Multi-Disciplinary Collaborative Pre-Caspian Shallow Subsurface Aquifer Study: Data Acquisition and Management, Petrophysical Interpretation, Static and Dynamic Modeling, and Volume Validation With Well Rest Data

Abstract

The development of the giant Tengiz and Korolev oil fields might require a large and reliable industrial water source for future development. This paper shares best practices from a multidisciplinary team effort in characterizing the shallow aquifer water sources in the Tengiz area. The data set above the Tengiz oil zone is characterized by limited cores and large number of penetrations with logs, as well as 3D seismic. A subsurface study of the Tengiz area Post-Salt aquifers is challenging because of the old vintage of existing logs and limited core in shallower section of wells targeting Tengiz and Korolev oil reservoirs. A subsurface data gathering program was executed to acquire new logs, core from two new wells A-1 and B-1 from Alb-Cenomanian, Upper Neocomian, Aptian and Jurassic formations. All core and log data in conjunction with seismic improved our understanding of the depositional environments, connectivity and areal extend of numerous sand bodies. Core porosity and permeability very well match with new wireline logs. Based on information gained and new interpretation data, we now have better understanding of the geology of potential water source sands. Alb-Cenomanian and Upper Neocomian deposits were found to be the two largest aquifers in the Tengiz area. The Alb-Cenomanian has high net-to-gross with extensive fluvial channel belt sandstones. Reservoir properties are very good and water volume is very large. The Upper Neocomian consists of ribbon-like fluvial channel belts (2-15m thick) embedded within floodplain deposits and interbedded thin (i.e., <2m) crevasse splay deposits. Reservoir sandstone is moderate to excellent quality. The Upper Neocomian has stratigraphic barriers above and below – internally it exhibits some baffles and barriers associated with floodplain shales. Aptian and Jurassic sections were evaluated to be unattractive as water sources. Because of sand quality and higher water volume, Alb-Cenomanian and Upper Neocomian formations were selected as the best candidates for water source. New seismic interpretation, log and core data were incorporated to construct static models. Dynamic models for shallow aquifers are being built; the models will be used to support the industrial water source development plan for Tengiz and Korolev oil fields.