High Temperature Solid-free Drilling Fluid Technology

A solid-free drilling fluid having stable properties at 220℃ has been developed with high temperature additives such as XCC (viscosifier), AADC (filter loss reducer) and FSCC (plugging agent). The detailed composition of the drilling fluid is:2%XCC+1% AA DC+3%SPNH+1%SMP+3%FSCC+0.5%Na₂SO₃. SEM experiment showed that shale cores taken from a well drilled with this drilling fluid had layered micro-fractures apparently plugged, and a dense tree-like polymer layer parallel to the direction of the micro-fractures was found on the surface of the shale cores. FT-IR experimental results showed that, after aging at 220℃, the drilling fluid still had stable mud properties, good rheology and filtration properties. The inhibitive capacity and lubricity of the drilling fluid can satisfy the needs of drilling operation. This drilling fluid was able to tolerate the contamination from 10% clay and 5% drilled cuttings, or from 10%KCl+20%NaCl salt solution. The LC50 of the drilling fluid measured was 80,000 mg/L, conforming to the stipulated discharge criteria. The drilling fluid has been successfully used to drill the Well 24 located in the Sebei-1 gas field.