Logging Evaluation of Permeability in Heterogeneous Conglomerate Reservoir

Conglomerate reservoir is mainly delta-submarine fan deposits from Oligocene of Paleogene Formation. In WS field, formation thickness of upper sandstone and shale profile is very thin with lower lateral changed conglomerate and granite basement. Reservoir lithology is mainly pebbled sandstone, sandy conglomerate, and granitic conglomerate with poor sorting, angular-sub-angular, low textural maturity, and complex pore structure. Affected by high radioactive from basement, gamma-logging reading of lower conglomerate is very high (>400 gAPI), so shale content cannot be calculated with conventional interpretation equation of gamma ray. Reservoirs with the same porosity have different permeability which makes test and production show a lot of differences. Permeability calculated by the statistical regression equation of core porosity and permeability was not consistent with the actual well test and production history. According to the different sedimentary environment and pore structure characteristics, sand and conglomerate reservoirs are divided into five types of flow unit and respective permeability calculation model is set up by using flow unit analysis method and integrating dynamic and static data (core analysis, perforation test, and production). Permeability interpretation results considering test and production information shows higher agreement with dynamic data. This method can help divide reservoirs with different potentials and then provide favorable basis for adding perforation and increasing production during field development.