Abstract

Directional Casing while Drilling (DCwD) in Ecuador has been technically evaluated as a well construction technique to reduce or mitigate operational problems associate with: 1) constructing wells that could not be drilled efficiently using conventional techniques in partial and total lost circulation scenarios, through swelling shale or with hole instability issues, tight hole or stuck-pipe applications; 2) or to reduce total operational costs by eliminating casing runs, short/wiper trips and increase ROP.

At last count there have been over 200 worldwide directional casing drilling runs both onshore and offshore. These runs have been successfully executed in some of the most challenging drilling theaters making DCwD a viable and cost reducing alternative which helps operators solve the previously mentioned problems. To support the introduction of DCwD in Ecuador, rigorous engineering analysis has been performed which involves both the economic and technical aspects to help determine what kind of casing drilling system and BHA configuration is most suitable to ensure a successful run.

Modeling sofwares have been used to evaluate drilling dynamics and hydraulic requirements enabling engineers to select a drillstring that is capable of performing the specified job and obtain the required performance improvement with DCwD. The digital analysis helps to accurately predict if the application is suitable and determine which parameters could be applied to efficiently and safely execute the DCwD application.

There are some factors or parameters that can be taken as benchmarks when analyzing both static and dynamic simulation results. Torque determines if the rig has the capacity to drive the system. Fatigue and buckling analysis provide inferences into casing pipe selection and connection type. Realistic friction factors used during the simulations will avoid obtaining erroneous results which could lead to serious drawbacks. Scenarios like magnetic interference, presence of conglomerates or boulders could limit the tools' used for a specific application. The recommended BHAs will be supported by the specific regional analysis in addition to successes in other similar worldwide applications.

Once the engineering analysis has been completed, economics are then considered. The directional casing drilling service cost versus the amount of saving obtained by applying this technology has to be thoroughly evaluated. Savings will be couched as either time and/or money. Both have to be evaluated in the short and long term to determine which applications would benefit from DCwD and which environments should be avoided. The authors will explain how this analysis is performed to obtain an adequate feasibility study to meet the client's objectives. They will also discuss the key performance objectives that must be considered during each step of the analysis.

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