Fa-Yang Jin

Amphoteric hyperbranched polymers with multistimuli-responsive behavior in the application of polymer flooding

Amphoteric hyperbranched polymers (AMHPMs) that respond to shear rate, temperature, salt, and pH were synthesized using a water free radical polymerization technique. The Mw of this novel polymer is much lower than that of the conventional linear hydrophobically associative polymer (HAPAM). The hydrodynamic size could be effectively tuned by adjusting the terminal functional groups of the hyperbranched monomer. In the semidilute regime, multiple hydrodynamic subchains and effective intermolecular associations between neighboring branches of polymeric chains cooperatively govern the comprehensive characteristics of AMHPMs. Rheological measurements revealed the pseudodilatant behavior in the lower shear rate region, followed by the pseudoplastic behavior of AMHPMs. Moreover, the elasticity of AMHPM-2 played a dominant role and no Gc is observed within the experimental frequency. Static experiments convincingly proved that the multiple subchains provided AMHPMs with a wider temperature-, salt- and pH-responsive region in comparison to that for HAPAM. Most importantly, the reversible hydrodynamic characteristic scale due to the mutual transformation from association to disassociation, and the excellent anti-mechanical degradation for AMHPMs in the simulative porous medium, further verified that this unique type of hyperbranched polymer is promising for the application of polymer flooding for enhanced oil recovery (EOR).

The Kinetic Analysis of Oxidized Oil During the High Pressure Air Injection by Thermal Kinetic Analysis

Studying the changing of the oil property with injected air is the prerequisite to apply the HPAI technique in heavy oil reservoir. For this purpose, the oxidation experiments have been carried to study the influence of pressure on heavy oil analyzed by thermogravimetry and differential scanning calorimetry. The results indicated that the oxidized oil with lower activation energy is easier to react with the oxygen. So the higher pressure has positive influence on the coke deposition with stable combustion front. Sufficient coke will bring the possibility for application of HPAI technique without ignition devices in heavy oil reservoirs.

The Kinetic Analysis of Coke Formation Under Differential Air-oil Ratio During High Pressure Air Injection

For studying the heavy oil property change during high pressure air injection process, constant temperature oxidation tube experiments have been finished to study the influence of air-oil ratio on the oxidation process with thermoanalysis methods. The results presented an increasing amount of formation coke was contained with the air-oil ratio increment. When the air-oil ratio reached 200:1, the oxidation process was promoted and the oxide was identified as “coke” with smell. Based on the Arrhenius method, it indicated the air concentration has positive influences on the coke deposition conducive to form and sustain stable combustion front.

Utilisation of multiple gas injection to enhance oil recovery for fractured-cavity carbonate heavy oil reservoir

Gas injection has been proven to be a valuable enhanced oil recovery (EOR) process for light oil reservoirs and ordinary heavy oil reservoirs, but it was rarely proposed as an EOR process for fractured-cavity carbonate heavy oil reservoir. This study aims to investigate the feasibility of the gas injection based on flooding and cycle stimulation method with respect to enhancing oil recovery for fractured-cavity carbonate heavy oil reservoir. Thus, a representative physical model of core was designed, and some gas flooding and cyclic gas stimulation experiments were conducted. The experimental results show that gas injection can enhance the oil recovery in fractured-cavity carbonate reservoir and carbon dioxide is the optimal injected gas in this study. Also, gravity drainage plays an important role in fractured-cavity carbonate reservoir besides the various recovering mechanisms in conventional reservoir. In addition, Tahe heavy oil has a strong capacity of oxygen consumption due to the high content of polar compound. [Received: May, 1, 2015; Accepted: February 29, 2016]

The effects of interfacial tension, injection rate, and permeability on oil recovery in dilute surfactant flooding

ABSTRACT Surfactant flooding as a potential enhanced oil recovery technology in depleted reservoirs after water flooding has been documented for several decades and has attracted extensive attention. This research explored the effect of interfacial tension among crude oil and surfactant, injection rate, and permeability on oil recovery in dilute surfactant flooding. The results indicated that the additional oil recovery increased with the reduction of the interfacial tension and the increase of the permeability. The additional oil recovery increased and later decreased with the increase of injection rate. The research is instructive for surfactant flooding application for enhanced oil recovery.

Variation of reservoir fluid property during the high pressure air injection process

ABSTRACT This research aimed at determining the variation of reservoir fluid property during the high-pressure air injection process. For this purpose, the forward multiple contact experiment was employed by pressure–volume–temperature (PVT) system to investigate the physical property variation of the crude oil and the complex oxidation reactions. The results show: under the relative low temperature and pressure condition, instead of carbon dioxide, carbon monoxide dominates the products in the air phase. The gas/oil ratio and volume ratio increased due to the generated gas while the viscosity and density achieved a descending trend. The colloid and bitumen in the oil phase reduced by half but the amount of wax achieved a small increase. The low-temperature oxidation and pyrolysis reactions caused the fluctuated change of the different compounds. The amount of light compounds decreased at the beginning and then increased while that of heavy compounds showed the opposite trend. But at last, due to the H/C ratio, the light compounds increased to more than their initial value.

The In Situ Profile Modification Effect of Deposited Coke in Carbonate Reservoirs

In the carbonate reservoir, the fracture and cavity increased the gas break possibility easily. When the air was injected into the reservoir, the oxidation reaction changed the physical property of the crude oil and increased its viscosity. In this study, a physical modeling experiment was applied to analyze the in situ profile modification effect of oxidized oil by artificial fracture and cavity core. The results showed that the oxidation reactions increased the crude oil viscosity and reduced mobility ratio. The gas break phenomenon was suppressed in some degree.

Preparation and Properties of Polymer/Vermiculite Hybrid Superabsorbent Reinforced by Fiber for Enhanced Oil Recovery

A series of polymer/clay hybrid superabsorbent composites (SACFs) comprising acrylamide, acrylic acid, sodium 2-acrylamido-tetradecyl sulfonate, fiber, and vermiculite by in situ intercalation and exfoliated method was successfully synthesized. The structure of SACFs was characterized by IR, SXRD, and SEM measurements. Much notable absorbency for SACF-2 was observed compared to that for SACF-1 in the absence of hydrophobic group in the high cationic solution due to the alkyl carbon chain and sulfonic acid group of hydrophobic moistures protecting the cations from attacking the carboxylate groups. What is more, high temperature fiber which acts as bridge connection for the polymeric network structure enhanced both toughness and strength for SACF-4 in the harsh conditions. At the total dissolved substance of 212000 mg/L for Tarim Basin injected water and the temperature of 120°C, desired absorbency as well as water retaining property for SACF-4 was observed during the long period of thermal ageing. Core flooding experiments demonstrated that SACFs could migrate as amoeba in the porous medium and accumulated in the narrow channel to adjust injection profile, promoting the subsequent water diverting into the unswept zones. Finally, characteristic parameters for SACFs calculated from flooding experiment further confirmed these polymer/clay hybrid composites reinforced by fiber would have robust application in the mature oilfield for profile control.