Research On Anti-high Temperature And Clay-free Drilling Fluid

The current conventional drilling fluid is usually with clay as a basis for adjusting of properties of fluid.The existence of the clay causes much sabmicron particles,which lead to reduce drilling rate and damage the oil gas reservoir.There is not clay disperse system in clay-free drilling fluid.The polymer provides all the functions for the drilling fluid.Clay-free drilling fluid has lower solid content.It can realize the protection of the reservoir,solve sand carrying and hole cleaning,reduce the resistance of bit to increase drilling speed.The paper researches the additives and develops a system of anti-high temperature and clay-free drilling fluid.Through a large amount of interior research,the paper synthesized a new sulfonic copolymer named SSDP,Which was viscosifier-fluid loss additive.Laboratoy study showed SSDP had excellent thermal stability,and had good performance in increasing viscosity,reducing water losses and inhibiting ability in fresh water or mud.SSDP can be used in anti-high temperature and clay-free drilling fluid.On the basis of the synthesized SSDP,the paper provided the optimal viscosifiers,filtrate loss control,lubricant,inhibitor for anti-high temperature and clay-free drilling fluid according to the laboratory research.At the same time,fresh water based,4%NaCl based, saturated salt water based and seawater based clay-free drilling fluids were developed.It was indicated from these practice that the fluid had excellent thermal stability.Fresh water based clay-free drilling fluids can work in temperature up to 160℃;4%NaCl water based and saturated salt water based clay-free drilling fluids can work in temperature up to 170℃;Seawater based clay-free drilling fluids can work in temperature up to 150℃.It provided a solution for viscosity reducing caused by polymer degradation when clay-free drilling fluid was used in high temperature.In addition,this fluid provided strong bentonite carrying capacity,inhibition ability and lubricity.It can reduce downhole problems and easily to control.The permeability recovery rate of reservoir cores was higher.The system has good performance and realizes the protection of the reservoir.