Research and Evaluation of Clay-Free Drilling Fluids with High Temperature Resistance

In order to eliminate dependence on clay by drilling fluid,overcome the degradation of conventional viscosifier and fluid loss agent at high temperature,protect reservoir and enhance penetration rate,a viscosifier or fluid loss agent called SSDP was synthesized by the sulfonic acid groups and cationic monomer,and on the basis of it,the anti-high temperature and water based clay-free drilling fluid was developed by selecting and compounding the viscosifiers,filtrate reducers,lubricants and anti-sloughing agent.The laboratory evaluation showed that the clay-free drilling fluid has better resistance to high temperature up to 160℃,has good resistance to unconsolidated rocks with the content of 10% or more; its lubrication peformance is close to that of oil-based drilling fluid; permeability recovery of polluted cores has reached to 90%,and shown its good reservoir protection effect.It could be seen that this drilling fluid can solve the problem of viscosity decrease caused by polymer degradation at high temperature,maintain safety and provide improved economic benefits in drilling engineering.