Percolation Experiment And Productivity Research On DH Gas Reservoir

The low-permeability tight gas reservoirs have a large proportion of reserves with the characteristics of low porosity,low permeability,low production,and high degree of difficulty to develop.The results of this paper are part of the National Major Research Project for Oil and Gas.It mainly studied the characteristics of seepage in the development of thick-bed,low-permeability and tight edge-water gas reservoirs.Based on this,the effects of seepage characteristics on gas well development and initial productivity were studied.This paper mainly used the experimental method to study the characteristics of seepage.We adopted the standard analytical method of core to study the ratio of vertical to horizontal permeability;the bubble method were adopted to carry out the test of the initial pressure gradient of 20 samples,and the experiments of actual formation conditions(at the constant confining pressure of 80 MPa,the changeable internal pressure,and formation temperature of 158?)were adopted to carry out the stress sensitivity test of seven rock specimens.At the same time,in order to analyze the results of the stress-sensitivity test,the centrifugal capillary pressure curve test,the whole rock analysis and the clay analysis experiment were carried out.In order to study the variation law of the original water saturation in the production process of gas wells,the seepage characteristics of gas flooding water under different pressure gradients were studied,and the relative permeability curves of gas flooding water under different pressure gradients of four cores were experimentally tested by standard methods.The patented method(measurement method for high-temperature and high-pressure gas-water permeability curves of formations 201310639669.0)measured the standard phase-permeability curves of 17 rock samples under the high-temperature,high-pressure and normal-temperature,low-pressure.And it compared and analyzed the differences and causes of results between high-temperature,high-pressure test and standard method test.The experimental results were applied to single well numerical simulation of gas wells,and the effects of the phase-infiltration curves and stress sensitivity under different initial pressure gradients,different velocity and different test conditions on gas well production dynamics and initial productivity were studied.After research,we got the following understanding:(1)The ratio of horizontal permeability to vertical permeability of reservoir cores is mainly distributed around 1.5.As the permeability increases,the initial pressure gradient decreases;the irreducible water saturation increasing,the initial pressure gradient increases.(2)For the gas reservoir,the stress sensitivity test shows that the stress-sensitivity is medium;the higher the clay content is,the greater the stress-sensitivity effect will be;(3)The results of relative permeability curves under different pressure gradients show that as the pressure gradient increases,the irreducible water decreases,the flow capacity of water-phase increases,the isotonic point shifts to the right,and the flow range of gas/water-phase becomes larger.(4)Compared with the standard test results of the gas-water seepage under normal-temperature and low-pressure,the gas-water relative permeability curves under high temperature and high pressure have lower irreducible water saturation,higher residual gas saturation,lower efficiency of water flooding gas,and smaller two-phase flooding range.(5)After considering the initial pressure gradient,stress sensitivity,high-temperature and high-pressure seepage,and high-pressure gradient seepage in the gas well dynamic simulation and prediction,the stable production time of the gas well was greatly reduced,the daily gas production and the cumulative gas production were reduced,and the recovery of gas reservoir was also reduced.