Polyol Membrane Structure Of Potassium Silicate Sealing Water Base Drilling Fluid And The Mechanism Study

Borehole stability is one graveness problem for drilling workers to be faced with all through the ages,both here and abroad the researcher did much effort on chemical stabilization borehole,and developed many systems ,such as the formate drilling fluid,the oil-based driling fluid,the synthetic drilling fluid, the silicate drilling fluid, the polyglycol drilling fluid,and so on. silicate and polyglycol act as inhibitor and lubricator respectively contained in drilling fluid system,having no compound application, combining the chemical effect(coagulation deposit) of potassium silicate and physical effect(cloud point influence)of polyglycol together, we can build up potassium silicate polyglycol drilling fluid system possessed of gel-cloud point influence 'membrane structure.these researches aim at giving full play to stabilizing borehole mechanism of membrane structure influence ,and exploit a new development direction for the stabilize borehole.The wellbore stability mechanism can be concluded like this:(l)sediments and gels produced plug the microfractures and pores of shale;(2)inhibit clay hydration and dispersion;(3)combination with inorganic salts prevent the entrance of water into formalion;(4)its interaction with clay minerals reduces the permeability.The mechanism of polyglycol approximately could be divided into three three acting stages: free diffusion, adsorption and permeation.This article carried out experimental study, using cloud point influence improves inhibition and plug.With the help of theoretics mechanismic mentioned above, we did detailed research on potassium silicate polyglycol water-based fluiding capacity of this drilling fluid. Finally, its typical formula are as follows: 4%bentonite+4%FP-V+0.4% HV-CMC +0.4%JT888 +3%JLX-B-S +1%KC1 +NaOH (pH:11.5).The system of the water-based drilling fluid is optimized.In the same way, the property of the system is appraised. It shows that this system owns good rheology property and filtration properties, strong inhibition, outstanding the tolerance to fouling (the tolerance to NaCl,MgCl₂,CaCl₂ and the cuttings is 6%,0.5%,0.5%,and 15%),good sealing characteristic,good thermostability(the tiptop is 125℃),and so on.At the same time, we find that system filter cake is possessed of the membrane structure.The membraneous efficiency is greater than 80%,and the press ability is greater than 850psi, so it is propitious to stabilize the borehole. It is clear that,potassium silicat-polyglycol water-based drilling fluids was a kind of virtual membrane structure-sealing agent system.