Liquid loading in gas wells: Experimental investigation of back pressure effects on the near-wellbore reservoir

Abstract

Liquid loading is a major operational constraint in mature gas fields around the world. It manifests itself as an increasing back pressure on the reservoir due to a rising liquid column in the well, which initially decreases deliverability, then ultimately causes the gas well to cease production. Theoretically, every gas well will experience this debilitating phenomenon in the latter stages of its producing life.In this paper, both laboratory experiments and numerical simulations are presented to shed more light on the physical process of liquid loading, with a focus on reservoir responses. On the one hand, core-flooding experimental setups of different scales were designed and constructed to investigate back pressure effects on transient flow through the near-wellbore region of the reservoir. On the other hand, the modelling of a gas well undergoing controlled flow and shut-in cycles was performed to validate core-scale observations at reservoir scale, using commercial integrated numerical software that connects a transient wellbore model to a transient reservoir model. The simulated transient characteristics of short-term downhole dynamics (e.g. liquid re-injection and co-current/counter-current flows) supported the Ushaped concept observed in the experiments.The detected temporal distribution of pore fluid pressure within the reservoir medium itself (referred to as the U-shaped pressure profile) was observed both experimentally at the corescale and numerically at the reservoir-scale. This pressure distribution can be used to explain re-injection of the denser phases into the near-wellbore region of the reservoir.

Study of the Performance of a New Kind of Downhole Gas-Liquid Separation with High Gas Content

“…The gas-liquid separation performance can be inferred from the experimental data by Eqs. (6) and (7). The values of the gas-liquid separation experimental results obtained when gravity plays a major role are compared with those from the inferred model and shown in Figure 6.…”

“…These liquids accumulate over a period of time in the bottom hole to form a fluid column, which causes additional hydrostatic pressure in the reservoir. Under this condition, the gas well energy flow declines [6][7][8][9]. Eventually, the accumulated fluid column in the wellbore will cause the gas well to stop production [10][11][12][13].…”