Guanglun Lei

Pore-Scale Investigation of Micron-Size Polyacrylamide Elastic Microspheres (MPEMs) Transport and Retention in Saturated Porous Media

Knowledge of micrometer-size polyacrylamide elastic microsphere (MPEM) transport and retention mechanisms in porous media is essential for the application of MPEMs as a smart sweep improvement and profile modification agent in improving oil recovery. A transparent micromodel packed with translucent quartz sand was constructed and used to investigate the pore-scale transport, surface deposition-release, and plugging deposition-remigration mechanisms of MPEMs in porous media. The results indicate that the combination of colloidal and hydrodynamic forces controls the deposition and release of MPEMs on pore-surfaces; the reduction of fluid salinity and the increase of Darcy velocity are beneficial to the MPEM release from pore-surfaces; the hydrodynamic forces also influence the remigration of MPEMs in pore-throats. MPEMs can plug pore-throats through the mechanisms of capture-plugging, superposition-plugging, and bridge-plugging, which produces resistance to water flow; the interception with MPEM particulate filters occurring in the interior of porous media can enhance the plugging effect of MPEMs; while the interception with MPEM particulate filters occurring at the surface of low-permeability layer can prevent the low-permeability layer from being damaged by MPEMs. MPEMs can remigrate in pore-throats depending on their elasticity through four steps of capture-plugging, elastic deformation, steady migration, and deformation recovery.

The Use of Amphiphilic Nickel Chelate for Catalytic Aquathermolysis of Extra-heavy Oil under Steam Injection Conditions

Amphiphilic nickel chelate catalyst was prepared and used in the viscosity reduction process of extra-heavy oil by aquathermolysis. The results showed that the amphiphilic nickel chelate had a good catalytic performance in the aquathermolysis, and the viscosity of extra-heavy oil San56-13-19 was reduced by 96.26% at 200°C. The structure and group composition of the heavy oil were tested and analyzed by thin layer chromatography, Fourier transform infrared, gas chromatography, elemental analyzer, vapor pressure osmometry, and hydrogen nuclear magnetic resonance before and after the aquathermolysis. It was found that the pyrolysis of asphaltene played a key role in viscosity reduction during the catalytic aquathermolysis. Many reactions happened during the catalytic aquathermolysis, such as pyrolysis; ring opening; ring closing of C–S, C–C, C–N, C–O, and hydrogenate; and desulfurization of C=C, C=N, C=O, and S=O. It also found that aromatic sulfonic nickel causes more changes of the asphaltenes and sulfur-containing groups.

The Use of a Nano-nickel Catalyst for Upgrading Extra-heavy Oil by an Aquathermolysis Treatment Under Steam Injection Conditions

Nano-nickel catalyst was prepared in microemulsion system, and used in the viscosity reduction process of extra-heavy oil by aquathermolysis. The results showed that the nano-nickel had a good catalytic performance in the aquathermolysis, and the viscosity of extra-heavy oil San56-13-19 was reduced by 90.36% at 200°C. The structure and group composition of the heavy oil were tested and analyzed by thin-layer chromatography-flame ionization detection, Fourier transform infrared spectroscopy, elemental analysis, vapor phase osmometer, and hydrogen-1 nuclear magnetic resonance before and after the aquathermolysis. It was found that the pyrolysis of asphaltene played a key role in viscosity reduction, and the O-containing products such as alcohol, carboxylate, and fatty acid can reduce the viscosity of heavy oil during the catalytic aquathermolysis.

An Experiment and Simulation of Elastic Microspheres Enhanced Oil Recovery (EMEOR)

Abstract Many chemical agents have been used to enhance oil recovery in the high water cut stage of heterogeneous reservoirs. In this article, a new agent “elastic microspheres” was designed and the composing parameters were optimized. Using a high temperature and high pressure viscometer, the viscoelasticity of elastic microspheres was characterized. Then the characteristics and influencing factors of elastic microspheres profile control and flooding were studied through sand-pack displacement experiments. At last, physical simulation and field tests were conducted. The results can effectively provide guidance for the popularization and application of the new profile control and flooding agent.

Preparation and Characterization of Micron-Sized Elastic Microspheres as a Novel Profile Control and Flooding Agent

A series of micron-sized elastic microspheres were optimally prepared through inverse suspension polymerization of acrylamide (AM) and N, N’-methylene bisacrylamide (MBA) in oil phase when [Span80 & Tween80] and ammonium persulfate (APS) were used to be dispersion stabilizer and initiator, respectively. Their profile control and flooding performance in mid-high permeability sand pack models were characterized in laboratory. The results show that the conversion rate is high, and the coagulum is low when the mass ratio of Span80 to Tween80 is 3:1. The particle size of the elastic microspheres can be controlled by varying the amount of dispersion stabilizer. The micron-sized elastic microspheres can plug sand pack effectively and selectively. The ultimate plugging rate is more than 90% and the ability of profile improvement is up to 70%. The results indicate that the micron-sized elastic microspheres have better profile control and oil flooding performance in the heterogeneous mid-high permeability reservoirs.

Novel Profile Control Treatment Using Pore-Scale Polymer Elastic Microspheres

In order to solve the deep profile control problem and improve oil recovery of the oilfield, a novel profile control agent pore-scale polymer elastic microspheres (PSPEMs) was synthesized. The swelling property of PSPEMs in aqueous solution was analyzed. Core flow test and double-tube sand pack models were used for studying profile control and flooding performance of PSPEMs in oil formation. The results show that PSPEMs have good swelling property in aqueous solution with high salinity, high temperature and high pressure. Fig 5 and Fig 6 show that PSPEMs are better than polyacrylamide polymer on profile control. Table 1 indicates PSPEMs can improve water injection profile of heterogeneous formation effectively and plug the high permeable layer first. The higher the concentration of PSPEMs, the shorter the time it spends to realize profile control. The results also confirm that use proper concentration of PSPEMs, the profile control efficiency can increase enormously.

Study on Acoustic Cavitation and Magnetic Coupling Wax Control Technology

Abstract To solve the wax deposition problem of high-pour-point and high-waxy oil wells, a new acoustic cavitation and magnetic coupling shaft wax control technology was proposed. Experimental research and field tests were conducted. This wax control technology can achieve the purpose of freezing point depression, viscosity reduction by emulsification, and wax control through the combined effect of cavitation, acoustic vibration, and magnetic intensification. Laboratory experiments showed that after acoustic cavitation and magnetic coupling treatment, the viscosity reduction ratio of high-pour-point oil was over 25.5% at 30°C; the freezing point was decreased from 32°C to 27°C, a 15.6% reduction; the wax crystal structure of the oil samples was changed from crude, thick, and dense to fine, thin, and sparse. Field tests showed that the acoustic cavitation and magnetic coupling wax control device can significantly extend the wells wax deposit cycle by more than 30 days and reduce the wax thickness (Yumen Oilfield). Using this technology, the flushing period was extended more than two times, with a maximum up to nine times, and the normal production time was also prolonged (Zhundong Oilfield in Xinjiang). The results are useful for the popularization and application of the new shaft wax control technology for high-freezing-point and high-waxy oil wells.

A new method for evaluating the injection effect of chemical flooding

Hall plot analysis, as a widespread injection evaluation method, however, often fails to achieve the desired result because of the inconspicuous change of the curve shape. Based on the cumulative injection volume, injection rate, and the injection pressure, this paper establishes a new method using the ratio of the pressure to the injection rate (RPI) and the rate of change of the RPI to evaluate the injection efficiency of chemical flooding. The relationship between the RPI and the apparent resistance factor (apparent residual resistance factor) is obtained, similarly to the relationship between the rate of change of the RPI and the resistance factor. In order to estimate a thief zone in a reservoir, the influence of chemical crossflow on the rate of change of the RPI is analyzed. The new method has been applied successfully in the western part of the Gudong 7th reservoir. Compared with the Hall plot analysis, it is more accurate in real-time injection data interpretation and crossflow estimation. Specially, the rate of change of the RPI could be particularly suitably applied for new wells or converted wells lacking early water flooding history.

Laboratory Research on Enhancing Oil Recovery of Three Bacteria D1-3

A group of petroleum-degrading bacteria were obtained from the sludge samples that collected from the Triassic Yanchang 6 reservoir. Of these, three strains with maximum degradation performance were tested in this study. The chromatographic analysis showed that the content of molecules with 30 or more carbons of oil was reduced by 18.36%. Core flood experiments with different flooding rate showed that the oil recovery of microbial flooding was increased by 8.76% than water flooding. The research ruled out that the three strains have well compatibility with the reservoir with remarkable result of petroleum-degrading.