Study On Deliverabuity Evaluation And Transient Seepage Theory Of Horizontal Wells In Water Drive Gas Reservoirs

The object of the study is horizontal well in the water drive gas reservoirs, this paper presents a study of the water drive gas reservoirs types, deliverability evaluation theory of horizontal wells in water drive gas reservoirs and the transient seepage theory of horizontal well in edge water and bottom water gas reservoirs.The water drive gas reservoirs are classified by the gas-water distribution, the reservoir pore space types, the drive index and the replacement coefficient of water invasion. In the study on deliverability evaluation theory of horizontal wells in water drive gas reservoirs, this paper firstly studies the deliverability evaluation theory of horizontal wells in dry gas reservoirs, on the basis of the research above, combining with the gas-water two phase seepage theory, this paper establishes a new method for determining horizontal gas well deliverability after water yielding. The deliverability of horizontal well which produces gas and water simultaneously is evaluated by analytical method and semi-analytical method, additionally, the sensitivity analysis of influence factors which affect the deliverability of horizontal well which produces gas and water simultaneously is also obtained in this process. While considering the effect of changing wellbore storage and skin effect, this paper establishes the mathematical models of well test analysis for horizontal well in edge water and bottom water gas reservoirs. The mathematical models are solved by orthogonal transformation, Laplace transformation and Fourier transformation. On the basis of obtaining the Laplace solutions of the mathematical models, the well test analysis type curves of the horizontal gas well in edge water and bottom water gas reservoirs are plotted with Stehfest inversion algorithm, additionally, the sensitivity analysis curves of influence factors which affect the well test analysis type curves are also obtained. The principal results are as follows:(1) On the basis of the thought of deducing the Joshi deliverability formula, combining with the gas-water two-phase seepage theory and considering the influence of the skin effect, the anisotropism and the high speed non-Darcy seepage, this paper establishes the binomial deliverability equation of the horizontal well with gas-water two-phase pseudopresure form.(2) A new thought of calculating the gas-water two-phase pseudopressure is proposed in this paper when the gas-water mass flow rate ratio or the volume rate ration is no longer a constant in the transient seepage.(3) Based on the analysis of deliverability test in the dry gas well with the form of single phase pseudopressure and square pressure form, the two IPR curves show a good consistency. Based on the analysis of deliverability test in the horizontal well which produces gas and water simultaneously with the form of single phase pseudo pressure and square pressure form, the calculated absolute open flow potential are smaller than the true value.(4) By using non-stabilized well test analysis result during the initial process when horizontal gas well does not produce water, combining with the current production performance data and pressure data, this paper establishes a new method for determining horizontal gas well deliverability after water yielding.(5) Based on the thought of the semi-analytical method, coupling the gas-water two phase seepage in the formation and the horizontal wellbore, a method of analyzing the deliverability under the consideration of the wellbore pressure drop in the horizontal well which produces gas and water simultaneously is given in this paper, additionally, the sensitivity analysis curves of influence factors which affect the flux in the radial direction in the horizontal wellbore is also obtained in this process.(6) While considering the effect of changing wellbore storage and skin effect, the pressure behavior of the horizontal gas well in edge water gas reservoir with infinite outer boundary in horizontal direction can be divided into nine periods. The well test analysis type curves of the horizontal gas well in edge water gas reservoir with infinite, closed and constant pressure outer boundary are also obtained, additionally, the sensitivity analysis curves of influence factors which affect the well test analysis type curves are also obtained.(7) While considering the effect of changing wellbore storage and skin effect, the pressure behavior of the horizontal gas well in bottom water gas reservoir with infinite outer boundary in horizontal direction can be divided into seven periods. The well test analysis type curves of the horizontal gas well in bottom water gas reservoir with infinite, closed and constant pressure outer boundary are also obtained, additionally, the sensitivity analysis curves of influence factors which affect the well test analysis type curves are also obtained.