Abstract
Purpose is the development of mathematical models to evaluate deformation of parameters of the rock mass-well geological and engineering system within the anisotropic media. Methods. Both mathematical and neural modeling of a stress state of the rock mass-well system under conditions of geological uncertainty has been applied for the studies. From the viewpoint of mathematical modeling, analysis of probability of factors, complicating drilling, should involve a number of assumptions for strength and deformation characteristics of rock mass layers corresponding to particular hole-making conditions. Findings. A mathematical model of horizontal wellbore and geological layers, occurring along the structure under the conditions of permanent comprehensive stresses, has been developed. An analytical and graphical form has been applied to implement one of the basic aspects of aggregation principles of strength changes in each particular lithological layer for identification of an ideal value of horizontal/inclined wellbore length relative to the rock mass depths scheduled by mining. Regularities of changes in deformation and spatial well stability within the complex reservoirs depending upon various process duties have been determined. A neural simulation-based model has been proposed to analyze deformation of rock mass layers having different strength characteristics. Originality. Interaction between geomechanical characteristics of rock mass as well as deformation and spatial stability of well design has been evaluated both qualitatively and quantitatively. Practical implications. An opportunity has been presented to forecast deformation of well walls taking into consideration different strength as well as structural and geological rock mass characteristics on the basis of neural simulation. The represented approach has been included on the register of the best scientific-based practices according to “Methods to recover low-pressure gas of Cenomanian producing complex” Project.
Highlights
Regularities of changes in deformation and spatial well stability within the complex reservoirs depending upon various process duties have been determined
Stress tensor development on the basis of well survey (WS) and the elaborated study of longitudinal well behavior relative to x, y, and z axes of geological space will show that their propagation velocity along z axis is by 1-2 orders less to compare with x and y directions
Conceptual model of the deformation process in the neighborhood of horizontal wells will not be identical for the cases when rock influence on vertical wellbores in the context of any alternatives of the anisotropic environments; the abovementioned depends upon the identity of each intersection point within the peripheries of vertical wellbores
Summary
Taking into consideration the effect of local concentrated stress varieties, the basic set of rock mass breaking techniques is based upon the mechanical decomposition of certain solid mass amount into small-size physical components able to higher than internal resistance within the rock structure.Stresses, favouring following disintegration of rock structure, may happen in following basic cases:– if action of external forces, arising when specific tools, which hardness is higher than that of the rocks themselves, are used for the rock mass;– if fluid stream moves under head and at a high rate; – if water hammer and air blast act;– if internal forces, formed with the help of highfrequency electromagnetic field and more intensive value of electric field, act (electric breakdown).rock mass disintegration processes will be represented by its mechanical disturbance (in varying amounts) when rock compositions and characteristics are preserved. Taking into consideration the effect of local concentrated stress varieties, the basic set of rock mass breaking techniques is based upon the mechanical decomposition of certain solid mass amount into small-size physical components able to higher than internal resistance within the rock structure. Rock mass disintegration may be followed by changes in its composition through different physicochemical processes (i.e. burning, melting, and dissolving). Resulting from such transformations, certain rock mass share will pass into gaseous or vaporous state with other properties which is typical for a physicochemical method of rock mass disintegration [1]
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