Drilling Fluid Technology for Horizontal Wells in the Deep Benxi-1 Gas Reservoir of the Ordos Basin

In the Deep formations of the Ordos Basin, the Benxi-1 is well-developed with cleats and fractures. The risk of wellbore collapse and sticking in long horizontal section is high. In this paper, the fabric characteristics, physical and chemical properties and mechanical properties of Benxi-1 rock are carefully evaluated, and the borehole instability mechanism is revealed from the angle of rock mechanical and drilling fluid chemical coupling. The prediction of collapse pressure in long horizontal section are carried out, which provides a basis for the reasonable formulation of drilling fluid density. Based on the distribution characteristics of Benxi-1 fractures, the particle size distribution of anti-sloughing plugging agent is developed to meet the high-efficiency sealing of fractures. The synergistic action of organic salt and potassium chloride is used to restrain the hydration expansion of clay. The wellbore stable drilling fluid technology suitable for horizontal wells with Benxi-1 Gas is formed. The borehole-stabilizing drilling fluid technology suitable for horizontal wells in the Benxi-1 gas reservoir was developed. The field application effect is good, the Benxi-1 does not collapse, the casing runs smoothly, which provides technical support for safe drilling of long lateral sections in the Benxi-1 gas reservoir.