No abstract

This paper describes workflow and results of an imaging project carried out on a seismic survey on the Karachaganak field, located on-shore Kazakhstan. The aim of the study is to gain a deep understanding of the reservoir architecture and reduce the uncertainties of the model. The business driver is to support the reservoir modeling for the next field development phase. Karachaganak is a mature oil and gas field, within the Pricaspian basin. The reservoir is an isolated heterogeneous carbonate bank, Permo-Carboniferous in age, ranging from four thousand to six thousand meters of depth. An evaporite layer serves as seal. The overburden is a clastic basin surrounded by four huge allochthonous salt diapirs. Given the high complexity of the area under investigation Reverse Time Migration was the most suitable algorithm for handling sharp velocity contrasts and to image sub-salt targets with a high accuracy and definition. A detailed interpretation of the reservoir and overburden horizons guided a geological based seismic velocity model building. Moreover, an innovative tomographic approach was able to both constrain seismic anisotropy and honor well markers simultaneously. The involvement of structural geologists is part of a regular procedure when embedding salt tectonics into the geophysical model is crucial. Indeed, the interpretation of the complex salt geometry was of paramount importance for the success of the project. Furthermore, leveraging on the available computational capacity, testing multiple scenarios in very short time allowed supporting the QA and QC processes, reducing the uncertainties in the most challenging areas. The final high-resolution image is consistent with well data, logs and cores, matching more than one thousand markers. A clear image of the inner reservoir reveals seismic stratigraphic features previously hidden. The combination of cutting-edge imaging technology, running on the best in class industrial supercomputer in the world, the expertise in geoscience and the commitment of a multidisciplinary team were the key factor to achieve these results. This work does not represent the current shared JV view on the subject.