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A Modified Reverse-Time Migration algorithm for Offset Vertical Seismic Profiling (OVSP) data is proposed. This algorithm performs depth imaging of target areas in the borehole vicinity without taking into account the overburden. Originally recorded seismograms are used; reliable results can be obtained using only the velocity profile obtained along the well. The downgoing wavefield emitted from a surface source is approximated in the target area using the transmitted P-wave, recorded by the receivers de-ployed in the well. This is achieved through a reverse-time extrapolation of the direct transmitted P-wave into the target area after its separation in offset vertical seismic profiling seismograms generated using a finite-difference scheme for solution of the scalar wave equation.
The proposed approach produces "kinematically" reliable images from reflected PP- and PS-waves and, furthermore, can be applied as a salt proximity tool for salt body flank imaging based on the transmitted PS-waves. Our experiments on synthetic and real data demonstrate that the modified Reverse-Time Migration provides reliable depth images based on offset vertical seismic profiling data even if only the velocity profile obtained along the borehole is used.

We consider multicomponent elastic Reverse-Time Migration (RTM) applied to offset VSP data. The wavefields extrapolations are performed using 2D elastic wave equations. In order to suppress migration artifacts caused by limited aperture or non-perfect wavefield separation, we apply the Least-Squares (LS) migration technique. In this work we study and validate the possibilities of such approach. The main tool is the singular values decomposition of the appeared system of linear algebraic equations. Results of multicomponent RTM and Least-Square RTM approaches are compared using the synthetic data example.

This work describes technology of elastic waves field computation for 3D non-parallel layered models. The technology is based on ray-method application. The idea is to separate calculations of the ray trajectories from source and receiver to the bound, instead of monitoring ray-trajectory directly from source to receiver. For each pair of source-receiver, at each border, surface sources (grid-defined functions of ray-in angle) are calculated and compared to define the incident (reflection or refraction) points. This information allows to select and trace the rays, coming to the receiver with defined accuracy, and therefore to form the wave field.

This paper deals with velocity model parameters estimation in case of smooth curvilinear reflective boundaries. Parameters approximation is guided with optimizing inversion of hodographs of direct, reflected and converted waves from different VSP sources. Velocities of pressure and share waves and its vertical gradients are determined. Reflective boundaries geometry is described by smooth splines. Model hodographs are calculated using ray tracing method. The optimizing inversion algorithm showed good results in numerical tests.

This paper deals with principles and practical realization of automatic model based wavefield selection of zero offset VSP and 2D/3D VSP data. Selection of basic types of waves propagating in real medium from initial wavefield is one of the key procedures in VSP data processing taking large time. Application of automatic selection program allows to accelerate data processing essentially and to increase its efficiency. Examples of automatic selection application to model and real VSP and 2D/3D VSP data are presented

Permeability is the major rock property, which define fluid migration ability though pores, vugs and fractures. Pore's, fracture's and vug’s carbonate reservoirs vary in value of permeability and property of its distribution by 3 main axes (directions). A fractures reservoir differs from others by high permeability anisotropy. One of the most effective ways of fractures zones definition and characterization is wave pattern analysis of near wellbore zone in combination with azimuthal borehole measurements of receptivity's heterogeneity of rocks.

One of the most important tendencies observed in the oil production sector nowadays is decreased production of light and medium-density oils. Resources of oils easy-to-recover by conventional methods are being exhausted with a high rate. Meanwhile, resources of hard-to-recover heavy oils and petroleum bitumens are huge worldwide. That is why the importance of exploration and production of heavy oil is continuously increasing. New exploration technologies contribute to commercial recovery of heavy oils. The basic ways of an intensification of extraction of natural bitumens and heavy oils are heat exposure methods. Particular feature of these methods is the great capital intensity in realization. In this connection it is a problem of the control of process of thermal influence taking into account of particular geological conditions and properties of rocks. This work considers the possibility to utilize VSP technologies for monitoring of thermal oil recovery, which allow promptly monitor one of the most informative seismic parameters responding to steam-heat treatment - P wave velocity

Full-wave finite difference modeling together with the following processing of model seismograms conducted before VSP measurements makes it possible to predict the expected geological results. Some examples of this methodology application for the different seismic and geological situations are considered. The possibilities to solve some problems of structural attitude resolution on the base of VSP data are estimated

Utilization of high-quality data on compressional and shear velocities acquired with high accuracy (due to many-fold measurements) allows evaluating contributions of individual formations in the total CDP or VSP wavefield, calibrating diagnostic features of AVO analysis (in predicting poroperm properties), stratify reflectors in detail through synthetic modeling, invert time sections into traces of formation parameters of the earth - velocities, densities and acoustic impedances in the process of generating geological models of reservoirs, etc.

The problem on tube waves excitation in a well, intersected by thin fluid-filled fracture under action of external seismic wave is considered in the report. This situation arises in VSP practice at hydro-fracturing. Based on averaging procedure the non-uniform pseudo-differential wave equation for slow eigen mode in fluid-filled fracture is derived in space-time representation for the long wave approximation by fracture opening. Numerical calculations show that high dispersive slow eigen mode is excited by fracture edges. This mode generates additional tube waves in a well. Registration of these tube waves can be used for fracture size characterization

The authors analyzed synthetic data computed for two modifications of the VSP method, i.e. offset and moving-source VSP, using the geological model containing a buried reef. The resulting sections were obtained by migrating the synthetic records. The modeled reef is manifested in the wavefields calculated with the aid of ray-trace and finite-difference modeling as events reflected from the surface of the reef and characterized with anomalously high apparent velocities. It is demonstrated that both time and depth imaging of the modeled reef is more reliable in moving-source VSP sections than in the offset VSP sections

In the present publication the review of properties of the wave field formed in system of layers, containing collectors, and divided among themselves by sliding contacts is discussed. The methodical approach which consists of construction of seismic model, performance of numerical modeling and also from the analysis of spectral structure theoretical and experimental wave fields is offered.  During interpretation splitting observational spectra on typical groups which can be in the further a basis mapping is used. Preliminary data about an opportunity of the identification of fluid-saturation and a contour of a deposit are obtained.

This paper presents case histories of successful application of the multicomponent offset VSP during field production phase.

Method implementation efficiency is analyzed according to the operations results performed by Joint Stock Company "Bashneftegeofizika" on the number of oilfields in the Western Orenburg area and subsequent drilling on the explored areas.

The functional potentialities of VSP, successfully applied in various tectonic areas of the Republic of Bashkortostan, are systematized in the Article. Ways of cooperation between OJSC "JSNC "Bashneft" and OJSC "Bashneftegeophizika", used as an example, show high efficiency and prospectiveness of the new form of cooperation between oil-extracting and servicing geophysical organizations - VSP-support of deep drilling at various stages of geological exploration.

In this article the urgency of applying the vertical seismic profiling in complex exploration work for oilfield study and their successfulness development is proved. Ways of cooperation between OJSC "JSNC "Bashneft"" and OJSC "Bashneftegeofizika", used as an example, show high efficiency and prospectiveness of
the new form of cooperation between oil-production companies and servicing geophisical organization - VSP-support of deep drilling at various stages of geological exploration.