Complexity of shale formation on C4 Block of Zhaodong Oilfield and its countermeasure
Most complex problems caused by wellbore collapse and instability encountered in the Bohai Bay oilfield happen in the mud shale formation.In the operations in the mud shale formation,mechanical and chemical factors are two main aspects affecting the stability of the wellbore.Problems including returned falling rocks,pipe stuck,pressure holding and hole enlargement are the main manifestations of the wellbore instability.Severe pipe stuck and pressure holding occurred during the reaming down process in the mud shale formation distributed in the 215.9 mm well section of F26-XX on the C4 Block of Zhaodong Oilfield in Bohai Bay.Based on the shale wellbore stability mechanism,adjustments in terms of drilling fluid performance,borehole trajectory,drilling procedures,and others were made to ensure the successful operation in this section.Given the problems and deficiencies in the drilling operation of the F26-XX well,this paper provides suggestions for the subsequent drilling operation in the mud shale well section of this block.
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