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.

Viscosity and degradation controlled injectable hydrogel for esophageal endoscopic submucosal dissection

Endoscopic submucosal dissection(ESD)is a common procedure to treat early and precancerous gastrointestinal lesions.Via submucosal injection,a liquid cushion is created to lift and separate the lesion and malignant part from the muscular layer where the formed indispensable space is convenient for endoscopic incision.Saline is a most common submucosal injection liquid,but the formed liquid pad lasts only a short time,and thus repeated injections increase the potential risk of adverse events.Hydrogels with high osmotic pressure and high viscosity are used as an alternate;however,with some drawbacks such as tissue damage,excessive injection resistance,and high cost.Here,we reported a nature derived hydrogel of gelatin-oxidized alginate(G-OALG).Based on the rheological analysis and compare to commercial endoscopic mucosal resection(EMR)solution(0.25%hyaluronic acid,HA),a designed G-OALG hydrogel of desired concentration and composition showed higher performances in controllable gelation and injectability,higher viscosity and more stable structures.The G-OALG gel also showed lower propulsion resistance than 0.25%HA in the injection force assessment under standard endoscopic instruments,which eased the surgical operation.In addition,the G-OALG hydrogel showed good in vivo degradability biocompatibility.By comparing the results acquired via ESD to normal saline,the G-OALG shows great histocompatibility and excellent endoscopic injectability,and enables create a longer-lasting submucosal cushion.All the features have been confirmed in the living both pig and rat models.The G-OALG could be a promising submucosal injection agent for esophageal ESD.