Application of Gravity Displacement Drilling Fluid and Low Friction Drilling Fluid in ST2-4 Well

Well ST2.4 in 152.4 mm hole 4350～4800 m interval well deviation 0°-61.1°, in the process of the middle-completion direct-push memory logging, the electric logging tool got stuck, the non-water hole channel of the 50.95 m electric logging tool could not set up a cycle, and the conventional unstuck fluid did not get unstuck after the first immersion, for the second time, the formula of the conventional unblocking agent was upgraded to an improved unblocking agent. Firstly, the clean water of the unblocking agent was replaced with 10% CaCl₂ salt water, and secondly, the concentration of the rapid penetrant fast T was increased to 30% , the third is to raise the density of the unblocking fluid to 0.5 g/cm³ above the mud density, and to replace the unblocking fluid to the bottom of the well by using the gravity replacement principle, thus successfully unblocking the electric measuring instrument, avoiding the loss of over ten million electric measuring instruments. The“Low viscosity, light slurry + heavy slurry slug” sand-carrying technology was used to keep the wellbore unblocked after the break-up, and the organic drag reducer YJJZ-1 was introduced to convert the conventional KCl polysulfonate system into the low friction drilling fluid to reduce the friction, through improving the quality of HTHP mud cake and strengthening the combination of anti-sloughing and inhibition of mud, the electric logging and casing running operations in the inclined section are completed.