Integrated study of Vatyogan oil field, West-Siberian region of Russia
The western Siberian basin contains some of the largest oil fields in Russia and the former Soviet Union. In early 2000, LUKOil, in cooperation with PetroAlliance, completed the largest integrated reservoir study ever undertaken in the region. The project spanning nearly four years culminated in an enhanced 3D geological and reservoir models of the giant Vatyogan oil field, which holds over 1 billion tons of calculated oil reserves.
The major technical objective was to utilize state-of-the-art technology to create a new 3D geological model of Vatyogan’s six major producing zones, which range in age from Upper Jurassic to Upper Cretaceous and cover a wide range of depositional environments. The new geologic model would form the basis for reservoir simulation models which would guide further operational and development activities in the field. Specific tasks to be accomplished with the new model include:
- In undeveloped areas: Estimate reserves and prepare a drilling program
- In developed areas: Identify areas of by-passed oil and develop an optimum infill drilling and enhanced recovery program to improve production.
A multi-disciplinary team of 25 specialists was involved in various stages of the project. The study began with the creation of a digital database of 3,800 wells from paper records. Newly acquired data such as: 2D and 3D seismic, log data, and high precision gyroscopic surveys were incorporated into the revised models.
This paper describes the processes employed in the project and highlights some of the stumbling blocks. Details are provided describing data management, geological modeling, upscaling and history matching of thousand of wells. Conclusions illustrate how data from the specialized logs and high precision gyroscopic surveys resolved numerous questions and contradictions in the existing data, providing improved reservoir structure analysis and more accurate fluid-contact depths–data which significantly impacted both the models and the simulation forecasts.
The West-Siberian oil-and-gas province is the largest in Russian territory, containing nearly 500 major oil and gas fields. The province lies within the extensive plain between the Ural Mountains to the west and the Siberian platform to the east. To the south, it is bordered by the Altay-Sayan mountain range (Fig. 1).
The West Siberian Basin formed as a result of thermal relaxation following an abortive Triassic rift episode.1 Up to 3 km of Triassic basalt and volcanic rocks are covered by alluvial fan and lacustrine deposits of the early Jurassic. The first marine transgression is in the middle Jurassic, but basin wide marine conditions were not established until the late Jurassic Greorgiyev and Bazhenov Formations. The early Cretaceous is characterized by a series of westward prograding deltas that fill the basin. Within the basin reservoirs, hydrocarbons can be found in almost all depositional settings, from basin floor turbidite fans to coastal plain channel deposits.
The largest concentration of major fields under development is found in the central part of the basin, in the Sredneobskaya region (Fig. 1). The giant Vatyogan oil field is located here, 30 km from the town of Kogalym.