Amphoteric/sulfonation polymer drilling fluid with performances of fluid-block prevention and film forming in low-permeability condensate gas reservoir

Key words:  low-permeability condensate gas reservoir  fluid blocking  ideal packing theory  film-forming agent  amphoteric/suKonation polymer drilling fluid  rheological property

Abstract:

In order to effectively minimize damage of fluid blocking, the mechanism and influence factors of fluid blocking were analyzed according to reservoir characterics of Tuha low-permeability condensate gas reservoir. The surface tensions of 8 various commonly used surfactants were evaluated by using the interfacial tension apparatus，and the optimal results are 0P-10 and ABSN with better capacity of reducing surface tension. Influences of two various kinds of film forming agents on rheo-logical properties and effect of reducing filtration were evaluated using visible sand-bed pressure loss apparatus. A system of amphoteric/sulfonation polymer drilling fluid with performances of fluid-block prevention and film forming was developed by techniques of fluid-block prevention，ideal packing temporary bridging and film forming. The combination proportions of three kinds of ultrafine calcium carbonate in this drilling fluid are 10% ,40% ,50%，and total concentration 13 4%，The properties of the low damage drilling fluid are as follows； API loss is less than 5 mL, loss in high temperature and high pressure is less than 10 mL, friction coefficient of mud cake is less than 0. 141, regained permeability is over 81%.