Feasibility studies of combining drilling with casing and expandable casing
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Nowadays, the biggest challenges in the oil business are the cost of operations versus the sizes of the prospect. We are drilling smaller targets and over the last few years, rig cost, service company rates and materials have gone up significantly in accordance to the oil price. Industry is continuously searching for new technologies to make the drilling of well safer, more efficient and cheaper. This thesis explores the possibilities of combining existing technologies to solve these challenges. Drilling with casing (DwC) is using standard casing as the drillstring, and leaving it in place to case the well. It has almost no limitations and has a potential of saving 20 – 30% of rig time by eliminating drillstring tripping and also minimizing downhole problems. With expandable technology, expanded casing can provide a larger diameter of the production casing. This can increase the productivity. Since both technologies have the same operational procedure, they could be combined into one operation. The concept is to use expandable casing as drillstring which will be expanded when the target depth is reached. To be able to expand the casing, one needs to drill with an underreamer to obtain a bigger hole and the BHA must be changed from a drilling into an expandable BHA. The conclusion of this thesis is that the drilling with expandable casing concept is possible. However, there are some technology challenges, especially on tools and on the strength of post expansion material. Limitations on drilling parameters such as: dog leg severity, RPM, mud properties etc also need to be considered to achieve a good expansion result. The case example analyzed, indicates that we can save almost 23% of the operation time by running this combined technology. Expenses can be reduced through lowered rig costs and the operational risk can be mitigated. A better understanding of the technology and operational procedures will help to further reduce the risks and make the technology more acceptable. If this new method succeeds, there will have a high potential for cost savings, higher production and better well control.
Master's thesis in Petroleum engineering