Bulat A.F., Slashchov І.M., Slashchovа O.A., Makeiev S.Yu., Ryzhov H.O. Improvement of gas field efficiency through the controlling of rock stress-strain state in the bore-hole working area

Details
Parent Category: Geo-Technical Mechanics, 2019
Category: Geo-Technical Mechanics, 2019, № 144

Geoteh. meh. 2019, 144, 4-19

https://doi.org/10.15407/geotm2019.144.004

Improvement of gas field efficiency through the controlling of rock stress-strain state in the bore-hole working area

1Bulat A.F., 1Slashchov І.M.,1Slashchovа O.A., 1Makeiev S.Yu., 1Ryzhov H.O.

1Institute of Geotechnical Mechanics named by N. Poljakov NAS of Ukraine

UDC 622.831.31

Language: Ukrainian

Abstract.

Gas migration in the rock massif is explained by the presence of interconnected pores, microcracks and cracks; therefore, rock stresses always play a decisive role as their changes can increase or reduce the rock permeability. Besides, such phenomenon as compaction, i.e. mechanical subsidence of the formation as a result of decreased rock pressure, may occur, which stops the bore-hole flow rates requiring urgent measures for increasing permeability of the rock massif. The bore-hole flow rate decrease is accompanied by great expenditures. Therefore, control of the rock massif stress-strain state and process of crack formation around the working area of the bore-holes with the help of the justified shape of the bore-hole surface is a pressing scientific task. Purpose of the research: to increase the gas fields efficiency by justifying design parameters for the working area of the production bore-hole. Research methods: systematization of scientific publications and experimental data, mathematical modeling by finite element method and initial stresses method, methods of engineering design of three-dimensional objects.

The geofiltration model of free gas transit into production bore-holes was further developed, which now differs by considering patterns of changes in the stress-strain state and volumes of the porous fractured space around of the bore-hole working area of arbitrary configuration. It is for the first time, when ratio is proposed for estimating supposed volumetric flow rates of gas entering the bore-hole on the base of finite element method used for evaluating increment of the ball part of the strain tensor and volumes of the destroyed elements in the geomechanical model. Interrelations between the established geomechanical parameters of the rocks destruction (i.e. pressure gradients, extent of inelastic deformation zones, fracture porosity and opening of fracture systems) around the bore-hole working area of arbitrary configuration and productivity of the gas bore-hole were determined.

With the help of different profiling methods, mathematical model of the bore-hole working area was created without profiling its surface. It is established that the choice of a rational configuration for the bore-hole working area allows, firstly, to intensify process of the rocks cracking, which significantly increases their permeability and flow rate, and secondly, to shift zone with increased stresses from the bore-hole walls deep into the rock mass and to increase their stability. Comparison of stresses distributions made it possible to identify advantages and disadvantages of these technologies, since high concentrations of stresses during cylinder cutting and more uniform field of stresses in case of a screw thread can differently effect the rocks and, accordingly, differently impact on the processes of their destruction. It is shown that, by changing shape of the gas bore-hole working area, it is possible to control stress-strain state of the surrounding rocks, increase the rocks fracturing and activate the gas flow. New devices for profiling and forming surface of the bore-hole working areas of arbitrary configuration were designed.

Keywords:

gas field, bore-hole working area, modeling of the rock stress-strain state, geofiltration methods, methods for activating the bore-hole flow rate

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About the authors:

Bulat Anatolii Fedorovych, Academician of the National Academy of Science of Ukraine, Doctor of Technical Sciences (D. Sc), Professor, Director of the Institute, Institute of Geotechnical Mechanics named by N. Poljakov NAS of Ukraine (IGTM, NASU), Dnipro, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it.

Slashchov Ihor Mykolaiovych, Candidate of Technical Sciences (Ph.D), Senior Researcher, Senior Researcher in Department of Mineral Mining at Great Depths, Institute of Geotechnical Mechanics named by N. Poljakov NAS of Ukraine (IGTM, NASU), Dnipro, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it.

Slashchovа Olena Anatoliyivna, Candidate of Technical Sciences (Ph.D), Senior Researcher, Senior Researcher in Department of Mineral Mining at Great Depths, Institute of Geotechnical Mechanics named by N. Poljakov NAS of Ukraine (IGTM, NASU), Dnepr, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it.

Makeiev Serhii Yuriiovych, Candidate of Technical Sciences (Ph.D), Senior Researcher, Senior Researcher in Department of Mineral Mining at Great Depths, Institute of Geotechnical Mechanics named by N. Poljakov NAS of Ukraine (IGTM, NASU), Dnipro, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it.

Ryzhov Hennadii Oleksandrovych, Junior Researcher in Department of Mineral Mining at Great Depths, Institute of Geotechnical Mechanics named by N. Poljakov NAS of Ukraine (IGTM, NASU), Dnipro, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it.

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