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CN-121972107-A - Deep well reinjection staged fracturing fluid recovery treatment method

CN121972107ACN 121972107 ACN121972107 ACN 121972107ACN-121972107-A

Abstract

The invention provides a deep well reinjection staged fracturing fluid recovery treatment method which comprises the steps of well shaft pretreatment, adding a formula amount of nano SiO 2 and a cosolvent after heating and pressurizing liquid CO 2 to obtain supercritical CO 2 fluid, carrying out staged displacement on fracturing fluid by using the supercritical CO 2 fluid, extracting fracturing fluid flowback fluid from a well head, carrying out centrifugal separation treatment on the collected fracturing fluid flowback fluid to obtain heavy-phase slurry and light-phase slurry, carrying out sedimentation centrifugal separation on the heavy-phase slurry to obtain a crude proppant, sending the obtained crude proppant into a cleaning kettle to clean to obtain a regenerated proppant, carrying out membrane filtration treatment on the light-phase slurry to obtain a crude fracturing fluid, and carrying out regeneration treatment on the obtained crude fracturing fluid to obtain the regenerated fracturing fluid. The method realizes the ultra-high-efficiency recovery of the fracturing fluid in the technical level, realizes the recycling circulation of waste and the source control of pollution in the environmental level, and finally comprehensively improves the sustainability and the competitiveness of deep well fracturing operation in the economic level.

Inventors

  • Ren Jingxing
  • WANG TIANTIAN
  • XUE JIANKUN
  • ZHANG QUAN
  • GE GUANGRONG

Assignees

  • 中煤科工西安研究院(集团)有限公司

Dates

Publication Date
20260505
Application Date
20260112

Claims (10)

  1. 1. The deep well reinjection staged fracturing fluid recovery treatment method is characterized by comprising the following steps of: Step 1, preprocessing a shaft, namely closing the shaft to react for 2-4 hours after acidic solution is injected into the shaft, pumping nano SiO 2 suspension into the shaft, and closing the shaft for 20-30 minutes; Step 2, preparing supercritical CO 2 fluid, namely heating and pressurizing liquid CO 2 , and then adding nano SiO 2 and cosolvent in the formula amount to obtain supercritical CO 2 fluid; Step 3, using supercritical CO 2 fluid to segment and displace the fracturing fluid injected into the stratum cracks in the earlier stage, so that the fracturing fluid is flowback to a wellhead, and continuously extracting and collecting the flowback fluid at the wellhead; The method specifically comprises the following substeps: step 3.1, injecting supercritical CO 2 fluid into the wellbore in sections to displace the fracturing fluid: Step 3.2, injecting supercritical CO 2 fluid added with proppants into a shaft in stages: step 3.3, pumping supercritical CO 2 fluid, wherein the amount of the pumped fluid is 1.05-1.1 times of the volume of the shaft, and the displacement is 8-10 m < 3 >/min; step 4, performing centrifugal separation treatment on the collected fracturing fluid flowback fluid to obtain heavy-phase slurry and light-phase slurry; And 5, carrying out sedimentation centrifugal separation on heavy-phase slurry to obtain a crude propping agent, sending the obtained crude propping agent into a cleaning kettle for cleaning to obtain a regenerated propping agent, carrying out membrane filtration treatment on light-phase slurry to obtain a crude fracturing fluid, and carrying out regeneration treatment on the obtained crude fracturing fluid to obtain the regenerated fracturing fluid.
  2. 2. The deep well reinjection staged fracturing fluid recovery treatment method of claim 1, wherein in the step 1, the acid solution comprises the following raw material components, by mass, 5-10% of EDTA, 3-8% of citric acid and 82-92% of water, wherein the mass percentages of the components are 100% in total; the injection rate of the acid solution is 0.3-0.5 m 3 /min.
  3. 3. The deep well reinjection staged fracturing fluid recovery processing method of claim 1, wherein in the step 2, liquid CO 2 is heated and pressurized to a temperature of more than 31.1 ℃ and a pressure of more than 7.38MPa, the addition amount of nano SiO 2 is 1-5wt% of the total mass of supercritical CO 2 fluid, the particle size of nano SiO 2 is 10-50 nm, the cosolvent is selected from any one of kerosene and alcohol, and the addition amount of the cosolvent is 3-15wt% of the total mass of supercritical CO 2 fluid.
  4. 4. The deep well reinjection staged fracturing fluid recovery processing method of claim 1, wherein the step 3.1 specifically comprises: injecting supercritical CO 2 fluid into the shaft at a displacement of 1-2 m3/min for 10-20 min; Injecting supercritical CO 2 fluid into the shaft at a displacement of 3-4 m < 3 >/min for 30-40 minutes.
  5. 5. The deep well reinjection staged fracturing fluid recovery processing method of claim 1, wherein the step 3.2 comprises three stages, each stage having a proppant concentration and particle size of: The first stage, wherein the concentration of the propping agent is 5-8%, the particle size is 70-140 meshes, the injection time is 15-30 minutes, and the pumping flow is 3-4 m 3 /min; The second stage, wherein the concentration of the propping agent is 12-18%, the particle size is 40-70 meshes, the injection time is 30-50 minutes, and the pumping flow is 3-4 m 3 /min; And in the third stage, the concentration of the propping agent is 18-22%, the particle size is 40-70 meshes, the injection time is 20-40 minutes, and the pumping flow is 2-3 m 3 /min.
  6. 6. The deep well reinjection staged fracturing fluid recovery processing method of claim 1, wherein in the step 4, a centrifugal factor of centrifugal separation processing is 1200 g-1500 g.
  7. 7. The deep well reinjection staged fracturing fluid recovery treatment method of claim 1, wherein in the step 5, sedimentation and centrifugal separation of heavy phase slurry specifically comprises the steps of separating under the conditions of a centrifugal factor of 1200-1500 g and a differential rotation speed of 5-15 rpm, and sieving an obtained solid product with a 100-mesh screen under the conditions of a vibration frequency of 40-60 Hz and an amplitude of 0.5-1.0 mm to obtain a crude proppant.
  8. 8. The deep well reinjection staged fracturing fluid recovery processing method of claim 1, wherein in the step 5, the obtained crude propping agent is sent into a cleaning kettle for cleaning, and the regenerated propping agent is obtained specifically comprises the following substeps: step 5.1, injecting the supercritical CO 2 prepared in the step 2 into a cleaning kettle for cleaning under the condition that the stirring speed is 50-60 rpm, so as to obtain CO 2 fluid rich in dissolved matters; The cleaning parameters comprise 48-52 ℃ of temperature, 14.5-15.5 MPa of pressure, 100-120L/h of CO 2 circulation flow and 20-30 minutes of cleaning time; And 5.2, after the cleaning is finished, decompressing and guiding the CO 2 fluid rich in the dissolved substances into a separation kettle, and removing CO 2 through stepped depressurization, wherein the step depressurization and CO 2 comprises the steps of reducing the pressure from 14.5-15.5 MPa to 7.5-8.5 MPa, preserving heat for 5-8 minutes, reducing the pressure from 7.5-8.5 MPa to normal pressure, and preserving heat for 10-15 minutes.
  9. 9. The method for recycling the deep well reinjection staged fracturing fluid according to claim 1, wherein in the step 5, an alumina ceramic membrane is adopted when the light phase slurry is subjected to membrane filtration treatment, the pore diameter of the alumina ceramic membrane is 0.1-0.15 μm, the operation pressure is 0.8-1.2 mpa, and the cross flow velocity is 3.5-4.0 m/s.
  10. 10. The method for recycling the deep well reinjection staged fracturing fluid according to claim 1, wherein in the step 5, the obtained crude fracturing fluid is subjected to regeneration treatment, and the method for obtaining the regenerated fracturing fluid comprises the following steps: Feeding the crude fracturing fluid into a reaction kettle provided with an ultraviolet lamp with 254 nm wavelength, and starting the ultraviolet lamp to irradiate for 25-35 minutes to obtain a first fluid; passing the fluid through a filter membrane having a pore size of 0.1 μm to separate components having a particle size of 0.1 μm or greater from the fluid to obtain a second fluid; And carrying out electrodialysis treatment on the second fluid, and utilizing an ion exchange membrane to selectively migrate and remove monovalent ions contained in the fluid under the action of a direct current electric field to obtain regenerated fracturing fluid.

Description

Deep well reinjection staged fracturing fluid recovery treatment method Technical Field The invention belongs to the field of recycling of fracturing fluid, and particularly relates to a deep well reinjection staged fracturing fluid recycling treatment method. Background The fracturing fluid used in staged fracturing operation can conduct surface pressure to form cracks in the stratum, carry propping agent to spread the propping agent in the cracks, and reduce loss of extraneous liquid in the stratum. At present, the problem of low efficiency of recovery of fracturing fluid after fracturing operation is mainly solved in that the conventional centrifugation and filtration technology is seriously insufficient in the treatment capacity of the fracturing fluid with complex components, effective separation of the components is difficult to achieve, a large amount of useful components cannot be recovered directly, the overall recovery rate is generally lower than sixty five percent, obvious resource waste is caused, the quality of regenerated fluid is poor, even though the content of chemical additives, high-valence metal ions and fine particles remained in the regenerated fluid is still higher after treatment, the existence of the impurities not only seriously influences the recycling performance of the fracturing fluid, but also is more likely to cause incompatible reaction with formation water in the reinjection process to induce scaling and formation damage, the existing chemical gel breaking and flocculation technology can introduce new chemical substances, the method of pickling propping agents can produce a large amount of waste liquid with heavy metals and high chemical amounts, serious secondary environmental pollution is extremely easy to be caused by improper treatment, the existing recovery technology is simply superposition of independent units, and full-aerobic integrated system design is not realized. The operation of the method depends on experience, and the process parameters are difficult to dynamically adjust according to the real-time water quality data, so that the treatment effect is unstable, and the overall operation cost is high. Disclosure of Invention Aiming at the defects and shortcomings of the prior art, the invention aims to provide a deep well reinjection staged fracturing fluid recovery treatment method, which aims to solve the technical problems of low fracturing fluid recovery efficiency and environmental pollution in the prior art. In order to solve the technical problems, the invention adopts the following technical scheme: A deep well reinjection staged fracturing fluid recovery treatment method comprises the following steps: Step 1, preprocessing a shaft, namely closing the shaft to react for 2-4 hours after acidic solution is injected into the shaft, pumping nano SiO 2 suspension into the shaft, and closing the shaft for 20-30 minutes; Step 2, preparing supercritical CO 2 fluid, namely heating and pressurizing liquid CO 2, and then adding nano SiO 2 and cosolvent in the formula amount to obtain supercritical CO 2 fluid; The supercritical CO 2 fluid is used for segmented displacement of fracturing fluid injected into a stratum fracture at the earlier stage, so that the fracturing fluid is flowback to a wellhead, and flowback fluid is continuously extracted and collected at the wellhead; The method specifically comprises the following substeps: step 3.1, injecting supercritical CO 2 fluid into the wellbore in sections to displace the fracturing fluid: Step 3.2, injecting supercritical CO 2 fluid added with proppants into a shaft in stages: step 3.3, pumping supercritical CO 2 fluid, wherein the amount of the pumped fluid is 1.05-1.1 times of the volume of the shaft, and the displacement is 8-10 m < 3 >/min; step 4, performing centrifugal separation treatment on the collected fracturing fluid flowback fluid to obtain heavy-phase slurry and light-phase slurry; And 5, carrying out sedimentation centrifugal separation on heavy-phase slurry to obtain a crude propping agent, sending the obtained crude propping agent into a cleaning kettle for cleaning to obtain a regenerated propping agent, carrying out membrane filtration treatment on light-phase slurry to obtain a crude fracturing fluid, and carrying out regeneration treatment on the obtained crude fracturing fluid to obtain the regenerated fracturing fluid. The invention also has the following technical characteristics: Specifically, in the step 1, the acidic solution comprises the following raw material components, by mass, 5-10% of EDTA, 3-8% of citric acid and 82-92% of water, wherein the total mass percentage of the components is 100%; the injection rate of the acid solution is 0.3-0.5 m 3/min. Further, in the step 2, the liquid CO 2 is heated and pressurized to a temperature of more than 31.1 ℃ and a pressure of more than 7.38MPa, the addition amount of the nano SiO 2 is 1-5wt% of the total mass of the supercritical CO 2 fl