CN103045211A - Method for preparing repeated fracturing blocking agent based on selective gel breaker - Google Patents
Method for preparing repeated fracturing blocking agent based on selective gel breaker Download PDFInfo
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- CN103045211A CN103045211A CN 201110326130 CN201110326130A CN103045211A CN 103045211 A CN103045211 A CN 103045211A CN 201110326130 CN201110326130 CN 201110326130 CN 201110326130 A CN201110326130 A CN 201110326130A CN 103045211 A CN103045211 A CN 103045211A
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Abstract
The invention discloses a method for preparing a repeated fracturing blocking agent based on a selective gel breaker. The method comprises the following steps of: (a) preparing polyacrylamide; (b) dissolving the prepared polyacrylamide; (c) adding a pre-crosslinker into the solution; (d) adding a second crosslinker into the solution; (e) adding the gel breaker into the solution, wherein the gel breaker is ammonium persulfate; and (f) reacting the mixed solution in an incubator, and thus obtaining a target product. By adopting the method, the repeated fracturing blocking agent required by the conventional oilfields can be successfully prepared; the method is simple and facilitates artificial operation; various performance parameters of the prepared repeated fracturing blocking agent are superior to those of the conventional pressure blocking agent, and a foundation is laid for the exploitation of the oilfields; and by selecting the proper gel breaker, the gel breaking performance of the product is improved.
Description
Technical field
The present invention relates to a kind of refracturing blocking agent preparation method based on selecting gel breaker.
Background technology
Low-permeability oil deposit is to refer generally to the oil reservoir that the oil reservoir of rate of permeation between 10-50 * 10-3 μ m2 consists of in China.Along with the continuous intensification of exploration and development degree, China's low-permeability oil pool total proven reserve and in the mining-employed reserves shared ratio more and more higher, keep and the promotion development of oil industry in the effect brought into play increasing.As take China National Petroleum Corporation (CNPC) as example, at the bottom of calendar year 2001, verify petroleum-in-place 145 * 108t, wherein hyposmosis reserves 44 * 108t accounts for 30%; Employ petroleum-in-place 110 * 108t, wherein hyposmosis reserves 21 * 108t accounts for 19%; Residue is verified and is not employed petroleum-in-place 35 * 108t, and wherein hyposmosis reserves 22 * 108t accounts for 62%.In the reserves of verifying then in the recent period, the shared ratio of hyposmosis reserves is larger, up to 65%～70%.How to employ and developed the low permeability oil field reserves, to the sustainable and stable development of China Petroleum with guarantee that the safe tool of China's oil is of great significance.
Low-permeability oil deposit is because reservoir properties is poor, and oil well output is low, and owing to complex pore structure, seepage state is unusual, causes its oil-field development feature and medium to high permeable oil reservoir to be very different, even the variation of matter occurs.LOW PERMEABILITY OILFIELD DEVELOPMENT has following essential characteristic:
(1) the oil well natural production capacity is low, just has commercial mining behind the fracturing reform and is worth;
(2) percolation law is not followed Darcy's law, has the trigger pressure gradient;
(3) natural energy is little, and pressure, production declining are fast, and primary recovery rate is low;
(4) the water injection well water-retaining capacity is low, and trigger pressure and water injection pressure rise fast;
(5) liquid production index sharply descends behind the oil well water breakthrough, and the stable yields difficulty is very large.
Hydraulic fracturing technology has been widely used in the exploitation in low-permeability oil gas field as the major measure of well production increment, intensified injection of wells, for the stable yields of oil-gas field has been made significant contribution.Improve near the seepage flow condition the shaft bottom by waterfrac treatment, linked up the oil gas gathering area and change the hydrocarbon flow flowing mode, improved Oil ﹠ Gas Productivity.The output of domestic hypotonic oil-gas field and the output that obtains by the waterfrac treatment transformation are all increasing sharply year by year.
Through oil, gas, the well after the waterfrac treatment, owing to be subjected to the at that time restriction of fracturing technology, material, equipment tool, the reason such as it is little that scale is owed, and material selection is improper, and plant capacity is limited can cause the hydraulic fracture flow conductivity significantly to reduce and ineffective gradually; Some then selects improper because of the well layer or the operation reasons also fails effectively to pass through simultaneously long period of development, and the major oil gas field has entered the development phase of middle and high Water-cut Period, and the difficulty of stable high yield is increasing; To this class Oil/gas Well, in order to obtain high yield and economic exploitation benefit, need to carry out refracturing.
USDOE in 1987 change the pressure break experiment of stress in many wells experiments, first proved stress field be subject to the impact of offset well crack.Dowell company is thought according to experiment and simulated ground stress research, exist supporting crack will change near the stress distribution of well in the stratum, make the crack initiation orientation of refracturing perpendicular to first crack, leave to redirect to again after the well certain limit and be parallel to first fracture azimuth and extend.Chen﹠amp; The researchs such as Minner are thought that pore pressure changes and are caused new crack approximately perpendicular to crack last time or with last time the crack was in an acute angle.Chevron Oil Tech Inc shows in the test in U.S. Lost Hill oil field, refracturing fracture azimuth and 30 ° of first fracture orientation skews; Unocal company has confirmed that in the test of the refracturing in Van oil field the refracturing crack may depart from 60 ° with fracture azimuth last time.The development of multiple fracturing technique that these have tested the promotion strong with research has obtained extremely significant economic benefit.For example, Rangely oil field, one of oil field that the U.S. develops the earliest, many well refracturings reach 4 times, and success ratio reaches 70-80%; Refracturing is 185 mouthfuls in 385 mouthfuls of recovery wells in Kuparuk River oil field, U.S. Alaska, and productivity index has on average improved twice after pressing.
A large amount of refracturing operations has also been carried out in the oil fields such as recent year grand celebration, triumph, long celebrating, huge port, Jilin, and has done certain exploration from theory and practice, has obtained some experiences and understanding.Since nineteen ninety-five, Southwest Petrol University has successively carried out STUDY ON REPETITIVE FRACTURING TECHNOLOGY with Liaohe Oil Field, long celebrating oil field, Xinjiang Oilfield and Shengli Oil Field, and with the changed course refracturing test that has launched the new seam of the stifled old seam pressure of high water-cut stage in length celebrating oil field, the Xinjiang Oilfield cooperation, obtain good effect of increasing production, opened up the new direction of refracturing research.
The process of stifled pressure integrated technique is to use first the long-acting shutoff of blocking agent or the temporary transient old crack of shutoff, and then other orientation presses off new crack on the stratum with waterfrac treatment technique, again transforms reservoir to reach, and improves the purpose of reservoir recovery.Behind the blocking agent shutoff crack, follow-up fracturing liquid must have extruding and penetration to it, therefore requires the refracturing blocking agent to have the performance higher than conventional blocking agent.
After entering old crack, refracturing blocking agent working fluid forms gel, under follow-up fracturing liquid effect, blocking agent will be subject to of the fracturing fluid extruding and penetration, therefore the performance of refracturing blocking agent will satisfy the requirement of two aspects: the one, and the strongly adherent between blocking agent-crack wall stops fracturing liquid to penetrate toward first man-made fracture; The 2nd, self has high strength blocking agent, can resist of the fracturing fluid extruding.Blocking agent not only has high intensity and adhesivity in a word, and certain stress deformation ability will be arranged.This just requires the breakthrough pressure of blocking agent will be higher than the squeeze that is subject to.
The appearance of refracturing crack steering mechanism is the major progress of multiple pressure technology, has roughly passed through three phases:
Early stage (1) 20 nineties in century, at first be the understanding that the refracturing fracture azimuth turns to, obtained at the scene checking: Chevron Oil Tech Inc is in U.S. LostHill oil field, utilize dipmeter survey refracturing fracture azimuth, then with the first time fracturing fracture orientation compare, the inferior average fracture azimuth of refracturing of 167 wells is N25 ° of E as a result, and the inferior first fracturing fracture orientation of well more than 100 is N55 ° of E, the two differs 30 °, illustrates that thus the fracture azimuth that refracturing forms is different from first fracturing fracture orientation; And the mechanism that the refracturing crack turns to also obtained further developing, and people recognize that gradually production process reservoir pore space pressure change finally can change the stressed condition of reservoir.
Because reservoir all directions pressure attenuation is unbalanced, in containing vertically fractured reservoir, form oval decay area, its longitudinal slit axial ratio vertical fractures axle is much longer, the decline of horizontal total stress approach of shear strength that is parallel to man-made fracture is just large than vertical (minimum) stress components, and this is the key of stress reorientation.If the STRESS VARIATION that produces is enough large, be enough to offset the impact of initial level deviatoric stress, the direction of minimum level stress will local half-twist so, in this case, the refracturing crack should be perpendicular to original crack growth, but refracturing is redirected and depends on many factors, comprises rate of permeation and the rate history of original deviatoric stress, primary fracture length, reservoir, so be redirected also not necessarily perpendicular to former crack in actual crack.
(2) the 20 later stages nineties in century, recognize to turn to refracturing to be rich in residual oil area and greatly to improve output and workable reserve by the effective communication reservoir, stimulated Chinese scholars to turning to the research of refracturing.Because the refracturing fissure extension mode still depends on the reservoir stressed condition, not controlled by objective stress condition take people's subjective will as shifting.Proposed to simulate the variation model of in-situ stress field under many wells (comprising oil well and well) and the varying flow rate condition therebetween, abroad.Result of study shows, the variation of in-situ stress field depend primarily on time that the distance apart from oil and water well, whole oil-gas field drop into exploitation, injection-production well not, the anisotropy of original level deviator stress, rate of permeation and produce fluence etc.And further carry out refracturing well and story selecting technology, people expect the technology such as integrated application expertise, artificial neural network technology and fuzzy logic, develop the model of refracturing well and story selecting, implement refracturing to find out those oil reservoirs that might turn to.
(3) enter 21 century after, turn to multiple fracturing technique to further develop, some experts and scholars of Southwest Petrol University have proposed a kind of new technology of forcing the crack to turn to, namely new crack multiple fracturing technique is pressed in stifled old crack.Through exploitation after a while, the low permeability layer in oil field has been in high water-cut stage, and the crude oil of primary fracture control is near whole extraction, and the crack has become the principal passage of water, but the still control under existing extraction condition of some well has certain residual recoverable reserves.If at this moment take to extend the effect that the conventional refracturing of primary fracture does not have certainly, best bet is that primary fracture is blocked, pressure break again, with primary fracture at an angle direction make new seam, but so both water blockoffs can increase petroleum production again.Namely study a kind of high-intensity crack blocking agent shutoff primary fracture, enter selectively after in blocking agent pumps into well and the shutoff primary fracture, but can not infiltrate formation pore and stop up blowhole, simultaneously shutoff perf effectively around pit shaft; Then adopt the oriented perforating technology again perforation to guarantee that (best orientation is perpendicular to the orientation of primary fracture) redirects perforation and impel the crack to turn in the orientation that is different from primary fracture, namely form new crack, thereby extraction least principal stress direction or near the oil gas of least principal stress direction drainage area realizes water-control oil-increasing.
Refracturing refers to the well layer of taking once or several times pressing crack construction measure is implemented fracturing reform again.As far back as the 1950's, just carried out refracturing abroad, development through more than 50 years, reservoir reevaluating, well and story selecting new technology, fracturing liquid, fractured well dynamic prediction, refracturing crack steering mechanism, refracturing optimization design and the aspects such as Study on Process, crack Diagnosis and effect assessment all are rapidly developed before refracturing, not only become the increasing yield and injection means of hydrocarbon-bearing pool, also become economical and effective and develop gordian technique hypotonic, ultra-low permeability reservoir.
After pressing crack construction finished, can the refracturing blocking agent break glue and greatly affect blocking agent to injury and the old crack plugging removal effect on stratum under formation condition, and it is concerning the success or failure of pressing crack construction process and the quality of effect.
Summary of the invention
The object of the invention is to overcome the shortcoming and defect of above-mentioned prior art, a kind of refracturing blocking agent preparation method based on selecting gel breaker is provided, this preparation method can successfully prepare the required refracturing blocking agent in existing oil field, and preparation process is simple, be convenient to workman's operation, the various performance parameters of the refracturing blocking agent for preparing all is better than existing pressure blocking agent, for the exploitation in oil field is laid a good foundation; And pass through to select suitable gel breaker, thereby improved the broken colloidality energy of product.
Purpose of the present invention is achieved through the following technical solutions: a kind of refracturing blocking agent preparation method based on selecting gel breaker may further comprise the steps:
(a) at first, preparation polyacrylamide;
(b) then, with the polyacrylamide amine solvent for preparing;
(c) then, add precrosslinker to it;
(d) add the second linking agent to it again;
(e) add gel breaker to it, described gel breaker is ammonium persulphate;
(f) mixing solutions is positioned in the thermostat container reacts, namely get target product.
In the described step (a), the envrionment temperature of preparation polyacrylamide is normal temperature.
State in the step (b), by clear water with the polyacrylamide amine solvent.
In the described step (c), precrosslinker is chromium ion.
In the described step (d), the second linking agent is organic phenolic aldehyde.
In sum, the invention has the beneficial effects as follows: can successfully prepare the required refracturing blocking agent in existing oil field, and preparation process is simple, is convenient to workman's operation, the various performance parameters of the refracturing blocking agent for preparing all is better than existing pressure blocking agent, for the exploitation in oil field is laid a good foundation; And pass through to select suitable gel breaker, thereby improved the broken colloidality energy of product.
Embodiment
Below in conjunction with embodiment, the present invention is described in further detail, but embodiments of the present invention are not limited only to this.
Embodiment:
A kind of refracturing blocking agent preparation method based on selecting gel breaker who the present invention relates to, its concrete steps are as follows:
(a) at first, preparation polyacrylamide;
(b) then, with the polyacrylamide amine solvent for preparing;
(c) then, add precrosslinker to it;
(d) add the second linking agent to it again;
(e) add gel breaker to it, described gel breaker is ammonium persulphate;
(f) mixing solutions is positioned in the thermostat container reacts, namely get target product.
In the described step (a), the envrionment temperature of preparation polyacrylamide is normal temperature.
State in the step (b), by clear water with the polyacrylamide amine solvent.
In the described step (c), precrosslinker is chromium ion.
In the described step (d), the second linking agent is organic phenolic aldehyde.
In order to obtain suitable gel breaker, the present invention done different gel breakers to the impact experiment of product, experimental result is as shown in the table:
As seen from the above table: benzoyl peroxide, Potassium Monopersulfate, three kinds of gel breakers of azo diethyl butyronitrile all can not thoroughly break glue, and oil-soluble benzoyl peroxide and azo diethyl butyronitrile are poorly soluble, are unfavorable for construction.And water miscible gel breaker A easy to operate (water-soluble), broken glue is thorough, can satisfy on-the-spot construction requirement.
The above only is preferred embodiment of the present invention, is not the present invention is done any pro forma restriction, and every foundation technical spirit of the present invention, any simple modification, equivalent variations to above embodiment does all fall within protection scope of the present invention.
Claims (5)
1. the refracturing blocking agent preparation method based on the selection gel breaker is characterized in that, may further comprise the steps:
(a) at first, preparation polyacrylamide;
(b) then, with the polyacrylamide amine solvent for preparing;
(c) then, add precrosslinker to it;
(d) add the second linking agent to it again;
(e) add gel breaker to it, described gel breaker is ammonium persulphate;
(f) mixing solutions is positioned in the thermostat container reacts, namely get target product.
2. a kind of refracturing blocking agent preparation method based on selecting gel breaker according to claim 1 is characterized in that, in the described step (a), the envrionment temperature of preparation polyacrylamide is normal temperature.
3. a kind of refracturing blocking agent preparation method based on selecting gel breaker according to claim 1 is characterized in that, in the described step (b), by clear water with the polyacrylamide amine solvent.
4. a kind of refracturing blocking agent preparation method based on selecting gel breaker according to claim 1 is characterized in that in the described step (c), precrosslinker is chromium ion.
5. a kind of refracturing blocking agent preparation method based on selecting gel breaker according to claim 1 is characterized in that in the described step (d), the second linking agent is organic phenolic aldehyde.
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| CN 201110326130 CN103045211A (en) | 2011-10-13 | 2011-10-13 | Method for preparing repeated fracturing blocking agent based on selective gel breaker |
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| CN 201110326130 CN103045211A (en) | 2011-10-13 | 2011-10-13 | Method for preparing repeated fracturing blocking agent based on selective gel breaker |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103952130A (en) * | 2014-05-05 | 2014-07-30 | 克拉玛依市红都有限责任公司 | Temporary blocking gel for low-pressure oil-gas well and preparation method thereof |
| CN105368437A (en) * | 2015-11-26 | 2016-03-02 | 陕西延长石油(集团)有限责任公司研究院 | Hydroxypropyl guar gum fracturing fluid containing potassium monopersulfate and preparation method thereof |
| CN112377165A (en) * | 2020-11-18 | 2021-02-19 | 中国石油天然气股份有限公司 | Fracturing physical simulation experiment method for creating new joints among old joints of horizontal well |
-
2011
- 2011-10-13 CN CN 201110326130 patent/CN103045211A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103952130A (en) * | 2014-05-05 | 2014-07-30 | 克拉玛依市红都有限责任公司 | Temporary blocking gel for low-pressure oil-gas well and preparation method thereof |
| CN105368437A (en) * | 2015-11-26 | 2016-03-02 | 陕西延长石油(集团)有限责任公司研究院 | Hydroxypropyl guar gum fracturing fluid containing potassium monopersulfate and preparation method thereof |
| CN105368437B (en) * | 2015-11-26 | 2018-02-06 | 陕西延长石油(集团)有限责任公司研究院 | A kind of hydroxypropyl melon fracturing fluid containing Potassium Monopersulfate and preparation method thereof |
| CN112377165A (en) * | 2020-11-18 | 2021-02-19 | 中国石油天然气股份有限公司 | Fracturing physical simulation experiment method for creating new joints among old joints of horizontal well |
| CN112377165B (en) * | 2020-11-18 | 2022-12-02 | 中国石油天然气股份有限公司 | Fracturing physical simulation experiment method for creating new joints among old joints of horizontal well |
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Application publication date: 20130417 |