CN109138954A - A kind of refracturing method of Unconventional gas - Google Patents
A kind of refracturing method of Unconventional gas Download PDFInfo
- Publication number
- CN109138954A CN109138954A CN201810993200.XA CN201810993200A CN109138954A CN 109138954 A CN109138954 A CN 109138954A CN 201810993200 A CN201810993200 A CN 201810993200A CN 109138954 A CN109138954 A CN 109138954A
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- Prior art keywords
- refracturing
- liquid nitrogen
- pressure
- refracturing method
- fracturing
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Classifications
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
Abstract
The present invention provides a kind of refracturing methods of Unconventional gas.The refracturing method includes the steps that liquid nitrogen assists pressure break.Refracturing method of the invention, which can make to generate in layer, turns to crackle, to increase substantially oil and gas production, has directive significance to field hydraulic fracturing work.
Description
Technical field
The present invention relates to a kind of methods of the refracturing of Unconventional gas, belong to Unconventional gas production technique neck
Domain.
Background technique
Increase with people to oil demand amount, oil exploitation speed are also getting faster, and petroleum resources be it is a kind of not
Renewable resource, how the exploitation petroleum of high yield low pollution becomes the problem of most paying close attention in petroleum works.
Multiple fracturing technique, which refers to, carries out pressure break twice or more than twice in same well, is current raising oil and gas production
A kind of important means.In oil producing operation at the scene, with the extension of production time after first pressure break, oil-production capacity is caused to exist
Decline after a period of time or the well pressure break after after a period of time, having found on other layers of position has bigger exploitation latent again
Power then carries out pressure break to it again.
There are mainly three types of modes for the current multiple fracturing technique implemented both at home and abroad: extruding new crack in layer, continues to extend original
There are crack and changed course refracturing.Refracturing operation for current Oil Field is it can be found that continue to extend primary fracture
For the poor effect of volume increase, carry out for the research for extruding new crack in layer.And conventional refracturing theory is obvious
Deficiency is exactly only to consider the influence of crustal stress and tensile failure fracture crack initiation development, and have ignored formation rock itself physical force
Learn the influence of change of properties and failure by shear mode.
In refracturing operation at present, conventional water filling refracturing can only play the effect for continuing to extend primary fracture,
For improving the poor effect of oil and gas production.
Summary of the invention
In order to solve the above-mentioned technical problem, the purpose of the present invention is to provide a kind of weights that can produce new secondary crack
Multiple fracturing process.
In order to achieve the above technical purposes, the present invention provides a kind of refracturing method of Unconventional gas, this is heavy
Multiple fracturing process includes the steps that liquid nitrogen assists pressure break, specifically includes injection liquid nitrogen, reinjects fracturing fluid；Or, by liquid nitrogen and pressure
It splits liquid while injecting.
Refracturing method of the invention, is added liquid nitrogen during refracturing, plays the role of assisting pressure break.Due to
The particularity of liquid nitrogen, on the one hand, when liquid nitrogen injects stratum, liquid nitrogen (- 196 DEG C) occurs significant after contacting with stratum (150 DEG C)
Change of temperature field leads to the contraction of reservoir stress, changes stratum original crack trend, generates new crack growth；On the other hand,
After liquid nitrogen is injected on stratum, reduction formation rock is acted on using its ultralow temperature, to generate new crackle.
In the refracturing method of Unconventional gas of the invention, the liquid nitrogen of use is a kind of special inert substance,
Under the action of not having an impact field hydraulic fracturing work, it can preferably assist generating steering crackle, to improve oil
Gas yield；Since cost is relatively low for liquid nitrogen, facilitate acquisition, and convenient for saving, largely live refracturing has been saved in Shangdi
The cost of operation, it is with good economic efficiency.
Detailed description of the invention
Fig. 1 is fractured layer schematic diagram in field hydraulic fracturing work.
Fig. 2 is the fracturing fluid injection pressure curve in embodiment 2.
Specific embodiment
In order to which technical characteristic of the invention, purpose and beneficial effect are more clearly understood, now to skill of the invention
Art scheme carries out described further below, but should not be understood as that limiting the scope of the invention.
Liquid nitrogen is a kind of non-corrosive and extremely low temperature inert fluid, can largely be absorbed heat in vaporization.
In a specific embodiment of the invention, a kind of refracturing method of Unconventional gas is provided, this is heavy
Multiple fracturing process includes the steps that liquid nitrogen assists pressure break.
In refracturing operation, the purpose of secondary fracturing is that crack is made to continue extension to produce more oil.And stratum
After liquid nitrogen assists generating secondary crack, new crack propagation can be then generated in this pressure break, is different from original crackle, newly splits
Line can have new trend in the earth formation, can detect new oil gas, and then improve oil and gas production.
Specifically, the refracturing method the following steps are included:
Liquid nitrogen is injected, fracturing fluid is reinjected；Or,
Liquid nitrogen is injected simultaneously with fracturing fluid.
More specifically, the main function of injection liquid nitrogen is so that stratum generates secondary crack, the injection rate of liquid nitrogen is according to weight
The case where multiple fracturing work preceding stratum and determine, in general liquid nitrogen is made to bury stratum.For example, for general reservoir,
The injection rate of liquid nitrogen can be 25m3-85m3。
Specifically, vaporization can be generated behind liquid nitrogen injection stratum, stimulation stratum generates new secondary crack, it is general and
The action time of speech, liquid nitrogen and formation rock is 2h-3h, and the abundant gasification of liquid nitrogen may be implemented.After the completion of liquid nitrogen vaporization, pressure
It splits liquid and improves bottom pressure rapidly and form pressure break, generate crack and simultaneously extend extension.What needs to be explained here is that for differently
Layer, those skilled in the art can voluntarily determine the raw material composition of the fracturing fluid used.
Specifically, after injecting liquid nitrogen and fracturing fluid, the step of load fluid is added in segmentation can be carried out；Specifically according to this field
Conventional operation carries out.The raw material composition of load fluid can be determined according to strata condition for the stratum of different lithology.
The ratio of sand total amount and load fluid is mulling ratio (sand ratio), and what is typically resulted in is average value, in FRACTURING DESIGN, according to difference
Stratum, preliminary sand ratio is generally since 5%-10%, and most high sand ratio can achieve 40%-70%.If using high viscosity pressure break
40%-50% can be improved in liquid, sand ratio；The fracturing fluid of general viscosity, can suitably reduce 10%-20%.
Specifically, segmentation is pumped into displacement fluid after load fluid is added, and the sand liquid carried in surface line and pit shaft is whole
In jacking crack, prevents remaining sand from sinking to shaft bottom and cause sand card.
Specifically, before carrying out injection liquid nitrogen and fracturing fluid, preparation can be first carried out, specifically includes circulation, examination
The step that pressure and examination are squeezed.
More specifically, circulation is fracturing fluid to be got to fracturing unit truck by tank truck, then return to tank truck by fracturing unit truck, followed by vehicle
Ring, when exporting normal drainage, end loop operation.
More specifically, pressure testing is to equipment and surface line progress load performance test more than head valve.Work as pressure
It is 1.2-1.5 times of prediction pump pressure, and when pressure stabilizing 5min pressure does not generate decline, is load performance qualification.
More specifically, it is to open head valve that examination, which is squeezed, circulation emptying valve is closed, starts fracturing unit truck by platform, is wanted by design
Ask discharge capacity that fracturing fluid is squeezed into stratum, pressure when balance and stability, terminates examination and squeeze operation from low to high.
Embodiment 1
Present embodiments provide it is a kind of to the old stratum for having carried out fracturing work, using liquid nitrogen auxiliary refracturing
Method, as indicated with 1, specific steps method is as follows for the structural schematic diagram of fracturing stratum:
Step 1: circulation, gets to fracturing unit truck by tank truck for fracturing fluid, then return to tank car by fracturing unit truck, is followed by vehicle
Ring is normal for circulation to export normal drainage.
Step 2: pressure testing, smooth starting fracturing unit truck high-pressure pump, to it is more than head valve equipment and surface line hold
Performance test is pressed, pressure is 1.2-1.5 times of prediction pump pressure, and pressure stabilizing 5min pressure does not generate decline.
Step 3: examination is squeezed, after pressure testing is qualified, head valve is opened, circulation emptying valve is closed, starts fracturing unit truck by platform,
Fracturing fluid is squeezed into stratum by design requirement discharge capacity, pressure is from low to high until balance and stability.Examination pays attention to inspection shaft during squeezing
The imbibition ability of the case where lower tubular column and fractured layer position.
Step 4: the liquid nitrogen stored is injected into well stratum after examination extruding force and discharge capacity are stablized by injection liquid nitrogen, infuse
Liquid nitrogen can generate vaporization after entering stratum, and liquid nitrogen and formation rock is enabled sufficiently to act on 2-3h, until liquid nitrogen vaporization finishes.
Step 5: pressure break, after liquid nitrogen vaporization, while injecting fracturing fluid, bottom pressure is made to improve formation pressure rapidly
It splits, generate crack and extends extension.
Step 6: load fluid is added, when fractured layer cracking initiation, load fluid can be added after stablizing with discharge capacity in pump pressure.It wants
The good mulling ratio of Discrete control is gradually increased and uniformly adds sand, guarantees that pressure and discharge capacity are steady, forbid midway termination of pumping.
Step 7: being pumped into displacement fluid, it is contemplated that after sand amount has been added completely into, be pumped into displacement fluid immediately, by surface line with
And the sand liquid carried in pit shaft all heads into crack, prevents remaining sand from sinking to shaft bottom and causes sand card.
Step 8: backwash or movable tubing string, anti-flushing well or movable tubing string immediately after replacement, when movable tubing string, pay attention to above mentioning
Speed control is not less than 5m in 0.5m/min, active strokes, prevents remaining sand from remaining in wellbore packer card and causes sand plug away between,
The accidents such as sand card.
Embodiment 2
The present embodiment carries out weight to artificial cuboid test specimen (300mm × 300mm × 600mm) using true triaxial fracturing unit
Multiple fracture simulation experiment.
Firstly, carrying out first fracture simulation under the conditions of zero confining pressure with the pressure fluid injection rate of 2mL/min, waterpower is split
It stitches crack initiation and closes pump stopping fluid injection immediately later；
Then appropriate liquid nitrogen is squeezed into the crack that first pressure break is formed, and by after test specimen placement for 24 hours, connection fracturing fluid injects
Pipeline carries out refracturing simulation with the injection rate of 2mL/min.
Meanwhile control group experiment is carried out, control group test specimen is not injected into liquid nitrogen after first pressure break, only places for 24 hours, so
Refracturing simulation is carried out afterwards, and whole process uses the injection rate of 2mL/min.
As a result as shown in Fig. 2, as seen from Figure 2, the seam pressure that rises in control group refracturing crack is 4.5MPa, and is infused
The seam pressure that rises for entering the refracturing crack of the experimental group of liquid nitrogen is only 2.5MPa, it is seen then that before refracturing, the injection of liquid nitrogen
Make rock sample resist the ability destroyed to decline to a great extent.On the other hand, control group refracturing curve has obvious peak value point, and peak
Pressure break curve declines rapidly after value, and experimental group refracturing curve does not have obvious peak value point, and pressure break curve is held near peak value
Continuous fluctuation, and the decline of pressure break curve is slowly, the fracture pattern that this species diversity shows that the experimental group time is formed is more complicated than control group.
As it can be seen that liquid nitrogen refracturing method initial cracking pressure is substantially reduced and is more likely to form complex fracture.
Claims (10)
1. a kind of refracturing method of Unconventional gas, which is characterized in that the refracturing method includes liquid nitrogen auxiliary pressure
The step of splitting.
2. refracturing method according to claim 1, which is characterized in that the refracturing method the following steps are included:
Liquid nitrogen is injected, fracturing fluid is reinjected；Or,
Liquid nitrogen is injected simultaneously with fracturing fluid.
3. refracturing method according to claim 1 or 2, which is characterized in that the injection rate of the liquid nitrogen is 25m3-
85m3。
4. refracturing method according to claim 1, which is characterized in that act on 2h-3h after injection liquid nitrogen.
5. refracturing method according to claim 1, which is characterized in that the refracturing method the following steps are included:
Liquid nitrogen is injected, fracturing fluid is reinjected；Or, liquid nitrogen is injected simultaneously with fracturing fluid；After injecting liquid nitrogen, 2h-3h is kept；
Load fluid is added in segmentation；
It is pumped into displacement fluid, completes the refracturing of the Unconventional gas.
6. refracturing method according to claim 5, which is characterized in that the refracturing method further includes circulation, examination
The step that pressure and examination are squeezed.
7. refracturing method according to claim 6, which is characterized in that the circulation is to beat fracturing fluid by tank truck
Tank truck is returned to fracturing unit truck, then by fracturing unit truck, is recycled by vehicle, when exporting normal drainage, end loop operation.
8. refracturing method according to claim 6, which is characterized in that the pressure testing be to equipment and surface line into
The test of row load performance.
9. refracturing method according to claim 8, which is characterized in that when pressure be prediction pump pressure 1.2-1.5 times,
And pressure stabilizing 5min pressure is not when generating decline, is that load performance is qualified.
10. refracturing method according to claim 6, which is characterized in that it is that fracturing fluid is squeezed into stratum that the examination, which is squeezed,
Pressure when balance and stability, terminates examination and squeezes operation from low to high.
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| CN201810993200.XA CN109138954A (en) | 2018-08-29 | 2018-08-29 | A kind of refracturing method of Unconventional gas |
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| CN103726819A (en) * | 2013-12-27 | 2014-04-16 | 中国石油大学(华东) | Method of low-temperature gas-assisted coalbed methane fracturing technology |
| CN104612648A (en) * | 2014-11-18 | 2015-05-13 | 河南理工大学 | Method and device for active water-nitrogen foam fracturing of low-pressure and low permeability coal bed gas well |
| CN105275442A (en) * | 2015-10-29 | 2016-01-27 | 中国石油集团川庆钻探工程有限公司长庆井下技术作业公司 | Old well re-transformation volume fracturing technology |
| CN105507871A (en) * | 2016-01-06 | 2016-04-20 | 西南石油大学 | Horizontal well liquid nitrogen ice crystal temperature plugging staged fracturing method for coalbed methane |
| US20160201442A1 (en) * | 2015-01-09 | 2016-07-14 | Halliburton Energy Services, Inc. | Leakoff mitigation treatment utilizing self degrading materials prior to re-fracture treatment |
| CN105822275A (en) * | 2016-01-12 | 2016-08-03 | 中国石油大学(华东) | Fracturing fracture-forming technique and method for shale |
| CN105888604A (en) * | 2016-04-14 | 2016-08-24 | 中国石油天然气股份有限公司 | Method applicable to repeatedly transforming stratum nearby shaft of low-pressure gas field old well to complete permanent blocking |
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2018
- 2018-08-29 CN CN201810993200.XA patent/CN109138954A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103726819A (en) * | 2013-12-27 | 2014-04-16 | 中国石油大学(华东) | Method of low-temperature gas-assisted coalbed methane fracturing technology |
| CN104612648A (en) * | 2014-11-18 | 2015-05-13 | 河南理工大学 | Method and device for active water-nitrogen foam fracturing of low-pressure and low permeability coal bed gas well |
| US20160201442A1 (en) * | 2015-01-09 | 2016-07-14 | Halliburton Energy Services, Inc. | Leakoff mitigation treatment utilizing self degrading materials prior to re-fracture treatment |
| CN105275442A (en) * | 2015-10-29 | 2016-01-27 | 中国石油集团川庆钻探工程有限公司长庆井下技术作业公司 | Old well re-transformation volume fracturing technology |
| CN105507871A (en) * | 2016-01-06 | 2016-04-20 | 西南石油大学 | Horizontal well liquid nitrogen ice crystal temperature plugging staged fracturing method for coalbed methane |
| CN105822275A (en) * | 2016-01-12 | 2016-08-03 | 中国石油大学(华东) | Fracturing fracture-forming technique and method for shale |
| CN105888604A (en) * | 2016-04-14 | 2016-08-24 | 中国石油天然气股份有限公司 | Method applicable to repeatedly transforming stratum nearby shaft of low-pressure gas field old well to complete permanent blocking |
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Application publication date: 20190104 |