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Abstract

UDC [(552.578.2.061.4:551.243):551.72]:550.822.7(571.5)

LITHOLOGICAL AND HYDRODYNAMIC FACTORS CONTROLLING CONDITIONS OF PRIMARY HORIZONTAL DRILLING AND DEVELOPMENT OF PRODUCING INTERVALS OF THE RIPHEAN NATURAL RESERVOIR IN THE YURUBCHENO-TOKHOMSKOYE OIL-GAS-CONDRNSATE FIELD

A. G. Vakhromeev, R. K. Razyapov, O. V. Postnikova, N. M. Kutukova, S. A. Sverkunov, R. U. Siraev.

The oil-gas-condensate Yurubcheno-Tokhomskoye field is one of the largest fields in the Eastern Siberia and one of the priority projects of OAO NK Rosneft. The field has unique properties and no analogs in Russia and in the world [1]. Oil and gas pools are confined to carbonaceous Riphean deposits that had formed about one billion years ago. Porosity of producing deposits is 0.5% to 2% and it lies within the range of error of porosity values derived from well logging. The Riphean dolomites are complicated by fracturing and cavernosity with highly-variable reservoir properties both vertically and laterally. This is probably the main reason of sharp differences in productivity of the neighboring wells. Many years of special core studies resulted in development of a conceptual model of the natural carbonaceous Riphean reservoir based on occurrence of horizontal fissured zones with increased permeability and near-vertical fractured, fractured-veiny, and karsticveiny reservoirs. The authors suggest a version to explain the hydraulic mechanism of continuous drilling mud losses in the zones. Hydrodynamic parameters of the pool (abnormally low formation pressure) complicate primary penetration in the producing horizon. All given geological and hydrodynamic factors influence horizontal drilling features and require adequate geological models for deciding on development of the field. The paper provides an option of horizontal drilling optimization and drilling costs saving.

Key words: horizontal fissured zones, karstic zones, Riphean, Eastern Siberia, catastrophic losses, drilling technology.

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