Drilling Data Raise Questions About Time of Events and Calculations

Abstract

Two seemingly simple questions were raised by technical papers about drilling data: What formula did you use? What time did the event occur? For anyone using data to analyze drilling performance or automate the process, getting both those things right is becoming increasingly important. And as drilling relies more on digital controls and sophisticated analysis, getting those data wrong has become a serious problem. One example is the standard measure used for the energy exerted to drill ahead—mechanical specific energy (MSE), for which there are multiple formulas to choose from. And even if the right one is used, its accuracy hangs on whether the needed steps were taken to properly gather the inputs to the formula. Time sounds like a straightforward problem—just ensure all the clocks are in sync. The reality is that there are corporate firewalls blocking access to the reference clocks, a wide range of time-stamping practices, and an increasing amount of calculated data in the information stream based on inputs that are lost in calculation. The MSE problem is simpler to solve but a lot of effort will be required to change the habits, and computer systems, supporting multiple formulas that can deliver significantly different results. Different formulas for MSE and other drilling measures were created over the years for various reasons ranging from the creator’s research interests or a desire to limit the inputs needed for calculating MSE. Pulldown menus on drilling data records have typically offered a menu of MSE options with names for formulas that vary; so, a user would need to know the formula to ensure the correct one was selected. “When the pulldown menu offers a pick list with four types of MSE provided by the vendors, you do not know if you are using the right one now,” said Fred Dupriest, a Texas A&M professor who presented a paper on the issue at the IADC/SPE Drilling Conference and Exhibition in March (SPE 208777). The paper reported on the work of a committee of 15 industry experts who chose a standard MSE formula which was laid out in the paper. It described how to gather the inputs and assigned names for the two approved versions—one for computing energy at the drill bit, and the other that included the drillstring. A second paper presented at the conference described the need to begin a long-term effort to define how to accurately measure, gather, and record time data (IADC/SPE 208732). “If data is not aligned correctly, you are not going to get the right result,” said Pradeep Annaiyappa, a senior director at Nabors for digital data initiatives at the drilling company, when presenting the time-measurement and recordkeeping paper.