The Stability Estimate&Application Of Upper Formation In SUDAM/Moga Oilifeld

SUDAN/Moga oilfield is a development project of Petro-energy&Sudan goverment. In this field, from0-200m belong to Tendi-senna formation, there are lots of accidents and complicate situations such as pipe sticking, mud loss as well as borehole collapse and so on at the beginning of this project. All those increase the drilling cost and extent well construction time. So to resolve the stability of borehole in the long distance unconsolidated sand formation is the key to complete this project.The element to borehole stability include geologic factor(the physical characteristics and drill-ability of unconsolidated sandstone), artificial factor (every complexity occurring in well-site, include drilling parameter, drill fluid, hydraulics optimization, bottom hole pressure change during tripping, fluid column pressure change for the content of cuttings and so on) and stress factor(when the formation is drilled, the stress of the borehole is changed, at the same time, the surrounding rock become instability too).In this paper, we find out the geologic factor, artificial factor, stress factor together with parameter optimize including drilling mud and drilling parameter which led the borehole instability in this field. Then, we analyze the mechanism and resolve means of mud loss and bridge plug which are the main forms of borehole instability in this field.These can cut down the drilling time and can advance the economic benefit. So this paper not only has theory sense but also can guide the operation in drilling process.