Managed Pressure Drilling Technique in the Well Y26ST of YD Oilfield

Large volume of bitumen and hydrogen sulfide flew into Well Y26 in the YD Oilfield while drilling into the Kazhdumi Formation, which resulted in the complexity of coexisting well kicks and lost circulation. Some methods were used to kill the well, but they were all unsatisfactory. Finally, the well was temporarily abandoned. Well Y26ST is a sidetracked hole of Well Y26. On the basis of experience gained from handling the bitumen in the original borehole, assessments for applicability and risks related to managed pressure drilling were conducted, so as to generate a drilling program for Well Y26ST. To cope with the kick of formation fluids during drilling, the methods both constant bottom hole pressure and pressured mud cap were used during sidetracking operation, the borehole pressures was controlled effectively, the invasion of wet bitumen, heavy oil and gas was minimized, lost circulation and other troubles in drilling were also avoided. Well Y26ST was penetrated the wet bitumen interval and cemented with liner successfully in Kazhdumi Formation,which shows that success of managed pressure drilling in Well Y26ST can provide a reference for drilling a long open-hole interval within active bitumen formation.