Mechanism Of Viscosity Reduction Research Articles

Study of viscosity reduction mechanism of oilfield polymer solution by spectroscopy method

The viscosity reduction mechanism of a polymer aqueous solution for oil displacement affected by factors such as salinity, cation type, iron ion and temperature need to be further elucidated. The functional group absorbance of polyacrylamide was determined by ultraviolet spectrophotometry. The spectral behavior of polyacrylamide was analyzed from the perspective of molecular structure, and the microscopic level of its viscosity was explored. The results show that the absorbance of the polymer is affected by the valence of the cation in the order of Fe2+ > Fe3+ > Al3+ > Mg2+ > Ca2+ > K+ > Na+. Anion has no effect on the viscosity of polyacrylamide. With the increase of temperature, the absorbance and viscosity of polymer solution decreased. This paper investigated the effects of salinity, cation type, iron ion concentration and temperature on the spectral behavior of polyacrylamide. It was found that the decrease of absorbance was consistent with the change of molecular conformation. The decrease in amide groups in polymer solution leads to a decrease in solution absorbance, while the increase in amide groups leads to an increase in solution absorbance. Therefore, the conformational changes of polyacrylamide molecular chains can be determined by amide groups. The UV spectrum of polymers can provide a theoretical basis for the study of viscosity reduction mechanism. The ultraviolet spectrophotometry is simple and intuitive, which provides guidance for the selection of oil displacement polymer and the research and development of high-performance polymer.

Synthesis and Mechanistic Investigation of an Amphiphilic Polymer in Enhancing Extra-Heavy Oil Recovery via Viscosity Reduction.

When applied to extra-heavy oil, conventional polymer surfactants exhibit poor efficacy in reducing viscosity and have limited adaptability. In this work, a novel amphiphilic polymer named PAADB was prepared by incorporating 2-acryloylamino-2-methyl-1-propanesulfonic acid (AMPS), benzyldimethyl [2-[(1-oxoallyl) zoxy] propyl] ammonium chloride (DML), and poly(ethylene glycol) methyl ether acrylate (BEM) into the main chain of acrylamide through free radical polymerization. PAADB exhibited outstanding interfacial activity, water-phase thickening ability, and emulsifying performance. The critical micelle concentration of PAADB was approximately 2500 mg/L, with a viscosity of 84.69 mPa·s at 50 °C. Additionally, interfacial tension experienced a notable decrease from 46.53 to 14.56 mN/m. At an optimal concentration of 4000 mg/L, PAADB reduced the viscosity of extra-heavy oil by over 92% across various temperatures and by more than 93% for different types of extra-heavy oil. PAADB demonstrated excellent emulsification ability and emulsion stability, effectively dispersing crude oil to create water-in-oil droplets measuring 35.33 μm in size. Meanwhile, molecular dynamics simulations further unveiled the viscosity reduction mechanism of PAADB. The hydrophilic groups within PAADB molecules are regularly distributed on the water interface, while the hydrophobic groups infiltrate the oil molecules to form a stable interfacial film. PAADB and asphaltene spontaneously form a sandwich structure, reducing intermolecular forces and disrupting the interlayer structure of asphaltene molecules. In general, this novel amphiphilic polymer demonstrates broad applicability and potential in extra-heavy oil recovery, providing valuable insights for the development of new heavy oil viscosity reducers (HOVRs).

Simulation analysis of the effect of a small amount of fine particle added to a slurry on the liquid behavior and forces acting on the main particles

The viscosity of highly concentrated slurries is reduced by adding a small amount of fine particle with the same material of main particles (high concentration ratio particles per total concentration) in the slurries. We investigated how added fine particles affect the liquid behavior and forces acting on the main particles in the slurry by using direct numerical simulations, and we examined one factor that contributes to the viscosity reduction mechanism in highly concentrated slurries containing a small amount of fine particle. The results indicated that whether fine particles are coated (they contact) on the surface or not have little influence on the change in forces acting on the main particles. In highly concentrated slurries containing a small amount of fine particle, there was a large change in the liquid velocity between and around the main particles. From these results, we proposed a possible mechanism to assist in reducing the viscosity of highly concentrated slurries containing a small amount of fine particle. The magnitude and direction of the forces acting on each main particle were non-uniform by adding fine particles, resulting in non-uniform strength within the main particle bed in the slurry, which could facilitate particle bed deformation and assist in reducing the viscosity.

Recovery mechanisms of shale oil by CO2 injection in organic and inorganic nanopores from molecular perspective

CO2 injection is the feasible method to enhance shale oil recovery and has attracted extensive attention in recent years. Since shale reservoir has omnipresent nanoscale pores, understanding the underlying CO2-EOR mechanisms at the nanoscale is of critical importance. In this work, we study the structural and dynamic properties of CO2/nC8 systems in organic kerogen and inorganic quartz nanopores by molecular dynamic simulation and clarify the dominant EOR mechanisms of CO2 injection in various mineral nanopores. We find a large positive slip velocity occurs when single-phase nC8 flows in quartz nanopore while it is no-slip boundary condition in kerogen nanopore. The CO2-regulated nC8 in quartz nanopore is the joint effect of slip, competitive adsorption and viscosity reduction. In the first stage, CO2 extracts the first adsorption layer of nC8 by competitive adsorption and forms a CO2 film on the quartz surface. The CO2 film reduces the slip velocity between nC8 and quartz surface and weakens the nC8 flow capacity. After CO2 adsorption is saturated, the CO2 mixes with nC8 in all flow regions and the effective viscosity of nC8 starts decreasing at this stage. The flow capacity of nC8 rises dramatically due to the viscosity reduction mechanism of CO2. In kerogen nanopore, it is no-slip boundary condition and CO2 mixes with nC8 in all flow regions directly instead of preferably adsorbed on the surface. Viscosity reduction is the dominant mechanism to affect nC8 flow behavior and nC8 flow capacity is enhanced monotonically as CO2 injection. Our study advances the understanding of the recovery mechanisms of shale oil by CO2 injection on nanoscale and provides the theoretical foundation for the optimization of CO2-EOR in shale oil reservoirs.

Viscosity Reduction Mechanism and Rheological Properties of Ethylene-Bis-Stearamide and Crumb Rubber Modified Asphalt

This study investigates the effect of ethylene-bis-stearamide (EBS) on viscosity reducing of crumb rubber modified asphalt (CRMA) and explores the interaction mechanism via molecular dynamics simulation (MD), microscope method and rheological experiment. It is confirmed that the EBS play an important role in reducing the viscosity of ethylene-bis-stearamide and crumb rubber modified asphalt (EBS-CRMA), especially when the content is within 3%. The micro morphology and MD results showed that the EBS is coating on rubber and asphaltenes and then forming lubrication film, which is the main reason leading to the viscosity decrease of EBS-CRMA. Additionally, other factors also have significant effect in reducing the viscosity of EBS-CRMA, including the more uniform distribution of asphaltenes, the enhanced diffusion ability of saturates and resins, the reduction of hydrogen bonds and soluble substances within asphalt phase. When EBS content exceeds 3%, the influence on viscosity of EBS-CRMA is not obvious with the EBS content continuously increasing. It can be concluded from Fourier Transform Infrared (FTIR) Spectrometer and MD results that the molecular aggregation, the concentration increase of intermolecular hydrogen bonds and the diffusion ability decrease of EBS-CRMA molecular system are main reasons. Meanwhile, the coating effect of EBS and soluble substances concentration within asphalt phase are limited as the EBS content over 3%.

Viscosity reduction mechanism of surface-functionalized Fe3O4 nanoparticles in different types of heavy oil

In-depth investigation of the viscosity reduction mechanism of nanoparticle viscosity reducers in various heavy oil types holds key strategic significance for the rational exploitation of global heavy oil resources. In this work, the dispersion stability mechanism of three surface-functionalized Fe3O4 nanoparticles (NPs) in kerosene was first explored by molecular dynamics (MD) simulation. Then Studies showed that the differences in asphaltene aggregation structures in different types of heavy oils make their initial viscosities significantly different. The addition of NPs could effectively reduce the viscosity of heavy oil and increase the diffusion coefficient of asphaltenes. Importantly, there were differences in the viscosity-reducing ability and viscosity-reducing mode of the NPs in different types of heavy oil. In Oil1, the NPs increased the peak of the radial distribution function curve, the number of hydrogen bonds (2.25–8.63), and the cluster size between asphaltenes (3.72–6.40). However, these property changes of asphaltenes in Oil2 are opposite. The NPs effectively broke the hydrogen bond between asphaltene (number of hydrogen bonds from 22.87–12.50) and reduced its cluster size (8.17–3.25). Among them, Fe3O4-OA and Fe3O4-KH570 showed the most excellent viscosity reduction performance in Oil1 and Oil2, respectively. Finally, by calculating the surface electrostatic potential of each molecule and the weak interaction between molecules, the microcosmic mechanism of the difference in the viscosity-reducing ability and mode of the NPs in different types of heavy oil was revealed. Overall, the NPs effectively depolymerized the high-density aggregation structure of asphaltene, thereby achieving the purpose of reducing the viscosity of heavy oil. However, in Oil1, the viscosity-reducing performance of NPs was mainly related to their ability to adsorb asphaltenes and their dispersion stability. In Oil2, the viscosity-reducing performance of NPs was dominated by their ability to destroy hydrogen bonds between asphaltenes.

Polymer surfactants as viscosity reducers for ultra-heavy oil: Synthesis and viscosity reduction mechanism

Polymeric surfactants have poor viscosity-reducing effect and little adaptability on ultra-heavy oils. We synthesized a novel polymeric surfactant, named PAMOs, by introducing 2-acrylanmido-2-methylpropanesulfonic acid (AMPS) and sodium alpha-olefin sulfonate (AOS) into the acrylamide (AM) backbone for viscosity reduction in ultra-heavy oil. The PAMOs with high surface and interfacial activity, strong emulsification, good molecular efficiency and viscoelasticity, which emulsified ultra-heavy oil effectively. The formed oil in water (O/W) emulsions with small droplet size and high stability. PAMOs also reduced the oil-water mobility ratio. At a concentration of 3 mg/mL, PAMOs reduced viscosity by more than 90% for different ultra-heavy oils (>15000 mPa·s), showing a broad range of suitability. Combining experimental and molecular dynamics simulation results, polymeric surfactants penetrate into the asphaltene molecular layers to form a “sandwich” structure, weakening the interaction forces between asphaltenes. The structure obtained via the ion-pair dipolar coupling between the polar groups, such as amide and sulphonic acid, and the asphaltene molecules. By strong hydrogen bonding between PAMOs and asphaltene, the supramolecular structure of asphaltene is destroyed and transformed into a low molecular structure. At the meantime, re-agglomeration is prevented by the steric hinerance of hydrophobic long chains, thus achieving viscosity reduction of ultra-heavy oil. It shown that polymeric surfactants have unique advantages in the field of viscosity reduction for ultra-heavy oil.

Study on the in situ desulfurization and viscosity reduction of heavy oil over MoO3–ZrO2/HZSM-5 catalyst

Heavy oil is characterized by high viscosity. High viscosity makes it challenging to recover and transport. HZSM-5, MoO3/HZSM-5, ZrO2/HZSM-5 and MoO3–ZrO2/HZSM-5 catalysts were developed to promote in situ desulfurization and viscosity reduction of heavy oil. The physical and chemical properties of catalysts were characterized by XPS, XRD, TEM, NH3-TPD, etc. The effects of temperature, catalyst type and addition amount on viscosity and composition of heavy oil were evaluated. The results showed that the presence of MoO3–ZrO2/HZSM-5 nanoparticles during aquathermolysis could improve the oil quality by reducing the heavy fractions. It reduced viscosity by 82.56% after the reaction at 280 °C and catalyst addition of 1 wt%. The contents of resins and asphaltic in the oil samples were 5.69% lower than that in the crude oil. Sulfur content decreased from 1.45% to 1.03%. The concentration of H2S produced by the reaction was 2225 ppm. The contents of sulfur-containing functional groups sulfoxide and sulfone sulfur in the oil samples decreased by 19.92% after the catalytic reaction. The content of stable thiophene sulfur increased by 5.71%. This study provided a basis for understanding the mechanism of heavy oil desulfurization and viscosity reduction.

Rheological properties and viscosity reduction mechanism of aromatic/naphthenic oil pre-swelling crumb rubber modified asphalt

Using light oil to pretreat the crumb rubber (CR) could reduce the viscosity of the modified asphalt, thereby enhancing its compatibility with asphalt binder and improving the workability of CR modified asphalt (CRMA). However, the effects of CR pre-swelling on rheological properties of CRMA and the viscosity reduction mechanism are not well understood, especially for commonly used aromatic and naphthenic oils. In this study, the comparative investigations on rheological properties of CRMA before and after pre-swelling process were performed by frequency sweep, temperature sweep, multiple stress creep and recovery (MSCR) and storage stability tests. Meanwhile, the molecular dynamic (MD) simulation method was applied to simulate the distribution, migration, and aggregation characteristics of aromatic oil, naphthenic oil, and asphalt components in CRMA from natural aggregation state to heating mixing and finally cooling, aiming to reveal the viscosity reduction mechanism. The results showed that aromatic and naphthenic oils can significantly reduce the viscosity of CRMA. In addition, the low-temperature crack resistance and storage stability of CRMA can be improved through pretreatment with aromatic and naphthenic oils, which is correlated with the oil content. However, the effects of aromatic and naphthenic oils pre-swelling processes on the high temperature properties of CRMA are different. The MD simulation results showed that the binding energy between asphalt molecules reduced after mixing with aromatic and naphthenic oils, which is which is the primary reason for the viscosity reduction of CRMA. However, there are differences regarding the distribution characteristics of these two oils within asphalt binder. The CR, aromatics, aromatic oil and resins were uniformly dispersed in CRMA system by aromatic oil, whereas the naphthenic oil was adsorbed onto the surface of CR and asphaltenes.

Research on molecular mechanism and prediction model of viscosity reduction of heavy oil by different types of gas

ABSTRACT Dissolved gas flooding techniques are widely used in the later stages of heavy oil reservoir development. The role of foam oil in enhancing oil recovery from heavy oil solution gas has been researched. However, it is difficult to analyze the molecular mechanism of foam oil in the dissolved gas property theory and viscosity prediction model proposed by other scholars. In this study, the microscopic mechanism of the interaction between gas molecules and heavy oil molecules in foaming oil was analyzed by the variation of bubble point pressure and viscosity of different dissolved gases (CO2, N2, CH4) in heavy oil samples. By comparing the variation of bubble point pressure of different dissolved gas samples, it was found that the interaction between gas molecules and heavy oil molecules seriously affected the solubility of gas in heavy oil at the same temperature and pressure. An increase in the solubility of the gas in the dissolved gas sample of heavy oil increases the bubble point pressure. The factors influencing the viscosity of heavy oil show that pressure has the least effect on the viscosity reduction of dissolved gas. The higher the concentration of dissolved gas, the more pronounced the viscosity reduction effect. However, the viscosity reduction performance of the dissolved gas in heavy oil became less effective as the temperature increased. Samples A, B, and C, at 15 mol% CO2 concentration, the dissolved gas viscosity reduction effect decreases by 13.75%, 9.7%, and 12.2% when the temperature is increased by 40°C. In addition, samples A, B, and C, at 50°C and 10 mol% gas solubility, the viscosity reduction effect of CO2 is 25.6%, 8.6%, and 19.7% lower than that of N2. Based on the influencing factors of viscosity reduction of heavy oil dissolved gas, this study modified the FJ viscosity prediction model and proposed a physically meaningful heavy oil viscosity prediction model. The model predicts the viscosity of heavy oil dissolved gas with over 90% accuracy (R2 > 0.9) and has some applicability to mixed component gases.

Preparation of graphene supported Ni–Fe bimetallic nanocatalyst and its catalytic upgrading and viscosity reduction performance for heavy oil

Graphene supported single metal catalyst can improve the dispersion of active components and enhance the viscosity reduction effect of heavy oil. However, there is little research on graphene-supported bimetallic catalysts in the field of heavy oil upgrading and viscosity reduction. In this paper, super heavy oil of Liaohe Oilfield was taken as the research object. Graphene was selected as the carrier material, and nickel and iron chlorides were used as precursors. Graphene-supported nickel-iron bimetallic nanocatalysts were prepared by solvothermal method, and their synthesis feasibility was proved by microscopic characterization. Then the prepared catalyst was used in the evaluation experiment of catalytic upgrading and viscosity reduction performance of Liaohe heavy oil. By analyzing the parameters of oil samples before and after catalytic upgrading and viscosity reduction, the catalytic upgrading and viscosity reduction effect was evaluated and the viscosity reduction mechanism was revealed. The results showed that the viscosity reduction rate of heavy oil with graphene supported Ni–Fe bimetallic catalyst was 42.38%. With the aid of decalin, the viscosity reduction rate of heavy oil could reach 71.43%. At this time, the content of heavy components, the average molecular weight of heavy components and the aromaticity fA of oil samples decreased after catalytic upgrading and viscosity reduction, while the aromatic condensation degree HAU/CA and the branched chain index BI increased, and the modification effect was significant. Among them, the average molecular weight of asphaltene decreased from 2266 to 1444, with the most obvious decrease. The decrease of heteroatom content in asphaltene led to a significant decrease in intermolecular force and hydrogen bonding, which was the main reason for the catalytic upgrading and viscosity reduction of heavy oil by graphene supported Ni–Fe bimetallic catalyst.

Study on the viscosity reduction effect and mechanism of aquathermolysis of heavy oil catalyzed by clay-supported Mn(II) complex

Study on the viscosity reduction effect and mechanism of aquathermolysis of heavy oil catalyzed by clay-supported Mn(II) complex

The mechanism of viscosity reduction of waxy oils induced by the electric field: A correlation between the viscosity reduction and the charged particle accumulation on wax particles

Wax molecules crystallize at ambient temperature, causing the crude oil to become a dispersed system, which poses challenges in the flow assurance of pipelines. Improving the cold flowability of crude oil is the fundamental solution to tackle these problems. Applying an electric field to waxy oil may markedly improve its cold flowability. The adhesion of charged particles on wax particles’ surface under the electric field has been demonstrated as the essential mechanism of the electrorheological effect. However, the correlation between the accumulated charged particles and the induced viscosity reduction has not been explored quantitatively. In this study, the viscosity and impedance of four crude oils before and after electric treatment were measured. The conductivity changes of the oils’ continuous phase were obtained by an equivalent circuit model. And then, the charged particles’ concentration before and after electric treatment was calculated by the Stokes equation. The results showed there is a positive correlation between viscosity reduction and charged particle concentration reduction in the continuous phase. Importantly, this correlation is also quantitatively applicable to the results of ten different waxy oils which has been published. This study provides a quantitative basis for the mechanism of electrorheological behavior of waxy oils.

Research and Development Trend of Viscosity Reduction by Catalytic Coupling Reaction of Crude Oil

In view of the increasing consumption of fossil energy, heavy oil with large reserves and wide distribution, as an important unconventional oil and gas resource, has attracted more and more attention in its exploration and development. However, due to the high content of heavy components in heavy oil, its viscosity is high, its fluidity is low, and its quality is poor. Therefore, the key to enhance heavy oil recovery is to reduce its viscosity, improve its fluidity and improve its quality. At present, steam huff and puff, steam flooding and in-situ upgrading and viscosity reduction of heavy oil are the conventional methods for heavy oil recovery. Considering the production cost, the hydrothermal catalytic cracking technology for heavy oil recovery is studied. However, most of these researches only focus on the preparation and application of catalytic viscosity reducer, and there is still a lack of in-depth and systematic research on its specific viscosity reduction mechanism. Therefore, on the basis of abundant active hydrogen provided by alcohol water reforming reaction, it is of great theoretical value and practical significance to design the application of high-efficiency heavy oil viscosity reduction catalyst by using the super molecular interaction of in-situ active minerals and exogenous metal complexes to catalyze the high-efficiency hydrothermal cracking of heavy oil.

The Effect of Sodium Bentonite in the Thermo-Catalytic Reduction of Viscosity of Heavy Oils

To study the synergistic catalysis of an ex situ catalyst and in situ clay in the aquathermolysis of heavy oil, in this paper, a series of bentonite-supported catechol-metal complexes were prepared, and the catalytic viscosity reduction performance in the aquathermolysis of heavy oil was investigated. Under the optimized conditions, the viscosity can be reduced by 73%, and the pour point can be lowered by 15.0 °C at most, showing the synergistic catalysis of the ex situ catalyst and in situ clay in this aquathermolytic reaction. Thermogravimetry, physical adsorption-desorption, and scanning electron microscopy were conducted to characterize the thermal stability and microstructure of the ex situ catalyst. The components of the heavy oil before and after the reaction were fully characterized. Six model compounds were used to simulate the aquathermolysis reaction process. In order to study the mechanism of viscosity reduction after the catalytic aquathermolysis reaction, the compounds were analyzed by GC-MS. It is believed that these results will be beneficial in the future for related research in this field.

Evaluation of viscosity reduction effect of oil-soluble viscosity reducer on crude oil

In this paper, several crude oil viscosity reducers were selected to evaluate their performance on the heavy oil Henan Oilfield, China. Through investigation, the viscosity reducing ability of these viscosity reducers were relatively general. Among them, EVA had the highest performance, reaching a viscosity reduction rate of 45.6%. The results were characterized by DSC analysis, wax crystal micromorphology analysis of saturated hydrocarbons and IR spectroscopy. Finally, possible viscosity reduction mechanism was discussed.

Effect of molecular weight on the properties of water-soluble terpolymers for heavy oil viscosity reduction

BackgroundWater-soluble polymers are increasingly attracting the attention of petroleum engineers for their excellent surface activity and viscosity-reducing properties in enhancing heavy oil recovery. However, the actual formation conditions are highly saline, for which we designed and synthesized a new salt-resistant water-soluble viscosity reducer. MethodsHydrophobically associating terpolymers, poly(Acrylamide/ N-vinyl caprolactam/ quaternary ammonium salt alkyl chains) (ANDs), were synthesized by free radical polymerization in an aqueous solution, and we obtained four different molecular weights of polymers by dialysis. Significant findingsThe results showed that the heavy oil viscosity reduction rates (VRR) of all four polymer solutions were above 98.3% under highly mineralized formation water and high-temperature reservoir conditions. Polymer AND-4 could show good salt tolerance at a high salt concentration of 5 × 104 mg/L NaCl and reached the best viscosity reduction rate of 99.07%. In addition, the polymers' thermal stability, hydrophobicity, surface activity, and salt resistance improved with the increasing molecular weight. Meanwhile, the critical micelle concentration (CMC) and the emulsifying performance improved. This study also discussed the mechanism of viscosity reduction by different molecular weight viscosity reducers. Notably, compared with previous heavy oil viscosity reducers, this work provides a new water-soluble polymeric viscosity reducer with high efficiency and salt tolerance. It also facilitates the design and application of functionalized viscosity reducers for enhancing oil recovery.

Characteristics, mechanisms, and environmental LCA of WMA containing sasobit: An analysis perspective combing viscosity-temperature regression and interface bonding strength

Warm mix asphalt (WMA) with organic additive technology has been highly recommended in asphalt pavement. However, the viscosity-reduction mechanism, viscosity-temperature relationship, and field application effects have yet to be well excavated. Therefore, the characteristics, mechanisms, and environmental benefits of WMA containing sasobit warm agent (SWA) were developed. Kinetic viscosity, Brookfield viscosity, modified BBS tests, and rheological property tests were performed. The results showed that WMA with SWA significantly lowered the mixing and compaction temperatures. They were reduced by 38.9 °C and 36.8 °C using 4% SWA, respectively, compared with 70# base asphalt. The bonding strength between WMA and asphalt or aggregate was also improved after adding SWA. Based on the balanced performance design, the optimum SWA dosage was 3%. Measured field data showed that the asphalt fume, BSO, and benzopyrene reductions were more than 80% in WMA pavement construction adding 3% SWA. Moreover, energy consumption and carbon emissions in the LCA of WMA pavement construction adding 4% SWA were reduced by 134.86 MJ/t (21.56%) and 112.03 kg/t (40.60%), respectively. Overall, the characteristic, mechanism, and LCA analysis of WMA with SWA confirmed its great potential and application prospects.

Recycling waste engine oil as a viscosity reducer for asphalt rubber: an insight from molecular dynamics simulations and laboratory tests.

Traditional asphalt rubber (AR) has a high viscosity and poor fluidity, which makes its construction very difficult. Reducing viscosity has been identified as one of the effective way of solving these problems. Meanwhile, the mass production and improper discharge of waste engine oil (WEO) have a serious impact on the ecological environment, and its rational reuse needs to be addressed. In this paper, molecular models of AR and WEO-modified asphalt rubber (WEOMAR) was established by molecular dynamics (MD) simulations. The influence of WEO on asphalt component's behavior was studied by radial distribution function (RDF) and diffusion coefficient (D). Then, the microscopic mechanism of viscosity reduction was evaluated. Furthermore, the viscosity reduction behavior of WEO in AR was analyzed and verified by basic properties and low field nuclear magnetic resonance (LF-NMR) laboratory tests. The results showed that the RDF peak value of rubber molecules in WEOMAR is 14.07 higher than that of AR, at r = 2.16Å. The D of saturated and aromatic components in WEOMAR obviously increased by 140% and 67.9%, respectively. The light component molecules increased after adding WEO into AR. The rubber molecule reduces the contact with asphaltene and resin, and the viscosity of AR is significantly reduced, which is confirmed by the macro tests.

A new method of water control for horizontal wells in heavy oil reservoirs

It is more difficult to control water production in horizontal wells than in vertical wells. It is challenging to predict the water-producing section of a horizontal well and realize staged oil recovery. With water breaking through the oil layer, the water cut of production wells sharply rises. This can even lead to early closure of production wells, which can seriously affect the economic benefits. When researchers explore water control of horizontal wells, they usually use the method of plugging the water-producing section. The success rate is often low due to water flow around the plugged section and pollution of plugging agents in the high-oil saturation area. On the basis of nitrogen for water cresting control, this paper studied the ability of a viscosity reducer (VR) and nitrogen (N2) compound system to inhibit the rise in the water crest. First, a series of two-dimensional quantitative experiments and visualization experiments were conducted to study the influence and mechanism of the VR and N2 system in controlling water cresting. The results show that compared to N2 control of water cresting (recovery improved by 2.70%), the compound system greatly improved the water control and oil increase effects of the horizontal well (recovery improved by 26.38%). The VR enters the area with high oil saturation through osmosis to reduce the viscosity of heavy oil and the water-oil mobility ratio. N2 enhanced the osmosis of the VR in the reservoir. In addition, rheological tests were performed of heavy oil mixtures, and the viscosity reduction mechanism of the VR was analyzed via diffusion-ordered spectroscopy (DOSY) and scanning electron microscopy (SEM). The experiment shows that after addition of the VR, the size of heavy oil deposit was reduced and the asphaltene surface was broken. The VR reduced the viscosity of heavy oil by depolymerizing macromolecular aggregates in heavy oil and preventing them from coming together again. Finally, a field test was conducted in a horizontal well, with a cumulative oil increase of 9286.86 bbl. The research results provide an important guiding significance for water control and oil recovery of horizontal wells.