Optimization of casing string placement in the presence of geological uncertainty in oil wells: Offshore oilfield case studies

• We defined the CPS problem and present full approach methodology of CPS problem for first time.
• A novel mathematical formulation and procedure for optimization of casing string placement including geological uncertainty is developed.
• A large and real case study was undertaken to demonstrate the value of considering uncertainty in drilling decision-making for optimization of casing string placement.
• We show optimum intervals for casing points in each section, the selection in these intervals depend on decision maker. We select the average of upper and lower amount of this interval as final optimum points.
• Savings cost at least of 2.4–15.2% are observed.

Designs of petroleum wells involve many activities and technical areas. These areas cover various engineering aspects and can be solved with contributions from applied mathematics. This paper presents a new casing point optimization methodology. A novel mathematical formulation and procedure for optimization of casing string placement including geological uncertainty is developed. Determination of optimal casing point locations is a challenging task because many engineering and geologic variables affecting each other and are often uncertain and nonlinear. In this paper, the casing string placement problem was formulated as the optimization function under uncertainty. The geological uncertainty is modeled with considering different scenarios of geology. The Lingo software was used as the optimization tool. In order to find the optimum decisions for different risk attitudes, a utility framework that enables the assessment of the uncertainty of the casing string placement decisions is used. A large case study was undertaken to demonstrate the value of considering uncertainty in drilling decision-making. Numerical simulation was carried out with this selected case study to find optimum points under different risk attitudes in each section of drilling for different wells. Finally we show the application of that methodology has better performance to cost savings at least of 2.4–15.2% in the important drilling management.