Study On Horizontal Well Productivity Influence Factors Of Low Permeability Gas Reservoir SH

SH gas reservoir is located in Ordos Basin,which has low reservoir permeability and belongs to the low permeability gas reservoir.It is the largest potential resources of the gas field,the evaluation of whose proved unproducing reserves is about 352.51×10~8m~3,accounted for 31.17%of the unused reserves.Although the horizontal well development technology has been successfully applied into the gas field,some puzzling phenomenon also exist.For example,statistics show that the productivity of vertical well in SH gas reservoir is 3.22×104m~3/d,but the horizontal well productivity of SH gas reservoir is 4.56×104m~3/d.Based on the practical problems encountered in the development of low permeability tight gas reservoirs in SH,and on the basis of a large number of domestic and foreign literature research,the influence factors of horizontal well productivity in SH gas reservoir are analyzed,and the following work is completed:1?The reservoir type of SH is analyzed.And the reservoir characteristics,such as porosity,rock mineral type,clay composition are identified.2?Conventional five sensitivity experiments are applied on the SH gas reservoir.The experiment results show that SH gas reservoir has weak velocity sensitivity,salt sensitivity,alkali sensitivity and medium weak acid sensitivity.Therefore,in the process of gas reservoir production,the change of gas flow rate and the change of reservoir fluid salinity have little effect on gas reservoir development.However,the change of pH value has some influence on the development of gas reservoir.3?The stress sensitivity experiment is also applied on SH gas reservoir.Research shows that SH gas reservoirs has medium weak stress sensitivity.Therefore,in the process of gas reservoir production,the stress sensitivity has a certain degree of influence on the development of gas reservoir.4?gas water two phase flow experiment is applied on SH gas reservoir.Result indicates that the permeability is severely damaged after water block,and most of the damage rate is above 0.5,which is especially serious on low permeability cores.After flooding,the saturation is more than 50%,and the external fluid is trapped in the rock.5?Through numerical simulation,it can be concluded that horizontal section length,fracture half-length and fracture conductivity can affect the horizontal well productivity of SH gas reservoir.6?Based on the above experiments and numerical simulation,the main influence factors of horizontal well productivity in SH gas reservoir are determined.Through above research,the characteristics of SH gas reservoir and the mechanism of reservoir seepage are studied.And the main influence factors that affect the productivity of horizontal well in low permeability gas reservoir of SH are defined.Therefore,the corresponding countermeasures and suggestions to improve the development effect of horizontal well in SH gas reservoir are put forward.Countermeasures and suggestions are included in the following:?In view of the fact that the horizontal section length,the number of fractured sections,and the high fracture rate of the pressure fracture cause the low level of SH gas reservoir,the horizontal well productivity can be improved by increasing the length of the horizontal section and increasing the fracturing scale;?The horizontal well productivity decreased by water block and mud filtration in the process of drilling,can be enhanced by reservoir protection.The research provides technical basis for the economic and effective development of SH gas reservoir.