RIASSUNTO
Abstract
With the increased usage of stronger and tougher tubulars in today's well construction, the ability to shear in the blowout preventor (BOP) without turning to larger operators is an economic necessity. Existing rigs need ways to drill with the high performance steelavailable today without having to grow the size of the BOP.
This paper will discuss the mechanics of shear and how it applies to V Shear technology of yesterday as well as the current Low Force Shear of today and tomorrow. The Low Force Shear technology provides the technology to extend the capabilities of present day BOPs through major improvements in shear ram design. These shears substantially reduce the forces needed to cut tubulars. Lower forces mean that both stronger and larger diameter tubulars can be managed with the same shear operators, adding value to the existing stack and saving the contractor a major outlay for increased BOP capabilities and corresponding handling equipment upgrades.
Low Force Shear technology is based in the philosophy of final shear area reduction. Getting more of the cross sectional area cut prior to the final shear reduces the forces required in that final shear by leaving a smaller remainder cross sectional area to be cut. By puncturing the tubular first and managing the design of the sheared material (chip management), the Low Force Shear begins effectively cutting material earlier and farther before reaching the final shear section.
As the development of the Low Force Shear is optimized for various diameters, material properties, and cross sectional areas, the opportunities expand to increase the range and variety of items in the well bore that can be cut that were not previously thought possible. This capability would greatly increase the security of the well. The future frontier is ""Shearing More"".
Introduction
Historically, the industry has addressed the challenge of shearing bigger and tougher tubulars with bigger and tougher cylinders. The impact of larger and higher pressure cylinders is more weight, more accumulator bottles and an overall larger system. In contrast, another approach is to look at the efficiency of the mechanism doing the shearing to reduce the force required to shear. With a more efficient system, the BOP can either shear existing requirements with smaller operators or shear more with the same operator.
In 2006 we began a project aimed at reducing the total force required to shear. At that time the project was intended to target the land market so the sizes of BOP and BOP operators could be reduced, shrinking the weight and size of the BOP's and control system that have to be handled regularly. The structure of the project was set up with the following goals.