Technical Topics

My App for Reservoir Engineering Calculations and Why I Created It

Starting in the oil field in the early 90s, it was always a source of disappointment that I never got to use the fabled HP calculator programs. With my shiny new reverse polish notation HP 42S, I eagerly created some simple Darcy flow programs, but they never lived up to all I had hoped for. With cementing and hydraulic fracturing occupying me at the time, I pushed it to the back of my mind until the advent of the iPhone coincided with my return to the reservoir.

“Why isn’t there a modernized version of the calculator programs, more fitting of the computational power that now exists in our hands?” I thought to myself … “When will someone update them?” …. After a few years, a realization dawned that if I really wanted it that badly, I should just make it myself. After all, who am I to expect someone else to do what I was not willing to do?

So began my foray into mobile device app creation. I normally choose a topic or task to devote to learning over each Christmas and New Year vacation period—much to my wife’s bemusement—and in 2013, this was it.

What did I want to create? Something in my pocket, that I had in all meetings, which could be used to QC the numbers and plans put forth. I was not interested in replacing detailed, rigorous desktop applications—rather, in rapidly calculating an approximately correct answer while a presenting engineer was talking, or a coffee conversation was occurring.

So ResToolbox 1.0 was born. It was met with some acclaim and adoption, but being a first attempt it suffered from some poor architecture and design decisions. Now, in 2017, I decided to re-release a refreshed version—ResToolbox 2.0—stripped of some of the clutter, with additional useful functionality, and this time free for all.

The ResToolbox 2.0 app can do

  • Oil, gas, and brine property correlations

  • Oil and gas simple nodal analyses

  • Type curve creation and aggregation

  • Flowline and compression correlations

  • Unit conversions

  • Volumetrics and more

These days, it is a source of some amusement and sometimes trepidation for Santos engineers—meetings often pause for a few seconds as I start to cross-check their assertions and understanding. Sometimes I’m able to identify areas for improvement; most times it is a validation of their work; and occasionally it is the best of all occurrences—the delicious “Hmm … that’s strange” moment that you know can only result in an improved understanding for all.

Some examples of the questions that can be quickly answered using the app include

  • What range of condensate gas ratios (CGRs) would the measured gas gradient be consistent with?

  • How many wells per month would we need to drill to maintain a 30 MMscf/D plateau?

  • Given a P10 and P90 range in expectations, what percentile does the measured result represent?

  • What would be the effect of using 2⅞-in. vs. 3½-in. tubing?

  • How much horsepower would it take to compress our gas into a trunkline?

I would like to sign off with two thoughts:

  1. If you want it, create it—don’t simply complain that others have not done so.

  2. Accuracy beats precision most times. Increasing reliance upon complex models and applications masks underlying assumptions, and runs the risk of conferring more confidence in an answer than is warranted. It is no accident that I have included so many quotations from renowned reservoir engineer Laurie Dake in this application.

Enjoy the app (iOS, Android). I use it almost daily, and I hope it is just as useful for you. Should you have any specific questions about it and/or suggestions for improvements, send me a note; there is a contact link in the Info section within the application.

Mark Burgoyne is a principal reservoir engineer for Santos. He has more than 25 years of industry experience, including in reservoir engineering and subsurface management roles with Santos as well as hydraulic fracturing, cementing, and coiled tubing roles with Schlumberger. He possesses a strong mix of subsurface understanding and the ability to develop real-world solutions for the complex challenges that oil fields present. Burgoyne holds a bachelor’s degree in chemical engineering, a master’s in petroleum engineering, and an MBA. 


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