This is fundamental to the crooked everyone here is

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Unformatted text preview: cts the output and, correspondingly, whether there is potential for the non-discerning to manipulate the results. For example according to some respondents: 134 “…There are a few unscrupulous people that cheat like crazy. The big one that is abused beyond belief is dependencies. And the programs are, I don’t know, lacking in robustness. The one that we’ve got, you know, is a classic one, porosity versus water saturation. There’s normally if you plot the data a correlation, but when does a correlation actually suggest a dependency of less than one and is it 0.5,0.6,0.7? I’ve actually, way back in my youth, when I was mucking about with all this, actually shown, that without violating anything, you could quite easily alter the [recoverable reserves] by 20%. This is fundamental to the crooked. Everyone here is in the business of procuring funds for their projects. It’s not a question of is it right or wrong. It’s because I’ve done this work and it suggests to me that this is a jolly good project. Now the man across the corridor is competing for the same funds so it is a competition. And may the best man win and nobody sets out to cheat but …” (C) and, “…people with a better understanding of statistics were able to “scoogle” and skew the outcome by putting in a particular distribution shape so you don’t actually change the numbers you just change the distribution and that can change the output.” (D) Whereas others argue: “…the shapes of the distributions is relatively insensitive thing.” (N), “…the type of distribution you use is not that important” (R1) and, “…it seems to be quite robust to any type of distribution that you put in” (R4) In an attempt to remove discretion from the analyst and impose more rigour on the process, some organisations do prescribe which distribution shape is used for each reservoir parameters in a Monte Carlo simulation: “We have recommendation that we use beta distributions. And that’s for consistency because we tried calculating the reserves of a prospect using the same input data with different distributions and we got quite a range of numbers out. So for consistency use beta and that’s it.” (J) Newendorp (1996 p387) warns of the dangers of using distributions in this way. Other respondents also warned against such this practice, arguing that it “forced” the data. These interviewees believed that distribution shapes should left to the discretion of the analyst so they can be “data-led”: 135 “Some companies will deliberately impose a lognormal distribution on everything they do. [This is] based on the belief that all of these ranges are lognormal. I strongly disagree with that. I think it’s … invalid and incorrect to do that and [that] you should be guided by the data.” (G) However, questions have been raised over which data companies should be led by (Simpson et al., 1999). Snow et al (1996) argue that statistical analysis of parameters from nearby wells is a valid method of determining the shape of input distribution to be used in a...
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This document was uploaded on 03/30/2014.

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