ASP Flooding Research Articles

Research on Characteristics and Centrifuge Treating Chemical of Floccules Generated by ASP Flooding Produced Water Treatment

Abstract The addition of composite water clear agents (acid, inorganic coagulant and organic flocculant) was an effective method for the treatment of the high ASP contents produced water about strong alkali system. However, it formed a large amount of flocs, which poses significant environmental pressure. In order to reduce the production of flocs, chemical analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and other methods were used to study the composition and structure of flocs generated in the treatment of produced water. It was found that the reason for the difficulty in flocs dewatering was that the gel generated by the action of polyacrylamide in produced water and water cleaning agent contained strong hydrophilic groups and formed a three-dimensional network structure. In view of this feature of flocs, concentrated treatment agent research was carried out from the ideas of degradation, coagulation, density regulation, etc. Field trials have shown that adding 1% of the treatment agent, the water content of the flocs after centrifugal treatment was reduced from 97% to 73% and its volume was reduced by 89%. The flocs concentration treatment agent solved the problem of large flocs production in the application process of composite water clear agents, and was of great significance in the oilfield environment protecting and green production.

Preparation and Characterization of Responsive Cellulose-Based Gel Microspheres for Enhanced Oil Recovery.

As an important means to enhance oil recovery, ternary composite flooding (ASP flooding for short) technology has achieved remarkable results in Daqing Oilfield. Alkalis, surfactants and polymers are mixed in specific proportions and injected into the reservoir to give full play to the synergistic effect of each component, which can effectively enhance the fluidity of crude oil and greatly improve the oil recovery. At present, the technology for further improving oil recovery after ternary composite flooding is not mature and belongs to the stage of technical exploration. The presence of alkaline substances significantly alters the reservoir's physical properties and causes considerable corrosion to the equipment used in its development. This is detrimental to both the environment and production. Therefore, it is necessary to develop green displacement control agents. In the reservoir environment post-ASP flooding, 2-(methylamino)ethyl methacrylate and glycidyl methacrylate were chosen as monomers to synthesize a polymer responsive to alkali, and then grafted with cellulose nanocrystals to form microspheres of alkali-resistant swelling hydrogel. Cellulose nanocrystals (CNCs) modified with functional groups and other materials were utilized to fabricate hydrogel microspheres. The product's structure was characterized and validated using Fourier transform infrared spectroscopy and X-ray diffraction. The infrared spectrum revealed characteristic absorption peaks of CNCs at 1165 cm-1, 1577 cm-1, 1746 cm-1, and 3342 cm-1. The diffraction spectrum corroborated the findings of the infrared analysis, indicating that the functional modification occurred on the CNC surface. After evaluating the swelling and erosion resistance of the hydrogel microspheres under various alkaline conditions, the optimal particle size for compatibility with the target reservoir was determined to be 6 μm. The potential of cellulose-based gel microspheres to enhance oil recovery was assessed through the evaluation of Zeta potential and laboratory physical simulations of oil displacement. The study revealed that the absolute value of the Zeta potential for gel microspheres exceeds 30 in an alkaline environment with pH values ranging from 7 to 14, exhibiting a phenomenon where stronger alkalinity correlates with a greater absolute value of Zeta potential. The dispersion stability spans from good to excellent. The laboratory oil displacement simulation experiment was conducted using a cellulose-based gel microsphere system following weak alkali ASP flooding within the pH value range from 7 to 10. The experimental interventions yielded recovery rates of 2.98%, 3.20%, 3.31%, and 3.38%, respectively. The study indicates that cellulose-based gel microspheres exhibit good adaptability in alkaline reservoirs. This research offers a theoretical foundation and experimental approaches to enhance oil recovery techniques post-ASP flooding.

Characterization of pore structures after ASP flooding for post-EOR

With the global assistance of oil fields entering the stage of improving oil recovery, diversified composite flooding technology has become one of the key research targets. This article takes composite flooding to improve oil recovery as the research object, explores the differential mechanism of crude oil displacement efficiency under water flooding and composite flooding conditions, and elucidates the dynamic evolution characteristics of pore structure before and after composite flooding. Results show that: (a) The permeability and porosity of Daqing oilfield cores have a good correlation. The porosity of cores after water driving and ternary composite driving mainly ranged from 23.6 % to 27.4 % and 22.8 %–26.8 %. The water-driving permeability mainly ranged from 168 × 10−3 μm2 to 2162 × 10−3 μm2. Ternary composite driving permeability mainly ranges from 302 × 10−3 μm2 to 2307 × 10−3 μm2. (b) Compared with water driving, quartz and clay minerals are corroded by alkali during ternary composite driving. (c) Under the condition of similar permeability, the average pore size of the core after ternary composite driving is smaller than the average pore size after water driving.

Numerical Investigation on Alkaline-Surfactant-Polymer Alternating CO2 Flooding

For over four decades, carbon dioxide (CO2) has been instrumental in enhancing oil extraction through advanced recovery techniques. One such method, water alternating gas (WAG) injection, while effective, grapples with limitations like gas channeling and gravity segregation. To tackle the aforementioned issues, this paper proposes an upgrade coupling method named alkaline-surfactant-polymer alternating gas (ASPAG). ASP flooding and CO2 are injected alternately into the reservoir to enhance the recovery of the WAG process. The uniqueness of this method lies in the fact that polymers could help profile modification, CO2 would miscible mix with oil, and alkaline surfactant would reduce oil–water interfacial tension (IFT). To analyze the feasibility of ASPAG, a couples model considering both gas flooding and ASP flooding processes is established by using the CMG-STARS (Version 2021) to study the performance of ASPAG and compare the recovery among ASPAG, WAG, and ASP flooding. Our research delved into the ASPAG’s adaptability across reservoirs varying in average permeability, interlayer heterogeneity, formation rhythmicity, and fluid properties. Key findings include that ASPAG surpasses the conventional WAG in sweep and displacement efficiency, elevating oil recovery by 12–17%, and in comparison to ASP, ASPAG bolsters displacement efficiency, leading to a 9–11% increase in oil recovery. The primary flooding mechanism of ASPAG stems from the ASP slug’s ability to diminish the interfacial tension, enhancing the oil and water mobility ratio, which is particularly efficient in medium-high permeability layers. Through sensitivity analysis, ASPAG is best suited for mid-high-permeability reservoirs characterized by low crude oil viscosity and a composite reverse sedimentary rhythm. This study offers invaluable insights into the underlying mechanisms and critical parameters that influence the alkaline-surfactant-polymer alternating gas method’s success for enhanced oil recovery. Furthermore, it unveils an innovative strategy to boost oil recovery in medium-to-high-permeability reservoirs.

Study on the Alkali-Free Three-Component Flooding System in the Daqing Oilfield.

ASP flooding is an important method to further improve oil recovery by a large margin. At present, it has entered the stage of industrial application, but there are still problems of scaling in the injection production system and high production maintenance costs. Based on the industrialized mature technology of weak alkali ASP flooding, sodium chloride is used to replace sodium carbonate, and the alkali-free three-component flooding (TC) system in the Daqing Oilfield is developed by mixing with petroleum sulfonate and partially hydrolyzed polyacrylamide. Based on the experiments of viscosity increasing, interface performance, stability, adsorption, and oil displacement effect, the differences between the alkali-free TC system and the weak alkali ASP system are compared and analyzed. The laboratory research results show that both systems are basically the same in terms of viscosity, viscoelasticity, shear resistance, interfacial activity, stability, and flowability. Due to the lack of alkaline water, the adsorption, emulsification, and oil displacement performance of the alkali-free TC system is slightly lower than that of the weak alkali ASP system. The recovery factor of core flooding can be increased by 27.31% over water flooding, which is 2.56 percentage points lower than that of the weak alkali ASP system. On the premise of the same 1% EOR effect, the agent cost of the alkali-free system is 17.02% lower than that of the alkali ASP system. This article innovatively verifies the feasibility of using NaCl instead of Na2CO3 and explains the mechanism of significantly improving oil recovery in composite systems under alkali-free conditions from the ion level. However, the emulsification effect of the alkali-free TC system is relatively weak. The next step of research would be to consider adding an E-surfactant to enhance the emulsification performance of the composite system. By improving the system composition, technical references are provided for the efficient development of other terrestrial sandstone oilfields.

Solar demulsification: Towards the oil-water interface broken of solar photo-thermo-electro coupling

The stability of the emulsified oil/water mixture depends on the strength and tightness of the interface, which is closely related to the adsorption and close packing of the active components on the interface. The core task of demulsification is to change the interface properties to enhance efficient oil-water separation. In this study, a coupling model of photo field, thermo field, and electro field was constructed to focus on fully considering the particularity of the demulsification, while improving the utilization efficiency of solar energy by presetting and matching a variety of energy flows and sub-processes. Taking oil/water emulsion from the ASP flooding as an example, the oil removal rate of 82.27% can be obtained, and efficient energy modes, namely high-intensity thermo field, uniform photo field and low-intensity electro field, are established. At the same time, the results show that the photo-thermo-electro field changes the properties of the oil-water interface, such as the interfacial tension, zeta potential and modulus. The mechanism of solar demulsification is that the solar thermal effect changes the motion state of the molecules at the interface, the coupling electro effect drives the migration of charged droplets and the stretching or deformation of the polymer chain, which combined with the photo field to degrade the polymer at the interface. Solar demulsification not only enables innovation in the form of energy and promotes its sustainable development, but also provides a green process in which solar thermo, photo, and electro are synergistically combined to achieve demulsification.

Study on influencing factors of wellbore scaling during ASP flooding

In the middle and later stages of oil and gas field development, the produced fluid carries a large amount of formation scaling ions. During the entire extraction process, changes in parameters such as temperature, pressure, and flow rate can disrupt the original equilibrium and cause collisions between scaling ions. The scale particles formed by chemical reactions aggregate and deposit on the cylinder wall, causing scaling. The accumulation of scale not only causes wellbore blockage, but also irreversible damage to the production well. In order to study the scaling problem of oil production wells, the scaling mechanism was studied through indoor experiments. On this basis, a numerical model for the formation of wellbore scaling was established, and the mass fraction distribution of CaCO3 scaling particles at different positions in the wellbore was studied. The results indicate that: (1) the main type of scale sample is calcium carbonate, and as the concentration of calcium carbonate and sulfate ions increases, the amount of scale and corrosion will increase; (2) As the concentration of bicarbonate ions increases, the amount of scaling increases and the amount of corrosion decreases. (3) The mass fraction of calcium carbonate scaling at the upper and lower parts of the oil pump cavity and the sucker rod coupling decreases with increasing temperature, decreases with increasing initial inlet speed, and increases with increasing scaling ion concentration. The research results of this paper provide theoretical and technical support for predicting the scaling law of production Wells, improving the pumping inspection period of pumping units and ensuring the safety of oil Wells.

Experimental Study on ASP Flooding Horizontal-Vertical Joint Development

ASP flooding oil technology, as a highly concerned method for improving oil recovery in recent years, has the advantages of high oil displacement efficiency and good environmental protection. Horizontal-vertical joint development technology is a method of achieving efficient oil-field development by optimizing well network layout, adjusting injection production parameters, and other means. It improves the pressure field and flow field distribution inside the reservoir, enhances sweep efficiency and oil recovery efficiency, thereby achieving the goal of increasing crude oil recovery rate. This article aims to explore the combined application effect and mechanism of ASP flooding oil technology and horizontal-vertical joint development technology through experimental research, providing new ideas and methods for efficient development of oil fields. The joint application of ASP flooding oil technology and horizontal-vertical joint development technology provides a new approach for efficient oil-field development. This joint application can not only improve the recovery rate of crude oil, reduce development costs, but also help reduce environmental pollution and achieve the sustainability of oil-field development.

Research on prediction model of scaling in ASP flooding based on data mining

As a result of alkali ASP flooding in oil and gas fields, strata and pipelines become seriously scaled, which poses a threat to the normal operation of crude oil production. We propose an intelligent knowledge reasoning model for dynamic scaling prediction in order to address the problems of high directivity, poor generalization ability, and poor application effect of existing scaling prediction methods. The model framework includes the knowledge acquisition layer which mainly relates to the manual acquisition of scaling prediction knowledge and the intelligent training of the knowledge base, and it includes the knowledge modeling layer that provides a set of standard domain common ontology and knowledge organization system using the ontology modeling technology, it also includes the knowledge inference layer which is the application layer of the model. The three layers collaborate and finally complete the scaling prediction through inference and expression. A total of 238 wells were selected for experimentation in the northern development area of the Xingshugang Oilfield. Experimental results indicate that the model has the highest accuracy of 91.87%. Additionally, the time series prediction trend for the six ions matches the trend of change in ion concentration in the scaling state, verifying the accuracy of the model’s predictions.

A molecular modeling and experimental study of solar thermal role on interfacial film of emulsions for elucidating and executing efficient solar demulsification

The adsorption and intermolecular interactions of surfactant and polymer at the oil-water interface are related to interfacial property, which determines whether an efficient oil-water separation can be obtained. Taking oil/water emulsion from the ASP flooding as an example, the thermal role of solar demulsification was studied through combined simulation calculation and experiment. First, a molecular dynamics model of an oil/water interface containing sodium dodecyl benzene sulfonate (SDBS) and polyacrylamide (PAM) was constructed and was used to explore the thermal role on interfacial behavior and intermolecular interactions. Then, the variation of interfacial properties was characterized experimentally as interfacial tension and interfacial rheology. Finally, the effect of solar thermal role on the oil/water emulsions was monitored via the particle size distribution and the ratio of oil removal. The results show that the thermal field changes the configuration and motion behavior of SDBS and PAM and weakens their interaction energy, promoting SDBS extension into the oil. Thus interfacial tension is increased and the rigidity and strength of the interface are decreased, which destabilizes and bridges the emulsion droplets, facilitating coalescence and eventual oil-water separation. As a result, the size of oil droplets was promoted and the oil removal ratio of 40.53 % was achieved. This work provided insight into the thermal role of solar demulsification, thus providing theoretical support for effectively coupling solar photo, electric, and thermal energy to high-efficiency solar demulsification.

Different approach to surfactant screening methods for ASP flooding

Different approach to surfactant screening methods for ASP flooding

Effect of oil displacement agent on corrosion behavior of NaCl - Alkali/ Surfactant/ Polymer flooding pipeline steel

The research examined the effect of oil displacement agent (Hydrolyzed polyacrylamide, Sodium petroleum sulfonate, NaCl) on corrosion behavior of 20# steel in simulated NaCl ASP flooding solution. Scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray Photoelectron Spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization were performed to investigate the corrosion mechanism of oil displacement agent on carbon steel. The results demonstrated HPAM (hydrolyzed polyacrylamide) and SPS (sodium petroleum sulfonate) can be adsorbed on the surface of carbon steel to played a role in corrosion inhibition. For-HPAM, the corrosion inhibition rate decreases at high concentrations, which was ascribed to the saturation of adsorption amount and the thinning of corrosion product layer at higher concentrations. For-SPS, the formation of hemi-micellar aggregates caused desorption of the inhibitor from the metal/solution interface at higher concentrations. For -NaCl, NaCl promoted the occurrence of corrosion. Although the adsorption of oxygen on the surface of carbon steel was inhibited by a higher concentration of Cl−, a corrosion cell was formed under the action of the adsorption layer of HPAM and SPS, which promoted localized corrosion.

Numerical Simulation by STARS (CMG) using Surfactants for Enhanced Oil Recovery in a Reservoir

In Ecuador, heavy crude oil represents 20% of the proven reserves at the national level. However, producing them has been challenging because of their low recovery factor due to their characteristics, high oil viscosities, and low mobility, among others. This makes developing and implementing improved or tertiary recovery methods and technologies necessary; therefore, the aim is to produce the maximum available resources in an environmentally friendly way. New advances in hydrocarbon extraction technologies in recent years have been tested and one of them, on which this research focuses, is using chemical methods in which solvents are injected to modify viscosity in aqueous solutions. Thus, displacing the oil generates very low interfacial tensions between the crude oil and water by adsorption in the liquid-liquid phase. Therefore, the selection of a reservoir that meets the required characteristics for the respective application of this method was carried out. Furthermore, increasing the sweep efficiency will optimize the mobility of the oil bank toward the producing wells, thus improving the recovery factor. Consequently, upon running the simulation, the results show that continuous surfactant flooding resulted in 84.5% recovery, SP flooding 89.4%, and ASP flooding with the highest recovery factor of 90.13%. This is due to the synergistic contribution of the IFT reduction using surfactant and the mobility ratio per polymer reduction, thus improving the overall sweep efficiency by a better margin. At the same time, alkali is responsible for decreasing the amount of the active surfactant used as it is a lower-cost agent [1].

Physical and numerical simulation of inter-fracture flooding in heterogeneous tight oil reservoirs

The existing tight oil reservoirs are mainly developed after hydraulic fracturing of horizontal Wells with low recovery. Traditional enhanced oil recovery (EOR) methods are difficult to apply in tight reservoirs, because huff-puff drives oil to the distal end, water breakthrough exists in inter-well flooding, and ASP flooding cannot enter the small pore throat of the tight reservoir. A new EOR method of inter-fracture flooding is proposed. This method solves the problem that the injection water cannot enter the matrix in tight reservoir by inter-fracture flooding. Inter-fracture flooding reduces the distance between the injection and production ends and reduces the risk of water channeling. Inter-fracture flooding increases the pressure gradient during water flooding in the reservoir and establishes an effective water displacement system in the heterogeneous tight reservoir. In this paper, physical simulation experiments and numerical simulation are designed to study the EOR effect of inter-fracture water flooding in heterogeneous tight reservoirs. The results showed the following: (1) Inter-fracture asynchronous water flooding (IFAWF) can improve oil displacement efficiency by 6%–16% compared with inter-fracture synchronous water flooding (IFSWF). (2) Compared with IFSWF, IFAWF can greatly improve the oil displacement efficiency of the core with low permeability in the heterogeneous model by more than 20%. (3) Effective water sweep cannot be achieved by IFSWF, but can be achieved by IFAWF. (4) IFAWF established effective displacement in 0.1mD tight heterogeneous reservoir. Studies have shown that inter-fracture flooding can lower the reservoir development permeability threshold and will be an important EOR method for tight oil and shale oil in the future.

Elucidation of the mechanistic aspects of chemical EOR in viscous oil systems

Chemical enhanced oil recovery techniques have been suggested as efficient alternatives to thermal methods in many thin/small viscous oil reservoirs in western Canada. These acidic oil reservoirs have been screened as good candidates for alkaline (A) and surfactant (S) floods. In this study, sand-pack core flooding experiments and pore-scale microfluidic tests were designed to give some new insights on the mechanisms of AS floods augmented with polymer (P) solutions in viscous oil systems.Viscous oil samples from Luseland field (14,850 mPa s at 25 °C) was used in all the experiments. The most efficient chemical generates ultralow interfacial tension, 0.002 mN/m, producing low viscosity type II (+) emulsion (740 mPa s, which is much lower than the viscosity of originating oil). The two pore volumes injection of this cocktail results in around 20% OOIP incremental oil recovery, which is almost doubled after injecting two pore volumes of extended water. The core effluents were all low viscosity oil in water emulsions, consistent with observations in batch mixing experiments. The incremental oil recovery to ASP flood is almost twice the recovery obtained in the polymer flood with nearly 4.5 times larger pressure build-up across the core. These observations suggest that the main mechanism is emulsification and oil entrainment rather than improvement in sweep efficiency.These speculated mechanisms based on the core scale observations were verified through the results of the microfluidic experiments. ASP solution can efficiently penetrate the residual ganglia or the edge of the water channels from which oil can be efficiently stripped. This oil is easily entrained in the form of low viscosity oil in water emulsions. Our results emphasize the critical role of polymer in the cocktail. In the absence of polymer, AS cannot efficiently penetrate the residual viscous oil leading to only a minuscule improvement in oil recovery.

Magnetic Hyperbranched Molecular Materials for Treatment of Oily Sewage Containing Polymer in Oilfield Compound Flooding.

With the continuous improvement in oilfield development and the application of tertiary oil recovery technology, the water content of oilfield-produced fluids has gradually increased, and a large number of oilfield sewage with complex components has also been produced after oil–water separation, and effective treatment is urgently needed. ASP flooding sewage contains alkali, various surfactants, polymers, microemulsion oil droplets, and solid impurities, which are difficult to be effectively treated by traditional water treatment agents and methods. In this study, aminopropyl triethoxysilane (APTES) was used to modify the nano-Fe3O4 coated with tetraethyl silicate (TEOS). The product was used as the ferromagnetic nano-core for the iterative reaction of Michael addition and ester amidation to synthesize a magnetic hyperbranched polyamide amine, and its performance in the treatment of ASP flooding wastewater was evaluated experimentally. For the preparation of APTES-modified Fe3O4@SiO2 (FOSN) product, TEOS was coated over Fe3O4 in an ethanol aqueous solution environment and then APTES was added dropwise. The first-generation branched product (1-FSMN) was obtained by the reaction of FOSN and methyl acrylate graft product (FOSN-M) with ethylenediamine, and the highest yield was 93.7%. The highest yield of the second-generation branched product (2-FSMN) was 91.6%. In this study, a composite flooding wastewater sample from a block in the Bohai oilfield was taken. The suspended solids content was 143 mg/L, the oil content was 921.09 mg/L, the turbidity was 135 NTU, and the zeta potential was −47 mV. The third-generation hyperbranched polymer (3-FSMN) and its quaternary ammonium salt (3-FSMN-Q) performed best in the appropriate dosage range, with the highest oil removal rate of 97%, suspended solid removal rate of 90.3%, turbidity reduction rate of 86.6% and zeta potential reduction rate of 88%. For 3-FSMN and its quaternary ammonium salt, the gravity/magnetic PAC compound treatment experiment was carried out. In the settlement time of only 5 min, 3-FSMN/PAC and 3-FSMN-Q/PAC can achieve the maximum oil removal rate of 87.1% and suspended solids removal rate of 87.3% for polymer containing wastewater from ASP flooding, and 86.3 and 86.0% for 120 mg/L. Its treatment capacity was much better than that of common treatment agent combination (CPAM/PAC).

Influencing factors and microscopic formation mechanism of phase transitions of microemulsion system

As a surfactant solution system, microemulsion has attracted much attention due to its ultra-low interfacial tension, high solubilization and thermodynamic stability in the process of enhanced oil recovery. Different from water phase system of polymer flooding and ASP flooding, the microemulsion system shows a special phase state, and its existence system may be water phase, oil phase or microemulsion phase. The microemulsion phase can be divided into upper phase, middle phase and lower phase microemulsion according to the composition of the system. Different phase microemulsions have different oil displacement efficiency, and the middle phase microemulsion reaches ultra-low interfacial tension with oil/water, and the oil displacement efficiency is the highest. In order to ensure the middle-phase microemulsion flooding as far as possible during the oil displacement process, it is necessary to study the phase change process of microemulsion and the formation conditions of microemulsion in detail, and clarify the influence of surfactant concentration, additive concentration, salt content, water–oil ratio and temperature on the microemulsion phase transformation and the formation mechanism of microemulsion. The research results have some guiding significance for the formulation selection and slug design of microemulsion flooding system.

Research and effect analysis on improving injection mode of weak alkali ASP flooding in poor oil layer block

In view of the large proportion of thin and poor layers in the weak-alkali ternary flooding block, the statistical analysis method is used to optimize the division of well groups with injection capacity, establish a strategy chart for different types of groups to maintain injection and tap potential, and optimize the well groups of different sand body connectivity types. The fracturing method strengthens the whole process of fracturing in the well area with poor injection capacity. The effective thickness water absorption ratio is over 80%, the maximum water cut reduction in the stage is 9.65%, the low water cut stable period is 16 months, and the recovery factor is increased by 8.77 percentage points. development effect.

Response to the Variation of Clay Minerals During ASP Flooding in the Saertu Oilfield in the Songliao Basin

In this paper, the variation of clay minerals and their influence on reservoir physical properties and residual oil before and after ASP flooding are analyzed. The results show that the total amount of clay minerals in reservoirs decreases after ASP flooding in the ultra-high-water-cut-stage reservoirs of the Naner Zone in the Saertu Oilfield, Songliao Basin. Therein, the illite content reduces, while the content of illite smectite mixed-layer and chlorite increases. The content of kaolinite varies greatly. The content of kaolinite decreases in some samples, while it increases in other samples. The clay minerals block the pore throat after ASP flooding. As a result, the pore structure coefficient and the seepage tortuosity increase, the primary intergranular pore throat shrinks, and the pore–throat coordination number decreases. Nevertheless, the dissolution of clay minerals reduces the pore–throat ratio and increases porosity and permeability. The variation of clay minerals after ASP flooding not only intensifies the reservoir heterogeneity but also affects the formation and distribution of residual oil. The residual oil of the oil–clay mixed adsorption state is a newly formed residual oil type related to clay, which accounts for 44.2% of the total residual oil reserves, so it is the main occurrence form of the oil in reservoirs after ASP flooding. Therefore, the exploitation of this type of residual oil has great significance to enhance the oil recovery in ultra-high-water-cut-stage reservoirs.

Effective EOR methods in high-viscosity oil fields: cyclical GEL-polymer flooding and ASP flooding

The presented work discusses increasing oil recovery factor using physicochemical EOR methods.
 This article presents the field pilot tests results related to cyclical gel polymer flooding technology as applied under the conditions productive reservoirs rich in high-viscosity oils (viscosity in reservoir conditions above 300 mPa s) of the Buzachi North oil field, extending the boundaries of application of these methods. The work used the methods of hydrodynamic modeling, mathematical analysis; the necessary parameters of fractures and super reservoirs for calculating the working volumes of the injected compositions were estimated using tracer studies.