Research On Water Blocking Damage Releasing By Borehole Heating Method In Tight Gas Formation

The efficient development of tight gas formation is severely restricted due to water blocking damage during drilling and completion.Reducing the surface tension of working fluids and hydraulic fracturing are applied to deal with the water blocking damage.However,they may result in low efficiency or secondary damages.It is very necessary to propose an efficient and environmentally friendly method for releasing the water blocking damage.In this of view,the possibility of borehole heating to release water blocking damage in tight gas reservoirs is explored,the influence of borehole heating on permeability and mechanical strength of tight sandstone are discussed.The mechanism of borehole heating to release water blocking damage in tight gas reservoir is revealed.The main achievements and conclusions are as follows:(1)Both the experiments and computer simulation indicate that the borehole heating can release the water blocking damage,temperature gradient has a greater impact on permeability near the wellbore within 1.2 meters.The closer to the borehole,the better the heating effect.(2)The threshold temperature of the permeability change of the tight sandstone in this paper is about 490℃ and the permeability will be greatly improved when the threshold is exceeded because tight sandstone microfracture is produced and communicated with each other to form seepage network,afterr cooling,micro cracks will not be completely closed.(3)There is a certain similarity in the change of mechanical properties of tight sandstone samples between real-time high temperature and high temperature cooling.The first 400℃regularity is not obvious,after 400℃ are rapidly deteriorating.Therefore,on the one hand,borehole heating is beneficial to the increase of reservoir permeability,and on the other hand,it will affect the wellbore stability.(4)In order to improve the reservoir permeability better,the heating temperature range can be selected at 490-600℃ and 600℃ is the best,the total heating time can be selected 240 hours,heating mode can be selected by combination of heating and cooling phase.