EFFECT OF WELLBORE GAS-LIQUID TWO-PHASE FLOWON WELL TEST OF FRACTURED HORIZONTAL WELLS IN TIGHT GAS RESERVOIR

Multistage fracturing horizontal well technology is one of the most commonly used methods for the exploitation of tight gas.Well testing of fractured horizontal wells in the tight gas reservoir is often associated with water rate.Wellbore gas-liquid two-phase flow will increase the flow resistance of wellbore fluid, which increases the effect of wellbore fluid flow on the well test interpretation.In order to understand the effect of wellbore gas-liquid two-phase flow on well test and improve the precision of well test interpretation of fractured horizontal wells producing water in tight gas reservoir, this paper presents a coupling well test model including gas-liquid two-phase flow in wellbore and seepage flow in tight reservoir.Well test type curves, pressure fields and fracture flow rate of fractured horizontal wells considering wellbore gas-liquid two-phase flow are obtained by using numerical solving method.The results show that the gas-liquid two-phase flow will increase the pressure and pressure derivative value in the well test type curves.It also will cause that pressure diffusion near the window point is faster than that away from the window point and flow rate of fractures near the window point is greater than that of fractures away from the window point.Hence, it can be concluded that the results interpreted by well test analysis may have large error without consideration for the wellbore gas-liquid two-phase flow in the fractured horizontal well test model.The assumption that the horizontal wellbore has infinite conductivity will cause the skin factor obtained by curve matching to be too large.The pressure of the test point considered as the pressure of window point will cause the initial formation pressure obtained by matching to be too small.The well test model of fractured horizontal wells considering wellbore two-phase flow proposed in this paper will provide an important technical support to interpret the well test data of tight gas wells producing water correctly.