Study on viscosification law of OAPB self-diverting acid by acid concentration and inorganic salt in coal

Abstract

In order to improve the diverting performance of self-diverting acid in underground coal mine, the effects of different concentrations of HCl and inorganic salt on steady state viscosity, micellar length and entangling density of oleylamidopropyl betaine (OAPB) self-diverting acid were studied by rheological measurement, dynamic light scattering and infrared spectroscopy. The results show that with the increase of HCl concentration, the steady-state viscosity and micellar length of the self-diverting acid all show a regulation of “increase first and then decrease”, and reach the highest value of 9.42 pa.s and 63 nm at 5% HCl concentration. With the increase of inorganic salt content, the micellar length of self-diverting acid gradually increases. When the content of CaCl2 and FeCl3 in self-diverting acid is 20 g, the micellar length reaches 141 nm and 287 nm, respectively. The steady state viscosity shows a trend of “increase first and then decrease” with the increase of inorganic salt concentration. The highest values are 18.34 pa.s and 24.18 pa.s when the content of CaCl2 and FeCl3 are 15 g and 10 g, respectively. The relative contribution of acid concentration, CaCl2 and FeCl3 to the diverting performance of self-diverting acid is 38.96%, 75.85% and 100%, respectively. Finally, some targeted opinions were put forward according to the application conditions of self-diverting acid in coal mine.