Torque and drag occurred during the drilling of an extended-reach well (ERW), when the drill string is pushed through the long horizontal hole section is a limiting factor for conventional drill pipe technology presented by standard steel drill pipes.

A drill pipe with enhanced buoyancy in the drilling fluid could decrease a weight of the entire drill string in the well and solve the problem to a certain extent. A drill pipe made of a high strength aluminum alloy and having cavities inside the pipe body wall could provide such a buoyancy effect. Once a feasible configuration is found, such a Buoyant Aluminum Drill Pipe (BADP) can be produced by a hot extrusion process by Russian metallurgists.

In order to evaluate the possibility of application and potential benefits of BADP in extended-reach drilling (ERD), a quantity of different configurations of BADP pipe body cross-section were analyzed in terms of potential length of ERW they make it possible to drill.

Computer aided design of BADP is based on exhaustive enumeration algorithm realized in MATLAB® and comes to calculation of explicit equations. It allows defining a maximum possible length of ERW at specified vertical depth for each BADP configuration analyzed, provided that the maximum equivalent stress in the pipe body does not exceed a maximum permissible level.

We used described method to find feasible configuration of BADP that corresponds to ERD limiters, like mechanics, hydraulics, industry standards, and has relevant advantage in well horizontal displacement over conventional drill pipes. The article presents geotechnical conditions and well geometric parameters where BADP could be most effective.

In this work we used finite element method realized in ANSYS® to estimate equivalent stress in BADP and multivariable regression to find explicit equations that estimate stress state in BADP under load.

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