基于分子模拟的超高温水特性及其对钻井液处理剂的潜在影响OA

Molecular dynamics simulation(MD)was employed to select an appropriate water molecular model for ultrahigh-temperature and high-pressure conditions.The bulk phase properties(density and viscosity)of water and the microstructure between water molecules(number of hydrogen bonds,water phase structure and diffusion coefficient)were investigated to reveal the variation characteristic parameters of ultrahigh-temperature and high-pressure water.The results show that the av-erage error of SPC/E water molecules for fitting the viscosity and density of the aqueous phase is about 3%.Under low-tem-perature and low-pressure conditions,the pressure has no influence on water molecular mobility,whereas the effect of tem-perature on the diffusion coefficient of water is more than 3 times that of pressure under high-temperature and high-pressure.With the increase of temperature,the thermal motion of water molecules increases,the number and lifetime of intermolecular hydrogen bonds decrease,and the diffusion coefficient increases,which changes the distribution structure of water molecules around the central water molecules.The changes of the characteristic parameters of the aqueous phase under high-temperature and high-pressure can affect the viscosity and rheological properties of water phase,which may further weaken the ability of polymer additives to capture water molecules.Consequently,the hydrogen-bonding interactions between polymer additives and water molecules may be reduced,leading to reduced solubility and accelerated reactions between polymer additives and the surrounding medium.