Development and application of guar gum crosslinked gel with adjustable gelation time for total loss treatment

To remediate the problem of severe or total losses,and meet the requirements of borehole plugging and pumping at different well depths,a novel crosslinked polymer gel(named HPG/Zr gel)with controlled gelation time and high gel strength was developed as loss circulation material,which mainly comprised hydroxypropyl guar gum,zirconium compound and triethanolamine.The influence of hydroxypropyl guar gum concentration,zirconium compound concentration,triethanolamine concentration and temperature on the gelation time of HPG/Zr gel was evaluated.In addition,the performance of HPG/Zr gel was investigated in terms of temperature resistance and shear resistance property,plugging ability and supporting cement slurry ability.According to the results,HPG/Zr gel can form a viscoelastic body with a network structure,and its gelation time can be practically adjustable.The results of the plugging experiment at different temperatures,pressures and pore sizes of quartz sand revealed that HPG/Zr gel could effectively plug sand pores at 150℃,and its pressure-bearing capacity can be up to 5 MPa.Employing its flow resistance and ability of supporting cement slurry,HPG/Zr gel was successfully applied in two geological boreholes by combining with cement slurry.Overall,the results of laboratory research and field tests indicate that HPG/Zr gel is useful for mitigating the lost circulation,and it is of huge importance to engineering applications.

Researches on the PAM／Cr^3＋ Gel for Deep Profile Control

The profile control hard-gel is composed of polyarylamide (5-6g/L), whose molecular weight is 4,000,000 - 7,000,000 and hydrolysis degree is 17.6%, and cross-linking oxidation-reduction agent (Na2Cr2O7 + NH4Cl), with an delayed organic acid crosslinker which contains lactic acid/propionic acid/ethanoic acid and ethylene glycol. After research of the influence factors, such as pH, temperature, salinity and the dosage of delayed crosslinker, the optimum condition(pH 5.2, temperature 55℃, salinity < 7g/L) was found. Gelation time (12-144h) can be controlled by adjusting the dosage of the delayed crosslinker. Deep profile control experiments are carried out on heterogeneous models, which contains three serial high permeable and low permeable cores arranged in a parallel. After water flooding (total recovery, 24.3%), the first, second and third high-permeable cores each are sealed in turn by the profile control agent, and the total displacement recovery increases to 46.8%, 62.2% and 69.1% respectively. So, the greater the sealed depth, the larger the enhancing recovery will be. Finally, the oil displacement mechanisms of deep profile control are discussed.

A review of nuclear magnetic resonance(NMR) technology applied in the characterization of polymer gels for petroleum reservoir conformance control

Polymer gel systems have been widely applied to control excessive water and improve oil recovery(IOR)in petroleum reservoirs.They are usually divided into two main types,in-situ cross-linked polymer gels,and pre-formed polymer gels.In recent years,nuclear magnetic resonance(NMR) technology has been gradually applied to the research of polymer gel systems due to its unique analysis advantages.This paper is intent to review these works systematically.For in-situ cross-linked polymer gel systems,NMR can be used to characterize the chemical structure changes of the polymer,the cross-linker,and the auxiliary agent in the formulation of the polymer gel systems.Moreover,the gelation time and the gel strength of the in-situ cross-linked polymer gel systems can also be measured by NMR.For pre-formed polymer gels,NMR can be employed to detect the chemical structure of the designed products.Last,the NMR method can evaluate the plugging,water control,and oil improvement performance of the polymer gels in porous media without using dopants.This review can help readers build a more systematic understanding of the application of NMR technology in polymer gel systems for IOR and help re searchers to more deeply study the performance of polymer gel systems.

Effect of Al2O3 on the Process Performance of ZrO2 Microspheres

Al2O3-ZrO2 microspheres were prepared by internal gelation method.The effects of Al3+on the stability of solution and performance of gel spheres were studied.Al3+had a great influence on the stability of the solutions,and the more of the amount of Al3+,the shorter of the stabilization time.Because Al3+did not copolymerize with Zr4+during the sol-gel transformation,the strength of gel sphere added with Al3+was low and deformed easily as it was squeezed.The results of our experiments well verify Glasser team’s speculation and conclusions.At the same time,based on the experimental results,we prepared Al2O3-ZrO2 composite microspheres with higher content of Al2O3 by controlling the pH of the solution.The change curve of viscosity with time and the stabilization time of the solution with different Al3+dosage were given,which could provide references for industrial mass production.Samples without hydrothermal treatment cracked severely,while the samples hydrothermally treated kept structural integrity with no cracks after calcined.Al2O3-ZrO2 microspheres with no segregation and phase separation were prepared and alumina evenly distributed in the zirconia matrix.When the content of Al2O3 was low,the tetragonal phase was stable.And the cubic phase was obtained when the content of Al2O3 was more.

Effects of nanoparticles, polymer and accelerator concentrations, and salinity on gelation behavior of polymer gel systems for water shut-off jobs in oil reservoirs

Excess water production is one of the crucial complications in the oil industry,leading to a rapid decline in oil production.To overcome this problem,different polymer gels are used to block the water's path to reduce water production.In the present work,polymer gel systems were prepared with polymers namely partially hydrolyzed polyacrylamide(PHPA),organic crosslinkers like hexamine,and hydroquinone with the incorporation of silica and alumina nanoparticles.Nanoparticles are used to enhance the stability of the gel framework in high salinity and high temperature reservoir environment.When designing the polymer gel system,factors such as pH,thermal stability,brine composition,injection rate,and chemical concentration were considered.Concentrations of PHPA and nanoparticles were varied from 1 to 2 wt% and 0.25e1.0 wt% respectively for the preparation of different gel systems.The concentration of the organic crosslinker was extended from 5000 to 11000 ppm for investigating the effect on gelation time.Brine concentration was chosen from 2 to 8 wt% to find the impact of high salinity.Succinic acid as an accelerator was also used to study the effect on gelation time,and it was found that the gelation time is reduced as the concentration of succinic acid increases.The prepared polymer solution was taken in a test tube and was kept inside a hot air oven at 95℃ to perceive the gelation time and nature of the produced gel.Results showed that nanoparticles do not influence the gelation time,but they considerably affect gel stability.However,concentrations of polymer,accelerator,and salt(salinity)have significant effects on the gelation behavior of the gel systems.

Enlisting a Traditional Chinese Medicine to tune the gelation kinetics of a bioactive tissue adhesive for fast hemostasis or minimally invasive therapy

Gelation kinetics is important in tailoring chemically crosslinked hydrogel-based injectable adhesives for different applications.However,the regulation of gelation rate is usually limited to varying the gel precursor and/or crosslinker concentration,which cannot reach a fine level and inevitably alters the physical properties of hydrogels.Amidation reactions are widely used to synthesize hydrogel adhesives.In this work,we propose a traditional Chinese medicine(Borax)-input strategy to tune the gelation rate of amidation reaction triggered systems.Borax provides an initial basic buffer environment to promote the deprotonation process of amino groups and accelerate this reaction.By using a tissue adhesive model PEG-lysozyme(PEG-LZM),the gelation time can be modulated from seconds to minutes with varying Borax concentrations,while the physical properties remain constant.Moreover,the antibacterial ability can be improved due to the bioactivity of Borax.The hydrogel precursors can be regulated to solidify instantly to close the bleeding wound at emergency.Meanwhile,they can also be customized to match the flowing time in the catheter,thereby facilitating minimally invasive tissue sealing.Because this method is easily operated,we envision Borax adjusted amidation-type hydrogel has a promising prospect in clinical application.