Modelling of deep wells thermal modes

Abstract

Purpose. Investigation of various heat-exchange conditions influence of the tower liquid on the deep wells thermal conditions.Methods. Methods of heat-exchange processes mathematical modeling are used. On the basis of the developed scheme for calculation, the thermal condition in a vertical well with a concentric arrangement of the drill-string was investigated. It was assumed that the walls of the well are properly insulated, and there is no flow or loss of fluid. The temperature distribution in the Newtonian (water) and non-Newtonian (clay mud) liquid along the borehole was simulated taking into account changes in the temperature regime of rocks with depth. To verify the calculation method and determine the reliability of the results, a comparative analysis of the calculated and experimental data to determine the temperature of the drilling liquid in the well was performed. Findings.A mathematical model for the study of temperature fields along the well depth was proposed and verified. A steady-state temperature distribution along the borehole is obtained for various types (Newtonian or non-Newtonian) tower liquid, with a linear law of change in rocks temperature with depth. It has been established that the temperature of the liquid flow at the face of hole and at the exit to the surface depends on the type of liquid used and the flow regime. It has been established that due to thermal insulation of drill pipe columns, heat-exchange between the downward and upward flow is reduced, which leads to a decrease in the temperature of the downward flow at the face of hole, providing a more favorable temperature at the face, which contributes to better destruction of the rock and cooling the tool during drilling.Originality. The nature of temperature distribution and changes along the borehole under the steady-state mode of heat-exchange in a turbulent and structural flow regime for both Newtonian and non-Newtonian circulating liquid are revealed. Practical implications.The proposed mathematical model and obtained results can be used to conduct estimates of the thermal conditions of wells and the development of recommendations for controlling the intensity of heatexchange processes in the well, in accordance with the requirements of a specific technology.

An approximate approach to estimation of dissociation rate of gas hydrate in porous rock bed

“…In the general case, modelling the transfer processes during the "gas hydrate -gas + water" phase transition is a rather complex problem that needs to be solved taking into account the transfer processes in the well [19] and changes in thermodynamic conditions along the well depth [20]. However, in the case when the gas hydrate layer thickness is much less than the depth of the well, the radius of the gas hydrate decomposition area is much larger than the radius of the well, and the upper and lower layers of the mine rock are impermeable to gas, then the problem can be solved within the framework of the one-dimensional approximation [21,22].…”

Method for optimizing the protecting pillars parameters in underground coal mining

“…The measures to conduct and maintain the NDS of the seam C 10 l have been developed on the basis of scientific research and practical experience of the mine workings exploitation in the mining and geological Western Donbas conditions [3,4,19]. Earlier, the possible rock pressure manifestations has been preliminary assessed and general recommendations for ensuring the stable state of the NDS of the seam C 10 l has been made.…”

“…One of the resource-saving trends in extraction of mineral resources is the optimization of the protecting pillars parameters, in which up to 70% of standard quality coal reserves are concentrated in exploited fields. This problem is complex to solve at the Western Donbas mines that is explained by specific mining and geological conditions [3,4]. Coal in this region is hard enough (hardness coefficient according to M. M. Protodiakonov f = 2.0 -3.5), and the enclosing rocks -argillites, siltstones and sandstones are weakly stable (f = 0.8 -2.5).…”

Determining the structure of a laminar detachable current in an open cavity

“…Of applied character, in solving the conjugated problems of hydrodynamics and thermal exchange, is the series of papers that employ a joint solution to the equations of motion and energy [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. If one examines, in the problem on a medium's motion in a cavity, the joint effect of the fields of speed, pressure, and temperature, a given problem then could be applied when the heat exchange is intensified.…”

“…The decomposition of the flow region into zones with upward and downward flows made it possible to formulate and solve analytically an interrelated parabolic system of linear equations based on the classic assumptions by Oberbek-Boussinesq. The thermal modes of deep cavities were simulated in [28].…”