Abstract

The majority of hydraulic fracturing work in Russia is being done in the Western Siberian basin where operators and service companies have gathered significant amount of experience and knowledge. The sweeping success of hydraulic fracturing in Western Siberia organically expanded to projects in Tymen-Pechora and Volga-Urals basin. Both basins are geologically, lithologically and stratigraphically vastly different from West Siberia. Adding the difference in the maturity of the fields, with significantly depleted reservoirs, high asphaltene and paraffin oil content varying the hydrocarbon properties, it is understandable that the extensive knowledge gained in Western Siberia cannot be translated to the less frequent but well engineered and planned stimulation campaigns in the Volga-Urals basin.

This paper presents a summary of the knowledge gained in Samara fields of the Volga-Urals basin, with emphasis on the results obtained and highlighting the differences with the Western Siberian approach to hydraulic fracturing.

Samara area is characterized with relatively low temperature, high permeability, low pressure, laterally and vertically restrained dome type sandstone and carbonate reservoirs that are located in tectonically active, high stress environment. Although correct candidate selection and fracture design, the degree of the pre-stimulation formation damage has proven to be significantly different from the comparative formations in Western Siberia hydraulic fracturing has proven again to be a successful stimulation method.

Carbonate reservoirs that constitute some 50% of the oil bearing rock in the area have seen the first acid fracturing treatments performed, including the introduction of various diverter methods in the area. The success of the pilot project is addressed as it sets a milestone in carbonate stimulation in the Volga-Urals basin.

Introduction

To understand the particularities of hydraulic fracture stimulation it is of extreme importance to understand the difference in the geological setting and the overall diversity in comparison to Western Siberia where the majority of hydraulic fracture operations in Russia have been done so far. Therefore the first part of this paper presents a description of the Samara region geology, formation properties and characteristics of the oilfields. This includes a geological overview, reserves distribution, drilling and completion practices, and production methodology and stimulation objectives.

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