Effect Of Polymer Flooding Research Articles

Evaluation of the development effect of polydynamic drive in Class IIB oil reservoir of Lamadian Oilfield

With the continuous deepening of oilfield development, the target of oilfield development is gradually shifting towards reservoirs with poor physical properties, and polymer flooding can better utilize such reservoirs.The heterogeneity of Class II B oil layer in Lamadian Oilfield is severe, and polymer flooding takes effect later, with a small decrease in watercut.A study was conducted on the evaluation of polymer flooding development effectiveness for Class II B oil layers through reservoir numerical simulation . Research has shown that when the initial watercut is constant, a lower injection pressure can increase the utilization degree of remaining oil in the middle and high permeability layers of Class II B oil layers. With the increase of injection pressure, the response time is shortened, and the decrease in watercut is reduced; As the watercut increases, the injection pressure should gradually increase in order to improve the recovery of low permeability reservoirs;As the watercut increases, the injection pressure should gradually increase in order to improve the recovery of low permeability oil layers;At a watercut of 95% and injection pressure of 7MPa, a field experiment was conducted with a molecular weight polymer of 12 million , and the response time was 6 months. The cumulative oil increase was 14675m3, achieving good polymer flooding effect.

Injectability of Partially Hydrolyzed Polyacrylamide Solutions Improved by Anionic-Nonionic Surfactant in Medium and Low Permeability Reservoirs

Injectability of the polymer solution is a very important factor that determines the effectiveness of polymer flooding for enhanced oil recovery. Here, the medium and low permeability oil reservoir was taken as a research object, and effects of relative molecular weight, concentration and core permeability on the flow and injection performance of a partially hydrolyzed polyacrylamide (HPAM) solution with and without anionic-nonionic surfactant (ANS) were studied by indoor outcrop core physical model experiments. It was found that the influence of HPAM concentration on the flow performance was related to the core permeability. When the core permeability was lower than 59 mD, the resistance factor and residual resistance factor of HPAM increased with increasing the concentration. High molecular weight and low core permeability were not conducive to the injectability of HPAM solutions. The addition of ANS was beneficial in enhancing the injectability of HPAM solution by reducing the critical value of injectability of HPAM solution, which was elucidated by the Hall curve derivative method. In the presence of ANS, the flow pressure gradient and the residual resistance factor of the HPAM solution decreased. It is believed that the injectability of HPAM solution improved by ANS in the medium and low permeability reservoirs can be attributed to decrease in fluid viscosity and competitive adsorption on the surface of porous media. The study provides a new idea and theoretical basis for improving the injectability of an HPAM solution and the application of polymer flooding and a polymer/surfactant binary flooding system in medium and low permeability reservoirs.

Optimization of EOR after combined flooding

After polymer flooding treatment, the oil recovery can be enhanced through the application of advanced technology. However, in practical applications, excess residues will be generated after polymer flooding treatment. Therefore, in the analysis and treatment of residues, the distribution law of residues after polymer flooding is analyzed, and the recovery process and distribution treatment process are carried out. optimization to achieve enhanced oil recovery after polymer flooding. After the polymer flooding treatment, the high concentration and high molecular weight polymer treatment can improve the recovery rate of crude oil, and on the basis of the polymer flooding treatment, the polymer flooding effect can be improved, which can effectively improve the crude oil recovery rate. recovery and improve the development efficiency of oilfields.

Study on intelligent analysis algorithm for achieving standard of polymer flooding well group

In order to master the development effect of polymer flooding well group, it is necessary to accurately analyze the influence of different factors in the whole polymer flooding process on the development index. Combined with the principle of big data analysis, based on the neighborhood rough set theory and Kmeans clustering algorithm, an intelligent analysis algorithm is proposed to determine the achievement of development indicators of polymer flooding well group. Firstly, the neighborhood rough set was used to reduce the attributes of the influencing factors of the Wells with and without the standards. Secondly, Kmeans algorithm was used to cluster the reduced influencing factors to delete the data inconsistent with the actual compliance. Finally, the clustering model is used to judge the standard status of other well groups, and the practical application effect is very good.

Preparation and properties of nano-silica hybrid hydrophobic associated polyacrylamide for polymer flooding

Polymer flooding was one of the most commercial enhanced oil recovery (EOR) methods. It was the key to study novel polymer which had special properties for improving the oil displacement efficiency. In this study, a nano-hybrid polymer ([email protected]) for polymer flooding was synthesized by in situ polymerization with monomers and silica nanoparticles (SNP). The composition, micro-morphology and rheological properties of PAAM and [email protected] were characterized by FT-IR, 1H NMR, TEM, and rheometer. Compared with pure PAAM, the nano-hybrid polymers showed excellent viscoelastic, temperature resistance and shear resistance properties. The nano-hybrid polymer with the nanoparticle content of 1.5% w/w had the best performance. Improved performance of [email protected] could be attributed to the rigid SNP was dispersed into the polymer to interact with the polymer molecules, which enhanced the network structure of [email protected] and made the network structure of [email protected] more complex. [email protected] could make rocks tend to be water wet, which was good for oil displacement. In the enhanced oil recovery tests, nuclear magnetic resonance (NMR) visualization technology was combined with traditional core displacement experiments to study the effect of polymer flooding. The solution with a concentration of 0.1% w/w [email protected] increased oil recovery by 7.82% contrasting only 2.53% for the solution with a concentration of 0.15% w/w PAAM. Observation of cores during displacement by nuclear magnetic resonance imaging revealed that [email protected] reduced the mobility ratio oil to water and increased sweep efficiency notably. [email protected] had more obvious advantage in performance and more economical than PAAM, which made [email protected] have a better application in EOR.

Analysis on Dynamic Characteristics of Polymer Flooding and Influencing Factors of Oil Flooding Effect

At the present stage of scientific research, the chemical industry is an important part, and its influence is very high. Oil industry is the key project of national development at present, especially in the aspect of polymer flooding, whether it is the mastery of dynamic characteristics or the analysis of effect influencing factors, we must insist on starting from a long-term perspective. Only in this way can the practical process of specific work be handled and solved according to the rational mode, reduce the shortage of old work and improve the analytical connotation of polymer flooding. This paper discusses the dynamic characteristics and influencing factors of polymer flooding effect, and puts forward reasonable suggestions.

Enhanced oil recovery mechanisms of polymer flooding in a heterogeneous oil reservoir

Abstract Taking reservoir rocks and fluids of the Daqing, Dagang and Changqing oilfields as research objects, the EOR mechanisms and technical approach of polymer flooding were discussed. By comparing the displacement performances of ordinary polymer, glycerol, polymer in “sheet-net” structure and heterogeneous weak gel at the same viscosity and concentration, the relationship between the viscosity of polymer displacement agents and displacement performance was demonstrated, and the method of improving polymer flooding effect was worked out. The main mechanism of polymer flooding to increase oil recovery is the swept volume expansion of water injection due to polymer retention in porous media. The viscosity of polymer agents has no positive correlation with polymer flooding effect. Although polymer of “sheet-net” structure has strong capacity in increasing viscosity, it has poor compatibility with pore throat structure of reservoir rock, low injectivity and low shear resistance. Heterogeneous weak gel system has higher adsorption and capture capacity in porous media, which is easy to retain in porous media, and can effectively establish seepage resistance in high permeability layers (zones). Compared with polymer solutions with the same viscosity or concentration, it has stronger ability to expand swept volume. Long term injection of polymer flooding agents will inevitably lead to fluid entry profile reversal, and thus worsening of polymer flooding effect. Alternate injection of high retention and low or non-retention displacement agents can further improve the displacement effect of polymer flooding agents.

Study on the Adaptability of Reservoir Polymer Flooding III Types Based on Computer Monitoring

With the continuous expansion of polymer flooding area of main reservoirs, the remaining oil reserves of class I and class II reservoirs decrease year by year. With the continuous decline of polymer flooding production, the difficulty of oil recovery will gradually increase. Therefore, we must explore III types of reservoir polymer flooding development, which can better improve the recovery of polymer flooding. At the same time, with the rapid development of wireless technology, we can monitor the polymer flooding of III types of reservoirs by computer. Through monitoring, we can better detect the effect of polymer flooding, which will better solve the problem of low fishing success rate and high cost. This paper analyzes the sedimentary characteristics of III types of reservoirs, and then analyzes the main influencing factors of polymer flooding effect.

Application of Well Pattern Adjustment for Offshore Polymer Flooding Oilfield: a Macro-Scale and Micro-Scale Study

The early polymer flooding development technology has been applied to the Bohai Bay oilfield. However, about 50% of the residual crude oil remains in the formation after polymer flooding. The ways to improve the effect of polymer flooding needs to be further investigated. In this paper, we simulated the development effect of well pattern adjustment technology during polymer flooding through laboratory experiments and analyzed the development effect of oil displacement and the distribution of remaining oil from macroscopic and microscopic aspects. The micro-electrode technology was applied to the macro-scale physics experiment to study the development effect and residual oil distribution. In this experiment, nine-spot injection pattern was changed to line-drive pattern during polymer flooding. The micro-scale physics experiment uses nuclear magnetic resonance technology to study the micro-scale distribution of residual oil in the high and low permeability core pores before and after polymer flooding. The experimental results show that in heterogeneous reservoir, the remaining oil is mainly concentrated in the large pores of the medium and low permeability layers at high water cut stage. During the polymer flooding stage, the polymer is squeezed into the large and medium pores of the high-permeability layer and small pores of the low-permeability layer, effectively increasing the sweeping area and displacement efficiency of the low-permeability layer. The residual oil remains mainly in the large pores of the medium and few permeability layers. During the subsequent water flooding stage, the medium permeability layer demonstrates the strongest displacement effect. The increase in yield of the low permeability layer was mainly due to the displacement of oil in the large pores in low permeability layer. After long-term water injection development, the oil recovery of large pores in the low-permeability layer is similar to that in the high-permeability layer. The remaining oil is concentrated in the small pores of the high-permeability layer and the medium and small pores of the low-permeability fiver. The low-permeability layer still has potential for development. Changing the well pattern system is conducted to provide uniform displacement of polymer solution, improving and enhancing the displacement effect of polymer flooding and subsequent water flooding, especially improving the displacement effect in the low permeability layer. In this experiment, the oil recovery of well pattern adjustment was increased by 4.77%. Through experimental research, we believe that polymer flooding with well pattern adjustment can not only expand the flow area by changing the flow field, but also further play the role of polymer profile control. The two mechanisms complement each other, 'effectively improving the unevenness of displacement and enhancing the oil recovery. The experimental results can provide new ideas and technical support for further improving the development effect of polymer flooding in offshore oilfields.

Study on the Development Effect Standard of Classified Well Groups for Polymer Flooding in Class II Reservoirs

Because of the development characteristics of the second type reservoir, the heterogeneity of the reservoir is obvious, and the development effect of polymer flooding in different well groups is quite different, which is not conducive to the adjustment and evaluation of later development. Therefore, it is necessary to classify the polymer flooding well groups in the second type reservoir according to the dynamic and static physical parameters, and evaluate the development effect of different types of polymer flooding well groups on this basis. By analyzing the dynamic and static data of polymer flooding blocks in type II reservoirs, this paper determines the influencing factors of well group classification evaluation, establishes the method of well group classification combined with grey correlation method and mathematical statistics analysis, uses reservoir numerical simulation technology to predict the development effect of polymer flooding for different types of well groups, gives the development effect standards of polymer flooding for different types of well groups, and plays a certain role in adjusting the development effect of polymer flooding in oilfields.

Macroscopic visual displacement of a polymer solution for enhanced oil recovery: Hele-Shaw cell experiments and computational simulation

Numerous laboratory studies and field application tests have shown that polymer flooding is an effective method to improve the oil recovery by displacing residual oil after water flooding. In this work, a series of visual model displacement experiments was conducted in Hele-Shaw cells to determine the effectiveness of polymer flooding in homogeneous and fractured media with a fracture parallel or perpendicular to the flow direction. The matrix with parallel fracture to the flow direction presented a delay in the oil production process during water and polymer flooding with respect to the homogeneous medium and the one with perpendicular fracture, where the highest recovery numbers during waterflooding and polymer flooding were achieved for the medium with perpendicular fracture to the flow direction, reaching 56 % of cumulative oil recovery. The displacement results and multiphasic simulation show that the homogeneous medium is an attractive candidate for additional recovery application with polymer flooding after water flooding when the oil production reached almost zero, although the production rate is lower than the one obtained for a porous medium with a fracture perpendicular to the flow direction.

Investigation on degradation mechanism of polymer blockages in unconsolidated sandstone reservoirs

Abstract Polymer flooding technology has shown satisfactorily acceptable performance in improving oil recovery from unconsolidated sandstone reservoirs. The adsorption of the polymer in the pore leads to the increase of injection pressure and the decrease of suction index, which affects the effect of polymer flooding. In this article, the water and oil content of polymer blockages, which are taken from Bohai Oilfield, are measured by weighing method. In addition, the synchronous thermal analyzer and Fourier transform infrared spectroscopy (FTIR) are used to evaluate the composition and functional groups of the blockage, respectively. Then the core flooding experiments are also utilized to assess the effect of polymer plugs on reservoir properties and optimize the best degradant formulation. The results of this investigation show that the polymer adsorption in core after polymer flooding is 0.0068 g, which results in a permeability damage rate of 74.8%. The degradation ability of the agent consisting of 1% oxidizer SA-HB and 10% HCl is the best, the viscosity of the system decreases from 501.7 to 468.5 mPa‧s.

Study on the Influence of Jelly in Polymer Flooding Injection System on Oil Displacement Efficiency

In this paper, the composition and production conditions of viscous gelatinous substances in the inner walls of filters and pipelines in polymer injection system are analyzed in detail, and the influence of gelatinous substances on the development effect of polymer flooding is studied. A new understanding of the influence of gelatinous substances on the development effect of polymer flooding is obtained. In view of the harmfulness of gelatinous substances, treatment suggestions are put forward and positive countermeasures are taken for industrial field. It has important reference value.

Polymer flooding in high-temperature and high-salinity heterogeneous reservoir by using diutan gum

Diutan gum, a biopolymer that has been widely used in cement and concrete industries, was introduced in this work to alleviate severe viscosity loss and the poor water solubility of polyacrylamide and its modified products in high-temperature and high-salinity reservoirs. Diutan gum is an exopolysaccharide secreted by sphingomonas. The rheological properties and capacity of diutan gum to enhance oil recovery in high-temperature and high-salinity heterogeneous reservoir (T = 130 °C, Total salinity = 223.07 g L−1, Vk = 0.93) was investigated and compared with those of two other kinds of biopolymer thickeners (xanthan and konjac gum), which are commonly used in oilfield development. The three biopolymers show pseudoplastic fluid properties in a steady-state rheological test: given the strong interactions in the double-helix structure of diutan gum, the number of the Newtonian zone and the shear rate of this zone are higher than the those of the two other biopolymers. The storage modulus (G′) of diutan gum are higher than its loss modulus (G″) in all the concentrations and frequencies measured through viscoelasticity tests. This result indicates that diutan gum exhibits remarkable elasticity in slow displacement speed while it seeping in porous media. The capability of establish flow resistance in high-permeability porous medium in high-temperature and high-salinity environment by three biopolymers was studied, and their viscosity and microscopic properties of injected and produced fluid were investigated to understand the reason why diutan gum can have good fluidity control ability. Oil displacement efficiency can be improved by the elasticity of the diutan gum even without an increase in displacement speed. The results of the oil displacement experiments in the heterogeneity model imply that diutan gum is more effective in improving the water injection profile of each layer than xanthan and konjac gum. The water channeling in the high-permeability layer is restrained, and the sweep ability of the displacement phase is improved. Furthermore, the effect of polymer flooding can be maintained for a long time. Under high-temperature, high-salinity and strong heterogeneity, diutan gum recovers 19.34% of original oil in place (OOIP). This value is higher than the values obtained with xanthan gum (14.15% OOIP) and konjac gum (8.60% OOIP). This finding implies that the diutan gum has great application potential in the development of high-temperature and high-salinity reservoirs with strong heterogeneity.

Effect of microscopic aggregation behavior on polymer shear resistance

ABSTRACTThe study of polymer aggregation behavior effect on shear resistance shed light on the synthesis of antishear polymer for oil displacement and enhances the application effect of polymer flooding. The effects of mechanical degradation on the properties of polymer solutions were studied by using partially hydrolyzed polyacrylamide (HPAM), hydrophobically modified HPAM (HMPAM), and dendritic hydrophobic associative polymers (DHAP), which are characterized by “granular,” “chain,” and “cluster” aggregation behavior, respectively. The results show that mechanical shearing can dramatically reduce the performance of polymer solution. The shearing resistance can be effectively enhanced by improving the polymer aggregation behavior. After being strongly sheared, hydrophobically associating polymers can still partially restore its network through hydrophobic association, therefore rebuild the solution viscosity. For DHAP, the broken molecular chains distribute more evenly in solution after shearing. In addition, the strength of reconstructed network structure of DHAP is better than that of HMAPM, which implies a better shear resistance. Furthermore, the hydrophobic association of linear polymers will increase their static adsorption on quartz sand. Meanwhile, DHAP with stronger spatial structure has less static adsorption, which is beneficial to maintain a higher polymer concentration in solution. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48670.

A Pore-Scale Investigation of Residual Oil Distributions and Enhanced Oil Recovery Methods

Water flooding is an economic method commonly used in secondary recovery, but a large quantity of crude oil is still trapped in reservoirs after water flooding. A deep understanding of the distribution of residual oil is essential for the subsequent development of water flooding. In this study, a pore-scale model is developed to study the formation process and distribution characteristics of residual oil. The Navier–Stokes equation coupled with a phase field method is employed to describe the flooding process and track the interface of fluids. The results show a significant difference in residual oil distribution at different wetting conditions. The difference is also reflected in the oil recovery and water cut curves. Much more oil is displaced in water-wet porous media than oil-wet porous media after water breakthrough. Furthermore, enhanced oil recovery (EOR) mechanisms of both surfactant and polymer flooding are studied, and the effect of operation times for different EOR methods are analyzed. The surfactant flooding not only improves oil displacement efficiency, but also increases microscale sweep efficiency by reducing the entry pressure of micropores. Polymer weakens the effect of capillary force by increasing the viscous force, which leads to an improvement in sweep efficiency. The injection time of the surfactant has an important impact on the field development due to the formation of predominant pathway, but the EOR effect of polymer flooding does not have a similar correlation with the operation times. Results from this study can provide theoretical guidance for the appropriate design of EOR methods such as the application of surfactant and polymer flooding.

Assessment of polymer flooding effects on the recovery of heterogeneous thick reservoirs with dominant channel

The formation of dominant channel has restricted the improvement in oil recovery in heterogeneous thick reservoirs greatly. How to effectively solve the problem has become a key issue in the development process. In this paper, firstly, the plugging effect of polymer flooding on the dominant channel is studied by visual microscopic-model displacement experiment. And then, we established a flow resistance model and simulated the effect of polymer flooding on improving dominant channel. The result shows that the present model matches the oilfield testing data greatly. And the higher the concentration, the more effective the plugging. When the polymer concentration is 2.0 g/L, the water content can reduce by 21.24% and the enhanced oil recovery can reach 13.69%. Besides, the efficiency of the reverse rhythm is higher than the positive rhythm under the same condition. This study has provided a quick and accurate assessment of the polymer flooding for the dominant channel in the heterogeneous thick reservoir.

The discussion of Well Selection and Layer Selection Method on Polymer Flooding Fracturing in Class II Reservoir

The main purpose of oil well fracturing is to alleviate the intra-layer contradiction and tap the remaining oil at the top of the thick reservoir for the primary reservoir. Aiming the problem such as long polymer injection interval, several layers, serious heterogeneity in plane and vertical in Class II reservoir, the main purpose of fracturing is to alleviate the plane and interlayer contradiction and tap the remaining oil at the edge of the buried river channel and at the position of inter-river variation. Because of the differences in geological characteristics and fracturing purposes, the method of selecting wells and layers for the primary reservoir has some inadaptability in the application of the Class II reservoir. In order to improve the fracturing effect of polymer flooding in Class II reservoir, it is necessary to explore the method of well selection and layer selection, in order to suitable for polymer flooding in Class II reservoir.

Upscaling of polymer adsorption

This article considers upscaling of polymer adsorption. Input to adsorption values employed in reservoir simulation models are typically obtained from core plug measurements. There are several orders of magnitude in scale difference between core plugs and grid cells in reservoir simulation models, which foster a need for upscaling of the adsorption values.Polymer concentration distribution on the lithofacies scale is investigated in this article. The effect of diffusion on concentration distribution is investigated analytically. The slow diffusion of polymer molecules retards mixing even at the lithofacies scale. We introduce a formula to estimate the redistribution of polymer due to capillary forces in a layered model, and this formula is validated through numerical simulations. From our considerations we conclude that it is questionable to assume a constant polymer concentration in lithofacies models. This impedes applying steady-state upscaling techniques. Such upscaling techniques will over-predict polymer adsorption.Different methods for upscaling adsorption are presented in this paper, and applied to a simplified layered model and to more realistic fine-scale numerical models based on the SPE10 model. These numerical models were populated with adsorption values obtained from published experiments conducted on samples from the Brent sequence modeled in SPE10. Simulations of tertiary polymer flooding on the upscaled models were compared to simulations of the same flooding sequences on the original fine scale models. The tested upscaling methods include a volume averaging technique employed by other authors, and a method were we distribute the adsorption values by the same functional relationship as in the fine scale model. In addition we introduce upscaling methods were we assign zero adsorption to fine scale grid cells with permeability below a given cut-off value. The cut-off value is obtained from a single phase simulation on the fine scale model. In our models the cut-off value methods yield the best match between the coarse scale and fine scale simulation results. The volume averaging technique over-predict the polymer adsorption.Results from both the lithofacies and geomodel scale indicate a tendency to over-predict polymer adsorption, which could lead to conservative estimates for the effect of polymer flooding.

Study on enhanced oil recovery by multi-component foam flooding

To obtain a foam system with better stability and oil resistance, this paper starts with the mechanism of enhanced oil recovery by foam flooding and makes use of a combination of surfactants to make foam more stable. A foam system with strong stability can be obtained by combining anionic surfactants with nonionic surfactants. Based on this idea, a new type of multi-component foam flooding system (system 1) is developed. The main molecule is zwitterionic surfactant with a concentration of 0.7% fourteen alkyl sulfonated fluorobetaine (SFN). The auxiliary surfactants are present at a concentration of 0.3% of Sodium Dodecyl Sulfate (SDS), a concentration of 1.8% of potassium chloride (KCL) and a concentration of 3.0% of anhydrous ethanol (C2H6O). In addition, adding a 1000 mg/L solution of partially hydrolyzed polyacrylamide (HPAM) into the system can enhance the strength of the interfacial film, increase the surface dilatation modulus and extend the equilibration time, thereby enhancing the stability of the foam. The comparative evaluation experiment results show that the foaming capacity, foam stability and comprehensive performance of system 1 are better than those of other common foam systems under the condition of 30% Sor and a 1:1 ratio of gas to liquid. For system 1, the number of bubble films L (lamella number) is less than 7, the boundary between the foam and crude oil is clear, and the interaction is small. The foam of system 1 has good oil resistance. The results of oil displacement show that the oil recovery using system 1 increases by 16.8 percentage points after polymer flooding, which is 4–6 percentage points higher than that of an ordinary foam system. The results of the oilfield test show that the development effect of polymer flooding in the B block is poor. In January 2017, system 1 was injected into the reservoir. The 23 wells in the B block responded well, and the effective ratio reached 92%. Compared with the previous stage, the daily fluid production increased by 215 m3, the daily oil production increased by 141.0 t, the water cut decreased by 9.2 percentage points, and the reservoir effect was obvious. This result provides a new idea for the later development of high water cut reservoirs.