Abstract: Controlling sidewall instability is a problem in drilling process of Weixinan oilfield group in Beibu gulf.Underground complicated accidents such as formation collapse,well lose,drill pipe sticking,and so on appears frequently.Therefore,the problem,which is low efficiency,many disabled drilling tool and high operation cost,hasn’t been solved in recent years.In the drilling operation of the first batch wells in Weixinan oilfield group,quite excessive complicated conditions and underground accidents happens,operation progress lagging severely.However,before the operation of the second batch wells,by analysis and conclusion of present data from previous drilling well,meanwhile developing many laboratory experiments and theoretical researches,the main mechanism causing the sidewall instability in this area is investigated and specific technological measures are proposed.By field application of research results,the incidence of underground complicated accidents in oilfield late drilling remarkably decreased,therefore,the sidewall instability problem disturbing the cycle of drilling in this area more than ten years is solved.In this paper,taking Wei2 area sidewall for example,research and application of sidewall stability technology is introduced,which offers precious experience for such oilfield in controlling sidewall instability.