Conceptual model of fluid recovery from the gas well bottom-hole

Abstract

The gas wells operation can be accompanied by the liquid phase condensation in the bottom-hole formation zone and in the tubing. With increase in the condensate amount, the rate of gas flow into the wellbore from the bottom-hole formation zone decreases and, as a consequence, its ability to transfer fluid particles from the bottom-hole to the wellhead is lost. This leads to the accumulation of fluid in the wellbore and, accordingly, to the decrease in draw-down pressure, which, in turn, leads to a drop in the production potential of gas wells. The aim of this paper is to make a conceptual study of the way to prevent the well self-kill (self-controlled well killing) process, which occurs as a result of condensation and accumulation of fluid in the wellbore and at the well bottom-hole. The method is based on the natural process - the manifestation of the effect of capillary rise of the fluid column in thin tubes. In the course of the work, various methods of the gas wells operation are analyzed, preventing condensate separation, as well as technologies for recovery of already accumulated fluid at the well bottom-hole. The mechanism of water rise by surface tension forces in capillary tubes of various configurations has been investigated. The features of multiphase flow in a vertical pipe have been considered. A series of calculations were carried out to determine the gas flow rate through the wellbore with different ratio of tubing string diameters. On the basis of the comprehensive consideration of the gas wells operation issues, the conceptual model of liquid removal from the bottom-hole using the capillary tubes located in concentric tubing is proposed.