| As the exploration and development of oilfield in China,more and more deep wells,super-deep wells,extended reach wells,and highly deviated wells have been developed and used to reach out to the complicated oil and gas formations,but during the drilling in these kind of formations,many problems have been encountered,such as lubrication and wellbore instability.Commonly,the oil-based drilling fluid has been chosen preferably to settle the problems,but which has some difficulties,such as high risk to contaminate the environment（strict environmental regulations）and hard to be treated after disposal.At present,there are many kinds of lubricants for water based drilling fluid,but none of them have both lubrication and plugging in the same time,so,it is the high time to develop a new lubricant with high efficient plugging and lubrication.This paper mainly prepared the lubricant by micro-emulsification to resolve the problems above.Base on fishlike phase diagram method,this paper has studied the micro-emulsion preparation method for TR-1/n-butyl alcohol/cotton seed oil/2.5%NaCl,which has supper-low interfacial tension(<10-1 mN/m).The particle size of micro-emulsion lubricant is less than 100nm,its morphology will change from rough sphere to irregular shape and then to bi-continuous phase.The results showed that,the micro-emulsion lubricant can effectively reduce the viscosity of crude oil and improve the wetting environment of reservoir rocks,and then resolve the water-blocking problem to some extent.Bulk pH and mineralization have little effect to performance of micro-emulsion lubricant,but the temperature affects greatly to that performance,especially to interfacial tension and phase volume fraction of micro-emulsion.Also,we have developed a pilot producing technical procedure for micro-emulsion lubricant WR-1,this product almost has no influence on rheology,but has excellent lubrication property and can reduce the filtrate loss to formation in some degree.In addition,it can retard the water entering the formation by rapid absorption and plugging.WR-1 has been used in 21 wells for Block Z23,Block Y 227,Block Y553,well Z129-1HF,well DP1 in Ordos Gas Field,and well D701 in Xinjiang Oil Field,the application showed that,the micro-emulsion WR-1 has good compatibility with common drilling fluid agents,and has excellent lubrication performance when drilling in complicated formation,and keeps the reduction ratio of lubrication coefficient high than 60.0%for a long time,furthermore,it also has a good byproduct–stabilizing the wellbore partly. |
