Mobility Control Ability Research Articles

Interaction of Amphiphilic Polymers with Medium-Chain Fatty Alcohols to Enhance Rheological Performance and Mobility Control Ability

To improve the efficiency of mobility control for polymer flooding, a novel thickening system was formed by adding medium-chain fatty alcohols to hydrophobically modified polyacrylamide (HMPAM) bri...

Synthesis and Properties of Branched Polymer Based on Modified Chitosan for Enhanced Oil Recovery

In this study, chitosan and polyamide-amine(PAMAM) were utilized to prepare a branched polymer based on modified chitosan (HPDCS) for enhanced oil recovery(EOR). The structure of the product was confirmed by FT-IR, 1HNMR and SEM. Compared with hydrolyzed polyacrylamide (HPAM), HPDCS exhibited better thickening properties and shear resistance due to its special branched structure and the flexible molecular chains can be deformed through the pore throat of the porous medium, which can avoid serious damage to the molecular chains. After a 45-hour reaction period with biological enzyme, the apparent viscosity of the HPDCS solution decreased significantly, and the viscosity retention rate was only 67.7%, indicating that the introduction of chitosan in the polymer could improve the biodegradability of polymers to a certain extent. Based on sandpacked tube displacement experiments, the HPDCS could build high resistance factor and residual resistance factor in the corresponding porous medium which indicated that the HPDCS performed excellent mobility control ability. Besides, compared with HPAM, the HPDCS solution of 2000 mg/L showed better oil recovery of 24.12% in the corresponding porous medium, which demonstrated that the branched polymer has a more outstanding EOR ability.

Performance improvement of CO2 flooding using production controls in 3D areal heterogeneous models: Experimental and numerical simulations

CO2 flooding is a promising technology used to enhance oil recovery as it increases oil production and sequesters CO2 in low permeability oil reservoirs. However, the areal heterogeneity of a reservoir can seriously affect CO2 flooding efficiency. The importance of production control treatments (sweeping area regulation, differential production pressure control, and real-time producing regulation) are thus proposed to improve the performance of CO2 flooding in areal heterogeneous reservoirs. Three dimensional (3D) physical models and core-scale numerical models with areal heterogeneity and 5-spot patterns are designed using dimensionless scaling groups. Conventional CO2 flooding and CO2 production control flooding are conducted successively in the 3D models, and flooding efficiency is evaluated through oil recovery increments and changes in the displacement pressure drop curves. Mechanisms of CO2 performance improvement using production control treatments are also discussed through the analytical analysis of gas distribution and gas/oil mobility ratio.3D experimental and numerical simulation results show that CO2 is displaced unevenly in the areal heterogeneous reservoir, leaving plenty of oil in the area of relatively low permeability. However, oil recovery of CO2 flooding in the areal heterogeneous reservoir can be doubled using production control treatments (sweeping area regulation, differential pressure control, or real-time producing regulation). The oil remaining in the area of relatively low permeability can be effectively displaced using sweeping area regulation, and both a larger sweeping area and a better CO2 flooding profile can be obtained using differential pressure control and real-time producing regulation. Through the analytical analysis of gas distribution and gas/oil mobility ratio, it is found that gas/oil mobility ratio is more sensitive to the areal heterogeneity, and real-time producing regulation has a powerful mobility control ability for CO2-EOR. Improvements in the performance of CO2 flooding using production control treatments provide a feasible technical strategy to treat with the areal heterogeneity and enhance the oil recovery for 5-spot well patterns in the areal heterogeneous reservoir.

Mobility control ability and stability investigation of nitrogen foam under high temperature and high salinity condition

The mobility disparity between oil and water accounted for the poor water swept efficiency. Previous research has testified that nitrogen foam can increase sweep area and control water and gas mobility. However, the former studies have largely covered the mobility control ability performance in some conventional reservoir rather than that under high temperature and high salinity. This paper presents the results of a laboratory study of nitrogen foam at the experimental condition (113 °C and 21.28 × 104 mg/L) on its mobility control ability investigation, including different gas-to-liquid ratio, injection rate and core permeability; additionally, a novel method on studying the stability of mobility control ability of foam was utilized. Nitrogen foam injection was conducted in core holder to investigate the shape discrepancy of each resistance factor and residual resistance curve. The results showed that the most moderate gas-to-liquid ratio and injection rate were 2:1 and 1 mL/min, respectively; foam performed more significant mobility control ability with the increase in permeability. After 5 days’ aging, nitrogen foam still got enough mobility control ability to block water channeling. The above results demonstrate that, under high temperature and high salinity condition, nitrogen foam still can act as a promising economical method for improving the mobility difference between water and oil by applying appropriate injection parameters.

Synthesis and rheological property of various modified nano-SiO2/AM/AA hyperbranched polymers for oil displacement

In this study, various modified nano-SiO2 functional monomers (nano-SiO2-KH540-MAH) were prepared and reacted with acrylamide (AM) and acrylate (AA) to synthesize a water-soluble hyperbranched copolymer (nano-SiO2/AM/AA) for medium- and low-permeability reservoirs and heterogeneous reservoirs by using the redox free-radical polymerization strategy. The HCl‒CH3CH2OH titration expectedly demonstrated that the monomers underwent a controlled modification. The copolymers were characterized by a series of experiments, including IR, 1H NMR and DLS methods. Furthermore, it was shown that, compared with the rheological properties of various modified copolymers, Polymer-40 has a better viscosity and elasticity due to the better molecular structure. An indoor displacement test demonstrated that the mobility control ability and the EOR ability had a favorite relationship with rheology. The RF, RRF and EOR of Polymer-40 were higher than the same parameters of other modified copolymers.

Gas channeling control during CO2 immiscible flooding in 3D radial flow model with complex fractures and heterogeneity

Fractures and heterogeneity commonly exist in ultra-low permeability reservoirs, which will cause serious gas channeling phenomena and lead to poor oil recovery during CO2immiscible flooding. CO2water alternating gas (WAG) flooding combined with gas channeling control treatments are recognized as effective approaches to enlarge the sweep efficiency of CO2. Performance of gel systems were evaluated to screen out a high-strength gel which can be utilized as fracture blocking agent. Then, performance of small molecule amines were evaluated to screen out a kind of small molecule amine which can be utilized as rock-matrix blocking agent. Performance evaluation results showed that high-strength gel with 8% modified starch + acrylic amide, 0.05% crosslinking agent, 0.15% initiator and 0.15% stabilizer could be served as fracture blocking agent, while etheylenediamine was proposed as rock-matrix blocking agent which could react with CO2 and generate solid particles to improve the heterogeneity of the reservoirs.To examine gas channeling control effect in actual reservoir conditions, a 3D radial flow model with complex fractures and heterogeneity was designed according to the actual oilfield, and five-spot pattern was employed in the model. Waterflooding, continuous CO2 flooding, and gas channeling control using high-strength gel, etheylenediamine and CO2 WAG flooding were conducted successively in the 3D radial flow model. After a series of treatments, the oil recovery was enhanced by 15.09%, which was significant for CO2 immiscible flooding in the field application. The gas channeling along major fracture and microfractures of the model was effectively controlled by high-strength gel, while fluid diversion could occurred after ethylenediamine injection due to the solid particles which could mitigate gas channeling along relatively high permeability areas of the rock-matrix, and the gas channeling phenomena can be further mitigated by the mobility control ability of CO2 WAG flooding.

Mechanical Properties and Flow Behavior of Polymers for Enhanced Oil Recovery

The mechanical properties and flow behavior in porous media of three different polymer systems including a hydrophobically modified acrylamide-based copolymer (HMSPAM), a partially hydrolyzed polyacrylamide (HPAM), and a polysaccharide (xanthan gum) were evaluated to establish their functional differentiation as mobility control agents in enhanced oil recovery (EOR). The rheological properties of the polymers were described by the power-law model to investigate their non-Newtonian behavior. The first normal stress difference (N1) and Weissenberg number (We) were also used to compare their elastic properties. The experimental results showed that, at comparable shear viscosity, HMSPAM exhibited significant elasticity compared to HPAM and xanthan gum. Shear resistance tests indicated that all of the polymers experienced an extra stress when converging into a capillary tube due to the “entrance effect.” Xanthan gum was the most mechanically stable polymer. Moreover, HMSPAM showed the superior reformability which was quantified by the regained viscosity with relaxation time. This could be explained by the rapid re-association of the hydrophobic interactions. Sandpack flood tests indicated that HMSPAM rendered extremely high mobility control ability during polymer flooding suggesting its potential in EOR. However, this polymer also experienced significant retention within the porous media (potential injectivity and plugging problems), which may be attributed to the formation of bulky associative polymer networks. In this work, UV spectrometry was employed to monitor the concentration of the produced polymer solutions and quantify the polymer retention within porous media. This analytical approach offers great reliability and simplicity. It was concluded that the use of a particular polymer system depends on the oil reservoir conditions and the target EOR application.

Formulation of a Self‐Assembling Polymeric Network System for Enhanced Oil Recovery Applications

ABSTRACTThe chemical formulation and rheological properties of a novel self‐assembling polymer (SAP) network system were investigated for potential application in enhanced oil recovery (EOR). The inclusion complexes formed by surfactant (S) and β‐cyclodextrin (β‐CD) can associate with hydrolyzed polyacrylamides (HPAM) in aqueous solution, and subsequently establish the SAP network, which exhibits advanced viscoelasticity at the optimum molar ratio (S:β‐CD = 2:1). Furthermore, this system presents enhanced surface activity and superior mechanical and thermal stability, as well as tolerance to elevated brine salinity and hardness due to the network “interlocking effect”. Sandpack flood tests suggest the excellent mobility control ability of this system during polymer flooding, and also a moderate permeability reduction capacity, which makes it more cost effective in oil fields than the currently used HPAM. Regarding EOR performance, this polymeric system (SAP) produced approximately 19% more incremental oil than the baseline HPAM under the same experimental conditions.

Performance Evaluation of S/P System and its Mechanism Analysis

Xinbei Oilfield in Jilin is a tectonic lithology reservoir with high porosity, high permeability, thin oil layers and severe heterogeneity, which has entered a period of high water-cut development. Aiming at actual demand of field development, making use of indoor apparatus monitoring and theoretical analysis method, the author evaluated the viscosity, interfacial tension, absorption characteristics, rheological property, viscoelasticity and displacement efficiency of 5 different binary composite systems composed of surfactants and polymer to optimize the binary flooding system. The results show that Daqing Lianhua/Polymer system can achieve ultra-low interfacial tension with crude oil with small absorption, well stability and little effect on viscoelasticity of polymer solution. The system has higher displacement efficiency and stronger mobility control ability, which is recommend as flooding system for oilfield.

The shearing effect on hydrophobically associative water‐soluble polymer and partially hydrolyzed polyacrylamide passing through wellbore simulation device

AbstractHydrolyzed polyacrylamide (HPAM) was the traditional polymer and hydrophobically associative water‐soluble polymer (HAWP) was the new polymer with three‐dimensional network both used to flood to enhance oil recovery. The wellbore area was the most important part before the polymer solution injected into stratum. In this article, the shearing effects of the two polymers were studied by a wellbore simulation device. The viscosities of HPAM and HAWP solutions were both decreased around perforation of wellbore simulation device. Interestingly, viscosity of HAWP recovered from stratum 0.2 m. Until stratum 1.6 m, its viscosity recovered almost 50% of original. The data of intrinsic viscosity showed that the molecular chains of HAWP and HPAM were both degraded without any recovery. The contradiction was further studied by particle size and its microstructure. The mean particle size and particle size distribution data both showed HAWP recovered but HPAM was not. The microstructures of HAWP by atomic force microscopy images further explain the recovery of viscosity. The disassembled molecular chain was self‐assembled into aggregate to newly network by hydrophobes with weaker linking than original solution. While the microstructure of HPAM was thoroughly split up to randomly coil without linking. In addition, the viscoelasticity of HAWP was also recovered to some extent but HPAM was not. All the results proved that HAWP has mobility control ability to displace oil in reservoir even if suffered severely shearing by wellbore. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The Development and Performance Evaluation of Hydrophobic Association Polymer Pre-Cross Linked Particulate

Due to the shortage of traditional pre-cross linked particulate, such as suspension property, temperature and salt tolerance, and injectivity, this paper developed hydrophobic association polymer pre-cross linked particulate based on hydrophobic association polymer. The performance evaluation of rheological behavior, microstructure and mobility control ability demonstrate that hydrophobic association polymer pre-cross linked particulate can partly dissolved in water, and has certain viscosity thickening and suspension property; it partly cross linking forming mesh structure, and has strong resilience; it can deform through the porous media after swelling, and has good mobility control ability.

Study on the Performance of Hydrophobic Association Water-Soluble Polymer with Strong Association Ability

In this article, the viscosifying abilities, rheological properties, and flow characteristics of hydrophobic association water-soluble polymer with high association ability were studied using technical methods of viscosity measurement, rheological and core flow experiments. The results illustrate that hydrophobic associated polymers with low molecular weight rely on a strong hydrophobic interaction, the intermolecular and intramolecular micellar structure formed in solution with a strong ability to increase viscosity. Hydrophobic association water-soluble polymer, comparing with partially hydrolyzed polyacrylamides polymer with low molecular weight, presents a better ability of shear stability under the condition of shearing and the solution structure strengthens gradually so as to increase viscoelasticity remarkably. The hydrophobic association water-soluble polymer with high association ability take on greater injectivity and mobility control ability in low permeability porous media solving the problem of low injectivity and poor control ability in mid-low permeability reservoirs, which improves polymers flooding effect in such reservoirs and underlie the reasonable design of polymer molecular structure.

Study on Properties of Pectinate Hydrophobically Associating Polyacrylamide Solutions

In this article, the viscosifying abilities, rheological properties, flow characteristics of pectinate hydrophobically associating polymer (PHAP) solutions with different hydrophobe content were studied using technical methods of viscosity measurement, rheological and core flow experiments. Researches on viscosifying of different PHAPs at 20°C and 65°C in distilled water and saline indicate that, with the raise of hydrophobe content, viscosity of polymer solutions increases first and then decreases, which means that there should be a critical hydrophobe content( CHC). Below CHC, the anti-shear ability of polymer solutions enhances as hydrophobe content rises; while the shear resistance would fall down when and after the content reaches CHC. In high permeability porous media, all polymer solutions take on greater injectivity, and RFF can all be higher than 5, yet with the increasing of hydrophobe content, RF goes up first and then declines. It could be an effective way to enhance mobility control ability, improve polymer flooding effect in high permeability reservoirs and design polymer molecular structure more reasonably, using the pectinate structure and hydrophobic association interaction between polymer moleculars.

Carbon Dioxide Foam Rheology in Porous Media: A CT Scan Study

Summary Carbon dioxide (CO2) foam has been widely studied in connection with its application in enhanced oil recovery (EOR). This paper reports an experimental study concerning CO2 foam propagation in a surfactant-saturated Bentheim sandstone core and the subsequent liquid injection with the aid of X-ray computed tomography (CT). The experiments were carried out under various system backpressures. It is found that CO2 foam flows in a characteristic front-like manner in the transient stage and that the water saturation keeps at relatively high level at the outlet of the porous media because of CO2 solubility and capillary end effect. The subsequent surfactant solution injection shows a significant fingering behavior, accompanied by a low flow resistance over the core. It is also found that CO2 foam flow shows higher liquid saturation near the outlet and lower pressure drops under higher system backpressures. This can be attributed to the solubility of CO2 in the liquid phase. The results indicate the advantage of using foam in EOR processes such as water alternating foam (WAF), in which foam flow has higher sweep efficiency and stronger mobility control ability compared, for instance, to water alternating gas (WAG). Nevertheless, care should be taken during the water-injection stage in order not to favor the fingering.