Solid Expandable Tubular Technology: The Value of Planned Installation vs. Contingency
Narrow pore pressure/fracture gradient windows commonly encountered in deepwater Gulf of Mexico (GoM) often require additional casing strings to reach the objective depths. The inability to make accurate predictions for pore pressures and fracture gradients may result in casing strings that do not reach the designed depth. Because of the limited number of conventional casing strings that can be run, operators attempt to push casing points, which can result in loss circulation, well ballooning, well flows and other operational difficulties. Planning a solid expandable tubular in the upper sections of the well design preserves hole size from the onset and allows more casing strings to be run, without having to push casing points to the frac-gradient limit. Preserving hole size contributes to drilling efficiency, reduces equivalent circulation density (ECD) and minimizes risk associated with small hole size in deeper sections of the wellbore. Running expandable tubulars reactively deeper in the well denotes more of a “survival” mode when operating parameters are more severe. Planned installations allow operators and engineers more time to assess how best to optimize the expandable tubular design. More time also permits analysis of details, such as the shoe joint, base casing connection and base casing weight, to obtain the desired pass through and drill out. Solid expandable tubulars run in the upper hole section still allow for contingency expandable liners in the deeper sections, if required. This paper compares two deepwater offset wells in Mississippi Canyon. In the first well, expandable casing was set deep and used as a contingency casing string. The second well incorporated a planned solid expandable tubular high in the wellbore as part of the base design. This paper explains the planning process for the second well and how this process optimized the use of a planned expandable liner. The planned expandable system in the second well also contributed to operational efficiency. The second well was drilled to depth in 48 days as opposed to the 140 required by the previous operator in the block to reach an equivalent depth on the first well. Actual pore pressure and fracture gradient data from the first well was used in the design of the second well.