The Study On Hole Cleaning Technology Of Extended Reaching Well In Cuba Area

The hole cleaning of extended reaching well(ERW)is one of key factor to drill an ERW successfully.The efficient hole cleaning technology is significant to reduce downhole problem and improve drilling efficiency on an ERW in Cuba area.This paper is studied on the fluid flow characteristics,the mechanism of cutting migration and the formation of cutting bed in high deviation well bore,and introducing hole cleaning evaluation measure by critical annular velocity to analyze critical annular velocity in each well section.The experimental analysis of rock sample which is from Cuba formation and the influence analysis of properties of drilling fluid are conducted.The main influence factors for hole cleaning of ERWs in Cuba area are confirmed.According to main influence factors a series of study is proceeded such as the optimization of well structure and drill string,the formula experiment of water-based mud and oil-based mud,the application of special equipment and tools and the detailed engineering measures.Combining with studies and site practice,the main cause of the formation instability and the difficult hole cleaning is the exist microcrack,high content of illite and montmorillonite in mud shale of Cuba,the optimization of well structure and drill string can improve critical annular velocity in the condition of unchanged flow rate.It can strengthen the stability against mud shale formation and improve the efficiency of cutting transportation that the formula of water-based mud and oil-based mud by experiment utilizing the rock sample from the site.The application of rotary steering system and hole cleaning tool etc.and the assist of engineering measures can obviously improve the effect of hole cleaning and satisfy the demand of ERWs in Cuba.