Sequence stratıgraphıc analysıs of the Galmaz field based on well loggıng data

Abstract

It is known that over 90% of oil, gas and gas condensate in Azerbaijan is produced from Productive Series (PS) of the Early Pliocene. In this respect, the detailed study of Pro- ductive Series deposits and their evolution conditions has a special value. Currently in most sedimentary basins of the world the latest highly informative methods of stratigraphic analysis are applied and one of these methods is sequence-stratigraphy, which is used in this study. The application of the concept of sequence stratigraphy enables an in-depth analysis of the study area to be conducted from a geological point of view. Despite the fact that the search for oil and gas deposits in the basins of Azerbaijan Republic has been going on for many years, there is a limited understanding of the distribution of elements associated with the oil system within the sequence stratigraphic structure. This is evidenced by the small number of scientific publications that exist in this area at the moment. To study in more detail the sedimentation process of PS of the Pliocene in the Galmaz field the genetically tied facies have been outlined and correlated within the framework of chronostratigraphic boundaries. As the study targets we have chosen the stages of Absheron, Akchagyl and PS of Pliocene in the Galmaz field. New data acquired by well logging techniques were re-examined in detail. To analyze and interpret the data , NeuralogTM and PetrelTM software were applied. From positions of the sequence-stratigraphy and taking into account the curve features (gamma ray log) predictions of the sedimentation environment of PS have been made. In the study process the sequences and system tracts have been outlined and studied, the sedimentation periods of the outlined sequences have been defined. It has been suggested to apply stratigraphic surfaces for tracing changes in regression and transgression surfaces. Clay and sand fractions of rocks were evaluated with further lithological analysis. On the gamma-ray curves, the intervals with intensity values less than 3.5 mR/h were considered as reservoir layers. At the same time, the normalized value of αSP, calculated from the curve of Spontaneous Polarization, was assumed to be greater than 0.6. Based on the sequence-stratigraphy analysis of oil-field geophysical data it has been established that the geological section of the Galmaz area was developing at various rates and in frequently changing energy mode. It has been also made clear that parasequences of the Absheron stage and Productive Series were formed in progradation mode by detritus brought by river flows. Akchagyl sediments play the role of the regional major cap in the basin.