The results of well over 300 installations of solid expandable tubulars have established this technology as a feasible and practical option in a wide range of applications. The issues now at hand are two-fold; how best to use the technology and where the applications bring the most value. Studying drilling operation histories helps determine how to identify and optimize the application of this technology.
An exhaustive analysis was performed using over 160 wells drilled offshore in the Gulf of Mexico (GoM) over a five year period. This dataset was populated specifically with 164 wells representing $2.84bn of drilling capital expenditure and 29.3 rig years drilled on floaters, jackups and tension leg platforms (TLPs). As part of the analysis, relevant non-productive time (NPT) was extracted and analyzed, and totaled over 6,900 hours. A simple analysis was also conducted to identify an optimum time to make the decision to run expandable casing. The study data shows that the optimum time to make that decision for openhole drilling liners in unexpected NPT situations is approximately two days. In addition, various sensitivities were run on this dataset to provide guidance for drilling engineers.
This paper documents how GoM well data is being used to establish a probabilistic approach to addressing common drilling challenges in a variety of environments and locales. It also specifically identifies how solid expandable tubular technology can be used to address and mitigate these challenges efficiently and reliably.
Unexpected flat time in drilling curves occurs when the operation requires changing bits, logging tools and drillpipe or when fighting unexpected situations such as losses, inflow or borehole instability. Although much NPT can be avoided with thorough pre-planning, unforeseen situations can easily occur.
Decision trees can be built that model when to continue fighting losses or when to run an expandable casing string.1 One of the difficulties for this model was knowing when to make the decision to do something different. Fighting losses with lost-circulation materials (LCM) or changing some other drilling parameters is cost-effective and usually quicker. However, a point exists in each process when it is more cost effective to change the course of action and try something different.
A continuing process of further action and feedback is routinely used to challenge the way wells are currently drilled.2 This work effectively also builds on their work, to identify a guideline for applying a relatively new technology.
Two studies have been conducted to identify how best to use solid expandable tubular technology in reducing NPT in drilling operations. The first study analyzed NPT to identify the optimum point for running solid expandable systems. The second study reviewed potential applications and how much time and cost savings might have been accrued.
In the midst of and even after accumulating and analyzing this dataset, solid expandable tubulars continue to evolve with the addition of equipment sizes and soon-to-be-developed sizes. These analyses were conducted assuming full equipment availability although some equipment is still forthcoming. Using this approach provides guidance for future applications.
