Higher Oil Recovery Research Articles

Investigation of the effect of surfactant co-injection on steam chamber expansion and oil production in steam-assisted gravity drainage in reservoirs with barrier layers

The use of surfactants as additives to enhance the performance of steam-assisted gravity drainage (SAGD) has been a promising concept for decades. While previous studies largely focused on homogeneous reservoirs, this study has investigated the impact of surfactants on steam chamber expansion, oil production, and recovery in SAGD applied to reservoirs with separated barrier layers of varying permeability, thickness, and configurations. A comparative analysis of SAGD and surfactant-aided SAGD (SA-SAGD) was conducted through experimental and numerical simulations using a 3D model based on the Long Lake Reservoir in Canada. The results showed that surfactant co-injection mitigated the negative impact of low-permeability layers on steam chamber growth, production rates, and oil recovery. Unlike in conventional SAGD, the steam chamber was able to penetrate through barrier layers thicker than 4 cm (equivalent to 4 m in the field) and with a permeability of 150 mD resulting in more than 50% higher oil recovery and a near two-fold increase in recovery rates when surfactant was used. Oil production rates were also 1.5 times higher than those achieved with SAGD alone. This study provides new insights into overcoming the limitations posed by barrier layers, offering potential improvements for SAGD operations in complex reservoir conditions.

Investigation on the improvement of shea butter yield and quality through enhanced pre-treatment methods: An analytical study on physicochemical properties

Shea butter is an organic ingredient used in direct consumption, or the manufacture of products in the food, pharmaceutical, and cosmetic industries. Some pre-treatment processes of shea nuts may not favor the high oil recovery and quality attributes, leading to products that may not conform to market standards for quality, stability, importation, and human consumption. This research emphasizes how roasting or boiling shea nuts for shea butter production enhances its quality by lessening its vulnerability to oxidative instability while simultaneously optimizing oil yield. Shea nuts were collected from an agro-processing company in Ghana. Physicochemical parameters such as refractive index, volatile, acid, iodine, saponification, and peroxide values were analyzed using standard analytical methods. Roasted, boiled, and untreated shea nuts produced a maximum oil yield of 53.53, 48.75, and 47.63 %, respectively. The findings of physicochemical properties of the shea butter samples as time increased from 10 to 50 min for roasted, boiled, and untreated shea nuts showed; an acid value from 8.50 to 17.49 mgKOH/g, 19.4 to 26.46 mgKOH/g and 18.20 mgKOH/g, iodine value from 40.91 – 48.23 gI2/100 g, 46.17 – 57.93 gI2/100 g, and 42.9 gI2/100 g, peroxide value from 2.45 to 4.69 meq/kg, 3.05 to 7.08 meq/kg and 2.15 meq/Kg, refractive index from 1.464 to 1.465, 1.464 to 1.469, and 1.463, saponification value from 181.90 to 187.90 mg KOH/g, 177.70 to 181.55 mg KOH/g and 180.60 mg KOH/g. The quality parameters indicate chances of rancidity. Roasting shea nuts was the optimal condition to produce high yield and quality shea butter than boiled shea nuts. The study recommends that regulatory agencies and consumers conduct regular inspections to verify that shea butter satisfies the appropriate quality and safety criteria for consumption and export.

Uncovering the impact of morphology of porous media and capillary number on immiscible oil recovery using computational fluid dynamics

Pore-scale simulation and analysis of oil displacement in digital rocks has shown great promise in tracking oil recovery in porous media. This paper examines three digital rocks with varying pore and throat radii but the same porosities, studying their behavior under immiscible oil recovery through waterflooding. Computational fluid dynamics was used to conduct numerical simulations to observe the impact of rock morphology on breakthrough times, residual oil saturations, and oil displacement patterns. The validity of the simulation mechanism is confirmed in both imbibition and drainage conditions through the pore doublet Chatzis' experiment. This study consisted of 33 separate simulations which varied in mobility ratios, interfacial tensions, and injection velocities. The findings suggest that smaller pore and throat radii result in higher oil recovery and water percolation and faster breakthrough times that facilitates the effects of viscous fingering. An increase in capillary number was found to have a significant impact on oil recovery in larger pores and throats.

Influence of Heterogeneous Reservoir on Carbon Sequestration and Carbon Displacement

Abstract Carbon Capture, Utilization and Sequestration (CCUS) is a method of burying CO2 captured in various ways into the reservoir and extracting the remaining oil from the reservoir. It is one of the important methods to reduce carbon emissions and achieve carbon neutrality in the next few decades, and it is also considered to be the most economical and effective method to slow down the greenhouse effect. It is very important to study the influence of reservoir heterogeneity on CO2 storage and oil recovery in order to make CCUS scheme store more CO2 and recover more remaining oil. Firstly, the numerical simulation model of reservoir is established in this paper. Its injection-production mode is gas injection in vertical wells at the top of the reservoir at a fixed gas injection rate, and oil production in horizontal wells at the bottom of the reservoir at a fixed pressure. Secondly, the distribution of reservoir porosity and permeability is designed, and four reservoir models are established: homogeneous reservoir, heterogeneous reservoir, positive rhythm heterogeneous reservoir and reverse rhythm heterogeneous reservoir. Finally, the effects of four reservoir models on CO2 storage and oil recovery are studied, and the migration law of CO2 is comprehensively analyzed according to the characteristics of reservoir pressure distribution. The reverse rhythm reservoir has the best CO2 storage effect, and the positive rhythm reservoir has the highest oil recovery. That is, when burying is the main method, the reverse rhythm heterogeneous reservoir is preferred; When oil displacement is the main method, positive rhythm reservoir is preferred. Among the four homogeneous or heterogeneous reservoirs, the migration law of CO2 in reservoirs is quite different, mainly due to the influence of reservoir heterogeneity. CO2 preferentially migrates from the dominant channels in the reservoir, but regardless of the reservoir type, the molar fraction of CO2 at the top of the reservoir is the highest. In addition, the CO2 invasion of four kinds of reservoirs in different stages of caprock is analyzed and its safety is analyzed. This study provides an effective reference for the establishment of numerical simulation models of different types of heterogeneous reservoirs, the migration characteristics of carbon dioxide in reservoirs and the effective operation and evaluation of CCUS scheme.

Mobilization of tight oil by spontaneous imbibition of surfactants

A series of spontaneous imbibition (SI) tests of tight oil were performed, together with oil distribution scans by computed tomography (CT) and nuclear magnetic resonance (NMR). Thus, the best surfactants to optimize the SI effect were obtained, the basic requirements to surfactants for efficient SI were determined, and the oil mobilization by SI revealed. The results show that anionic surfactants significantly outperform non-ionic, cationic, and zwitterionic ones in SI process. Excellent systems can be further obtained by mixing anionic surfactants with others (e.g. 1:1 mixtures of AES:EHSB). The requirements to interfacial properties of surfactants for achieving efficient SI at permeabilities of 0.05, 0.5, and 5.0 mD are: 100 mN/m, < 40°; 10−1–100 mN/m, < 55°; and 10−1–100 mN/m, < 70°, respectively. Although a high oil recovery of 38.5% by SI was achieved in small cylindrical cores (ϕ2.5 cm × 3.0 cm), the joint SI and CT tests in larger, cube-shaped cores (5.0 cm × 5.0 cm × 5.0 cm) showed that the SI process could only remove the oil from the outermost few millimeters of the cores with permeabilities of 0.05 and 0.1 mD, indicating the great difficulty encountered for their development. The NMR showed that the SI treatment preferentially removed oil from smaller pores rather than medium or large pores.

The Effect of Alpha Olefin Sulphonate (AOS) Surfactant Injection on Sandstone Rock on Increasing Oil Recovery with Variations in Salinity, Concentration, and Temperatures: A Laboratory Study

In this study, Alpha Olefin Sulphonate (AOS) surfactant was injected. This laboratory test aims to verify the correlation between a surfactant solution’s low IFT value and its ability to yield a high oil recovery value. The salinity used in this research was 5000 ppm and 15000 ppm. Then it was mixed with AOS surfactant at concentrations of 0.5%, 1%, and 2%. At the same time, the temperatures used are 30 °C and 60 °C. After testing, it was found that a solution with a salinity of 15,000 ppm and a surfactant concentration of 2% had the lowest IFT value and was proven to have a total RF of 73%.

Synthesis of amphiphilic silicon quantum dots and its application in high efficiency imbibition oil recovery in low permeability reservoirs

In this work, a novel three-step method was used to modify the surface of silicon quantum dots to synthesize amphiphilic silicon quantum dots (A-SiQDs) with higher interfacial activity. The particle size of A-SiQDs was only 3.5 nm. By adding a small amount of dodecyl dimethyl betaine (BS-12), the performance of A-SiQDs was further improved. Through particle size and zeta potential testing, it can be seen that the mixed system of A-SiQDs and BS-12 had good temperature and salinity resistance, and can be stable at 120 °C and 50,000 mg/L NaCl. Meanwhile, the mixed system exhibited superior interfacial activity compared with individual A-SiQDs and BS-12. The mixed system can lower the interfacial tension from 32.15 mN/m to 1.82 mN/m and transform the rock surface from an oil-wet to a strong water-wet state. This ensured the excellent imbibition ability of the mixed system, which can increase the oil recovery to 35.7 %. Finally, from the perspective of force, the influence of nanofluids on oil stripping and migration was analyzed to reveal the imbibition mechanism. This paper proposes a facile three-step method for synthesizing A-SiQDs, and also provides a novel nanomaterial for high efficiency imbibition in low-permeability reservoirs.

Systematic Review of Solubility, Thickening Properties and Mechanisms of Thickener for Supercritical Carbon Dioxide.

Supercritical carbon dioxide (CO2) has extremely important applications in the extraction of unconventional oil and gas, especially in fracturing and enhanced oil recovery (EOR) technologies. It can not only relieve water resource wastage and environmental pollution caused by traditional mining methods, but also effectively store CO2 and mitigate the greenhouse effect. However, the low viscosity nature of supercritical CO2 gives rise to challenges such as viscosity fingering, limited sand-carrying capacity, high filtration loss, low oil and gas recovery efficiency, and potential rock adsorption. To overcome these challenges, low-rock-adsorption thickeners are required to enhance the viscosity of supercritical CO2. Through research into the literature, this article reviews the solubility and thickening characteristics of four types of polymer thickeners, namely surfactants, hydrocarbons, fluorinated polymers, and silicone polymers in supercritical CO2. The thickening mechanisms of polymer thickeners were also analyzed, including intermolecular interactions, LA-LB interactions, hydrogen bonding, and functionalized polymers, and so on.

Surface charge change in carbonates during low-salinity imbibition

Optimizing the injection water salinity could present a cost-effective strategy for improving oil recovery. Although the literature generally acknowledges that low-salinity improves oil recovery in laboratory-scale experiments, the physical mechanisms behind it are controversial. While most experimental low-salinity studies focus on brine composition, this study investigated the influence of carbonate rock material on surface charge change, wettability alteration, and spontaneous imbibition behavior. Zeta potential measurements showed that each tested carbonate rock material exhibits characteristic surface charge responses when exposed to Formation-water, Seawater, and Diluted-seawater. Moreover, the surface charge change sensitivity to calcium, magnesium, and sulfate ions varied for the tested carbonate materials. Spontaneous imbibition tests led to high oil recovery and, thus, wettability alteration towards water-wet conditions if the carbonate-imbibing brine system’s surface charge decreased compared to the initial zeta potential of the carbonate Formation-water system. In the numerical part of the presented study, we find that it is essential to account for the location of the shear plane and thus distinguish between the numerically computed surface charge and experimentally determined zeta potential. The resulting model numerically reproduced the experimentally measured calcium, magnesium, and sulfate ion impacts on zeta potential. The spontaneous imbibition tests were history-matched by linking surface charge change to capillary pressure alteration. As the numerical simulation of the laboratory-scale spontaneous imbibition tests is governed by molecular diffusion (with a time scale of weeks), we conclude that molecular diffusion-driven field scale wettability alteration requires several hundred years.

Nanotechnology Applications in Enhanced Oil Recovery (EOR)

Enhanced Oil Recovery (EOR) techniques are crucial for maximizing crude oil extraction from reservoirs, especially when traditional methods leave significant amounts of oil untapped. Recent advancements in nanotechnology have introduced innovative solutions to longstanding challenges in the oil industry. This research paper explores the application of nanotechnology in EOR, emphasizing the unique properties of nanoparticles that make them highly effective in this context. Nanoparticles, defined by their nanometer-scale dimensions, exhibit high surface area to volume ratios, quantum effects, and enhanced reactivity. These properties enable various mechanisms in EOR, including improved wettability, reduction in interfacial tension, enhanced thermal stability, selective plugging and fluid diversion, and catalytic effects. The study details how silica and titanium dioxide nanoparticles can modify rock surface properties, leading to better water imbibition and oil displacement. It also discusses how surfactant-coated nanoparticles can reduce the interfacial tension between oil and water, facilitating easier oil flow. Furthermore, the research highlights the role of metal oxide nanoparticles, such as aluminum oxide and zinc oxide, in enhancing thermal conductivity and stability during thermal EOR methods like steam flooding. The ability of polymer-coated nanoparticles to selectively plug high-permeability zones and redirect injection fluids is examined, demonstrating how this can lead to a more uniform sweep and higher oil recovery. The catalytic properties of certain nanoparticles, such as iron oxide, are also explored for their potential to promote in-situ chemical reactions that generate gases aiding oil displacement. Field applications and case studies underscore the practical benefits of nanotechnology in EOR. Examples include the use of silica nanoparticles in Middle Eastern oil fields, polymer-coated nanoparticles in Canadian heavy oil reservoirs, and iron oxide nanoparticles in Indian oil fields. These case studies have shown significant increases in oil recovery rates and operational efficiencies. However, the research also identifies several challenges that must be addressed for the widespread adoption of nanotechnology in EOR. These include the high costs and scalability issues associated with nanoparticle production and deployment, potential environmental and health risks, and the need for customized solutions to cater to the unique conditions of different reservoirs. In conclusion, while nanotechnology presents promising advancements in EOR through various mechanisms, overcoming challenges related to cost, scalability, and environmental impact is crucial. As research progresses, nanotechnology is poised to play a vital role in enhancing oil recovery and meeting global energy demands.

CO2 foam to enhance geological storage capacity in hydrocarbon reservoirs

Geological CO2 storage is an emerging topic in energy and environmental community, which is, as a commonly-accepted sense, considered a powerful approach to mitigate the global carbon emissions during the transition to net-zero. The geological media initially considered cover the saline aquifers, oil and gas reservoirs, coal beds, and potentially basalts. Up to now only the first two choices have been proven to be the most capable storage sites and successfully implemented at pilot/commercial scales. Here, novel strategies were proposed for the first time, by synthesizing and utilizing new high-dryness CO2 foam, to enhance geological CO2 storage capacity in oil and gas reservoirs. As a major storage site, the oil and gas reservoirs ranked only second to the saline aquifer, due to their huge underground spaces, and more importantly, spontaneous economic benefits by injecting CO2 for geological storage. However, at any development stage, particularly late stage with high water cut, CO2 injection usually tends to cause gas channeling and therefore result in low-efficient storage. In this paper, a series of dynamic evaluation experiments are carried out to investigate the effect of newly-synthesized high-dryness CO2 foam in oil and gas reservoirs. A comprehensive set of parameters, including the fluid production volume, rate, efficiency, pressure, porous media weight, water cut, mobility reduction factor, oil-gas-water ternary phase saturation, etc., are specifically analyzed. The lab results show that when the foam quality is 85 %, the oil recovery performance and gas phase saturation reach their highest values, of 82.68 % and 75.36 %, respectively; meanwhile, the water consumption is at the lowest level, 43.88 g/mol, for the CO2 storage in oil and gas reservoirs. This indicates the synthesized high-dryness CO2 foam, attributed to its superb stability, modifies the mobility ratio, suppresses the viscous fingering, and finally results in higher oil recovery and more CO2 storage. Similar work has been done for the reservoirs with permeabilities from high to low levels. The study provides experimental evidences that suggest benefits from applying CO2 flooding in oil and gas reservoirs.

Power consumption of electric centrifugal pumping plants under extraction of highly watered oil

Relevance. Currently, oil fields in Russia are mainly developed using the method of artificial maintenance of reservoir pressure to achieve high oil recovery. The use of artificial impact on productive formations by the method of water injection contributes to the premature irrigation of production wells. Water content of productive layers in oil fields significantly complicates the technology of oil production. With the increase in water content of the surface fluid, the power consumed by the engine increases. Minimization of energy consumption is quite relevant, as oil is produced with significant expenditures of electrical energy. It is important to investigate the dependences of the electric energy consumption on the well water cut. Aim. To study the dependence of energy consumption of submersible electric centrifugal units operated in oil production wells on water cut. Methods. Submersible electric centrifugal installations for oil production. Results. In order to study the effects of formation water cut on electrical energy specific consumption, wells with a water cut of more than 90% were selected. Using the formula, the authors have calculated the electrical energy specific consumption for oil production. The analysis of the results of the calculated data showed that in producing wells with a water cut of up to 90 %, the average specific electric power consumption for oil production is within the recommended standards. In wells with the water cut more than 90%, the average specific electric power consumption for oil production exceeds recommended specific norms of electric energy consumption during operation of oil producing wells equipped with electric centrifugal installations. Based on calculated data, the dependence of the specific electrical energy consumption for oil production on the water cut of reservoir products was plotted, and wells with a water cut of more than 90% were selected. The analysis of the graphical dependence showed that in wells with an oil water cut of more than 90%, the specific energy consumption reaches maximum values ​​(the specific energy consumption increases by 40%).

Reusable Underwater Superoleophobic Polyacrylamide Membranes for Effective Oil‐Water Separation and Dye Removal

AbstractWater contamination by oily wastes continues to rise with industrialization and pose a threat to marine ecosystem and public health. Water repellent special wettability membranes have been fabricated for oil removal. These superhydrophobic membranes have been fabricated utilizing hazardous chemicals such as fluorinated compounds, which again have shown toxicity. In contrast, environmentally friendly separation membranes are required for oily wastewater treatment. In this regard, we fabricated underwater superoleophobic membrane based on β‐cyclodextrin and acrylamide for efficient and effective water‐oil separation. Acrylamide polymeric membrane was prepared by free radical co‐polymerisation by incorporating acrylic acid and β‐cyclodextrin as monomer via crosslinking with N,N‐methylene bis‐acrylamide. FT‐IR and PXRD used for characterizing the prepared hydrogel and studied for morphological analysis by FE‐SEM. The oil and water wetting characterization of gels were evaluated, in ambient and submerged conditions. The dried gel showed gradual decrease of contact angle for both oil and water indicating liquid absorption with time. However, in completely water wetted state hydrogel was superoleophobic with a very high oil contact angle of ≥170°. The pre‐wetted hydrogel efficiently and effectively separated oil/water mixtures with ~99 % separation efficiency. Additionally, its effectiveness was monitored over several days of continuous separation operation. Interestingly, the hydrogel was also able to remove dye from water. The underwater superoleophobic acrylamide‐β‐cyclodextrin hydrogel demonstrated high oil recovery efficiency and indicated the potential for repeated oil‐water separation process.

Design of Intelligent Control Systems for Layered Water Injections in Oilfields

With rapid socio-economic growth and increased energy demand, exploration and exploitation of oil and gas resources have become crucial. Long-term exploitation leads to problems such as pressure drop and production reduction in oil fields, and water injection technology has become a common method to improve these problems. The traditional direct water injection for oil extraction has problems such as high injection cost and low oil recovery efficiency. Therefore, an intelligent control system for different oilfield reservoirs is needed. This study focuses on the layered water injection intelligent system based on advanced sensor technology, digital signal processing and intelligent algorithms. The article reviews the advantages of layered water injection system and the current research status, designs an intelligent control structure including hardware circuits and modular software processes, and adopts adaptive particle swarm optimization algorithm as the core of intelligent control.

Phytochemicals in recovered seed oils from by‐products of common quince (Cydonia oblonga) and Japanese quince (Chaenomeles japonica)

AbstractNearly 100% of Japanese quince (Chaenomeles japonica) and common quince (Cydonia oblonga) fruits are processed. It generates large amounts of seeds. One of the possible utilization of seeds is oil recovery. Seeds of both quinces were tested for their oil recovery using two methods—solvent‐free protocol by mechanical press and ultrasound‐assisted extraction (UAE) applying n‐hexane, and phytochemistry of obtained oils was studied. The oil yield was nearly twice higher from common quince than Japanese quince (20.9% and 11.2%, respectively) for UAE. Compared to UAE, screw‐pressed allowed for 67% oil recovery. In general, the phytochemical profile of both quince seed oils was similar with some differences in the content of individual compounds. The two quince seed oils were dominated by the same molecules in different compound groups: fatty acids—linoleic acid; tocochromanols—α‐tocopherol; phytosterols—β‐sitosterol, and triterpenoid—squalene. Common quince seed oil was richer in tocochromanols, squalene, and linoleic acid, whereas Japanese quince seed oil was richer in phytosterols. The present study showed the oil potential of fruit industry by‐products and the relatively high oil recovery by the environmentally friendly/healthy technique of extraction (solvent‐free) to achieve ultimately high‐quality products in a “Natural‐Safe‐Green” strategy.Practical applications: Production of fruit each year, especially those used for processing, for example, common quince (C. oblonga), has been increasing in recent years, likely, so has processing and amounts of generated by‐products, including seeds. To reduce the costs, CO2 emissions, and other environmental safety aspects of production, different techniques of plant oil recovery are considered. The extraction method affects oil yield as well as its phytochemical composition. The generated information in the present study can contribute to improved effectiveness of the use of plant material thereby providing environmental, health, and economic benefits.

THEORETICAL JUSTIFICATION OF THE THERMAL METHOD – STEAM CYCLIC TREATMENT OF WELLS OF THE X DEPOSIT

Enhanced oil recovery from active fields is equivalent to the discovery of new fields, making this issue critical to all oil-producing countries around the world. Of course, among all modern methods of increasing oil recovery from reservoirs, thermal methods are the most technically and technologically prepared. They make it possible to extract oil with a viscosity of up to 100 MPa and at the same time increase the final oil recovery by 30-50%. In particular, the thermal steam method is widely used both in fields in the CIS countries and abroad. The main factors that determine the growth of oil production using thermal methods include: Availability of significant resources of high-viscosity oil. Application of highly effective technologies for influencing oil deposits. Availability of necessary heat and power equipment. Use of heat-resistant equipment for wells and on the surface. Effective control and regulation of processes inside wells. The widespread development of methods for thermal oil production is associated with the solution of a complex set of scientific and technical problems. Among these tasks, special attention is paid to: The study of oil recovery mechanisms in various geological and physical conditions. The determination of opportunities for effective use of the features of the geological structure of specific fields. The development of combined methods for increasing oil recovery, including thermal methods and others, in order to improve technological processes and achieve high oil recovery rates at the level of 50-60%. The aim of this article is to analyze and justify the choice of a specific thermal oil production technology, namely the method of steam-cyclic well treatment, which is especially relevant for the production of high-viscosity oils.

Pressurized liquid extraction of soybean oil using intermittent process with ethanol and hexane as solvent: Extraction yield and physicochemical parameters comparison

AbstractThis research demonstrates pressurized liquid extraction (PLE) in an intermittent process in obtaining soybean oil using less solvent than conventional extraction. Temperature (T), solvent rinse volume (VS), contact time between the solvent and the matrix (St) in each cycle and number of cycles (C) were screened. Yield, fatty acids profile (FAs), and triacylglycerols were evaluated. After preliminary testing, T and St were tested for yield while VS, C, and P were fixed at 60% of total volume of the fixed bed extractor, 3 cycles, and 10.34 MPa respectively. The highest oil recoveries were 94.40% (85°C, 13 min, with hexane) and 86.16% (80°C, 12 min, with ethanol). The mass ratio of solvent/feeds resulted in a yield increase of 1.47% (hexane) and 3.99% (ethanol). The concentration of β‐sitosterol (≤182.78 mg/100 g of oil, hexane; ≤71.64 mg/100 g of oil, ethanol) and the fatty acid profile were not affected by the different solvents or process. The main fatty acids were linoleic (≤51.12%, ethanol; ≤40.31%, hexane) and oleic (≤24.98%, ethanol; ≤26.62%, hexane). The main triacylglycerols identified were LLO, LLL, and OOL. The results indicate that soybean oil can be obtained by a new process that uses a safe and renewable solvent, indicating that PLE in an intermittent process can replace conventional extraction without changing the main characteristics of the oil, with good yield using less solvent.Practical applicationsThe practical application of this research is related to the possibility of demonstrating the feasibility of PLE in obtaining soybean oil using pressurized ethanol. The solvent used in most oilseed extraction plants is commercial hexane, a toxic and non‐renewable solvent. The experiments were carried out with pressurized hexane to demonstrate the economy of solvents and compare with the results obtained when pressurized ethanol was used as a solvent. The ethanol study aimed to show high extraction yields, even using a polar solvent in soybean oil extraction. High yields and oil characterization showed that it is possible to use a green and clean technology to obtain vegetable oils.

Rotary thermal desorption technology for treatment of oil-based drilling cuttings in shale gas industry

Oil-based drilling cuttings are hazardous wastes in shale gas exploitation and need careful treatments to reduce environmental pollution and waste of resources. One of most widely employed waste-treatment technologies is the thermal desorption due to its high oil recovery efficiency. However, it usually suffers low heat exchange efficiency, thus leveraging operation costs and equipment instability. Toward the end of alleviating limitation, this study rationally designs the structure of the heating component under the guidance of the flat wall heat conduction theory, and uses numerical simulation to analyze the heat transfer of the structure. A rotary thermal desorption technology was thus developed and evaluated. The simulation results showed that given a short time of 800 s the temperature difference between device and cuttings became less than 5 K, indicating good heat exchange efficiency. Large inlet radius of device and high inlet velocity of heat transfer oil were critical parameters to maintain high heat transfer rate. Through industrial experiments verification, the 0.14–0.2 % oil content of treated cuttings qualified the environmental standards. The components of the recovered oil were recyclable C9-C23 alkanes, and the dichromate oxidizability of recovered water was less than 500 mg/L limit. Comparing with other technologies, the scores suggested that this technology was a promising candidate for treating oil-based drilling cuttings.

Effect of N2 impurity on CO2-based cyclic solvent injection process in enhancing heavy oil recovery and CO2 storage

CO2-based CSI (CO2–CSI) process is an effective EOR technique for heavy oil reservoirs after primary production. However, the application of CO2–CSI in the field is limited by the massive requirement and cost of pure CO2. To address this limitation, the effect of N2 impurities on the CO2–CSI process is evaluated by experiments using a 1D sand pack model. The results illustrated that the oil recovery significantly decreases when the N2 content surpasses 17.2 % because of the low solubility of N2 content in the oil phase and the lower viscosity reduction effect. Additionally, the N2 impurity component in the reservoir displaces some of the pore volume available for CO2 storage, but the CO2 storage ratio, the CO2 storage amount out of the consumption amount, is similar to that of the pure CO2–CSI process. An economic analysis is conducted for the material cost of each unit oil production in cases with different N2 impurities. The results indicate that the material cost follows a pattern of initially declining and then rising along with the increase of N2 content. In this study, the optimal N2 content in CO2 for the CSI process is approximately 17 %, considering its high CO2 storage ratio, high oil recovery factor, and low material costs compared to other N2 purity schemes. The findings of this study provide valuable insights for optimizing the solvent components in the CO2–CSI process, contributing to the economic and sustainable development of heavy oil resources and considerable CO2 storage.

Experimental Investigation of IOR Potential in Shale Oil Reservoirs by Surfactant and CO2 Injection: A Case Study in the Lucaogou Formation

The current oil recovery of the Lucaogou shale oil reservoir is predicted to be about 7.2%. It is crucial to explore improved oil recovery (IOR) technologies, and further experimental and field research needs to be conducted to study the complex mechanism. In this study, laboratory experiments were carried out to investigate the performance of one-step and multi-step depletion, CO2 huff-n-puff, and surfactant imbibition based on nuclear magnetic resonance (NMR). The sweep efficiencies were assessed via NMR imaging. In addition, hybrid methods of combining surfactant with CO2 huff-n-puff and the performance of injection sequence on oil recovery were investigated. The experimental results indicate that oil recoveries of depletion development at different initial pressures range from 4% to 11%. CO2 huff-n-puff has the highest oil recovery (30.45% and 40.70%), followed by surfactant imbibition (24.24% and 20.89%). Pore size distribution is an important factor. After three more cycles of surfactant imbibition and CO2 huff-n-puff, the oil recovery can be increased by 11.27% and 26.27%, respectively. Surfactant imbibition after CO2 huff-n-puff shows a viable method. Our study can provide guidance and theoretical support for shale oil development in the Lucaogou shale oil reservoir.