Abnormal liquid loading in gas wells of the Samandepe Gasfield in Turkmenistan and countermeasures

Abstract

With complicated formation mechanisms, liquid loading in gas wells during gasfield development may significantly affect the productivity of gas wells and the ultimate recovery rate. Dynamic monitoring data of the Samandepe Gasfield in Turkmenistan shows that liquid loading can be found extensively in gas wells. Their formation mechanisms and negative impacts on gasfield development severely restrict the productivity enhancement of this gasfield. With their origins taken into consideration, liquid loads in gas wells were classified into three types: formation water, condensed liquid, and external liquid. By using the hydrostatic pressure gradient method and through PLT monitoring, properties of liquid loads in the Samandepe Gasfield were determined. In addition, formation mechanisms related to liquid loading in gas wells were obtained through analyses of critical fluid-carrying capacities and by using gas-reservoir production data. The following findings were obtained. Liquid loading was commonly found in this gas well with majority of reservoir formations in lower well intervals flooded. However, the formation mechanisms for these liquid loads are different from those of other gasfields. Due to long-term shut-down of gas wells, killing fluids precipitated and pores in lower reservoir formations were plugged. As a result, natural gas had no access to boreholes, killing fluids were impossibly carried out of the borehole. Instead, the killing fluid was detained at the bottomhole to generate liquid load and eliminate the possibility of formation water coning. Moreover, since the gasfield was dominated by block reservoirs with favorable physical properties and connectivity, impacts of liquid load on gasfield development were insignificant. Thus, to enhance the recovery rate of the Samandepe Gasfield significantly, it is necessary to expand the gasfield development scale and strengthen the development of marginal gas reservoirs.