Geomodel 2020

The work is devoted to the future discoveries forecast of oil and gas fields in the junction zone of the north-east of Western Siberia and the north-west of the Siberian platform. Actual materials were used on geology, tectonics, oil and gas potential, on 27 oil and gas deposits of the Yamal-Nenets District and Krasnoyarsk Region in the studied area. In the studied territory groups of deposits were selected according to the largest size of reserves. These groups of deposits are supposed to have been formed as a result of the activation of geodynamic processes in certain periods of the geological history of the region. Hydrocarbon location sections were reorganized and the relief of the modern surface was developed during shearing strains, compression and stretch. The features of the surface topography are considered as local geodynamic settings, which can be indicators of deep geological objects with a specific geometry. New large-size and smaller hydrocarbon deposits mainly associated with non-structural conditions will hopefully be discovered in the area under study in the future. Local geodynamic conditions data becomes an additional factor making it possible to assess oil and gas bearing prospects and pave the way for new discoveries.

The scope of multilayer field development tasks includes not only issues of production economic efficiency, but also a complex approach to the program of additional appraisal of development targets. Adequate development of additional appraisal strategy during production drilling allows to effectively lower uncertainties and risks in full development of fields with complex structure. The report describes the main features of the downthrown block development targets of the Vostochno-Messoyakhskoye field, as well as the main factors that influenced step-by-step drilling strategy development and effective additional appraisal. Thanks to advance drilling for the lower productive horizon, it was possible to clear up a number of key ambiguities on transit formations, refine the strategy of operating wells drilling and bring additional development targets into production.

This article describes the effectiveness of using the simulated annealing method to solve a series of direct gravimetric problems based on gravimetric monitoring data. It is shown that the use of the developed algorithm makes it possible to increase the reliability of the mathematical model and significantly reduce working time when analysing the measured gravitational field over the developed oil and gas fields. The proposed method is developed as one of the subsystems of a special GIS designed for storage, processing, analysis and visualization of gravimetric monitoring data at an oil and gas field. The article describes the operation of the algorithm and demonstrates the results of modeling. For calculations, a sequence of horizontal prismatic bodies was selected, a priori calculation parameters are indicated, and criteria for searching for optimal solutions are developed.

The importance of solving the problems of geomechanical analysis in recent years is undisputable. Main method of estimating the components of the anisotropic elastic moduli tensor is multi-element acoustic logging. The task of recovering components is complex, which leads to the use of various approximate models. Usually a model of a transversely isotropic medium is considered, which is governed by five independent components. To model their dispersion curves, the authors previously applied the semi-analytical finite element method (SAFE). However, due to the finite computational domain, one of the main difficulties is the extraction of target modes from physically unreasonable ones. To address this difficulty, the authors used zero conditions at the external boundary of the computational domain and proposed an approach for selecting physically existing borehole modes based on the analysis of their polarization, radial and spatial distributions of the kinetic energy density and the symmetry class of the eigenfunctions. In this paper, we consider and analyze the methods for improving the extraction of target borehole modes based on the introduction of radial expansion and an absorbing layer outside the main computational domain. The implementations of such layer as "Perfectly Matched Layer" (PML) and "Absorbing Layer" (AL) are considered.

This paper stresses the need for reinterpretation of seismic data for brown fields on the basis of data from the field located on the territory of the Greater Caucasus. Emergence of new technologies stimulates operators to shift their focus to traditional oil provinces that were explored a long time ago. The added advantage of working in such fields is that they already have all the necessary infrastructure in place and their remaining reserves can be accessed and brought into production at fairly low cost. Successful rejuvenation of brown fields requires a combination of design and engineering expertise, competent use of technologies, knowledge and experience. This is the first time that a fault-block model has been proposed for the studied field, which established the water-oil contacts consistent with the test results and helped make a more accurate estimation of field’s reserves.

In order to reduce the uncertainty in the location of facies zones, the "geobody" technique was applied: three-dimensional bodies associated with highly permeable reservoirs were substracted based on the acoustic impedance cube. Several cycles of constructing a geological and hydrodynamic model have been carried out with the identification of problem areas in hydrodynamics and their further consideration in the geological model. After obtaining the final version of geobodies distribution, it was possible to derive permeability-effective porosity dependences for each facies zone. The use of the "geobody" methodology made it possible to clarify the facies zones, which positively affected interference history matching of production and injection wells and allowed to identify wells that penetrate sand lenses, which positively affected the predictive ability of the model. The developed methodology made it possible to increase the verification of the geological model during history matching, lower basic uncertainties, such as the location of shale barriers and underforecasting of reservoir properties, which helped to increase the predictive ability of the model for optimal well planning.

The article is devoted to increasing the efficiency of well testing in the construction of seismic models of oil and gas objects. We suggest using the adaptive approach, which has been developed by us, to processing and interpretation of well testing data; it will increase the efficiency of management of the processing and interpretation of well testing data. The essence of the approach consists of dividing the process into stages, developing for each stage a multivariate decision scheme, and formal criteria for evaluating the results. A conceptual framework has been developed for the implementation of the proposed approach as applied to the processing and interpretation of well testing data in order to construct seismic models of terrigenous deposits in Western Siberia. We propose formalized criteria for assessing the quality of processing results of well testing data, modeling of well testing curves, and determination of petrophysical parameters. The results obtained are illustrated on practical data on oil fields in Western Siberia.

Neural networks (NN) are widely used for solving various problems of geophysical data interpretation and processing. The application of the neural network approximation (NNA) method for solving inverse problems, including inverse multi-criteria problems of geophysics that are reduced to a nonlinear operator equation of the first kind (respectively, to a system of operator equations) is considered. The NNA method assumes the construction of an approximate inverse operator of the problem using neural network approximation designs (MLP networks) on the basis of a preliminary constructed set of reference solutions to direct and inverse problems. Techniques for estimating the practical ambiguity (error) of approximate solutions to inverse multicriteria problems are considered. Results of solving the inverse two-criteria 3D problem in combination with magnetometry are presented. It is shown that the NNA method allows one to stably solve nonlinear multicriteria inverse 3D problems with many desired parameters in real-time, with accuracy acceptable for practice. The experience of calculations shows that the error in solving the two-criteria problem is less than the one-criterion.

When developing reservoirs with natural fracturing, a number of effects arise due to changes in the stress state of rocks. One of these problems is the closure of part of the natural fractures, which causes a change in the permeability of the reservoir pressure. Reducing reservoir pressures leads to an increase in effective stresses acting on the fractures walls, which leads to a decrease in their opening, and, as a result, to a significant decrease in the permeability of fractures.

Currently the proportion of Achimov deposits put into production in the north of Western Siberia has increased. Such projects require a flexible approach to realization of the production strategy and the ability to make adjustments to it quickly and efficiently. A similar approach was implemented on the BU21-3-1 formation of the Vostochno-Messoyakhskoye field, during drilling which the model was updated and improved in real time, new forecasts and recommendations were issued, when unforeseen formation features arised. In consequence of a comprehensive analysis of existing and newly obtained seismic, petrophysical and geological information obtained during the drilling of exploration and production wells, it was possible to collect integral view of the deposits, to refine and detail the geological model of the BU21-3-1 formation. Taking into account possible outcomes, a detailed program was worked out to reduce geological uncertainties, such as the presence of water-gas-oil contacts, a structural factor, the distribution of facies, their thickness, and reservoir poroperm properties. The implemented methodology allows to predict the distribution of the reservoir and oil-saturated thicknesses, in the case of low predictive ability of seismic attributes, only in case that the source of data are of good quality (3D seismic surveys, inversion cubes, borehole seismic), as well as the correlation of elastic properties in drilled wells and cubes.