need to use an expensive treadmill in a scientific laboratory limits the general applicability of PBT as a community-based intervention. A possible solution is to rapidly stop the treadmill belt during walking using the e-brake as the perturbation event. Importantly this could be performed on a commercially available, lower cost treadmill. Therefore, the purpose of this study was to evaluate the effectiveness of a commercial treadmill during PBT. Methods Seventeen participants completed either 9 weeks of PBT or conventional balance training based on ACSM guidelines. During an initial and final testing session participants balance recovery performance was evaluated. Participants were released from a forward static lean angle and asked to recover with a single step, during this test their movement was recorded and subsequently used to determine the Margin or Stability pre- and post-training. Participants were tracked for 6 months following the intervention and falls were recorded on a weekly basis. Results and Summary: There was no difference in balance recovery performance between groups following the training intervention and there was no difference in fall rate between groups in the 6-month follow-up period. We conclude that overall using the e-brake of a commercial treadmill is ineffective as a PBT strategy as it elicits no greater benefit than conventional exercise training.

Experimental investigation of EOR mechanisms for cyclic steam injection assisted by flue gas

In Colombia, Cyclic Steam Stimulation (CSS) is deployed as an EOR method to recover heavy oil. However, flue gas from steam generators is a stable long-term CO2 emission source in oil fields. And the adverse effects of this greenhouse gas cannot be ignored, becoming a concern in all countries worldwide. In this study, the cyclic steam-flue gas co-injection process (CSS-FG) is proposed as an alternative to improve the performance of CSS, extend the lifetime of this technology, and collect and use the flue gas from steam generators to reduce greenhouse-gas emissions. In this investigation, CSS and CSS-FG were experimentally represented and compared to understand the effect of flue gas addition on the recovery mechanisms at the different stages of CSS, using a one-dimensional core physical simulation. For CSS representation, five steam injection cycles were carried out, and flue gas was added in a sixth cycle to analyze the effect of flue gas on the recovery factor after several stages. Likewise, in the CSS-FG displacement, five cycles were developed, where flue gas-steam was injected since the second to the fifth cycle. The results show that the final oil recovery factors of CSS-FG using 15% of flue gas molar ratio was 41.1%, compared to 15.2% of CSS. In addition, after five-cycle steam stimulation, the recovery factor increased up to 9.2% by adding flue gas in the sixth cycle. The differences in the recovery factors confirmed the synergy between the flue gas and steam even in mature stages of steam stimulation, which facilitated the identification of the recovery mechanisms associated with adding this gas. Phase interaction between the flue gas and heavy oil is promoted during the injection stages. Thereafter, flue gas expands rapidly in the production period, offering a push mechanism that accelerates the fluids production rate. Additionally, the porous medium pressure increases, and the fast depletion rate near the production port when adding flue gas cause foamy oil formation, improving the mobility of heavy oil since the dissolved gas cannot release from the oil because of its high viscosity. These experimental results provide theoretical guidance for improving the effectiveness of the CSS and demonstrate that CSS-FG is an essential method for reducing greenhouse-gas emissions in oil fields.

Localization and development of residual oil reserves using geochemical studies based on neural network algorithms

At the late stage of field development, residual oil reserves undergo a significant change from mobile to sedentary and stationary. These reserves are mainly located in technogenically and production altered, watered layers and areas of deposits. Localization and development of such sources of hydrocarbons is an effective method of increasing the final oil recovery factor in mature fields, due to the presence of a ready-made developed infrastructure for production, transportation and refining, as well as the availability of highly qualified personnel. This article considers an approach that allows, based on neural network algorithms, the estimation the volumes and localization of residual oil reserves in multi-layer deposits in combination with the analysis of geochemical studies of reservoir fluids. The use of machine learning algorithms allows a targeted approach to the development of residual reserves by automated selection of wellwork. This approach significantly reduces the manual labor of specialists for data processing and decision-making time.