Research On Plugging Anti-collapse Water-based Drilling Fluid Technology

The sealing ability of the drilling fluid is a key factor in drilling,preventing the borehole from collaps.In recent years,even though the drilling fluid in anti-collapse has made great progress,the system of anti-collapse drilling fluid still needs completing and researching.In addition,at home and abroad,there is no unified standard of the evaluation of the drilling fluid in sealing.Different researchers tend to use different methods to evaluate sealing effect,which incredibly hinders the communication between researchers and restricts the development of drilling fluid in sealing.Therefore,this paper established with submicron pore filtration medium to evaluate sealing ability.The filtration membrane with an average pore size of 0.22 micron is used in high temperature and high pressure filtration experiment,in which the amount of filtration and filter cake permeability can response sealing effect.A new method of drilling fluid sealing performance evaluation is established.Its operation method is simple and easily to repeat,which can be used to evaluate the materials of sealing.In addition,the experiment based on the testing system of core permeability damage on the formations is correlated with high temperature and high pressure filtration experiment.It’s also a way of evaluating indoor drilling fluid sealing ability.The test method in this paper is carried to evaluate the sealing materials and the sealing effect.By a lot of experiments,calcium carbonate,nano emulsion,silicon powder and FT312 are chosen as sealing agents in a better effect.By compound with experiments,the best effect of the four kinds of sealing agents combination and quantity is got as follows:6%CaCO3+5%nano-emulsion + 5%silicon nanometer emulsion powder + 5%FT312.On this basis,the research has formed a seal type prevent collapse water-based drilling fluid formula:5%bentonite+0.3%FA-367+0.1%XY-27+0.2%Na2CO3+6%CaCO3+5%nano-emulsion+5%sili con-powder+5%FT312+7%KCl+0.6%CMC +4%SMP-Ⅱ+4%SPNH+8%FRH.Through the experiment,the indoor developed water-based drilling fluid is evaluated in its sealing ability.Results show that the water-based drilling fluid has good sealing performance,which in the shale formation,can reduce the wellbore permeability,reinforce the stability of borehole.At the same time,the drilling fluid system also has good lubricity,inhibition,and calcium-salt-pollution resistance.Experiment of the performance of the sealing drilling fluid researched in lab has been made in the Gaomiao area.In this area,7 wells appeared a 3.76%(average)rate of accident without using the seal drilling fluid.And the well in experiment goes well in drilling.Research by the drilling fluid reduces the accident rate,providing reference for the collapse prevention drilling fluid.