Distribution of Jurassic Clastic Reservoirs in the Sudochi Depression of the East Ustyurt Basin (Uzbekistan) Based on the Results of Seismic Reservoir Characterization

Abstract

Abstract The goal of the current work is a detailed study of the reservoir architecture, stratigraphy, and properties of Uzbekneftegas (UNG) assets within the Sudochi depression of the East Ustyurt basin, that is urged by low success rates of drilling and declined gas production. Until today, the approach to drilling exploration and production wells was based on the concept of conformably layered reservoirs, that has changed dramatically as a result of the current work. Limitations in data quality and availability was the most challenging aspect of this study. Image processing of the seismic data in the color domain has increased the resolution of the seismic data. Together with spectral decomposition, chromatic extraction yields valuable results in analysis of seismic facies, a tool for automatic well tie allowed to extract the wavelets of best shapes and time-depth relationships (TDR) in optimal time. Rock physics study was performed and justified the feasibility of acoustic inversion. A post-stack inversion was performed to describe reservoir properties and distribution. Application of seismic reservoir characterization techniques and integration of the other domain data resulted in the interpretation of the depositional environment, geometry, and quality of Jurassic reservoirs. As a result of the successful implementation of the mentioned tools, the reservoirs of East Ustyurt basin are seen to be represented by alluvial and fluvial deposits, which are traced and predicted in inter-well space. This information was a valuable input to geological and dynamic models. Different overprints of paleodepositional settings on the reservoir architecture, heterogeneity, and facies distribution of each study area can explain why drilled wells were not identically productive. Eventually, consideration of the seismic reservoir characterization results has significantly changed the location of planned exploration and production wells and led to drilling successful wells with high production rates. The novelty of the work is in the results obtained for the South-Eastern part of Ustyurt basin, specifically the Berdakh high and the Sudochi depression. We have interpreted paleogeographic development in Jurassic period, the reservoir architecture, quality and facies distribution by seismic reservoir characterization tools and integrated analysis of other data, that has not been extensively studied and published before. This study can contribute to the development of the region.