Drilling Fluid Technology for Long Open Section of the Third Interval of the Ultra-deep Well SHBP-1

Based on experiences obtained previously, downhole troubles such as borehole wall instability and mud losses may be encountered in drilling the well SHBP-1. By analyzing the roots of the downhole troubles and the technical difficulties, a set of measures to deal with the downhole troubles were formulated. A highly inhibitive drilling fluid was formulated with inhibitive agents KCl and SMJA, mosaic membrane forming agent SMNA-1, nanometer plugging agent SMNF-1. These additives greatly enhanced the inhibitive capacity, plugging performance and HTHP filtration control ability of the drilling fluid. Field operation showed that the rheology of this drilling fluid was easy to control, and the inhibitive capacity of the drilling fluid can be achieved by maintaining 0.5% SMJA, 3% KCl and 2.5% SMNA-1 in the drilling fluid. When drilling mud loss formations, 2% SMNF-1 and ultra-fine calcium carbonate were added into the mud to control mud losses while drilling. With these measures, mud losses were avoided and the drilling operation was successfully completed. Percent hole enlargement of the third interval was only 3.49%. Borehole wall instability and mud losses in the third interval of the well SHBP-1 were thus resolved, providing a technical clue for other similar wells to be drilled in this area.