| The SDN gas reservoir is one of fluvial facies gas reservoir with low permeability,low pressure tight sand.The reservoir has low porosity and low permeability,low abundance,large area,low yield,deep burial,unconventional concealed features,which is the main block in the field of future production.Since 2009,the gas reservoir has experienced three stages of cluster well evaluation,horizontal well production test and the overall construction of horizontal well.The fractured horizontal well is widely used in the development of the gas reservoir.Due to flow characteristic of fracturing horizontal well is different from the common horizontal wells,it is very important to research the seepage law of fractured horizontal well and apply it to gas reservoir engineering and dynamic analysis.This paper takes fractured horizontal well of SDN gas reservoir as the main research object.Based on reservoir geology characteristics and production dynamic characteristics,this paper synthetically utilize the gas reservoir stable or unstable seepage theory,gas reservoir engineering theory,Gas recovery engineering theory,mathematical physics method,complex seepage method to analyze deliverability,seepage and pressure dynamic characteristics,single well controlled reserves and rate maintenance capability,reasonable working system.The main results are as follows:1.According to the horizontal well with multiple fracturing fractures in SDN gas reservoir,the flow mechanism is divided into the flow of layer to the fracture,the flow of the fracture to the horizontal wellbore and the flow of the toe end to the end of the shaft.Based on the complex potential theory,pressure drop superposition principle and momentum theory,this paper have presented the productivity equation of horizontal wells with multiple fractures is established and principle and Calculation method of total output of gas well.The study shows that the thickness of gas layers,the length of horizontal section,the length of fracture,the number of fracture and the flow conductivity are the main factors that affect the productivity of fractured horizontal wells.2.This paper has established horizontal wellbore flow model in SDN gas reservoir,the model has researched the relationship between the vertical well section,deviation,horizontal well section and length of each section.The deviation pressure drop loss decline to a great extent,however the vertical pressure loss is relatively low.Compared 81%down to above 15%,the loss of pressure drop is very small from the end to toe in horizontal section.Wellbore pressure lost increase with the increasing daily gas productivity and tube diameter.3.According to the research of homogeneous low permeability gas reservoir fractured horizontal flow and well testing trait,the dynamic pressure curve appears pure well reservoir effect,early crack liner flow,early fracture pseudo radial flow system liner flow and system radial flow 5 stages in turn.The start-up pressure gradient mainly effect the upward amplitude of system liner radial flow differential pressure curve(when it comes to 0,the differential pressure shows a horizontal line in value 0.5).The bigger of well storage coefficient and the longer of pure well reservoir,the later of liner fracture flow is.With the skin factor increased,the peak of differential pressure increased at the early stage.4.Based on the mathematical model solution,the paper established a seepage flow model in fractured horizontal wells with low permeability total porosity gas reservoirs and drawn a typical curve reflecting the seepage and pressure characteristics.a typical curve is divided into seven stages:pure well reservoir effect,early crack linear flow,early fracture quasi radial flow,formation linear flow,formation radial flow,matrix system quasi steady flow and late quasi radial flow.The studies on the influence factors of seepage and pressure dynamics have shown that,the starting pressure gradient mainly affects upward amplitude of pressure derivative curve in pseudo radial flow stage of later total system,and when there is no starting pressure gradient,the pressure derivative is a horizontal line of 0.5.The smaller the elastic storage capacity ratio,the lower the concave depth of the pressure derivative of the quasi steady flow.The greater the flow coefficient,the shorter the duration of at the stage of formation radial flow,the earlier the emergence of quasi steady state flow and concave downward of the pressure derivative curve.5.Controlled reserves of 8 fractured horizontal wells in SDN gas reservoir was reached by flow material balance,history fitting and trial and error method.And calculation method of formation pressure at the end of stable production was built.Based on these,theoretical method for stable production period of horizontal wells was advanced.6.The ellipsoid model predict critical carrying liquid flow volume of the vertical section,the Fiedler shape function and deviated wells ellipsoid model derive critical carrying liquid flow volume of the deviation,the K-H fluctuation theory predict critical carrying liquid flow volume of horizontal well of horizontal well section.The writer set up the vertical well section,deviation,horizontal well section vertical well section,inclined wells,horizontal section of the horizontal well critical carrying liquid flow prediction model,on this basis,this paper utilizes empirical method,gas productivity index method and critical with fluid flow method for determining reasonable working system of 8 fractured wells in SDN air reservoir.7.In consideration of influence about actuating pressure gradient and moving boundary characteristic,the paper The analysis respectively established unstable production decline analytical model on the assumption that the outer boundary is infinite or the circle is closed or the circle is fixed pressure.On the basis of the respective solutions,the curve of production decline and cumulative production are drawn.The research shows that the flow boundary characteristics,the starting pressure gradient,the size and the condition of the outer boundary,the horizontal section length is the main factor that affects the typical curve.In a certain extent,this paper enriched the basic theory and gas reservoir engineering method of fracturing horizontal well,which provide some theoretical guidance for the reasonable and effective development of tight gas reservoir. |
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