Experimental Study On Seepage Characteristics Of Porous Media Based On Transient Pressure Pulse Method

Natural gas hydrate is considered to be one of the most important potential clean energy sources in the 21 st century because of its large reserves,wide distribution and high energy density.The permeability characteristics of hydrate reservoirs are important parameters to judge the feasibility of commercial exploitation.The progress of experimental study on seepage characteristics of hydrate was studied,and the existing shortcomings were summarized.The basic principle of the transient pressure pulse method and its application status were analyzed.The feasibility of the transient pressure pulse method to the experimental study on the seepage characteristics of the hydrate was analyzed and discussed.Then the hydrate saturation measurement system based on the time domain reflection technique and the experimental system which is suitable for measuring permeability under a certain condition based on the principle and solution of transient pressure pulse method,were established to study the effect of hydrate contained in porous medium on permeability.Several experiments were carried out to calibrate the domain reflection probe,test the permeability with different saturation of carbon dioxide hydrate in the porous medium and the permeability of sediments from Shenhu area,South China Sea.The results show that the permeability decreases exponentially with the increase of carbon dioxide hydrate saturation in the porous media.By comparing the permeability model results with the experimental result,it is found that the carbon dioxide hydrate that grew under the experimental condition are close to the capillary central model of the parallel-capillary model,the state of hydrate in the porous medium is dominated by suspension mode and contact mode.The result of transient pressure pulse method is very close to that of the constant current method.Compared with the permeability measurement experiment conducted by the traditional steady state method,transient pressure pulse method has higher measurement accuracy,shorter time-consuming,lower perturbation and good adaptability.The preparation method of the remodeling used in this paper has some perturbation to the internal structure of the sample,so that its permeability measurement is slightly lower than that of the South China Sea.Under the same effective confining pressure,different pore pressure state,the measurements of sediment permeability are similar.The main contribution of this paper is to design an experimental device of sediment permeability measurement based on transient pressure pulsed method,measure the permeability of hydrate-bearing sediments,verify the relationship between hydrate saturation and permeability,measure the permeability of sediments from Shenhu area,South China Sea.Which is of reference value for reservoir evaluation,production capacity calculation and industrial extraction scheme for hydrate exploitation.