CN109138959A - A kind of supercritical CO2Cumulative fracturing process - Google Patents

Abstract

The present invention proposes a kind of supercritical CO₂Cumulative fracturing process is related to Oil and Natural Gas Engineering field, the supercritical CO₂Cumulative fracturing process includes: step 1, by supercritical CO after perforation completion₂Cumulative fracturing string tripping in target interval, supercritical CO₂Cumulative fracturing string includes multiple fracturing sections for corresponding to target interval setting of sequence setting；Step 2, CO is injected₂And persistent pressure, to CO₂After reaching cracking pressure, its corresponding injection through-hole, CO are opened by the pressure break unit of the fracturing section of bottom₂Enter the corresponding reservoir of target interval by the injection through-hole and impacts pressure break reservoir；Step 3, CO is persistently injected₂Until stopping injection after reaching design quantity；Step 4, step 2 and step 3 are repeated, multiple fracturing sections is passed sequentially through from the bottom to top and injects supercritical CO into reservoir₂.The supercritical CO₂Cumulative fracturing process sufficiently combines supercritical CO₂The characteristics of with high pressure cumulative, realizes the multiple cumulative pressure break of same interval, reaches better effect of increasing production.

Description

A kind of supercritical CO2Cumulative fracturing process

Technical field

The present invention relates to Oil and Natural Gas Engineering fields, in particular to for one of unconventional oil and gas development process Supercritical CO₂Cumulative fracturing process.

Background technique

In recent years, with the large-scale development of conventional gas and oil, existing conventional gas and oil resource of adopting is no longer satisfied me State's rapid economic development demand, unconventional petroleum resources exploitation are gradually brought into schedule.Currently, shale gas, tight gas, coal bed gas etc. The exploitation of unconventional energy resource generallys use conventional hydraulic fracturing process, and achieves certain development effectiveness.But this method exists The problems such as fracturing fluid recovery (backflow) is difficult, water resources consumption is big, reservoir pollution is serious.For this purpose, people take up research newly in recent years The anhydrous fracturing process of type, it is therefore an objective to reduce the usage amount of water, while avoid the additive in fracturing fluid to reservoir and natural environment It damages, makes great efforts to obtain fracturing developing effect efficiently, environmentally friendly.

CO₂It is one of the main constituents of air, colourless, tasteless, nontoxic cannot burn can not be combustion-supporting, normal temperature and pressure Lower density is bigger than air, can be dissolved in water.When temperature reaches 31.04 DEG C, pressure reaches 7.38Mpa, CO₂It is up to supercritical state State.Supercritical CO₂A kind of specialized fluids different from gas and liquid, its density close to liquid, viscosity then close to Gas, surface tension are very easy to diffusion close to zero, have very strong penetrating power, can enter any greater than its molecule In the short space of size.

Due to supercritical CO₂Unique physical property, when being used for fracturing reform, show big advantage: 1. CO₂It is easy to get, and nonflammable explosive, is easy to control and transports；2. supercritical CO₂Viscosity it is low, close to gas, surface Power is very low, and close to zero, the coefficient of friction resistance is low, is easy flowing；3. supercritical CO₂Fluid not will lead to clay swelling in reservoir, from The generation of the harm such as water-blocking effect, rock wettability reversion is fundamentally avoided, effective protection reservoir is without damage；4. being faced with super Boundary CO₂Pressure break is carried out, the row of returning is rapid and thorough, is a kind of clean fracturing fluid of Low Damage, moreover it is possible to shorten the production cycle；5. opposite In conventional fracturing fluid, supercritical CO₂Fracturing fluid diffusivity is strong, and penetrating power is strong, it is easy to penetrate into hole in reservoir and Microcrack is conducive to generate a large amount of microcrack network.

Summary of the invention

The purpose of the present invention is to provide a kind of supercritical COs₂Cumulative fracturing process sufficiently combines supercritical CO₂And high pressure The characteristics of cumulative, realizes the multiple cumulative pressure break of same interval, reaches effect of increasing production more better than conventional fracturing process.

In order to achieve the above objectives, the present invention proposes a kind of supercritical CO₂Cumulative fracturing process, wherein the supercritical CO₂ Cumulative fracturing process includes:

Step 1, after the complete well of perforating oil gas well, using oil pipe by supercritical CO₂Cumulative fracturing string tripping in target interval is simultaneously It is fixed, the supercritical CO₂Cumulative fracturing string includes multiple fracturing sections of sequence setting from top to bottom, multiple fracturing sections The target interval setting is corresponded to, is mounted on pressure break unit in each fracturing section, and on the side wall of each fracturing section Injection through-hole is offered, the corresponding injection through-hole can be opened and be closed to the pressure break unit；

Step 2, by the oil pipe to the supercritical CO₂CO is injected in cumulative fracturing string₂And persistent pressure, to CO₂ After reaching cracking pressure, its corresponding injection through-hole, CO are opened by the pressure break unit of bottom₂Pass through the injection through-hole Into the corresponding reservoir of the target interval and become supercritical CO₂, the supercritical CO₂Impact reservoir described in simultaneously pressure break；

Step 3, continue to the supercritical CO₂CO is injected in cumulative fracturing string 100₂, until stopping after reaching design quantity Only inject；

Step 4, step 2 and step 3 are repeated, passes sequentially through the injection through-holes of multiple fracturing sections from the bottom to top to reservoir The interior injection supercritical CO₂。

Supercritical CO as described above₂Cumulative fracturing process, wherein the pressure break unit includes sliding sleeve, metal ball and pin Nail, the sliding sleeve are equipped with the ball seat with the metal ball corresponding matching, and the sliding sleeve is set in the fracturing section and corresponding The injection through-hole is closed, the sliding sleeve is fixedly connected by the pin with the side wall of the fracturing section, the fracturing section Bottom end is equipped with limiting section, and the internal diameter that the internal diameter of the limiting section is less than the fracturing section forms limited step, and the pin is cut Afterwards, the sliding sleeve slides downwards to the limited step and open the injection through-hole, multiple cunnings of sequence setting from top to bottom The internal diameter for covering its ball seat is sequentially reduced；The step 2 includes:

Step 21, to the supercritical CO₂Investment and the sliding sleeve corresponding matching of bottom in cumulative fracturing string The metal ball simultaneously sets the metal ball on the sliding sleeve of bottom；

Step 22, by the oil pipe to the supercritical CO₂CO is injected in cumulative fracturing string₂And persistent pressure, to It sets the corresponding pin of the sliding sleeve to be cut, sliding sleeve slides downwards set and to open its corresponding described injection logical Hole, CO₂Enter the corresponding reservoir of the target interval by the injection through-hole and becomes supercritical CO₂, the supercritical CO₂ Impact reservoir described in simultaneously pressure break.

Supercritical CO as described above₂Cumulative fracturing process, wherein in the step 2, to the supercritical CO₂Cumulative CO in fracturing string₂After pressure reaches test pressure value, suspend CO₂Injection and observe the supercritical CO₂Cumulative pressure break pipe Pressure value changes in column, if it is to reach to set requirement that pressure value loss, which is no more than 5%, in 5 minutes, continues to the supercritical CO₂ Cumulative fracturing string injects CO₂。

Supercritical CO as described above₂Cumulative fracturing process, wherein the test pressure value is 25MPa.

Supercritical CO as described above₂Cumulative fracturing process, wherein the supercritical CO₂Cumulative fracturing process further include:

Step 5, using fracturing blender truck by proppant and CO₂It is mixed to form fluid-mixing, and mixing fluid pump note is arrived In the reservoir, to support the crack in the reservoir.

Supercritical CO as described above₂Cumulative fracturing process, wherein the supercritical CO₂Cumulative fracturing process further include:

Step 6, stewing well is carried out according to payzone situation, carries out the row's of returning operation after stewing well.

Supercritical CO as described above₂Cumulative fracturing process, wherein the shear strength of the pin is higher than the reservoir Formation fracture pressure 5-8MPa.Supercritical CO as described above₂Cumulative fracturing process, wherein the height of the sliding sleeve is less than 0.4 meter.

Compared with prior art, the invention has the characteristics that and advantage:

Supercritical CO proposed by the present invention₂Cumulative fracturing process can be realized the multiple synergy pressure of single layer for same reservoir It splits, crack is not easy to extend after being particularly suitable for stratum crack initiation, it is difficult to form the reservoir of effectively seam net, sufficiently improving stratum can press The supercritical CO of the poor reservoir of property₂The effect of pressure break.

Detailed description of the invention

Attached drawing described here is only used for task of explanation, and is not intended to limit model disclosed by the invention in any way It encloses.In addition, shape and proportional sizes of each component in figure etc. are only schematical, it is used to help the understanding of the present invention, and It is not the specific shape and proportional sizes for limiting each component of the present invention.Those skilled in the art under the teachings of the present invention, can Implement the present invention to select various possible shapes and proportional sizes as the case may be.

Fig. 1 is supercritical CO proposed by the present invention₂The structural schematic diagram of cumulative fracturing string；

Fig. 2 is the structural schematic diagram of pressure break unit in the present invention；

Fig. 3 is supercritical CO proposed by the present invention₂Structural schematic diagram when cumulative fracturing string first time cumulative pressure break；

Fig. 4 is supercritical CO proposed by the present invention₂Structural schematic diagram when cumulative second of pitching of fracturing string；

Fig. 5 is supercritical CO proposed by the present invention₂Structural schematic diagram when the 4th cumulative pressure break of cumulative fracturing string.

Description of symbols:

100, supercritical CO₂Cumulative fracturing string；10, tubular column main body；

11, fracturing section；20, pressure break unit；

21, sliding sleeve；211, ball seat；

22, metal ball；23, pin；

24, through-hole is sprayed；25, limiting section；

12, fracturing section；13, fracturing section；

14, fracturing section；31, sliding sleeve；

41, sliding sleeve；51, sliding sleeve；

32, metal ball；42, metal ball；

52, metal ball.

Specific embodiment

With reference to the drawings and the description of the specific embodiments of the present invention, details of the invention can clearly be understood.But It is the specific embodiment of invention described herein, purpose for explaining only the invention, and cannot understand in any way At being limitation of the present invention.Under the teachings of the present invention, technical staff is contemplated that based on any possible change of the invention Shape, these are regarded as belonging to the scope of the present invention.

Fig. 1 to Fig. 5 is please referred to, the present invention proposes a kind of supercritical CO₂Cumulative fracturing process, the supercritical CO₂Cumulative pressure break Method includes:

Step 1, after the complete well of perforating oil gas well, using oil pipe by supercritical CO₂100 tripping in target interval of cumulative fracturing string And fixed, supercritical CO₂Cumulative fracturing string includes multiple fracturing sections 11 of sequence setting from top to bottom, and multiple fracturing sections 11 are The corresponding target interval is arranged, and is mounted on pressure break unit 20 in each fracturing section 11, and open on the side wall of each fracturing section 11 Equipped with injection through-hole 24, corresponding injection through-hole 24 can be opened and be closed to pressure break unit 20；

Step 2, by oil pipe to supercritical CO₂Liquid CO is injected in cumulative fracturing string 100₂And persistent pressure, to CO₂ After reaching cracking pressure, its corresponding injection through-hole 24, CO is opened by the pressure break unit 20 of bottom₂Pass through the injection through-hole 24 enter the corresponding reservoir of target interval and become supercritical CO₂, supercritical CO₂Impact simultaneously pressure break reservoir；

Step 3, continue to supercritical CO₂CO is injected in cumulative fracturing string 100₂, until stopping note after reaching design quantity Enter；

Step 4, step 2 and step 3 are repeated, passes sequentially through the injection through-holes 24 of multiple fracturing sections 11 from the bottom to top to reservoir Interior injection supercritical CO₂。

As shown in Figure 1 and Figure 2, supercritical CO₂Cumulative fracturing string 100 includes tubular tubular column main body 10, tubular column main body 10 are vertically arranged and multiple fracturing sections 11 including sequence setting from top to bottom, and multiple fracturing sections 11 correspond to same reservoir, often Correspondence is equipped with pressure break unit 20 in a fracturing section 11, and injection through-hole 24, pressure are offered on the side wall of each fracturing section 11 Corresponding injection through-hole 24 can be opened and close by splitting unit 20.

Supercritical CO proposed by the present invention₂It is multiple to can be realized single layer for same reservoir for cumulative fracturing process and tubing string Synergy pressure break, crack is not easy to extend after being particularly suitable for stratum crack initiation, it is difficult to which the reservoir for forming effectively seam net can be mentioned sufficiently The supercritical CO of the poor reservoir of high stratum compressibility₂The effect of pressure break.

Supercritical CO proposed by the present invention₂Cumulative fracturing process, when cumulative fracturing work, High-pressure supercritical CO₂Moment releases It puts, acts on reservoir, reservoir is made to form more and complicated fracture network；The instantaneous pressure break of high pressure reduces supercritical CO₂Leak-off is made Industry has higher success rate, and is also suitable for Thief zone and misses serious reservoir fracturing improvement；After the completion of pressure break, CO₂The easy row of returning, and To the injury very little of reservoir.

Supercritical CO₂Cumulative pressure break can utilize supercritical CO₂Special property, in conjunction with Mohaupt effect, in fracturing process It is middle to generate apparent technical advantage: (1) supercritical CO₂Penetrating power is strong, is able to enter any micro- greater than its molecular size In small space, be conducive to the formation of microcrack；(2)CO₂After the completion of pressure break, it is easy the row of returning, and the injury caused by reservoir is small； (3) mode of this cumulative pressure break can impact reservoir using instantaneous high pressure, more cracks and seam net be formed, to stratum It is transformed more efficient；(4) the instantaneous fracturing process of this cumulative, effect reservoir generate the crack period, avoid due to overcritical CO₂High osmosis energy can not establish the consequence of reservoir high pressure and fracturing, be also applied for Thief zone, the serious reservoir fracturing of leakage； (5) relative to the mode of explosive charge, this cumulative fracturing operation is stronger, safer, and the damage to tubing string and tool is smaller.

In the present invention, to supercritical CO₂The CO injected in cumulative fracturing string 100₂For high-pressure liquid CO₂, by ground High pressure pump group is persistently pumped into, above-mentioned high-pressure liquid CO₂Specific pressure according to down-hole pressure determine, be generally higher than corresponding reservoir Formation fracture pressure.Wherein, formation fracture pressure refers to, in the wellbore, stratum can be made when strata pressure reaches a certain value Rupture, this pressure are known as formation fracture pressure.It is generally intended to carry out the test of geologic parameter before and after drilling well, as earthquake is surveyed Examination, the methods of well logging, formation fracture pressure are exactly that test in this course obtains.

In the present invention, as high-pressure liquid CO₂By the overcritical of ground layer for heating to high temperature and pressure when continuing downlink along oil pipe CO₂, specifically, the calculation formula of formation temperature are as follows: and formation temperature=surface temperature+(1.5~3) × well depth/100, for example, one As about 60 DEG C of oil/gas well bottom hole temperature (BHT) or so of 2000 meters, and when temperature is more than 31.1 DEG C, when pressure is more than 7.38MPa, CO₂Just It is above-critical state, therefore CO when entrance stratum₂For supercritical CO₂, fracturing process is supercritical CO₂Pressure break.When injection through-hole 24 The moment of opening, above-mentioned High-pressure supercritical CO₂Expansion suddenly generates shock wave, enters reservoir in blasting from, pressure is higher than Formation fracture pressure can generate high-energy shock wave to reservoir, facilitate the generation of complex fracture network.In above process, although CO₂Suddenly after expansion, temperature can be decreased due to joule thomson effect, but enter CO after reservoir₂It can be heated rapidly To above-critical state, still great impact force can be generated to reservoir.

In an optional example of the invention, pressure break unit 20 includes sliding sleeve 21, metal ball 22 and pin 23, sliding sleeve 21 It is equipped with the ball seat 211 with 22 corresponding matching of metal ball, injection through-hole 24 is offered on the side wall of fracturing section 11, sliding sleeve 21 is arranged In fracturing section 11 and corresponding closing injection through-hole 24, sliding sleeve 21 are fixedly connected with the side wall of fracturing section 11 by pin 23, are pressed The bottom end for splitting section 11 is equipped with limiting section 25, and the internal diameter that the internal diameter of limiting section 25 is less than fracturing section 11 forms limited step, pin 23 After cutting, sliding sleeve 21 is snapped down to limited step and opens injection through-hole 24, its ball of multiple sliding sleeves 21 of sequence setting from top to bottom The internal diameter (and internal diameter of sliding sleeve 21) of seat 211 is sequentially reduced.

Further, step 2 further includes step 21 and step 22, wherein

Step 21, to the supercritical CO₂Investment and 21 corresponding matching of sliding sleeve of bottom in cumulative fracturing string 100 Metal ball 22 simultaneously sets metal ball 22 on the sliding sleeve 21 of bottom；

Step 22, by oil pipe to supercritical CO₂CO is injected in cumulative fracturing string 100₂And persistent pressure, wait set The corresponding pin 23 of sliding sleeve 21 is cut, and the sliding sleeve 21 set glides and opens its corresponding injection through-hole 24, CO₂Pass through spray Through-hole 24 is penetrated to enter the corresponding reservoir of target interval and become supercritical CO₂, above-mentioned supercritical CO₂Impact reservoir described in simultaneously pressure break.

Supercritical CO proposed by the present invention₂Cumulative fracturing process, by the sliding sleeve 21 of the fixed different inner diameters of pin, pressure break is made (internal diameter of sliding sleeve gradually increases the sliding sleeve 21 of the setting different inner diameters of metal ball 22 of investment different-diameter from the bottom to top, throws before industry Its diameter of the metal ball entered also successively increases), to realize the multiplicating cumulative fracturing work of same interval, fracturing effect is more It is good, reach effect of increasing production more better than conventional fracturing process.

In the present invention, sliding sleeve 21 has accommodating cavity up and down, and ball seat 211 is arranged on the inner wall of sliding sleeve 21, gold After belonging to the investment of ball 22, sets and close the accommodating cavity of sliding sleeve 21 on ball seat 211.

In the present invention, 23 shearing strength of pin will be designed according to formation fracture pressure；By changing the anti-of pin Cut intensity, adjustable supercritical CO₂Pressure size in cumulative fracturing string 100, thus meet the pressure break demand of Different Strata, Enhance the practicability of this method.

In an optional example, cracking pressure is that (shearing resistance of pin is strong for the maximum shear stress that can bear of pin 23 Degree), the maximum shear stress that pin 23 can be born is higher than the formation fracture pressure 5-8MPa of corresponding reservoir, preferably poly- to generate It can impact effect.

In an optional example of the invention, multiple injection through-holes 24 are offered on the side wall of each fracturing section 11, Multiple injection through-holes 24 are uniformly distributed along the circumferential direction of fracturing section 11.

In an optional example of the invention, the height of sliding sleeve 21 is less than 0.4 meter, to guarantee entire supercritical CO₂It is poly- The size of energy fracturing string 100 will not be too long, so that supercritical CO₂Easier it can enter in same layer crack (reservoir).

In an optional example of the invention, tubular column main body 10 includes 4 fracturing sections 11, i.e. supercritical CO₂Cumulative pressure Four pressure breaks can be carried out for same reservoir by splitting tubing string 100, and under normal circumstances, four pressure break yield can achieve a pressure break 1.5-2 times of yield.

In an optional example of the invention, supercritical CO₂Cumulative fracturing process further include:

Step 5, using fracturing blender truck by proppant and liquid CO₂It is mixed to form fluid-mixing, and mixing fluid pump note is arrived In reservoir, to support the crack in reservoir, sealed fracture is avoided, to complete cumulative pressure break.

In an optional example of the invention, in fluid-mixing, it is calculated by mass percentage, proppant accounts for 2- 5%.

In an optional example of the invention, supercritical CO₂Cumulative fracturing process further include: step 6, according to payzone feelings Condition carries out stewing well, carries out the row's of returning operation after stewing well.

In an optional example of the invention, in step 2, to supercritical CO₂Liquid in cumulative fracturing string 100 CO₂After pressure reaches test pressure value, suspend liquid CO₂Injection and observe supercritical CO₂Pressure in cumulative fracturing string 100 Value variation reaches if pressure value loss is no more than 5% in 5 minutes and sets requirement, can continue to supercritical CO₂Cumulative pressure It splits and injects liquid CO in tubing string 100₂。

In an optional example of the invention, test pressure value is 25MPa.

Now to have the supercritical CO there are four fracturing section₂For cumulative fracturing string 100, proposition that the present invention will be described in detail Supercritical CO₂Cumulative fracturing process.

As shown in Fig. 3, Fig. 4 and Fig. 5, the supercritical CO₂Cumulative fracturing string includes the pressure break of sequence setting from top to bottom Section 11, fracturing section 12, fracturing section 13 and fracturing section 14 are equipped with sliding sleeve 21 in fracturing section 11, are equipped with sliding sleeve in fracturing section 12 31, sliding sleeve 41 is installed in fracturing section 13, sliding sleeve 51 is installed in fracturing section 14, wherein internal diameter (and the sliding sleeve 21 of sliding sleeve 21 Ball seat 211 internal diameter), the internal diameter of sliding sleeve 31, the internal diameter of sliding sleeve 41 and sliding sleeve 51 internal diameter successively increase, correspondingly, metal The diameter of ball 22, the diameter of metal ball 32, the diameter of metal ball 42 and metal ball 52 diameter successively increase.

As shown in Figures 3 to 5, supercritical CO proposed by the present invention₂Cumulative fracturing process specific implementation process is as follows:

Firstly, connecting supercritical CO using oil pipe after oil well cementing perforation₂It is super to face in 100 lower going-into-well of cumulative fracturing string Boundary CO₂Cumulative fracturing string 100 enters shaft bottom interval of interest (perforated interval) by wellhead assembly and pit shaft, then by supercritical CO₂It is poly- The bottom hydraulic anchorage of energy fracturing string 100；

To supercritical CO₂Cumulative fracturing string 100 is lower to target interval and after fixing, investment and the matched metal of sliding sleeve 21 Ball 22, allows the setting sliding sleeve 21 of metal ball 22, opens CO₂High-pressure pump begins through oil pipe to supercritical CO₂Cumulative fracturing string 100 Inside it is pumped into CO₂To certain pressure value (such as 25Mpa), pump is closed, observes supercritical CO₂Pressure value changes in cumulative fracturing string 100, and 5 If a minute interior overpressure loss is no more than 5% and reaches requirement, indicating plugging effect, well (whole system sealing effect is good It is good), implementable next step operation；

Under the conditions of whole system sealing effect is good, CO is opened₂High-pressure pump continues to supercritical CO₂Cumulative pressure break pipe CO is pumped into column 100₂Until reaching 23 shearing strength of pin, pin 23 can be cut at this time, and sliding sleeve 21 and metal ball 22 are along pressure The inner wall for splitting section 11 is snapped down at limiting section 25, and injection through-hole 24 is opened, High-pressure supercritical CO₂Enter storage in explosive state Layer, while persistently injecting CO₂, until reaching design requirement, complete first time cumulative pressure break；

If the first time pressure break for interval of interest can not achieve the desired results, need to set sliding sleeve using metal ball 32 31 carry out second of pressure break, set sliding sleeve 41 using metal ball 42 and carry out third time pressure break, set sliding sleeve 51 using metal ball 52 The 4th pressure break is carried out, each fracturing process is identical with first order pressure break, sealing effect is had to check for after pitching, again turn on pump Pressurization, and then realize and be directed to the multiple supercritical CO 2 cumulative pressure break of same reservoir；

Utilize supercritical CO₂Multiple cumulative pressure break presses off stratum, after forming seam net, continues to supercritical CO₂Cumulative pressure break pipe It is pumped into load fluid, displacement fluid etc. in column 100, by the way that proppant to be pumped into crack, avoids crack closure.

Finally, determining the stewing well time according to payzone situation, the row's of returning operation is finally carried out, entire fracturing process is completed.

For explaining in detail for the respective embodiments described above, purpose, which is only that, explains the present invention, in order to be able to More fully understand the present invention, still, these descriptions cannot with any explanation at being limitation of the present invention, in particular, Each feature described in different embodiments can also mutual any combination, so that other embodiments are formed, in addition to having Opposite description is specified, these features should be understood to can be applied in any one embodiment, and be not limited merely to Described embodiment.

Claims (8)

1. a kind of supercritical CO₂Cumulative fracturing process, which is characterized in that the supercritical CO₂Cumulative fracturing process includes:

Step 1, after the complete well of perforating oil gas well, using oil pipe by supercritical CO₂Cumulative fracturing string tripping in target interval and fixation, The supercritical CO₂Cumulative fracturing string includes multiple fracturing sections of sequence setting from top to bottom, and multiple fracturing sections are right It answers the target interval to be arranged, is mounted on pressure break unit in each fracturing section, and open up on the side wall of each fracturing section There is injection through-hole, the corresponding injection through-hole can be opened and be closed to the pressure break unit；

Step 2, by the oil pipe to the supercritical CO₂CO is injected in cumulative fracturing string₂And persistent pressure, to CO₂Reach After cracking pressure, its corresponding injection through-hole, CO are opened by the pressure break unit of bottom₂Entered by the injection through-hole The corresponding reservoir of the target interval simultaneously becomes supercritical CO₂, the supercritical CO₂Impact reservoir described in simultaneously pressure break；

Step 3, continue to the supercritical CO₂CO is injected in cumulative fracturing string 100₂, until stopping note after reaching design quantity Enter；

Step 4, it repeats step 2 and step 3, the injection through-hole for passing sequentially through multiple fracturing sections from the bottom to top is infused into reservoir Enter the supercritical CO₂。

2. supercritical CO as described in claim 1₂Cumulative fracturing process, which is characterized in that the pressure break unit include sliding sleeve, Metal ball and pin, the sliding sleeve are equipped with the ball seat with the metal ball corresponding matching, and the sliding sleeve is set in the pressure break In section and the corresponding closing injection through-hole, the sliding sleeve are fixedly connected by the pin with the side wall of the fracturing section, institute The bottom end for stating fracturing section is equipped with limiting section, and the internal diameter that the internal diameter of the limiting section is less than the fracturing section forms limited step, institute After stating pin cutting, the sliding sleeve slides downwards to the limited step simultaneously open the injection through-hole, sequence setting from top to bottom The internal diameter of multiple its ball seat of sliding sleeve is sequentially reduced；The step 2 includes:

Step 21, to the supercritical CO₂The gold of investment and the sliding sleeve corresponding matching of bottom in cumulative fracturing string Belong to ball and sets the metal ball on the sliding sleeve of bottom；

Step 22, by the oil pipe to the supercritical CO₂CO is injected in cumulative fracturing string₂And persistent pressure, wait set The corresponding pin of the sliding sleeve is cut, and the sliding sleeve slides downwards set simultaneously open its corresponding injection through-hole, CO₂Enter the corresponding reservoir of the target interval by the injection through-hole and becomes supercritical CO₂, the supercritical CO₂Impact And reservoir described in pressure break.

3. supercritical CO as claimed in claim 2₂Cumulative fracturing process, which is characterized in that the shear strength of the pin is high In the formation fracture pressure 5-8MPa of the reservoir.

4. supercritical CO as claimed in claim 2₂Cumulative fracturing process, which is characterized in that the height of the sliding sleeve is less than 0.4 Rice.

5. supercritical CO as described in claim 1₂Cumulative fracturing process, which is characterized in that in the step 2, to described super Critical CO₂CO in cumulative fracturing string₂After pressure reaches test pressure value, suspend CO₂Injection and observe described overcritical CO₂Pressure value changes in cumulative fracturing string, if pressure value loss is no more than 5% and reaches and set requirement in 5 minutes, continue to The supercritical CO₂Cumulative fracturing string injects CO₂。

6. supercritical CO as claimed in claim 5₂Cumulative fracturing process, which is characterized in that the test pressure value is 25MPa.

7. supercritical CO as described in claim 1₂Cumulative fracturing process, which is characterized in that the supercritical CO₂Cumulative pressure break Method further include:

Step 5, using fracturing blender truck by proppant and CO₂It is mixed to form fluid-mixing, and the mixing fluid pump is infused to the storage In layer, to support the crack in the reservoir.

8. supercritical CO as described in claim 1₂Cumulative fracturing process, which is characterized in that the supercritical CO₂Cumulative pressure break Method further include:

Step 6, stewing well is carried out according to payzone situation, carries out the row's of returning operation after stewing well.