Stiff Foam Drilling Technology in Drift Sand Formation

Heavy drift sand formation exists in the upper formation 250-750 m of block 1 in Yemen,so concurrent problems such as wellbore instability,serious loss circulation and low ROP present during the drilling of this section.Those problems can not be solved through conventional drilling with lost circulation materials,blind drilling with fresh water as well as air drilling and stable foam drilling.Therefore,this paper proposes the ebonite foam drilling method.Through foaming agent optimization test of ebonite foam drilling fluid in the laboratory,we selected FMA-100 as the foaming agent based on foam quality,anti-contamination performance of foaming agent,ebonite foam half-life,and economic benefits analysis.In the test it demonstrated the optimal added amount to be 0.3%-0.6%,then preliminarily optimized the drilling fluid formula.To prevent wellbore collapse and lost circulation with low return velocity and appropriate equivalent circulation density,this paper optimizes operation parameters,drilling equipment,and forms program of drilling the drift sand formation applicable for Yemen 1 Block through theoretical calculation and analysis.The program was then applied in Well Abyed-2 of the same block and it not only successfully resolved the lost circulation and collapse coexisting problem in the large size loose drift sand formation,but also improved the ROP of drift sand formation to 3.2 times the average ROP of adjacent Wells.The successful use of ebonite foam drilling program in this well lays solid foundation for forming drift sand formation ebonite foam drilling technology.