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Summary
Automation and digitalization of drilling require shared knowledge about the state of the drilling process: Is the bit on-bottom drilling or is the string in-slips; is there an overpull or is there a formation fluid influx? The research question addressed here is whether it is possible to define clear, sharable, and usable definitions of what a drilling process state is, and an agreed method to calculate it. The method to define the drilling process state originates from the fact that a drilling operation can be described by a set of partial differential equations, respecting boundary conditions. Therefore, the set of possible discrete changes of boundary conditions defines the set of all possible drilling process states. The possible state values for each of these boundary conditions can be clearly defined by a set of logical expressions utilizing boundary values at the partial differential equations. Each boundary condition is called a microstate. If the set of microstates is linearly independent and complete, then the overall state of the drilling process is uniquely described by the state of each of the microstates. The boundary values are either measured or estimated using a digital twin of the drilling process. In either case, an uncertainty is associated with the boundary value. It is therefore possible to estimate the probability of being in one state or another for each of the microstates. This is an important property as often the actual state of the drilling process is uncertain. If several digital twins or measurements are available, it is also possible to use sensor fusion to update the uncertainty of the boundary value. A common drilling process interpretation engine and well-defined drilling process states may help with the coordination of multiple advisors participating in the control of the drilling process. An example is given showing how an event-based drill- a- stand procedure involving several external advisors is automatically executed using a common source for the interpretation of the drilling process state. A shared definition and method of calculation of the drilling process state is a fundamental element of an infrastructure to enable interoperability at the rigsite. This work is part of the Drilling and Wells Interoperability Standard (D-WIS) initiative. D-WIS is a cross-industry work group providing the industry with solutions facilitating interoperability of computer systems at the rigsite.
