Using advanced logging methods combining NMR and spectroscopy an Oil Saturation Index (OSI) is computed that correlates well with the productive layers of the Bazhenov formation. This article describes a method of estimating the OSI from log data, proposes a model for log interpretation in the Bazhenov Formation sediments and compares the results to core analysis. We present results from three wells.

The Medvezh'e gas deposit is the first test site for large-scale industrial construction in the northern part of Western Siberia, where the ground is composed of fine soils that have been frozen for many years.By the fifth or sixth year of operation of almost all of the gas-fields in Medvezh'e, the foundations of a number of the physical structures had unde~one substantial deformation. This in turn has led to distortion of the frames of buildings and equipment, bending of pipelines, and vibration of components of the turbines at the final compressor stations (FCSs). The turbine vibrations have resulted in premature wear of the components, pipeline failures, and other problems. Over time, there has been an increase both in the amplitude of the deformations and the number of sites where they originate [1, 2].An analysis performed by the ranking method to determine the reasons for the equipment failures and production losses shows that the failures due to the development of unfavorable geological-frost conditions are comparable to the failures that occur due to technological factors and errors in construction [3].The limited amount of capital that companies have to spend on ensuring the operational reliability of the gas-producing equipment makes it imperative that those resources be used more efficiently.More than twenty years of experience in the operation of the facilities in Medvezh'e shows that in order to determine the steps which must be taken in the short term to keep the stresses from reaching unacceptable levels and eliminate the deformation, develop long-range plans to rebuild and modernize the equipment, and thus make more efficient use of the available funds, it will be necessary to conduct a comprehensive diagnostic evaluation of the objects as integrated geotechnical systemsincluding the soils of the foundations, the foundations themselves, and the superstructures [3][4][5].Studies have shown that in most cases the deformations are caused by changes that occurred in the geological-frost conditions in the soils of the foundations of structures and that were not foreseen in the building plans [6, 7].It was established that the decisive factor determining the load-carrying capacity of a pile foundation of a structure built on frozen ground is the dynamics of the temperature field in the soil surrounding the foundation. A deviation of the actual temperature regime of the soil part of the foundation from the design regime will lead to loss of the load-carrying capacity of the foundation and, thus, to sudden failures requiring reconstruction of the building [8].The method traditionally used to determine the thermal regime of the soils of foundations at the design stage is calculation of the average annual temperature and the depth of the seasonal thawing and freezing [9]. The method is based on the solution of a homogeneous unidimensional heat-conduction equation in a quasi-steady approximation, which makes it possible to obtain estimates of the required quantities that are close to the steady-state values....

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This paper describes the results of an integrated approach to selecting the optimal interval of horizontal well drilling followed by hydraulic fracturing as part of a pilot project of developing unconventional hydrocarbon reserves in the oil-source rock of Bazhenov suite in the southern licensed territory of the Priobskoye field. The battery of research included a lithological identification based on composition and presence of movable hydrocarbons in voids, permeability and porosity assessment, as well as assessment of mechanical properties and stress profile with intent to develop a reservoir fracturing model that would guarantee the best coverage of potentially producing interval of the section. Bazhenov suite rocks have a fairly complex and vertically unsteady mineralogical composition, and their voids are characterized by a complex structure. Research results helped build a lithological model that allows capturing the intervals of occurrence of rocks with void structure, which demonstrates presence of movable oil. The presence of movable oil was also confirmed by the integrated petrophysical model that allowed a quantitative assessment of porosity and permeability of identified potentially producing intervals. Identification of anisotropic dynamic moduli of elasticity using the cross-dipole full-wave acoustic logging (FWAL) in the open hole, as well as identification of elastic and structural behavior based on core samples helped develop single-well models of mechanical properties. Their further adjustment to core data using hydraulic fracture control results and reiterated FWAL helped formulate several scenarios of the fracturing process. The key method of identifying structural and compositional complexes in the well section is clustering based on two well logging techniques, i.e. pulsed neutron gamma logging and nuclear magnetic logging. While developing the integrated petrophysical model of Bazhenov suite oil-source rocks, we saw demand for a practical classification that could offer the most comprehensive description of clusters identified by logging. This classification of rocks was developed on the basis of rock composition data obtained during lithological and geochemical tests of core samples. Voids description was based on the results of petrographic analysis and NML data, which helped identify voids with potential fluid flow for two structural and compositional complexes of Bazhenov suite rocks. Bazhenov suite interval in the southern licensed territory (SLT) of the Priobskoye field is characterized by high fracturing gradients, which means a hydraulic fracture cannot be contained in absence of vertical stratification and anisotropy. A lithological and petrophysical model augmented by the mechanical properties simulation results was employed to assess vertical fracture growth, which helped formulate the best design of hydraulic fracturing to contain the fracture within the potentially producing interval and ensure the longest half-length of the fracture and the largest stimulated reservoir volume. A comprehensive approach to assessing section properties that identify both presence of movable hydrocarbons and potential for successful hydraulic fracturing helped find the interval of hydraulic fracture initiation that best supports high production rates. The study demonstrates that containment of fracture in a potentially producing interval is one of the key drivers and a controlling factor of successful hydraulic fracturing operation.