Abstract

Lemezinskoe oil field is situated in Iglinsky region, Republic of Bashkortostan, 84 km to the east of Ufa and 35 km to the south-east of the regional center Iglino. The field is located in the region with well-developed infrastructure. In the regional tectonic setting the field lies in the northern part of the Belsk Depression, Pre-Ural Foredeep Basin. It is associated with a buried Lower Permian reef build-up (P1ar-P1s). Oil shows of various intensity and nature were recorded in the Kungurian, Artinskian and Sakmarian sequences. Commercial oil reserves of Lemezinskoe field are discovered in the porous and permeable limestones of the productive Artiskian-Sakmarian reservoirs. The reef build-up consists of carbonates which differ in their mineral composition, origin, structure and texture as well as porosity and permeability. The oil is heavy, viscous, waxy and sour.

One production target is identified within the field and two reservoirs which are located at a considerable distance from each other. The key parameters of the developed Artiskian-Sakmarian Reservoir 1 (Reservoir 2 is not developed due to its location in the sanitary-protection zone) are summarized below.

The reservoir layers within the body of the reef are characterized by discreet spatial distribution. In most cases the permeable streaks are isolated by tight carbonate rocks. Well-to-well correlation of the reservoir intervals is impossible due to the heterogeneous lithology of the section. Geological cross-sections show the distribution of the reservoir intervals only in the wells whereas in the interwell space the presumed distribution pattern is rather schematic and simplified (Fig. 1). One distinct feature of Lemezinskoe field as a reefal build-up is lack of biodegrated oil or gas cap.

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