| China’s sandstone thermal reservoirs are large in scale and widely distributed.However,it faces the problem of difficult tailwater recharge in the process of recharging water for heat development.The suspended particles in the recharge fluid accumulate at the seepage channels and form blockages near the wellbore,reducing the permeability of the near well zone and eventually causing the recharge volume of the recharge well to drop or the recharge pressure to rise.Therefore,an efficient,low-cost unblocking and injection technology that does not pollute the reservoirs is needed.Based on the reservoirs characteristics of sandstone thermal reservoirs and the mechanism of rotary jet unblocking,this thesis proposed rotary jet unblocking technology for low efficiency wells in sandstone thermal reservoirs.During the process of unblocking operation,after the rotary jet unblocking tool is lowered through the tubing,a high pressure rotary jet is generated to flush the wellbore directly,and the tool is driven up and down through the tubing to flush and unblock the blocked section of the recharge well in all directions.This method has the characteristics of no pollution to the formation,low cost and high applicability,and is expected to solve the problem of difficult recharge of low efficiency wells in sandstone thermal reservoirs.In order to study the unblocking effect of rotary jet for sandstone thermal reservoirs,this thesis adopted a combination of theoretical analysis and experimental studies to carry out the research.Firstly,the numerical models of the rotary jet flow field in the wellbore and the particle distribution model in the wellbore were established by ANSYS Fluent software,so as to study the influence law of spray distance and displacement on the rotary jet flow field and the particle transport and distribution during the jet flow.In the terms of ground experiments,this thesis carried out experiments on jet pressure wave transfer efficiency,screen tube descaling experiments under different kinds of jets and jet flushing experiments on the sandstone of the Guantao Formation.These experiments were carried out to study the effect of screen tube descaling and flushing of sandstone by high pressure jets.Based on the numerical simulation and ground experimental conclusions,this thesis designed a rotary jet tool applicable to unblocking and descaling of low efficiency wells in sandstone thermal reservoirs,prepared a rotary jet unblocking construction plan for low efficiency wells in sandstone thermal reservoirs,carried out rotary jet unblocking operation for two well times,and compared the well conditions and recharge volume of recharge wells before and after the operation.The research results showed that the high pressure jet had an effective effect of unblocking and descaling the screen tube,and it had a certain effect of erosion and crushing the sandstone outside the screen tube.Based on the conclusions of numerical simulations and ground experiments,this thesis proposed construction suggestions in sandstone thermal reservoirs unblocking operations.After the rotary jet unblocking operations,the recharge volume levels and well conditions of two sandstone thermal storage inefficient wells were effectively improved.This thesis provided a theoretical basis and experimental reference based on rotary jet technology for unblocking and increasing seepage in sandstone thermal reservoirs,and provided some reference and guidance for the application and promotion of rotary jet unblocking technology for unblocking and increasing seepage in low efficiency wells in sandstone thermal reservoirs. |
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