Oil and gas exploration: statistical decision criteria.

Wignall, Thomas Kenneth (1967) Oil and gas exploration: statistical decision criteria. Masters thesis, Memorial University of Newfoundland.

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Abstract

Bayesian a priori probabilities are applied in the field of petroleum exploration to give the optimum decision criteria in locating oilwells and oil-fields. -- Principal Component functions and discriminant functions are defined which make use of information available: geological, geophysical, or geochemical. The field studies confirm that these functions are very valuable in discriminating between producers and non-producers, achieving up to 95% success as the results given in the appendix prove. -- The principal component scores and discriminant scores may be allotted to control points (oil and gas wells) on a map. Contours may then be mapped using the figures as probability indices. Thus new wells, fields, basins and provinces might be discovered, snice these maps could be used along with structural contour maps to pinpoint new wells with a high probability of success. -- The following functions defined in the thesis are all new: -- (1) A favourability factor, F, using saturation rations, x₃, and shaliness, x₂, where F = (x₃-1.5)(3.0-x₂), should prove most useful in helping to discover stratigraphic and hydrodynamic traps; also in deciding whether to complete a well. -- (2) Principal Component Functions which diagnose what weight should be given to each variate responsible for the deposits of petroleum. This function is similar to the one given by Krumbein but is more powerful. A map using Principal components scores should help in the discovery of new resources. -- (3) Discriminant functions are defined which are up to 95% effective indiscrimination between dry holes and producing wells. Discriminant scores provide the most useful mapping. The field studies indicate that the data of petroleum wells is particularly amenable to discriminatory analysis; also the key variate or variates become very apparent, when an appropriate test is carried out. -- Conclusion: A field study should now be carried out using the criteria defined. Information is difficult to collect as the Petroleum companies quite obviously do not wish to divulge any data which would aid their competitors. However, any data supplied to me will be treated as strictly confidential and I will process the data and supply results and conclusions to any interested bodies who are willing to participate in the project. The more control points (wells) we have, the more useful the results will be. The data I require are two sets of stratigraphic or geophysical statistics from each field or basin: a set of producing wells and a set of non-producers. This is the project which I am now working upon, as a follow-up to this thesis.

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