Research and application of solid-free rubber plug press spacer fluid in deep wells

In cementing jobs in deep wells in Qaidam Basin, due to some substandard drilling fluid properties or poor sealing of rubber plug, some cement slurry reacted with displacing drilling fluid and got flocculated, which caused cementing problems and the electric log could not be lowed to hole bottom. For this reason, the solid-free rubber plug pressed spacer fluid was developed. By evaluating experiments on the performances of resistance to cement contamination, high temperature and subsidence stability of rubber plug pressed spacer fluid, the best formula of plug pressed spacer fluid was selected for deep well completions. Field application shows that the solid-free spacer fluid of 300~500 m between the plug and displacing drilling fluid can effectively prevent the remaining cement in the casing from being flocculated with drilling fluid and also slow down settling and piling up of solid particles. In 37 deep wells where solid-free plug spacer fluid was used, the one-time success rate of electric log for completion cementing quality was 100%, effectively shortening the period of completion operations.