Research On Horizontal Well Technology Of Exploiting Fractured Carbonate Gas Reservoir

On the basis of the research and analysis on the way of exploiting the carbonate reservoirs,for this problem of exploiting the gas field Ⅰ in the Central Tarim with horizontal well,carry on a reseach from these aspects of geology,drilling,well completion,production and economy:(1)Through the research on the geological characteristics of the gas field Ⅰ in the Central Tarim,set up a model as a instance to simulate the different effects between the vertical well and horizontal well on exploitation of the carbonate reservoirs in the Central Tarim;The coMParative analysis shows that when using horizontal well,in the initial production period,the production pressure is small,the anhydrous and stable production time is long,so that the eventual recovery factor is high to prove that it is fit to use horizontal well to exploring the carbonate reservoirs in the Central Tarim.(2)On the basis of the accurate calculation of the ring compressed consumption,the text has given a method to improve the theory of designing the hydraulic parameters in the horizontal wells and assess the ability of horizontal wellbore’s hydraulic extension of the wells in gas field Ⅰ in the Central Tarim.The research has proved that ①in the horizontal well,the ring compressed consumption gradient become bigger and bigger as the density of drilling fluid grows and it is possible to use the upper limit of the safe density window to ensure the safety of the horizontal wellbore’s hydraulic extension.②the total ring compressed consumption grows as the horizontal distance grows and at the same length of the horizontal section as the height of cutting bed.③the displacement greatly effects the length of horizontal wellbore’s hydraulic extension and the length become longer swiftly as the displacement become bigger.(3)These questions of geological features and difficulties in completion in the gas field Ⅰ in the Central Tarim have been analyzed.On these basis,the suitability of completion has been researched.The results show that when the horizontal wellbores are in a condition of normal production,the reservoir did not produce sand.The mode of completion in the upper Ordovician should be decided by production pressure and acidification.The openhole completion can be used in 26 and 62 well area.It is suggested that a method to complete must support the borehole wall.And the bolehole is so stable in Ordovician hawk mountain group that the openhole completion can be used.(4)Fractured carbonate gas reservoir is Equivalent to continuous medium in the far zone from borehole,in the near zone of borehole,Fracture must be considered.we build flow model in porous media in Fractured carbonate gas reservoir.according to small element method,conservation of mass and law of conservation of momentum,the dissertation deduced three horizontal wellbore pressure model of the intersection of horizontal wellbore and fractures,then,the dissertation builds the steady-state coupled model gas reservoir and wellbore between The seepage of gas reservoir and wellbore flow and solved it.we researched how fracture density and horizontal wellbore length affect on productivity of fractured gas reservoir.We can draw a conclusion that gas rate increases while the fracture density increases,but the rate growth become smaller and smaller.The gas rate of horizontal wells first increases as horizontal wellbore length increases,but when horizontal wellbore length is bigger than 900m,the gas rate nearly maintain constant.(5)The dissertation analyzed the horizontal well economic evaluation method and built economic benefits coMParison model between horizontal wells to vertical wells and the single well economic evaluation model of horizontal well,and researched the relationships between horizontal well development total profit and development time,and between the maximum net profit and the length of horizontal well.We found that maximum net profit increases first and then decreases as the horizontal well was producing;therefore the well has an optimal production time.We also found that the maximum net profit increases first and then decreases as horizontal wellhole extended,therefore there was an optimal horizontal wellhole length.It provided theoretical guidance to optimize development time and reasonable length of horizontal wellbore.Research findings are important to guide development of fractured gas reservoir,enhance recovery of the fractured oil&gas reservoir economic benefits.