HYDRAULIC CALCULATION OF FLUSHING FLOW PARAMETERS DURING SWABBING OF WATER INTAKE WELLS

Abstract

The paper presents a methodology for the hydraulic calculation of flushing flow parameters during the development and yield stimulation of water intake wells by swabbing. A computational model for the movement of seepage flows in the near-screen zone of the well during the working stroke of the swab has been developed. Flow rate and head balance equations for the wellbore and gravel pack have been formulated and solved, taking into account the bypass flow rate under the swab, water inflow from the formation through the gravel pack, formation intake capacity, fluid level rise in the tubing above the screen, and pressure drop under the swab. Analytical relationships have been derived to determine the rise of the water piezometric level in the tubing above the screen relative to the static level, and the pressure drop under the swab during its upward movement. This allows for calculating the flushing velocity values in the gravel pack depending on the swab position in the screen, its movement speed, the well's geometric parameters and hydraulic characteristics, as well as calculating the technological parameters of the screen treatment depending on the degree of its clogging.

A calculation example is provided. It is shown that the flushing velocity in the pores of the gravel pack depends on the position of the moving swab in the screen. The highest velocities are characteristic of the lower part of the screen, where the maximum drawdown is initially formed under the swab at the beginning of the upstroke. Subsequently, as the swab lift height in the screen increases, the flushing velocity decreases following an exponential relationship.

It has been established that the absolute values of flushing velocities increase with the depth of water above the top of the screen and the swab movement speed. Therefore, when treating shallow wells, flushing velocities can be increased by raising the swab lifting speed.