Identification of High-Porosity Reservoir Sands From 3D-Seismic Attributes Using Neural Network Technique in South Umm Gudair Field, Kuwait

摘要

The South Umm Gudair Field is a multi-accumulation structure with the most prolific production of oil from a Ratawi Oolite reservoir (Neocomian). The historic ultimate seal held by the thick Ratawi Shale Member, displays embedded multilayered oil bearing reservoir sands. Sands were sedimented as thin tidal bars anastomosed with distributary and tidal channels deposited under pro-deltaic to delta front environment. To delineate this complex reservoir, a neural network technique was applied to estimate effective porosity integrating well information and 3D multi-attributes between seismically mapped sequences. This method is more efficient than conventional estimation with the ability to build a non-linear relationship between seismic traces and target porosity logs for interpolation. The combination of 20 seismic attributes including impedance derived by model based inversion was selected on the basis of ranking of error factors. The network was trained with effective porosity available at well locations. It subsequently recognized not only that pattern, but also similar patterns by generalization in the study area. The effective porosity cube was generated by the processing of 3D seismic data with this trained network. The representative sections extracted from this volume highlight the limited extent of reservoir sands within the sequences which has also been supported by the simulations of lithofacies with Sequential Gaussian method using well data. The trajectory of the proposed lateral wells are designed in sequences-2 & 4 to intersect the porous sand at the optimum location to ensure good drainage of these reservoir units. The reservoir sand corresponding to upper sequence-4 shows widespread development in the western part of the area of interest with better connectivity, but is shaling out eastward of the field. The paper focuses on the methodology of identification of thin lenticular high porosity reservoir sands to plan for side-tracking existing deeper wells and drilling appraisal & delineation wells.