水泥浆的沉降失重研究

An Investigation in the Slurry Pressure Decrease due to Settling

以往关于水泥浆在无滤失条件下的胶凝失重观点，因忽视了沉降不稳定因素的影响而具有片面性。根据室内试验，把失重曲线上失重速率第一次出现增加以前的候凝期定义为沉降期；系统地提出了沉降失重观点，并对其进行了检验。结果表明：①导致沉降期水泥浆失重的主要原因不是胶凝悬挂，而是固相沉降，即由于最初悬浮于水泥浆中的固相沉积出来，自由液卸压，使浆柱的孔隙压力降低，但最多降到静水柱压力，由此导致沉降失重；②提高水泥浆的沉降稳定性可以减小或完全避免沉降失重，因而是有效控制早期失重速率和防止气窜的根本措施；③快凝是提高水泥浆沉降稳定性的有效途径。

Former opinions of slurry pressure decrease due to settling without water loss are onesidedness because of neglecting the influence of settling unstability.A newopinon of pressure decrease due to settling(PDS) is put forward and tested.The settling period(SP) is defined from the beginning of WOC to the starting for pressure decrease velocity to increase on the pressure falloff curve.The results show:(1) The main reason for pressure decrease in SP is a settling rather than gelling,that is ,the solid phase suspened in slurry settles out and the pore pressure decreases at most to hydrostatic pressure,which is PDS;(2) PDS can be reduced or completely prevented by improving the slurry stability which is an essential measure to control the velocity of early pressure decrease and prevent gas migration;(3) Fast settling is an effective way to improve the slurry stability. 