Example Thepetroleum undertaking should consider the possibility of variations in a range of parameters such that it is known that drilling and well design is acceptable within defined parameter limits for: Surface (well spud) location: to allow movement to avoid boulders, local topography etc , shallow gas etc Target location: to allow for movement of the well target location during drilling Pore or fracture pressure gradients: to allow for planning of mud weight etc Reservoir fluid composition: the petroleum undertaking should consider the possibility of encountering all fluid phases in the well design Well trajectory: tolerable limits to the proposed well path (in the context of the geology and pore/overburden pressure regime anticipated and Casing scheme: changes to the casing scheme in a wellie. casing sizes, shoe depths, cementing, etc, the need for additional casing strings (contingent strings, variation in the setting depth of casing shoes, etc.
