Abstract:The practical aspects are discussed in the geodynamic studies of the massive vugular-fractured oil-and-gas reservoir in the Riphean carbonate rocks of the Yurubcheno-Tokhoma oil-gas-condensate field in the Baikit petroliferous district. This field is a part of the Yurubcheno-Tokhoma zone that includes the Kuyumba oil-and-gas field, Omorinsk gas-condensate field (a satellite field) and the promising Kamovsky, Vaividinsky, Shushuksky, Seismorazvedochny and Kordinsky areas [Kontorovich et al., 1988]. Potential recoverable resources are predicted to amount to two billion tonnes of fuel equivalent in this zone, which area exceeds 60000 km 2 , also known as the Kuyumba-Yurubcheno-Tokhoma oil-and-gas accumulation zone [Trofimuk, 1992;Trofimuk et al., 1989;Kharakhinov, Shlenkin, 2011]. A key factor for the economically effective development of the deposits in the Baikit petroliferous district is the feasibility of efficient primary recovery of oil and gas by horizontal wells to be drilled to large depths to reach the complex fractured natural reservoirs in the Riphean carbonate rocks. This paper discusses one field as an example from the Baikit petroliferous district and summarizes the results of the detailed studies of the geodynamic and hydrodynamic conditions of the oil-gas-condensate reservoir in the Riphean rocks. The reported results are compared with the actual field data, including the annulus pressure sensor measurements [Vakhromeev et al., , 2015. The previous findings are confirmed and extended: when vertical fractures are penetrated by drilling, and the hydraulic pressure variations amount to 0.5-1.5 % of the formation pressure, the effect of alternating mud-loss / kicks occurs in the nearwellbore zone due to the high permeability of the reservoir and the lack of the skin-effect in the bottomhole zone . The allowable ranges of the variations in the dynamic bottomhole pressure are estimated and justified for primary penetration into the oil-saturated vugular-fractured strata. Within an allowable range of pressure rates, a horizontal well can be drilled with minimal complications caused by alternating adjustable mud-loss and kick effects. Based on our study results, prerequisites are determined for developing the new technology of penetrating into pay zones in carbonate vugular-fractured reservoirs with anomalously low formation pressure rates.Key words: geodynamics; production drilling; horizontal well; mud-loss; drilling technology; Riphean carbonate reservoir For citation : Vakhromeev A.G., Sverkunov S.A., Ivanishin V.M., Razyapov R.K., Danilova E.M., 2017. Geodynamic aspects in the study of complex mining and geological conditions for drilling into oil-and-gas reservoirs in the Riphean carbonate rocks: an overview of the problem as exemplified by the deposits in the Baikit petroliferous district. Geodynamics & Tectonophysics 8 (4), 903-921. GEODYNAMICS & TECTONOPHYSICS P U B L I S H E D B Y T H E I N S T I T U T E O F T H E E A R T H ' S C R U S T S I B E R I A N B R A N C H O F R U S S I A N A C ...

In the southern areas of the Siberian platform, geological and mining conditions are highly complex for design, drilling and construction of deep wells for oil and gas. Complicating factors are related to specific features of deforming cavity-fractured carbonate reservoirs. Geological models of carbonate reservoirs should be designed on a case-by-case basis, taking into consideration the conditions of each specific field, including its complex filtration field, confirmed deformation of filtering fractures with constant parameters of the cavern component, etc. If an incomprehensive geological model is used for production planning with a lack of a well-based approach to the development of a carbonate reservoir, design well flow rates may not be achieved, the field reserve coverage will be reduced and, consequently, the oil recovery ratio will be lower. When developing oil, gas and brine deposits, it is required to consider the natural-technical system of 'reservoir-reservoir' (mechanical impact)-'reservoir fluid system and well' (hydrodynamic impact) on the basis of a comprehensive analysis of its interrelated and interdependent components. Our study shows that each part of the system contributes directly to the entire complex. The stress state of the rock mass in the fluid-permeable part of the natural fractured reservoir and fluid-saturated reservoirs is dynamically changeable during the fluctuations of the pressure field of the reservoir hydrocarbon system at the initial penetration of a well into the reservoir. The authors analyzed the natural-technical system 'well-fluid-saturated bed' as a real on-line model of leaking-hydraulic fracturing based on a standard pressure vs. time curve during hydraulic fracturing. Based on the knowledge of the ongoing processes in carbonate cavern-fractured reservoirs, it becomes possible to predict the reaction of the rock mass during hydraulic repression (i.e., during the initial penetration of a well into the reservoir) and depression (during testing and operations of a production well). All pressure effects hydraulically applied to the reservoir fluid system can lead to changes in the stress state of the natural reservoir. The stress state with significantly changing permeability parameters of filtering fractures is among the most complex states of stress [Belonin et al., 2005; Borevsky, 1986]. It is important to take into account that such stress state transition during the drilling GEODYNAMICS & TECTONOPHYSICS

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