Polymers for Enhanced Oil Recovery Technology

Recently enhance oil recovery (EOR) technology is getting more attention by many countries since energy crises are getting worse and frightened. One of the reasons for this is due to the shortage of current oil resources and difficulties in finding a new oil field. Indonesia is one of the examples, before 2004 Indonesia is a net oil exporting country but after that Indonesia is a net oil importing country. The oil demand in the country is increasing while the oil production capacity is decreasing. In fact, when a new oil reservoir is drilled, the oil amount obtained from it is about 20-40% of the potential and hence there is still 60-80% oil left in the reservoir. Application of EOR technology gives an additional chance to get out more oil from the reservoir, possibly about another 20%. Polymer is the material that plays an important role in the application of EOR technology, especially surfactant and hydrogel polymers. In the technology, surfactant polymer is injected to the reservoir to reduce an interfacial tension between oil and water and is able to wipe out the trapped oil from the reservoir rock and hence increase the oil production. While an injection of hydrogel polymer to the reservoir is to increase a viscosity of fluid containing water so that the fluid is more difficult to flow than the oil, and as a result, the oil production increases. The most common polymer used for this application is polyacrylamide group.     

用深部处理剂JY-8提高注聚区残余聚合物的利用率

针对目前各油田聚合物驱转为水驱后,一般出现含水上升快,产油量大幅度下降的情况,以及油层内残余的大量聚合物未得到利用,而目前开发的残余聚合物再利用技术存在一些缺点,未得到推广应用,研制出新型复合处理剂JY-8。新型复合处理剂JY-8可与聚合物形成强度较高的凝胶体,将地层内残余聚合物有效地固定和絮凝,是很好的固定剂和絮凝剂,实现了“二剂合一”,达到对地层进行深部调剖、驱油的目的;同时,通过调整复合处理剂JY-8的加量等可调节成胶时间和凝胶强度。室内评价和现场应用表明,与以前的技术相比,复合处理剂JY-8可使油层内的残余聚合物利用率从原来的8％提高到15.65％,使聚合物驱后续水驱的采收率增加值从原来的10.33％提高到18.1％,在油井上起到了很好的增油、控水效果。     

Investigation on the Adaptability of the Polymer Microspheres for Fluid Flow Diversion in Porous Media

Large amounts of water producing from producers have been a great concern for petroleum engineers. In an attempt to inhibit water production and promote oil productivity, various water control agents and techniques have been devised for enhanced oil recovery purpose for decades with some good successes reported commercially. Mainly field-targeted specifically, however, these chemicals are limited in expansive reservoir applications for failing to tolerate harsh formation conditions of high temperature (HT) and high salinity (HS). Besides, their low injectivity is also another proper impediment. In this presentation, we synthesized a new agent of polymer microspheres using inverse emulsion polymerization technique to divert fluid patterns in deep porous media for reservoirs encountered recovery enhancement problems. These microspheres are made to tolerate HT and HS conditions, and can be pumped into deep pore space with relative ease. With the help of nuclear magnetic resonance (NMR) and nuclear pore membrane filtration techniques, a series of experimental procedures were conducted to test the adaptability of newly produced polymer microspheres to targeted pore structure in enhancing the sweeping efficiency of injection fluids. Both laboratory core tests and NMR data show good characteristics of polymer microspheres in modifying injection profile, demonstrating a good capability to divert fluid flow patterns in deep porous media and enhance oil productivity.     

Flow behaviors of a viscoelastic polymer solution at 3D micro pore-throat structure

Polymers are abundantly used in oil production industry, especially in enhanced oil recovery process. The underground oil reservoir is a kind of porous media where complex microscopic geometries lead to strong shearing and extensional components. This research focuses on a novel method used to investigate the flow behaviors of hydrolyzed polyacrylamide solution at a micro pore-throat structure with a comparison with Newtonian flow of water. For polymer solution, the flow velocimetry revealed the viscoelastic flow has two main characters compared with Newtonian fluid. First, the instability or non-linearity of polymer flows led to bending and distorted streamlines. The instability of the flow is mainly caused by the growth of high stress generated in the viscoelastic polymer fluid as it accelerates and decelerates into and out from the narrow throat, respectively speaking. The second character is the back-streams at the outlet of the throat.     

Research on Configuration of Polymer Molecular Aggregate and Its Reservoir Applicability

This article researches the effect of configuration of polymer molecular aggregate on the performance of polymer solution and its reservoir applicability, taking configuration of polymer molecular aggregate, first normal stress difference, resistance coefficient, residual resistance coefficient, and oil recovery as the evaluation indexes, guided by physical chemistry, polymer materials science, and reservoir engineering, by means of chemical analysis, instrument detection, and physical simulation. Results show that the apparent viscosity of polymer solution is closely related to the configuration of molecular aggregate. However, that reflects neither the transporting and migrating ability of molecular aggregate in porous media nor the applicability of polymer solution for reservoir core pore. Compared with “linear-branched chain” polymer, network polymer has a regional “laminated-net” structure, which has a stronger ability to adsorb and wrap hydrone, when deformation occurs, internal friction of which is larger, and apparent viscosity of which is higher with isoconcentration. Changing the configuration of molecular aggregate can enhance the tackify performance of polymer, but crosslinking or association degree must be controlled properly. Otherwise, the applicability of polymer solution for reservoir core pore will become poor, thus influencing the oil incremental effect of polymer flooding.     

Performance evaluation of a new nanocomposite polymer gel for water shutoff in petroleum reservoirs

Abstract

A new polymer gel nanocomposite is fabricated for excess water production control (water shut off) in petroleum reservoirs and its rheological behavior is evaluated in the presence of sea water and formation water at the temperature of 100?°C. It is shown that at a high salinity without using SiO₂ nanoparticles, the elastic modulus of synthesized polymer gel in the presence of sea water and formation water are 12.5?Pa and 9.8?Pa respectively. However by incorporation of SiO₂ nanoparticles in the polymer gel matrix, the elastic modulus of synthesized polymer gel in the presence of sea water and formation water can be improved to 13.56?Pa and 11.57?Pa respectively, which is quite interesting from reservoir engineering viewpoint. Equilibrium Swelling Ratio (ESR) of the nanocomposite polymer gel in sea water and formation water decreases as the concentration of the SiO₂ increases. Thermal stability of the polymer gel is investigated by differential scanning calorimetry (DSC) measurements. The inflexion temperature of the polymer gel is improved by incorporation of 2000?ppm SiO₂ nanoparticles. The fabricated polymer gel nanocomposite in this work can have potential application in reduction of excess water production during enhanced oil recovery (EOR) operations in petroleum industry.     

Characterization of Remaining Oil After Polymer Flooding by Laser Scanning Confocal Fluorescence Microscopy

In the mid- to late period of oil field development, it is important to consider the microscopic distribution of remaining oil of the reservoir in time, for it is the foundation of enhanced oil recovery. Focusing on the present insufficient research status of microscopic distribution of remaining oil after polymer flooding, this article first put forward and developed a set of fluorescence microscope technology of frozen core analysis of remaining oil, and used this technology combined with laser confocal microscopic detection technology to study microscopic distribution rules of remaining oil before and after polymer flooding. Through comparison and analysis on the difference of microscopic distribution form of remaining oil, the experimental results show that polymer flooding has different effects on different types of remaining oil. Using this technology, analysis of many different distribution forms of remaining oil involving the same mode of occurrence in different layers, different parts of the same layer, and different types of the same layer can be more clearly distinguished. Using polymer flooding pertinently according to the different distribution form of remaining oil will make the use of polymer more efficiently and the recovery higher.     

Solution Association Characterization of Hydrophobically Associating Polyacrylamide Obtained from Produced Fluids

The hydrophobically associating polyacrylamide (HAPAM) obtained from produced fluids with compositional homogeneity was systematically investigated by zero-shear viscosity, fluorescence, sand-pipes experiment and adsorption behavior. The results showed that HAPAM obtained from produced solution through porous media has been possession in hydrophobic association character. The critical association concentration (CAC) determined by viscosity method, fluorescence spectroscopy method and micro-pore method have no obvious change compared with the original polymer. The hydrophobic associative capability of HAPAM obtained from produced fluids was smaller than that of original HAPAM. Compared to original PAM and PAM obtained from produced fluids, HAPAM obtained from produced fluids still exhibits promising applied potential. It reveals the possibility that HAPAM obtained from produced could be re-used for enhance oil recovery.     

Experimental demonstration of diffusocapillary flow in an oil droplet

The phenomenon of diffusocapillary flow is demonstrated utilizing a vegetable oil droplet suspended in a host medium composed of Dow Corning 200 silicone fluids. The host fluid was prepared in such a way that the average polymer length was varied across the surface of the droplet, thus creating an interfacial tension gradient with concomitant Marangoni flow.     

In situ organically cross‐linked polymer gel for high‐temperature reservoir conformance control: A review

Polymer gel has been established as water‐blocking agents in oil recovery application. In this practice, a mixture known as gelant is injected into target area and set into a semisolid gel after a certain adequate time. Besides profile modification and water shutoff, the role of the polymer gel in conformance control is to block high permeability regions, before diverting injected water from high permeability to low permeability zones of the reservoir. It is to boost the oil displacement and sweep efficiency. This is the key to improve oil recovery in the heterogeneous oil reservoirs. However, very limited gels are applicable for harsh conditions, especially in high‐temperature reservoirs. Organically cross‐linked polymer is 1 of the materials for conformance control at high‐temperature reservoirs. Many experimental works and field applications have exhibited the potential of this technology. This paper presents a concise review on this polymer gel for conformance control at high‐temperature wells. Firstly, in situ organically cross‐linked polymer gel has been introduced, and the reason of the use over other types of polymer gels is summarized. The early studies of organically cross‐linked gel systems are also discussed, followed by the chemistry and the gelation mechanisms. An extensive review on factors that affect gelation kinetics and field applications is also discussed in some detail.     

含双噻唑基聚合物的合成及电流变性能研究

采用2，2’-二氨基-4，4’-双噻唑与联苯胺合成一种含有双噻唑基的共轭聚合物，通过红外、扫描电镜、热重分析等测试了该物质的结构及热稳定性等，并通过将聚合物分别分散在硅油和溴代二苯甲烷中制备电流变体，测试其电流变性能。结果表明：含双噻唑基的共轭聚合物作为电流变体的分散相表现出了良好的电流变性能，同时发现分散相和分散介质的密度相近时有利于电流变性能的提高。     

Application of the CPA equation of state to reservoir fluids in presence of water and polar chemicals

The complex phase equilibrium between reservoir fluids and associating compounds like water, methanol and glycols has become more and more important as the increasing global energy demand pushes the oil industry to target reservoirs with extreme or complicated conditions, such as deep or offshore reservoirs. Conventional equation of state (EoS) with classical mixing rules cannot satisfactorily predict or even correlate the phase equilibrium of those systems. A promising model for such systems is the Cubic-Plus-Association (CPA) EoS, which has been successfully applied to well-defined systems containing associating compounds. In this work, a set of correlations was proposed to calculate the CPA model parameters for the narrow cuts in ill-defined C₇₊ fractions. The correlations were then combined with either the characterization method of Pedersen et al. or that of Whitson et al. to extend CPA to reservoir fluids in presence of water and polar chemical such as methanol and monoethylene glycol. With a minimum number of adjustable parameters from binary pairs, satisfactory results have been obtained for different types of phase equilibria in reservoir fluid systems and several relevant model multicomponent systems. In addition, modeling of mutual solubility between light hydrocarbons and water is also addressed.     

Empirical Correlations for Viscosity of Polyacrylamide Solutions with the Effects of Salinity and Hardness

A series of experiments have been conducted to characterize and quantify the effects of shear rate, salinity, and hardness on the viscosity of polymer solutions. A set of correlations were developed to predict the viscosity of polymer solutions. These correlations consider the individual and combined effects of shear rate, salinity, and hardness on the viscosity of polymer solutions. The power-law model for the viscosity behavior has been modified to accommodate the influence caused by these three factors. Nonlinear regression was performed on the experimental data to develop the proposed correlations. The proposed correlations can be integrated into any reservoir simulator for polymer injection and should prove useful for the initial screening for the selection of the polymer for enhanced oil recovery applications in oil reservoirs.      

Confocal Raman microscopy of supercritical fluid dyeing of polymers

Supercritical CO2 was used as a medium to introduce azo-dyes into polymers (PMMA and PET). Confocal Raman microscopy has been applied using dry metallurgical and oil objectives to measure the concentration of dye as a function of distance from the surface to the core of the polymer samples. A significant gradient of dye concentration normal to the surface, down to the depth of ca. 100 microm, has been observed. In addition, cross-sections of cut dyed polymer samples have been analysed using a conventional mapping approach. The comparison between confocal depth and conventional mapping approaches has demonstrated that the use of the oil objective can provide reliable qualitative information on dye distribution in these systems. These confocal Raman experiments demonstrate the potential of this method in applications to polymeric materials processed with supercritical fluids.     

A Review on Waterflooding Problems in Nigeria's Crude Oil Production

For many reasons, a reservoir may approach the end of its primary life having recovered only a small fraction of the oil in place. Occurrence of this makes secondary recovery operations feasible and economically attractive through waterflooding. Waterflooding is dominant among fluid injection methods and is responsible for the current high level of production rate of crude oil. Nigeria's current average crude oil production is estimated at 2.2 million barrel per day and its' reserve at 38.4 billion barrels. The problems associated with waterflooding and oil production are formation damage, scale deposition and corrosion of well tubular. These problems are costing the oil industries a huge loss annually, this article suggests control and monitoring of these problem through modeling and simulation of oil reservoirs in Nigeria oil fields.     

Similarities and Differences of Low Salinity Polymer and Low Salinity LPS (Linked Polymer Solutions) for Enhanced Oil Recovery

Linked polymer solution (LPS) is nano-size particles made of hydrolyzed polyacrylamide (HPAM) cross-linked with aluminum citrate. The propagation of LPS has been compared to non-cross-linked polymers at low brine salinity condition. The possible differences in properties and potentials for oil recovery have been investigated using water-wet and intermediate-wet cores. The target oil for polymer flooding (PF) is assumed to be the portion of the reservoir that has been bypassed by water during waterflooding and not the residual oil saturation in flooded zones. Our recent studies have shown that a positive synergy can be obtained by combining low salinity and PF. It has been claimed in the literature that cross-linking polymer such as colloidal dispersion gels (colloidal dispersion gels (CDG), micron-size aggregates) or LPS (nano-size particles) would extend the application of polymers to also include change in residual oil saturation. The results of this study indicated higher pressure buildup when low salinity LPS was propagated through brine saturated cores compared to low salinity polymer solution. The pressure buildup was even stronger for high salinity LPS injection. In two phase flow experiments, both polymer and LPS under low salinity condition, showed approximately similar propagation and oil recovery potential when injected into water-wet and intermediate-wet cores.     

Synthesis and electrorheological characterization of emulsion polymerized SAN‐clay nanocomposite suspensions

Styrene‐acrylonitrile (SAN) copolymer‐clay nanocomposite was synthesized by emulsion polymerization, which is the easiest method of intercalation (e.g., melt or solution intercalation). Existence of the intercalated polymer was verified by Fourier transform‐infrared spectroscopy and X‐ray diffraction (XRD) analysis. From XRD, we confirmed the insertion of styrene‐acrylonitrile copolymer between the interlayers of clay, whose separation consequently becomes larger than that of the polymer‐free clay. Thermogravimetric analysis showed that the thermal stability of the organic polymers was sustained. Using electrorheological (ER) fluids composed of intercalated particles and silicone oil, we observed typical ER behavior, such as higher shear stress in the presence of an electric field and increasing yield stress with particle concentration. We further observed the critical shear rate at which the ER fluids exhibit pseudo‐Newtonian behavior.     

Light scattering as a probe of liquid surfaces and interfaces

The field of quasi-elastic light scattering from thermally excited capillary waves at liquid surfaces is reviewed, with particular attention to scientific advances since 1992. These include surface-induced freezing in molecular fluids, the cross-over from capillary to elastic Rayleigh waves on the surfaces of gelling polymer solutions, the experimental demonstration of mixing of capillary and dilatational surface modes and the observation of effects due to processes tending to reduce the stability of the dilatational waves on surfactant solutions. The potential of this technique for surface and interface science is discussed.     

Identification and quantification of alkene-based drilling fluids in crude oils by comprehensive two-dimensional gas chromatography with flame ionization detection

Comprehensive two-dimensional gas chromatography with flame ionization detection (GC x GC-FID) was used to measure alkene-based drilling fluids in crude oils. Compared to one-dimensional gas chromatography, GC x GC-FID is more robust for detecting alkenes due to the increased resolution afforded by second dimension separations. Using GC x GC-FID to analyze four oil samples from one reservoir contaminated with the same drilling fluid, C(15), C(16), C(17), C(18) and C(20) alkenes were identified. The drilling fluid that contaminated these samples also differed from another commercially obtained fluid, which only contained C(16) and C(18) alkenes. These results should motivate the petroleum industry to consider GC x GC-FID for measuring drilling fluids.     

Synthesis and electrorheological properties of polyaniline-Na+-montmorillonite suspensions

We synthesized polyaniline-Na⁺-montmorillonite nanocomposite particles using an emulsion intercalation method and prepared electrorheological (ER) fluids by dispersing the synthesized nanocomposite particles in an electrically insulating silicone oil. The conducting polymer (polyaniline) was inserted into the layers of clay, and this insertion of polyaniline was confirmed by X-ray diffraction. For the first time, ER properties were determined via a rotational rheometer equipped with a high voltage generator.