I had a long discussion with a drilling leader who constructed a 1D Wellbore Stability Model in one critical horizontal well and he wanted to compare the results with the model that I built for the same well, he asked me the following questions: Why the mud weight recommended in your model is 9.5 ppg and the result obtained from my model is 9.125 ppg ? Are you sure we can drill this section without any wellbore stability issues?. When somebody ask you these kind of questions mean that is not clear about all the variables involved in a geomechanich model. Usually drilling people only are interested in drilling fast, they do not care about the model, stresses or tectonic, they just need the mud weight to drill the well, never mind if they drill a «hole» instead of a «well».
Everybody can use geomechanics software, is easy to learn how to «click» and get results. However just because you can click a button that calculates «Shear Failure Gradient» does that mean that the calculation is correct? Do you know if the calculation you’re doing is appropriate for the geological setting or the lithology? Are you assuming normal stress regime or equal horizontal stresses when maybe you should not?
To build a geomechanical model you have to look at the geological evidence to support it, which means good interpreting many forms of data, such as: seismic, frac-data , core data, outcrop, pressure tests, etc.. Making decisions based on a geomechanical model that is not founded on geological evidence but is simply calculated from logs is very risky, and risk means high uncertainty.
When this engineer showed me the resulst of his prediction with three decimal places, I instantly became incredulous of the work behind it. Was he just doing a calculation?. I particularly believe that true advances in geomechanics will come not from calculating more things, or teaching more people to calculate things, but in improving our ability to interpret geologic and tectonic data, this will reduce drastically uncertainty.
‘Before include data into any software, it is critical to clearly understand this data, to avoid being a person that unthinkingly clicks buttons in a software application to complete a workflow, in other words (“Nintendo Geoscientists”).’
How to convince drilling people that Petroleum Geomechanichs is an interpretative science not engineering? Difficult task !!
