Perm Journal of Petroleum and Mining Engineering (Mar 2019)
Using discriminant analysis for the interpretation of gas logging data on the example of the Pavlov oil field
Abstract
The article is devoted to the development of new methodology of gas-logging interpretation based on materials from drilled wells of the Pavlovsky oil field in the Lower-Middle-Visayan terrigenous oil and gas complex in the interval of the Tula terrigenous horizon С1tl, with using elements of mathematical statistics - stepwise discriminant analysis, for which the gas chromatographic data (the total gas content of hydrocarbons in the drill mud and component composition of the gas-air mixture) as well as data of luminescent-bitumen analysis of drill cuttings were used as variables. In addition, logging data were used - gamma-ray logging, neutron-neutron logging for thermal neutrons and the difference between the bit diameter and the well diameter. Based on the results of the analysis, the probability of attributing observations to oil-saturated sandstones, which takes into account gas logging and well logging, was calculated. In addition to oil-saturated sandstones, rocks occurring in this oil-gas-bearing complex were studied: mudstones, aleurolites, clayey sandstones and non-oil saturated sandstones. To visualize the results, a geological and geophysical diagram was plotted on which were shown: rock saturation according to well survey, rock saturation according to well logging and lithological column according to well survey and logging, as well as all variables that participated in the discriminant analysis. Based on the discriminatory analysis, three ranges of values were identified: 1) an area with observations related to oil-saturated rocks; 2) an area with observations related to non-oil-saturated rocks and 3) an area with observations of unclear saturation with indicators that are intermediate (the transition zone is possibly oil-saturated or washed reservoirs).
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