Modeling of drilling water supply wells with airlift reverse flush agent circulation

Abstract

Purpose. Determination of the influence of mining and geological conditions of drilling hydrogeological wells with backwash on the technological parameters of the airlift method of cleaning it from drilled rock and the properties of the ascending flow of aerated washing liquids. Methodology. The tasks were solved by a complex research method, including analysis and generalization of literary and patent sources, analytical, experimental studies, using computer and mathematical modeling methods. Findings. An algorithm for the functioning of the airlift circulation method during rotary drilling with backwash has been developed. The algorithm takes into account: hydrostatic and hydrodynamic pressures, and the effect on them of the rate of drilling of the well; the effect of the sludge content in the upstream. The effective values of the airflow rate, the density of the water-air mixture and the velocity of its upward flow are established. A method for estimating the effective values of technological parameters and their changes in the upward flow of the mixture is proposed. A model has been developed that allows analyzing the dependences of the air flow rate, the density of the mixture and the rate of its ascent on the parameters of the well being drilled. The model is applied to typical drilling conditions of a large-diameter water intake well at the Samskoye groundwater deposit on the Mangystau peninsula. Originality. A mathematical algorithm has been developed for the functioning of the airlift backwash method when drilling large-diameter water intake wells. The method is based on the analysis of the pressure balance in the descending and ascending flows of the washing agent. For the case of backwash, a formula for estimating the content of sludge in it was obtained. A method has been developed for determining the average effective density of the mixture in terms of the height of the well, as well as the air content in it. Based on the average effective values, a method is proposed for estimating changes in the density of the mixture, its flow rate and velocity along the upward flow. Practical value. The proposed algorithm is the basis of a computer model that allows you to determine the dependences of the values of the density of the mixture, the content of air and sludge in it and the rate of ascent, from the depth of the well, the depth of the mixer descent, the speed of deepening, the specified velocity of the upward fluid flow, as well as the diameters of the well and drill pipes. Specific modeling results have been obtained in relation to the Samskoye groundwater deposit of the Mangystau peninsula.