Properties and Field Application of LFW (Low Free Water) Drilling Fluid

Wellbore instability is known to be a significant problem that has plagued mud engineers for many years. In order to solve this problem, mud engineers have studied on pressure control, increasing inhibition of drilling mud, and plugging the formation, but the relationship between flowing state of free water in drilling fluid with wellbore instability has been always ignored. The authors discuss the properties and field application of the low free water (LFW) drilling fluid in more than 10 wells drilled in China. It is a new kind of drilling fluid, which has less free water contrasting with counterparts. In addition, it is also a new concept to solve wellbore instability. Field application shows that LFW drilling fluid can increase bearing capability of the formation, decrease the density of drilling fluids when finishing drilling, and shorten the drilling time.