Historically, conventional drilling has been considered the method of choice for drilling challenging wells; substitute methods have been used only if conventional drilling has failed or proved ineffective. Some of these innovative alternatives are Casing while Drilling (CwD), expandable liners, and liner drilling (LD). This study investigates how inclusion of these enabling technologies in the basis of design (BOD) can help operators achieve greater benefits in comparison to use in contingency plans. Casing/Liner Drilling has been successfully employed as a solution to lost circulation and wellbore instability. Moreover, casing/liner seats can be optimized and pushed further, taking advantage of Plastering Effect wellbore strengthening. Due to the different drilling dynamics of Casing/Liner Drilling, special measures should be taken to maximize the effectiveness. Unfortunately, sometimes the implementation of these measures is compromised since they have not been included in the BOD. This study reviews these issues and provides recommendations. Open-Hole Solid Expandables can be used in telescopic deep-water well plans, primarily to save borehole diameter and hence improve production. Usually more troublesome zones are encountered as we drill deeper, hence the time window to leave the wellbore open will be shorter. It is recommended that expandable liners be used further up the wellbore in a lower risk environment as opposed to trying to save diameter after the casing has been set higher due to drilling problems. Examples are provided demonstrating the benefits of including the technology in the BOD. As wells get more challenging, the industry needs to pull alongside the enabling technologies accordingly. CwD, LD, and Solid Expandables are proven drilling hazard mitigation technologies, which if included in the well plan early can be implemented more effectively than if considered as contingency plans.
Lost circulation and wellbore instability have plagued the drilling industry since its onset. Despite extensive research aimed at understanding the occurrence mechanism for these unwanted events, the solution has been the same for a long time; setting additional casing and adding lost circulation material to the drilling fluid have been the only option. On the other hand, the complexity of wells and severity of problems have constantly increased to the point that some prospects are simply undrillable with conventional methods, or they incur a huge time/cost burden that challenges the economic feasibility of the project. Only in the past decade have new solutions such as Managed Pressure Drilling (MPD), CwD, solid expandables, etc., emerged that allow new prospects to be explored, and provide new life for fields considered for abandonment because they had reached the technical limit of conventional methods.
