Efficiency Of Polymer Flooding Research Articles

Accelerating Dissolution of Polyacrylamide in Offshore Oil Field

The solubility of polyacrylamide significantly reduces the efficiency of polymer flooding in offshore oil fields, because of the low performance of polyacrylamide and the special environment. The objective of this paper is to investigate a novel approach to accelerate the dissolution of hydrolyzed polyacrylamide (HPAM) by adding a co‐solvent cholamine (MEA). We investigated the effects of MEA on the microstructure and the performance of HPAM. Results showed that the addition of MEA and the temperature rise greatly shortened the dissolution time of HPAM, while improved the rheological property and seepage behavior. The enhanced solubility of polyacrylamide and the performance of polymer solution can be attributed to the enlarging of the molecular clew size, the stretching of molecular chains and the lowering of the glass transition temperature of HPAM. The new approach has high practical and the economic values for applications of the polymer flooding technology in offshore oilfields with complex reservoir conditions.

Investigation of Isotherm Polymer Adsorption in Porous Media

The injection of chemical solutions plays an important role in increasing the recovery factor of mature fields. Chemical flooding is considered as an attractive alternative to conventional waterflooding; it can improve the area sweep efficiency not only at the macroscale but also in the microscale by control mobility of displaced fluid. Adsorption of polymer in reservoir rock is an extremely important parameter for chemical flooding. Adsorption represents a loss of chemical agent from solution and, consequently, a net reduction in the surfactant–polymer slug. Therefore, the efficiency of polymer flooding is significantly diminished both technically and economically. However, numerical simulation of multicomponent adsorption is still limited and adsorption processes in a polymer–rock system have not yet been well developed, especially for highly heterogeneous reservoirs. In this article, adsorption was modeled by the Langmuir isotherm theory. The simulation results indicated that polymer adsorption strongly depends on polymer concentration, shear rate, pH, salt concentration, and reservoir heterogeneity. Effective control of such parameters can reduce the effect of polymer adsorption to minimize chemical loss and improve the economic efficiency of chemical flooding processes.

The Complementary Technologies to Improve Polymer Flooding Efficiency for Class II Reservoirs of Daqing Oilfield

With the amount of polymer used in oil field increases year by year and the development results turn worse, people started to pay more attention to the technologies which can improve the polymer flooding recovery of class II reservoirs. Polymer flooding efficiency can be enhanced through methods such as detail geologic analysis, project design optimization and strengthen procedure management with applying mature supporting technologies. In this paper, the necessity of improving the polymer flooding effect of class II reservoir is introduced. The technologies to develop polymer flooding efficiency are proposed. The applying results of these technologies show that meticulous reservoir simulation and deepen recognize of structure and reserve and residual oil distribution are the base of improving polymer flooding efficiency. Optimizing polymer injection design to match the oil reserve is the key part of improving polymer flooding efficiency. Deepening technology research and building workflow of different measures and adjustment technologies at different production stages are efficient ways to improve polymer flooding efficiency. Insisting on the comprehensive adjust pattern of normal molecular weight with normal molecular concentration, individual design, scale injection, profile control in time, adjust with time and strengthen procedure management are the predominant guarantee of improving polymer flooding efficiency.

Assessment on the Transport of Polymeric Solution through High-Salinity Reservoirs Containing Divalent Cations

Water salinity and hardness have been regarded as main limitation for field application of polymer floods. It causes not only reduction of polymer concentration, but also injectivity loss in the near wellbore. Based on the mathematical and chemical theory, extensive numerical simulations were conducted to investigate performance of polymer floods in the high-salinity reservoirs. According to results from simulations, the high salinity reduces the viscosity of polymer in contacting area. That causes a poor sweep efficiency of polymer flooding. Moreover, the presence of divalent cations makes the project of polymer flooding worse. That is because of excessively increased bottom-hole pressure in injection well by the precipitation of polymer. The quantitative assessment of polymer floods needs to be required before field application. Therefore, the results in this paper are helpful for optimal polymer flooding design under harsh reservoir conditions.

Experimental and numerical investigation of polymer flooding in fractured heavy oil five-spot systems

Microscopic and macroscopic displacements of polymer flooding to heavy oil at various levels of salinity and connate water saturation have been investigated. Both oil-wet and water-wet conditions in fractured five-spot micromodel systems, initially saturated with the heavy crude oil are utilized. The primary contribution is to examine the role of salinity, wettability, connate water, and fracture geometry in the recovery efficiency of the system. The microscopic results revealed that the increase in the connate water saturation decreases the oil recovery, independent of the wettability conditions. Moreover, the increase in salinity of the injected fluids lowers the recovery efficiency due to the decrease in polymer viscosity. One the other hand, the microscopic results emphasized the wettability role in the simultaneous flow of oil, the connate water, and the polymer phases. In addition, switching from the oil-wet to the water-wet medium has manifested increase in the oil recovery during polymer flooding as compared to water flooding owing to its severe mechanisms of pulling and stripping. To simulate the experimental results, the UTCHEM software has been applied, which has validated the observed data for different fractured patterns, and at various connate water and salinity of polymer solution. Furthermore, the visualized results uncovered a light stripping mechanism in the high permeable fracture. The findings of this study can be beneficial to the better understanding of the microscopic/macroscopic displacements during polymer flooding in fractured heavy oil five-spot systems. It also illustrates the successful application of the UTCHEM for predicting the roles of connate water, salinity and fracture geometry in efficiency of polymer flooding in fractured five-spot micromodels. • Monitoring microscopic/macroscopic displacements. • Role of salinity, connate water saturation and fracture geometry. • UTCHEM simulation of micromodel experiments.

Effect of small scale flow barriers heterogeneities and connate water on displacement efficiency of polymer floods to heavy oil reservoirs

AbstractThis work concerns a fundamental understanding of how heterogeneities induced by flow barriers and connate water affect the displacement efficiency of polymer floods, which has rarely been studied in the available literature. Here, a series of water/polymer injection experiments to heavy oil performed on five‐spot glass micromodels containing randomly distributed shale structures is presented. It has been found that macroscopic efficiency of polymer flooding majorly depends on flow barriers distribution/configuration; shale content and geometrical characteristics; presence of connate water and wettability of medium. Microscopic pictures revealed that the main parts of connate water were trapped in some pores/throats near and especially behind the shale streaks; also, presence of connate water causes a reduction of sweep efficiency due to premature breakthrough of displacing fluid in an oil‐wet media. In absence of connate water, polymer solution could linger and stick to the pore walls to delay the time for a polymer to channel to the production site. Results of this work disclose requirements for a detailed geologic study of barrier size and distribution for successful design of EOR processes in heterogeneous reservoirs.

Experimental Investigation of Microscopic/Macroscopic Efficiency of Polymer Flooding in Fractured Heavy Oil Five-Spot Systems

This paper concerns on experimental investigation of biopolymer/polymer flooding in fractured five-spot systems. In this study, a series of polymer injection processes were performed on five-spot glass type micromodels saturated with heavy crude oil. Seven fractured glass type micromodels were used to illustrate the effects of polymer type/concentration on oil recovery efficiency in presence of fractures with different geometrical properties (i.e., fractures orientation, length and number of fractures). Four synthetic polymers as well as a biopolymer at different levels of concentration were tested. Also a micromodel constituted from dead-end pores with various geometrical properties was designed to investigate microscopic displacement mechanisms during polymer/water flooding. The results showed that polymer flooding is more efficient by using hydrolyzed synthetic polymers with high molecular weight as well as locating injection well in a proper position respect to the fracture geometrical properties. In addition, by monitoring of microscopic efficiency, pulling, stripping, and oil thread flow mechanisms were detected and discussed. The results showed that flow rate, fluid type, polymer concentration, and geometrical properties of pores influence the efficiency of mentioned mechanisms. Furthermore, it was detected that polymer's velocity profile play a significant role on oil recovery efficiency by influencing both macroscopic and microscopic mechanisms. This study demonstrates different physical and chemical conditions that affect the efficiency of this enhanced oil recovery method.

Mobility control and enhanced oil recovery using partially hydrolysed polyacrylamide (PHPA)

Polymers are often used as mobility controller for enhanced oil recovery. The present paper deals with the application of partially hydrolysed polyacrylamide (PHPA) polymer in enhanced oil recovery after the conventional water flooding. Experimental results show that viscosity of PHPA solution increases significantly on addition of small quantity of polymer, which in turn decreases the mobility ratio. The effect of frontal-advance velocity on the total relative mobility at different concentration of polymer has been discussed. A series of flooding experiments were performed in a flooding apparatus to observe the efficiency of polymer flooding at different concentration of PHPA. The crude oil is collected from Ahmedabad oil-field, India (total acid number of 0.038 mg KOH/g, gravity of 38.86° API and viscosity of 119 mPa.s at 30°C). The additional oil recoveries vary 16% to 20% of original oil in place (OOIP) depending on the polymer concentration.

An Easy Calculation Method on Sweep Efficiency of Chemical Flooding

According to the geological parameters of Shengli Oilfield, sweep efficiency of chemical flooding was analyzed according to injection volume, injection-production parameters of polymer flooding or surfactant-polymer compound flooding. The orthogonal design method was employed to select the important factors influencing on expanding sweep efficiency by chemical flooding. Numerical simulation method was utilized to analyze oil recovery and sweep efficiency of different flooding methods, such as water flooding, polymer flooding and surfactant-polymer compound flooding. Finally, two easy calculation models were established to calculate the expanding degree of sweep efficiency by polymer flooding or SP compound flooding than water flooding. The models were presented as the relationships between geological parameters, such as effective thickness, oil viscosity, porosity and permeability, and fluid parameters, such as polymer-solution viscosity and oil-water interfacial tension. The precision of the two models was high enough to predict sweep efficiency of polymer flooding or SP compound flooding.

Experimental Study of Polymer Flooding in Fractured Systems Using Five-Spot Glass Micromodel: The Role of Fracture Geometrical Properties

Water flooding is being widely used in the petroleum industry and has been considered as a simple inexpensive secondary recovery method. But in fractured formations, existence of fracture system in reservoir rock induces an adverse effect on oil recovery by water flooding. Polymer flooding has been successfully applied as an alternative enhanced oil recovery method in fractured formations. But, the role of fracture geometrical properties on macroscopic efficiency of polymer flooding is not yet well-understood, especially in fractured five-spot systems. In this work five-spot glass micromodel, because of micro-visibility, ease of multiple experimentations and also presence of the unexplored issues, was used to experimentally investigate the influence of fracture geometrical characteristics such as fracture orientation, fracture spacing, fracture overlap and etc on the macroscopic efficiency of polymer flooding. The tests were performed on the fractured models which are initially saturated with the crude oil at fixed flow rate conditions and in a horizontally mounting. The results revealed that the macroscopic efficiency of polymer flooding depends on fracture geometrical properties. Fracture orientation showed more imposing effect than other fracture geometrical properties, and fracture with 45 degree inclination to the mean flow direction, gives greatest oil recovery factor. Large spacing fractures give more recovery than small spacing ones and in case of overlapping, fractures with less overlapping help polymer to better propagate which could be related to their greater effective fracture length. This pre-called effect could be responsible to show how continuity and width to length ratio of fractures affect recovery factor, less fracture discontinuity as well as more length to width ratio of fracture give more swept zone. Also, increasing number of fractures decreases oil recovery factor. The results of this work can be helpful to better understanding the role of fracture geometrical properties on macroscopic efficiency of polymer flooding in five-spot fractured systems.

Experimental studying of pore morphology and wettability effects on microscopic and macroscopic displacement efficiency of polymer flooding

Pore morphology and wettability of a porous medium have dominating effects on microscopic displacement efficiency, and consequently on the ultimate oil recovery. To provide a better understanding of the effects of these parameters on microscopic displacement mechanisms and macroscopic performance of a polymer flood process, a comprehensive experimental study was conducted using five two-dimensional glass micromodels. A combination of three wettability conditions and five different pore structures was used in this study. The selected scenarios include four homogeneous synthetic pore networks at water-, mixed- and oil-wet conditions. A random network that represents the pore space in Berea sandstone was also used for further investigation. Image processing technique was applied to analyze and compare displacement mechanisms and displacement process efficiency in each experiment. Microscopic mechanisms, such as oil and polymer solution trapping, configuration of wetting and non-wetting phases, flow of continuous and discontinuous strings of polymer solution, polymer solution snap-off, distorted flow of polymer solution, emulsion formation, and microscopic pore-to-pore sweep of oil phase were observed and monitored in conducted experiments. Experimental results showed that water- and mixed-wet media generally have comparable and higher recoveries in contrast with oil-wet media. Moreover, the results confirmed a significant dependency on the pore structure and wettability of the media on both displacement mechanisms as well as oil recoveries. This experimental study illustrates the successful application of glass micromodel techniques for studying enhanced oil recovery (EOR) processes in a five-spot pattern, and also provides a useful reference for understanding the displacement mechanisms involved in a polymer flood process at different pore morphologies and wettabilities of porous media.

Experimental Study of Polymer Flooding in Low-Viscosity Oil Using One-Quarter Five-Spot Glass Micromodel

A polymer flooding technique is developed to reduce the amount of residual oil saturation that cannot be recovered through waterflooding or gas injection processes. Using polymer flooding in the case of high-viscosity oil has been successful due to reducing mobility ratio (M), whereas there is conflict in efficiency of polymer flooding in the case of low-viscosity oil. In this study, to investigate the behavior of polymer flooding in low-viscosity oil, the transparent materials (glass) were used to construct a micromodel and to study various aspects of micro-displacement. By using a micromodel, the displacement of the fluid and menisci was observed and investigated with the aid of images captured by a camera. In this work, two kinds of quarter five-spot glass micromodel patterns were designed and developed and considered as pores medium. These patterns were saturated with light and low-viscosity oil samples from an Iranian fractured reservoir and then flooded by a polymer slug in low-pressure and low-temperature conditions. Three polymer types, hydrolyzed polyacrylamide (HPAM 25%), very low hydrolyzed polyacrylamide (<5%; PA) and xanthan, were utilized to inspect the effects of polymer type, concentration, injection rate, pore structure, and presence of connate water on recovery of low-viscosity oil. The results of experiments illustrated that recovery from HPAM is higher than both xanthan and very low hydrolyzed polyacrylamide. Rate sensitivity tests showed that increasing rate injection induced a decrease in recovery. Flooding in two different micromodel patterns demonstrated that higher permeability leads to lower recovery. In addition, experiments indicated that the presence of connate water caused a reduction in recovery. Finally, compared with waterflooding, polymer flooding resulted in a considerable growth in ultimate oil recovery.

Visualization of Mobility-Control by Polymer Waterflooding through Unconsolidated Porous Media using Magnetic Resonance Imaging

This article addresses the use of Centric Scan SPRITE Magnetic Resonance Imaging (MRI) technique to visualize the performance of polymer flooding as a mobility-control technique. The fronts and interfaces between displaced and displacing fluids are monitored. The development of a piston-like displacement front, as a result of polymer-augmented waterflood, and the effect of polymer concentration on the development of a favorable water displacement front are directly observed. MRI demonstrates to be a useful imaging tool for the evaluation of the efficiency of polymer flooding. Experiments indicate a close agreement between fluid saturations determined by MRI and fluid saturations estimated from material balance.

Computerized Tomography Study of the Microscopic Flow Mechanism of Polymer Flooding

The microscopic flow mechanism of polymer flooding was examined using an industrial microfocus computerized tomography system. On the basis of scanned slices acquired in the process of water flooding and polymer flooding, three-dimensional visualization of oil and water distribution in different flooding conditions was achieved with a series of image processing methods, including pre-processing, interpolation, segmentation, and three-dimensional construction, which are effective techniques for both the qualitative description and the quantitative characterization of the microscopic flow mechanism. This study has confirmed the suggestion that the displacement efficiency of polymer flooding is higher than that of water flooding, and effectively revealed the microscopic mechanism of oil recovery in polymer flooding. The water/oil mobility ratio was improved after polymer flooding, which resulted in a break of the “equilibrium” flow field that was formed during water flooding and the redistribution of the regions of oil saturation. The remaining oil was flushed out as the result of the flow redirection and the viscoelastic effect of polymer flooding. Compared to water flooding, polymer flooding increased the microscopic sweep efficiency as well as the microscopic displacement efficiency, and thereby the ultimate oil recovery.