Search

A weighted fracturing fluid with superlow guar gum concentration was developed by synthesizing a polyboric acid cross-linker. The density of this fluid is 1.365 g/cm3 and can withstand very high temperature up to 175°C. In this study, a weighting agent was selected, and crosslinking ligands and boric acid were optimized. The crosslinking performance, base fluid viscosity, rheology, and gel-breaking performance of this fracturing fluid were studied. Compared with the conventional weighted fracturing fluid, the concentration of guar gum in the new weighted fracturing fluid can be reduced by 30% at the same temperature condition; moreover, crosslinking can be delayed by 2 minutes. The concentration of gel breaker used in this fluid can be significantly reduced to 0.005%∼0.01%. Two field tests were conducted in Jidong oil field, and both of them achieved great success.

A novel adsorption type gel plugging agent (ATGPA) was prepared using acrylamide (AM), acrylic acid (AA), diallyl dimethyl ammonium chloride (DMDAAC), 2-acrylamido-2-methylpropanesulfonate (AMPS), formaldehyde (HCHO), resorcinol (C6H6O2), and thiocarbamide (CH4N2S) as raw materials under mild conditions. ATGPA was characterized by infrared (IR) spectroscopy, elemental analysis, and scanning electron microscope (SEM). It was found that ATGPA exhibited higher elastic modulus (G′) and viscous modulus (G′′) than AM/AA gel plugging agent (AAGPA) under the same scanning frequency. It was also found that ATGPA had moderate temperature resistance and salt tolerance. Core plugging tests results indicated that ATGPA could achieve up to higher plugging rate (PR) than AAGPA (97.2% versus 95.7%) at 65°C. In addition, ATGPA possessed stronger antiscouring ability by core plugging experiments at 65°C.