When most operators think of solid expandable casing, they primarily focus on their application as it relates to solving hole problems while minimizing any loss of hole size incurred by running a casing string. A new application for solid expandable casing quickly growing in popularity uses the tubulars to sidetrack through a milled window. Solid expandable casing can minimize, if not eliminate, many of the obstacles associated with sidetracking.
The historic drawback of losing hole size through the window exit can be largely eliminated by using solid expandable casing. These tubulars enable the hole section to be drilled beyond the expandable casing with larger drill pipe and bottomhole assemblies (BHAs), including measure-while-drilling (MWD) and logging-while-drilling (LWD) tools, which may have been impossible with a conventional sidetrack. Larger production tubulars and related completion equipment add to the value generated by using the solid expandable casing. This technique can also be instrumental in initiating slot recoveries that might not otherwise be economically viable.
As with other applications of solid expandable casing, a successful installation requires proper pre-job planning. This paper reviews issues critical for success and also looks at specific examples of installations performed to date. Other technologies associated with expanding the solid casing will also be discussed in the context of wells already completed or in the planning stages. The economic benefits of this technique will also be explored.
Solid expandable tubulars have proven to be a viable technology that enables operators to reach reservoirs that cannot be reached economically using conventional technology. As these systems continue to evolve, new applications are being pursued and implemented1. Early wells that applied solid expandable tubulars consisted mainly of simple vertical wells or wells that required some form of simple remediation, such as repairing deteriorated casing. The strategy of using expandables in more challenging wells developed as a result of process refinements and system enhancements from lessons learned. This steady progression has not only resulted in more reliable products but also increased operator acceptance and broader applications on deviated, difficult wells.
A myriad of drilling and casing issues can prompt the decision to sidetrack. When faced with the prospect of plugging and abandoning (P&A) a mature well, operators may opt to sidetrack from an existing well and search for a new target zone. This procedure may be the only alternative to drilling a new well to reach another target. However, it is often uneconomical to P&A a well and drill a new one, especially in a deepwater environment. Often the simplest plan abandons the existing zone to recomplete or redrill to the new target by milling a window and drilling off a cement plug, or milling off a permanent whipstock.
Initial concerns to using solid expandable casing through a milled window have given way to confidence in a practical solution that has proven to be economical, reliable, and repeatable. Increasing the range of applications is due in part to a technological legacy resulting from over 250 solid expandable tubular installations that include over 260,000 ft of expanded pipe, and over 7,000 expanded connections.
Using conventional casing or liner technology to sidetrack results in the loss of an entire casing size, reduces the size of the hole in the production zone, and restricts the flow of hydrocarbons to the well, which decreases the well's economic viability. Operators may be able to reach total depth (TD) with conventional sidetrack casing and tools but the result is a hole size smaller than desired.
Presently, two relevant cases exist for recompleting and revitalizing wells using solid expandable tubular technology. The first case involves recompleting wells that are no longer meeting productivity expectations or that require a wellbore in another reservoir location to achieve optimal drainage. Using solid expandable tubulars in a window exit process allows for a larger completion through a casing sidetrack (Fig. 1).