Preparation and properties of fluid loss reducer for anti-CO32- pollution in ultra-high temperature and high salt drilling fluids

Abstract

Aiming at the problems of poor system stability and large-filtration loss after CO2 pollution in oil and gas drilling at ultra-high temperatures deep wells, an ultra-high temperatures anti-CO32- pollution strong adsorption-drilling fluid defiltration loss agent (PMSC) was prepared using acrylamide (AM), sodium p-styrene sulfonate (SSS), N-vinylpyrrolidone (NVP) and dimethyldiallylamlammonium chloride (DMDAAC) as raw materials. The structure and morphology of PMSC were characterized by Fourier infrared spectroscopy, nuclear magnetic resonance, and thermogravimetric analysis. The performance test shows that PMSC has the ability to resist saturated saline (36 % NaCl) and composite saline. In addition, it has better anti-CO32- (5000 ppm) pollution and filtration reduction performance than the same product at ultra-high temperature (210 ℃), and FLAPI is only 6.8 mL. The mechanism of PMSC anti-CO32- pollution and filter loss reduction was analyzed by particle size distribution, SEM, and UV–visible spectrophotometer. PMSC forms crosslinked network structures in drilling fluid. Amphoteric polymer increases the competitive adsorption capacity with CO32-, firmly adsorbs on the surface of clay particles, and forms a thick hydration film. This suppresses the coalescence effect of CO32- contaminated drilling fluid caused by high temperature and promotes reasonable particle size distribution. Finally, a compact filter cake is formed to reduce filtration loss. Due to the good filtration loss performance of PMSC under ultra-high temperatures and CO32- pollution, PMSC is expected to become a promising drilling fluid filtration loss agent used in formations with high CO2 salinity at ultra-high temperatures.