Abstract:The anti-deviation and fast drilling technology of oil and gas well is a difficult problem for oil engineering. The shallow strata in western Sichuan have a remarkable characteristic of soft and hard lithology interlacing, which leads to the problem of well deviation. This problem was solved mainly by the foreign vertical drilling system, and the drilling cost is high. Pre-bending BHA is a low-cost anti-deviation technology, but there is still a lack of scientific applying evaluation method in the soft and hard staggered formations. In this paper, a method of choosing pre-bending drilling tools which considering the influence of soft and hard lithology interlacing and strata dip angle is proposed systematically. The calculation of inclination force in soft-hard cross strata is realized, and then the pre-bending drilling tools which can provide sufficient anti-inclination force is selected for application. The analysis results show that the pre-bending drilling assembly can provide sufficient anti-deviation force when the dip angle of formation is less than 25 and the cross index of hard and soft is less than 3 in western Sichuan. The technology has been applied in the field, and the pre-bending drilling assembly has achieved good anti-inclination and speed-up effect. It proves that the evaluation method is accurate and simple to use, which can provide reliable reference for low-cost anti-inclination technology in soft-hard staggered formation.