Analysis of casing while drilling shows faster drilling, higher production rates

Data from more than 250 wells drilled with casing-while-drilling technology provides an extensive database for risk modeling assessment and prediction.

Bruce Houtchens, Fidelity Exploration and Production Co.; Jeff Foster, Tesco Corporation; Bob Tessari, Turnkey E&P

Applying a risk model to new technology is difficult because there is no experience base for quantifying either the probability of an event occurring or the consequences of the event. This is particularly true when the technology has operational components that go against normal practices such as with Casing While Drilling (CWD). Casing is used as the drillstring to solve problems that one would normally expect to be made worse by drilling with a smaller wellbore clearance, higher annular velocity and little ability to make conditioning trips.

To date, Tesco’s CWD system has been used to drill more than 375 onshore and offshore wells, totaling more than 2.5 million ft in a variety of formations with different characteristics. Results of these wells in difficult drilling areas show that CWD is more efficient and encounters less trouble time than conventional drilling, saving operators time and money. The savings can be seen in daily operating costs, personnel safety and insurance premiums for the operators and drilling contractors.

These wells have provided an experience database that can be used for risk modeling assessment and prediction. CWD wells studied include those drilled in formations ranging from very soft to medium hard and drilled vertically and directionally.

Experts make all estimates of chance by considering known facts, past experience and all possible scenarios.¹ Obtaining the knowledge and experience on which to base modeling scenarios is the purpose of collecting CWD drilling data from wells drilled in a variety of formations. Comparisons of selected CWD wells to conventionally drilled wells in the same formation provided a basis for drawing conclusions as to the risks posed by CWD technology.