Analysis/Visualization of a Well Drilling Window

Abstract

A way to analyze/visualize the options available to safely and effectively drill an oil or gas well through a pore pressure/fracture gradient (drilling) window is presented. This method has not been previously recognized or developed and switches the focus from the traditional view using a pressure gradient (mud weight or density) to a view using pressure relative to the pressure that would be supplied by the mud weight that is in the well at a static condition (the baseline). This analysis/visualization has many advantages. It is easy to integrate Managed Pressure Drilling Operations, Horizontal wells, information from logging while drilling tools and in a real-time environment allows for the impact of operational fluctuations to be readily assessed and modeled. It is also envisaged that this analysis/visualization will enable regulatory authorities to better assess the safety of well operations reinforcing their ability to influence safe and effective drilling.

1 . An analysis/visualization of pressures existing and imposed within a wellbore during the drilling operation, such that the risks and consequences of actions and unknown values can be readily seen by all members of the drilling team. Specifically, a baseline of well pressure due to the mud density within the well (corrected for pressure and temperature) is established and (estimated or measured) pore pressures and fracture gradients depicted relative to this baseline in pressure units. 
     
     
         2 . A means whereby potential operational decisions and the impact of these decisions can be accurately, comprehensively and quickly assessed by members of the drilling team prior to such decisions being made, such that un-necessary risks can be avoided and such that mitigations to issues that arise during the drilling operation can be properly evaluated. 
     
     
         3 . A means whereby the impact and operation of a Managed Pressure Drilling (MPD) system can be readily visualized and controlled. 
     
     
         4 . A means whereby well pressures (relative to the static pressure caused by the mud density) can be plotted on the x-axis with either True Vertical Depth or Actual Measured Depth plotted on the y-axis. The ability to use Actual Measured Depth enables this approach to be very effective/applicable to horizontal or high angle wells. For horizontal wells, the plot may be rotated such that the user is far better visually connected to the orientation of the well. 
     
     
         5 . A means whereby (in real time) any well exposure to an underbalanced occurrence can be combined with knowledge of the well formations (for example, from LWD) and as a result be assessed and quantified, such that appropriate action can be taken. 
     
     
         6 . The application of this approach to all wells, not just wells such as those shown in the examples. This new analysis/visualization will work for all well geometries and operating conditions. The examples chosen are just examples to clarify the merits of the approach. The examples are shown using “oilfield units” (that is feet and psi). The same approach can be used for other unit systems such as the metric system. 
     
     
         7 . A means of updating the conventional/traditional approach to this issue (which has been used for many years—approaching 100 years), to account for the combination of the difficulties encountered in drilling wells which are far more challenging today and the availability of a vast array of new technology and information that is now available during the drilling of a well.