GRAVITATIONAL INSTABILITY OF GAS-LIQUID FLOW AT DEVELOPMENT OF GEOTHERMAL FIELDS

Abstract

The relevance of the study is caused by the search for ways to increase the efficiency of the development of geothermal fields on the basis of ensuring the stable operation of the system for the production and transportation of steam-water fluid. Purpose: to determine the nature and conditions for the development of instability of the steam-water flow in production wells and transport pipelines during the development of geothermal fields. Methods: application of the laws of classical dynamics to an element of a moving medium, taking into account the features of a gas-liquid flow; analysis of the conditions for the emergence and development of gravitational instability of the steam-water flow during the development of geothermal fields. Results. One of the mechanisms related to the macroscopic temporal instability of a gas-liquid flow is described, and the features of its implementation in systems for the production and transportation of heat agent during the development of geothermal fields are considered. The emergence of instability is associated with a spontaneous change in the momentum of the flow, expressed in a change in the mass flow rate, its development is associated with the presence of conditions in which a change in the momentum of a moving medium leads to similar in sign change of moving force. It is noted that the Ledinegg instability is one of the manifestations of this mechanism, which can also be realized in connection with a change in the gravitational force acting on the flow, due to a change in the density of the gas-liquid mixture with a change in flow rate. The features of the implementation of this mechanism in a steam-water well during the development of geothermal fields are considered and its connection with the completeness of practically determined productivity curves of wells is established. A condition for the manifestation of inversion of productivity curves is formulated. Conclusion. The gravitational instability of the flow in pipes is caused by a spontaneous change in the momentum of the flow and is associated with the presence of conditions in which a change in the momentum of the moving medium leads to a change in the force that causes the movement, which enhances the change in the momentum. In this case, the effective development of this instability in ascending flows is carried out upstream, in descending flows – downstream.

Keywords

• geothermal field
• gas-liquid flow
• production well
• steam-water mixture
• gravitational instability
• productivity curve