Abstract

Geopetroleum studies, assessment of operated or non -operated acreages, and evaluation of new opportunities use correlation sheets and facies distribution maps. These documents are elaborated from lithological interpretations based on conventional logs (gamma ray, density, neutron, sonic, resistivity). The main challenge the geologists can face is to interpret huge intervals covered by heterogeneous log data in numerous wells in a very short space of time. Currently available software packages cannot be used as they lack the tools required to automatically analyze, standardize and process simultaneously all the wells. Interpretations are usually carried out on a small number of selected wells, which are processed one after the other. A leading edge methodology supported by dedicated software tools is presented here. It is composed of five steps: harmonization of log names, units and sampling rates; cleaning of logs; multi-well pre-processing; faciological modelling; multi-well quality control and facies maps creation. It was developed to process consistently all the available data sets and obtain homogeneous and reliable lithological evaluations in a shorter time. The interest in the implementation of such a method is illustrated from the example of a petroleum synthesis which was realized on 160 wells in the mid Norway Haltenbanken-Dønna Terrace areas. This method and the associated statistical tools have been also successfully applied in many other petroleum contexts and many geographical areas including the Middle-East. The use of all available logs improves the quality of the results and assures homogeneous interpretations. A significant reduction in costs and durations is observed in all the studies that have applied this methodology. This positive effect increases with the size of the well data base to be processed. Typical reduction factors from 3 to 10 are experienced. In addition, studies that would be prohibitively long and expensive with classical methods become possible.

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