CN107989592B - Staged fracturing method for horizontal well - Google Patents

Staged fracturing method for horizontal well Download PDF

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CN107989592B
CN107989592B CN201610956610.8A CN201610956610A CN107989592B CN 107989592 B CN107989592 B CN 107989592B CN 201610956610 A CN201610956610 A CN 201610956610A CN 107989592 B CN107989592 B CN 107989592B
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fracturing
sand
perforation
fluid
proppant
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CN107989592A (en
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蒋廷学
路保平
卫然
卞晓冰
詹美玲
李双明
王海涛
苏瑗
肖博
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China Petroleum and Chemical Corp
Sinopec Research Institute of Petroleum Engineering
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Sinopec Research Institute of Petroleum Engineering
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    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/25Methods for stimulating production
    • E21B43/26Methods for stimulating production by forming crevices or fractures
    • E21B43/267Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09KMATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/60Compositions for stimulating production by acting on the underground formation
    • C09K8/62Compositions for forming crevices or fractures
    • C09K8/66Compositions based on water or polar solvents
    • C09K8/665Compositions based on water or polar solvents containing inorganic compounds
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09KMATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/60Compositions for stimulating production by acting on the underground formation
    • C09K8/62Compositions for forming crevices or fractures
    • C09K8/70Compositions for forming crevices or fractures characterised by their form or by the form of their components, e.g. foams
    • C09K8/706Encapsulated breakers
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09KMATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K2208/00Aspects relating to compositions of drilling or well treatment fluids
    • C09K2208/26Gel breakers other than bacteria or enzymes

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  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Mining & Mineral Resources (AREA)
  • Physics & Mathematics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)

Abstract

The invention provides a staged fracturing method for a horizontal well, which comprises the step of sequentially implementing N sand carrying fluid injection stages, wherein the volume density of a proppant used in the Nth sand carrying fluid injection stage is smaller than that of the proppant used in the previous N-1 sand carrying fluid injection stages, and N is a natural number larger than 1. Furthermore, the fracturing fluid used in the Nth sand-carrying fluid injection stage is selected from the fracturing fluid with the ratio of storage modulus to energy consumption modulus of (2.0-5.0): 1. The method ensures the uniform displacement effect of each cluster of cracks by improving the suspension performance of the propping agent and/or the fracturing fluid, and ensures that each cluster of cracks uniformly feed liquid and sand so as to achieve synchronous gel breaking and flowback of the fracturing fluid in the whole-section cluster of cracks, thereby reducing the occurrence of the over-displacement phenomenon in staged fracturing of a horizontal well, improving the after-pressure effect and realizing the maximization of the stable production period.

Description

Staged fracturing method for horizontal well
Technical Field
The invention relates to the technical field of horizontal well staged fracturing, in particular to a horizontal well staged fracturing method for reducing displacement, and particularly relates to a horizontal well staged fracturing method for reducing displacement in the field of horizontal well fracturing of hypotonic and compact sandstone, carbonate rock, shale and coal rock.
Background
At present, the staged fracturing technology of the horizontal well becomes a main development technology of low-permeability and compact sandstone, carbonate rock, shale and even coal rock, and plays great economic and social benefits in production practice. The high-viscosity glue liquid is used for displacement in the construction process of the technology, but different from the vertical well fracturing, the horizontal well staged fracturing technology has the over-displacement phenomenon, and the over-displacement amount of some horizontal well staged fracturing technologies can reach more than 2 times of the normal value. No matter the open hole sliding sleeve or the bridge plug perforation combined technology is adopted, in order to prevent the adverse effect of horizontal shaft sand setting on ball throwing seat sealing or bridge plug seat sealing, high-viscosity glue solution is sometimes used for excessive replacement. This is extremely detrimental to the fracture-propping profile protection of horizontal well staged fracturing and can also severely impact the post-fracturing effect. Mines often find that the actual fracturing effect of horizontal wells does not achieve the expected simulated prediction results, and the main reason may be that it is the source of this.
From a technical point of view, the main reasons for the over-substitution are found at present: 1) the diameter of the horizontal shaft is only more than 200 millimeters, so that the settling distance of the proppant is allowed to be limited; 2) the density of the proppant is larger than that of the fracturing fluid, and for example, the general bulk density is 1.7g/cm3Above, far more than 1.03g/cm of fracturing fluid3(ii) a 3) The design amount of the fracturing pad fluid is larger, and the crack still continues to extend after the pump is stopped, especially when the content of brittle minerals such as quartz is high.
The adverse effects of over-displacement on the fracturing effect are mainly: 1) after the pressure is seriously reduced, the flow conductivity of the near-wellbore fracture at the initial stage is completely lost, so that the effect of 'making dumplings' is generated; 2) if synchronous gel breaking control is not good, the fracturing fluid of the first fracturing section is hydrated and broken in advance, so that the fracture is closed prematurely due to large filtration loss, and fatal influence is brought to remedial measures of the diversion capacity of the fracture of the near well; 3) in the past, a method of uniformly perforating each cluster is adopted, so that the fracture overstrike effects of different clusters are different when the same section is fractured, the overstrike amount closer to a shaft is more, and the contribution of each cluster of perforation to the yield is not exerted in a balanced manner.
In conclusion, the development of a new horizontal well staged fracturing technology capable of greatly reducing the over-displacement amount to realize the maximization of the post-fracturing effect and the stable production period has obvious practical significance.
Disclosure of Invention
The invention aims to provide a novel horizontal well staged fracturing technology capable of reducing or preventing over-displacement, in particular to a horizontal well staged fracturing method capable of reducing over-displacement in the field of horizontal well fracturing of hypotonic and compact sandstone, carbonate rock, shale and coal rock so as to improve the post-fracturing effect and maximize the stable production period.
The basic design idea and the aim of the invention are to reduce the occurrence of the over-displacement phenomenon in the staged fracturing of the horizontal well by improving the suspension performance of the proppant in the fracturing process of the horizontal well. Furthermore, uniform liquid feeding and sand feeding of each cluster of cracks can be guaranteed by improving the suspension performance of the fracturing fluid, optimizing the density of the cluster perforation or end desanding and the like, so that synchronous gel breaking and flowback of the fracturing fluid in all-section cluster of cracks are achieved, and the phenomenon of over-displacement in staged fracturing of the horizontal well is further reduced.
According to the invention, the staged fracturing method of the horizontal well comprises the steps of sequentially implementing N sand carrying fluid injection stages, wherein the volume density of the proppant used in the Nth sand carrying fluid injection stage is less than that of the proppant used in the previous N-1 sand carrying fluid injection stages; and N is a natural number greater than 1. That is, in the fracturing method provided by the present invention, low density proppant is used in the last sand ratio stage.
And N represents N sand carrying liquid injection operation stages which are sequentially carried out in the fracturing construction process. According to the invention, the value of N can be selected according to the actual construction conditions of lithology, reservoir parameters, construction requirements and the like of the oil well. For example, N may be a natural number from 2 to 7; specifically, N may be 2, 3, 4, or 5, etc.
In construction, the nth carrier injection phase generally refers to a carrier injection operation phase in which the injection amount of the carrier is equivalent to the normal displacement amount, i.e., the injection amount of the carrier is equivalent to the volume of the wellbore.
Preferably, the Nth sand-carrying fluidThe bulk density of the proppant used in the injection stage was 1.2g/cm3Hereinafter, it is preferably 1.2 to 0.8g/cm3For example, 1.05 to 1.15g/cm3
Further preferably, the proppant used in the Nth sand-carrying fluid injection stage is selected from proppant having a bulk density of 1.05-1.5g/cm3Low density proppant of less than 1.05g/cm bulk density3E.g. 1.05-0.80g/cm3) One or more of ultra-low density proppant and self-suspending proppant. The amount of the proppant is preferably the amount of the proppant in the mixed mortar, which is completely replaced by the same amount as the replacement amount, and can be obtained by calculation according to the total volume of the shaft (calculated by the middle position point of each perforation section) and the ratio of the final construction sand liquid.
The self-suspending proppant is also called a self-suspending fracturing proppant, and is not particularly limited in the present invention, and self-suspending proppants commonly used in the art may be applied to the present invention.
According to the method provided by the invention, from the perspective of the proppant, the low-density/ultra-low-density proppant and the novel self-suspending proppant are added at the final stage of sand adding, so that the suspension performance of the proppant can be improved, and the phenomenon of over-displacement in subsequent displacement construction can be further reduced or avoided.
According to a preferred embodiment of the invention, the ratio of the storage modulus to the dissipation modulus of the fracturing fluid used in the Nth sand-carrying fluid injection stage is (2.0-5.0):1, preferably (2.1-4.0):1, preferably (2.5-3.0): 1. The storage modulus and the dissipation modulus of the fracturing fluid are determined and adjusted by one skilled in the art by conventional methods and will not be described herein.
Preferably, the ratio of the storage modulus to the energy consumption modulus of the fracturing fluid used in the Nth sand-carrying fluid injection stage is greater than the ratio of the storage modulus to the energy consumption modulus of the fracturing fluid used in the previous N-1 sand-carrying fluid injection stages. In the prior art, the ratio of the storage modulus to the energy consumption modulus of the used fracturing fluid is generally below 2:1 in the whole sand-carrying fluid injection operation stage. Thus, in some embodiments of the invention, the ratio of storage modulus to dissipation modulus of the fracturing fluid used in the previous N-1 stages of sand carrier injection is below 2: 1.
Further, the visco-elastic coefficient of the fracturing fluid used in the Nth sand-carrying fluid injection stage is larger than that of the fracturing fluid used in the previous N-1 sand-carrying fluid injection stage. I.e. using a chased viscoelastic increasing fracturing fluid in the last sand ratio stage.
According to the invention, the displacement construction is carried out after the nth sand-carrying fluid injection stage.
According to a preferred embodiment of the invention, the fracturing fluid used in the nth sand-carrying fluid injection stage (i.e. the after-dressing fracturing fluid) is preferably a surfactant fracturing fluid, a clean polymer fracturing fluid or a fiber fracturing fluid.
According to the invention, in the previous N-1 sand-carrying fluid injection stages, for the fracturing of low-permeability and compact sandstone, carbonate rock and coal rock, the viscosity of the fracturing fluid is 50-100 mPa.s; for shale oil and gas fracturing, the viscosity of the fracturing fluid is 2-40mPa.s, preferably 2-10mPa.s if the fracturing fluid is slickwater, and 20-40mPa.s if the fracturing fluid is glue solution.
On the basis of meeting the requirements of fracturing fluid crack formation and sand suspension performance, the lower the viscosity of the fracturing fluid is, the more beneficial to uniform liquid inlet and sand inlet among cluster cracks of each section is. Generally, a fracturing fluid having the above viscosity range is used at the initial stage of fracturing. On the basis, in the final sand carrying fluid stage equivalent to the normal displacement amount, surfactant fracturing fluid, clean polymer fracturing fluid or fiber fracturing fluid with good viscoelasticity is used. Generally, the ratio of the storage modulus to the dissipation modulus should be maintained above 2 times to further improve the sand suspension of the fracturing fluid and prevent the sand setting effect of the horizontal wellbore.
The specific formula and the dosage optimization scheme of the after-tracking fracturing fluid can be determined by combining actual core data and indoor comprehensive performance evaluation results.
In accordance with the present invention, in the previous N-1 sand-carrying fluid injection stages, for conventional lithology (commonly referred to as hypotonic and tight sandstone, carbonate and coal) fracturing, 70-140 mesh and 20-40 mesh proppants were used as proppants; for shale gas fracturing, three proppants of 70-140 meshes, 40-70 meshes and 30-50 meshes are used as the proppants. The proppant used in the previous N-1 sand-carrying fluid injection stages is the proppant conventionally used in the artThe bulk density is larger and is generally 1.5g/cm3The above.
The proppant for conventional lithologic fracturing can be a small amount of 70-140 meshes of proppant for polishing the bending friction resistance of the near-well fracture; the shale gas fracturing propping agent is generally 70-140 meshes of propping agent, the using amount of the propping agent is large, and the propping agent not only can polish the bending friction of the near-well fracture, but also has the function of propping the micro-fracture.
The specific preferred performance requirements of the proppant may be determined in conjunction with the results of the indoor comprehensive performance evaluation.
According to the preferred embodiment of the invention, during the fracturing construction, each perforation cluster is subjected to end sand removal fracturing, and the end sand removal fracturing based on the filtration loss and the end sand removal fracturing based on the size of the fracture are preferably performed simultaneously.
Preferably, the construction sand-liquid ratio of the end sand-removing fracturing based on the fracture size is screened according to the wellhead pressure change rate by a trial and error method, and the wellhead pressure rise rate is preferably higher than 6MPa/min, preferably 6-25MPa/min, more preferably 8-20 MPa/min. In some embodiments, the sand-to-liquid ratio may be, for example, 16-26%.
From the angle of optimization of technological parameters, uniform liquid feeding and sand feeding of each cluster of cracks are ensured, the aim is easy to achieve through a combination measure of proper low viscosity and proper low discharge capacity, and the combination of high viscosity and high discharge capacity can cause the cracks of the clusters close to a shaft to lose sufficient liquid feeding and sand feeding machines. By adopting the design and construction technology that each section is subjected to end sand removal fracturing, the uncontrollable effect caused by overlarge continuous extension length of the fracture after the pump is stopped can be prevented; at this time, the extension of the fracture ends is stopped, and even if the fracture ends are partially displaced, the fracture entrance resistance is greatly increased, so that the fracture width is continuously increased, and the chance of extending the proppant in the fracture length direction is greatly reduced. On the basis of accurately evaluating the comprehensive fluid loss coefficient of each section of cluster reservoir, the probability of realizing end screenout can be increased by adopting two end screenout mechanisms to implement synchronously; the sand-removing effect of the end part caused by large filtration loss is realized, and the sand-removing effect of the end part caused by narrow and wide gaps is realized.
The end screenout fracturing based on the fluid loss is designed by referring to a fluid loss coefficient, and the end screenout fracturing depends on the existing mature process design flow of the fluid loss coefficient, so that the process is not redundant. As for the end desanding technology caused by narrow and narrow gap, a trial and error method can be adopted, construction is carried out by using a certain higher construction sand-liquid ratio, pressure response characteristics are observed after the sand-liquid ratio mixed mortar enters a stratum, and if the pressure rising rate in unit time (min) is less than 1MPa/min, the sand-liquid ratio does not achieve the end desanding effect; however, if the pressure rise rate under a certain construction sand-liquid ratio is far greater than 1MPa/min, the sand blocking occurs in the crack close to the well casing, and the design concept of end desanding is not met. Thus, through a plurality of tentative sand adding tests, the optimal construction sand-liquid ratio capable of achieving the end sand removal effect can be obtained.
The synchronous gel breaking technology is the best measure for compensating the over-displacement effect. By optimizing the concentration profile of the gel breaker of each section of fracture fracturing fluid, the final aim is to ensure that the fracturing fluid in all the sections of clusters is subjected to back flow and is subjected to instantaneous and complete gel breaking and back flow after being pressed, so that the passive situation caused by over-displacement can be compensated.
In the present invention, the non-uniform synchronization technique is further developed. According to the preferred embodiment of the invention, in the fracturing construction process, a non-uniform synchronous gel breaking method is adopted for gel breaking, and preferably, the gel breaker used in each section of perforation cluster fracturing fluid contains 3-1 weight percent: 1, preferably 1:1, non-encapsulated and encapsulated ammonium persulphates; and designing construction parameters for alternately injecting the non-capsule ammonium persulfate and the capsule ammonium persulfate so as to realize the alternate distribution of the capsule ammonium persulfate and the non-capsule ammonium persulfate on the fracture height section. Even if the non-capsule type ammonium persulfate is broken and the proppant is settled, the capsule type ammonium persulfate is not broken synchronously, and therefore, the support profile of the proppant in the longitudinal direction is further improved.
In the present invention, the non-encapsulated ammonium persulfate means an ammonium persulfate-containing capsule breaker, and is not particularly limited, and any ammonium persulfate capsule breaker commonly used in the art may be applicable. The capsule ammonium persulfate can also be an ammonium persulfate microcapsule gel breaker.
According to a preferred embodiment of the invention, the method comprises performing a pre-fracturing reservoir evaluation prior to the fracturing construction, preferably the pre-fracturing reservoir evaluation comprises obtaining a brittleness index, a rock mechanics parameter, a natural fracture characteristic parameter and a comprehensive fluid loss coefficient.
The evaluation of the reservoir before the fracturing takes the compressibility evaluation as a core, and particularly, the determination of the comprehensive fluid loss coefficient is particularly important, which is related to whether the subsequent end sand-removing fracturing technology can be really realized. The comprehensive fluid loss coefficient can be obtained according to conventional methods such as geology, well logging, core experiments, small-scale test fracturing (especially analysis of pressure drop data) and the like, which are conventional methods and are not redundant. Preferably, all data is checked as far as possible from the field measurement data, and then applied, such as dessert prediction, preferably in combination with one or more post-compression gas (liquid) profile results for comparative verification.
And determining the positions of the geological and engineering double desserts based on the results of the reservoir evaluation before the fracturing, and designing the positions and the distribution of the perforation clusters. Generally, the better the brittleness, the greater the number of clusters. Preferably, the perforation cluster distribution is designed according to the brittleness index, and when the brittleness index is less than 65%, each perforation segment is designed with 2-4 perforation clusters, and when the brittleness index is more than 65%, each perforation segment is designed with 4 perforation clusters or more (such as 4-6 perforation clusters); the cluster spacing is preferably 25-30 m.
From the angle of optimization of the cluster perforation, in order to ensure the uniform displacement effect of each cluster of cracks, the variable perforation density is designed. According to a preferred embodiment of the invention, the perforation density of the perforation clusters decreases in the direction of the wellbore and is in the range of 8-24 perforations/m; preferably, the total number of perforations per perforation segment is in the range of 45 to 75 perforations, preferably 50 to 70 perforations. I.e., clusters closer to the wellbore, the lower the perforation density (e.g., 10 perforations/m), and vice versa, e.g., 16-20 perforations/m. Under the condition that the discharge capacity of the fracturing fluid exceeds 15m3/min, the total number of the perforations of each perforation section is 60-70 holes.
As for the design of the density of the holes of each cluster calculated from the near wellbore, the density of the perforation is adjusted comprehensively according to the average viscosity, the displacement, the cluster spacing and the like of the section, and the range of the density of the perforation can be designed to be 8-24 holes/meter. The higher the average viscosity and the displacement, the larger the cluster spacing, and the perforation density of the clusters close to the shaft can be properly amplified.
According to other processes possibly involved in the method provided by the invention, the subsequent liquid drainage and production seeking process are carried out according to the conventional horizontal well staged fracturing regulation.
In some embodiments of the present invention, a horizontal well staged fracturing (optimization) method is provided, comprising the steps of:
1) performing reservoir stratum evaluation before pressing to obtain brittleness index, rock mechanical parameters, natural fracture characteristic parameters and comprehensive fluid loss coefficients;
2) determining the position of the geological and engineering double desserts based on the evaluation result of 1), designing perforation cluster distribution and then perforating, wherein
When the brittleness index is more than 65%, each perforation section is designed with 4 or more than perforations,
the perforation density of the perforation clusters decreases progressively along the direction of the shaft and ranges from 8 to 24 holes/m,
the total number of perforations of each perforation segment is 45-75 holes, preferably 50-70 holes;
3) pumping the pad fluid to form a gap and sequentially performing N stages of sand-carrying fluid injection, wherein,
n is a natural number of 2-5;
in the previous N-1 sand-carrying fluid injection stages, for fracturing low-permeability and compact sandstone, carbonate rock and coal rock, the viscosity of the fracturing fluid is 50-100 mPa.s; for shale oil gas fracturing, the viscosity of the fracturing fluid is 2-40mPa.s, preferably, the viscosity of the fracturing fluid is 2-10mPa.s if the fracturing fluid is slickwater, and the viscosity of the fracturing fluid is 20-40mPa.s if the fracturing fluid is glue solution; and is
In the Nth sand-carrying fluid injection stage, a fracturing fluid with the ratio of the storage modulus to the energy consumption modulus of more than 2:1, preferably 2.0-5.0:1, more preferably 2.5-3.0:1 is used;
in the previous N-1 sand-carrying fluid injection stages, 70-140 meshes and 20-40 meshes of proppant are used for proppant for low-permeability and tight sandstone, carbonate rock and coal rock fracturing, and three kinds of proppant of 70-140 meshes, 40-70 meshes and 30-50 meshes are used for proppant for shale gas fracturing; and is
The volume density of the carrier fluid in the Nth sand-carrying fluid injection stage is 1.05-1.5g/cm3Low density proppant of less than 1.05g/cm bulk density3One or more proppants of the ultra-low density proppant and self-suspending proppant of (a);
4) performing replacement construction;
5) performing end sand-removing fracturing on each section of perforation cluster by using end sand-removing fracturing, preferably synchronously performing end sand-removing fracturing based on filtration loss and end sand-removing fracturing based on fracture size;
screening the construction sand-liquid ratio of the end sand-removing fracturing based on the size of the crack according to the pressure change rate by a trial and error method, and selecting the construction sand-liquid ratio which enables the pressure rise rate to be 6-25 MPa/min;
6) implementing non-uniform synchronous gel breaking
And (3) adopting a non-uniform synchronous gel breaking method to break gel, preferably, the gel breaker used by each section of perforation cluster fracturing fluid contains the following components in percentage by weight of 3-1: 1 non-capsule type ammonium persulfate and capsule type ammonium persulfate; and designing construction parameters for alternately injecting the non-capsule ammonium persulfate and the capsule ammonium persulfate so as to realize the alternate distribution of the non-capsule ammonium persulfate and the capsule ammonium persulfate on the fracture height section.
The details or explanations of the above steps 1) to 6) can be referred to the above. When it is practicable, the above steps 1) to 6) do not have to be performed in a strict order, and the order of performing the above steps may be appropriately adjusted as long as the object of the present invention is achieved.
The invention also provides application of the horizontal well fracturing method in low-permeability and tight sandstone, carbonate rock, shale or coal rock horizontal well fracturing.
The invention has the following technical characteristics and excellent effects
The invention provides a novel horizontal well staged fracturing technology for preventing displacement, which is an important component of main fracturing, and by carrying out steps of pre-fracturing reservoir evaluation taking compressibility evaluation as a core, cluster perforation scheme design, fracturing fluid viscosity and viscoelasticity design, proppant optimization, fracturing injection parameter optimization, non-uniform synchronous gel breaking technology and the like, the suspension performance of the proppant and the fracturing fluid is improved, the uniform displacement effect of each cluster of fractures is ensured, and uniform liquid inlet and sand inlet of each cluster of fractures are ensured, so that synchronous gel breaking and flowback of the fracturing fluid in all the clusters of fractures are achieved, the displacement phenomenon in staged fracturing of a horizontal well is reduced, the post-fracturing effect is improved, and the maximization of a stable production period is realized. The method has the advantages of reasonable design, simple construction process and simple and convenient operation, and has wide application prospect in horizontal well fracturing.
Detailed Description
The invention having been described in detail in the foregoing specification, the invention will now be further described in connection with specific examples, but it will be understood that the scope of the invention is not limited thereto. In the following embodiments, steps not described in detail can be operated by those skilled in the art according to actual situations. The components used in the examples, such as drag reducer, thickener, etc., are not particularly limited.
Examples
In the south of the east of Chuan, a well has a vertical depth of 2298m, a depth of 3623m and a horizontal section of 1060 m. The reconstruction is carried out according to the following construction parameters and steps.
And acquiring Young modulus, Poisson's ratio and ground stress data according to the well logging data interpretation result, correcting the data according to the core experiment result, and selecting a position with high brittleness, high gas content and good permeability as a reservoir dessert.
Calculating the brittleness index of the dessert position to be 45-55% according to mineral components and mechanical parameters, designing 2 clusters (with the hole density of 10 holes/m, 16 holes/m) -3 clusters (with the hole density of 10 holes/m, 16 holes/m and 22 holes/m) of perforation in each section, and gradually reducing the hole density along the direction of a shaft; the cluster spacing is 25-30 m, and the total number is 16.
The method is characterized in that crack propagation software Meyer is adopted to optimize the viscosity of the slickwater to be 3-6 mPa & s, the viscosity of the glue solution fracturing fluid to be 30mPa & s, and the ratio of the storage modulus to the energy consumption modulus to be 2.8, wherein the slickwater main agent is 0.05-0.1% of a drag reducer, and the glue solution fracturing fluid main agent is 0.3% of a thickening agent.
By combining crack propagation software and indoor experiments, the comprehensive optimization of the dosage and the particle size of the propping agent is as follows: 38m was used in the first 3 stages of sand-carrying fluid injection370-140 mesh, 20m340-70 mesh and 8m3Three 30-50 mesh proppants (the bulk density is 1.63-1.78 g/cm)3) In the last sand-carrying liquid injection5m is used in the entering stage (4 th sand carrying fluid injection stage)3Ultra-low density proppant (bulk density 1.02 g/cm)3). Total amount of proppant is 71m3
The first stage of fracturing construction is a pad fracturing stage, and slick water with the viscosity of 3 mPas is adopted. By combining crack propagation software and indoor experiments, the comprehensive optimization construction procedure is as follows: at 2m3Displacement injection at/min 15m3A hydrochloric acid pretreated wellbore; then at 2-14m3Permin displacement injection 100m3A slickwater having a viscosity of 3 mPas.
The second stage of the fracturing construction is a small-particle-size propping agent low sand ratio joint expansion stage (the first sand-carrying liquid injection stage), and slick water with the viscosity of 4-5 mPa & s and 70-140 meshes of propping agent (the volume density is 1.63-1.78 g/cm)3). By combining crack propagation software and indoor experiments, the comprehensive optimization construction procedure is as follows: the discharge capacity is stabilized at 14m3Permin, injecting 70-140 mesh proppant in a slug mode, wherein the sand ratio of the proppant is 2-12%, and the isolating slug is 35m3. At this stage, 1310m of slickwater of 5 to 6 mPas is co-injected338m of 70-140 mesh proppant3
The third stage of the fracturing construction is a high sand ratio joint filling stage (a second sand carrying fluid injection stage) of a medium-sized propping agent, and slick water with the viscosity of 6mPa & s and a 40-70 mesh propping agent (the volume density is 1.63-1.78 g/cm) are adopted3). By combining crack propagation software and indoor experiments, the comprehensive optimization construction procedure is as follows: the discharge capacity is stabilized at 14m3Permin, injecting 40-70 mesh proppant in a slug mode, wherein the sand ratio of the proppant is 14-16-18% in sequence, and the isolating slug is 40m3. At this stage, 190m of slickwater of 6 mPas is injected320m of 40-70 mesh proppant3
The fourth stage of fracturing construction is a large-size proppant high-sand ratio joint filling stage (the third sand-carrying fluid injection stage), and adopts glue solution with the viscosity of 30mPa & s and 30-50 meshes of proppant (with the volume density of 1.63-1.78 g/cm)3). By combining crack propagation software and indoor experiments, the comprehensive optimization construction procedure is as follows: the discharge capacity is stabilized at 14m3And/min, injecting 30-50 mesh proppant slug with sand ratio of 20%. At this stage, 30 mPas of glue solution is injected40m330-50 mesh proppant 8m3
The fifth stage of fracturing construction is an ultralow-density proppant plugging seam opening stage (the fourth sand-carrying fluid injection stage), and adopts glue solution with the viscosity of 30mPa & s and 30-50 meshes of ultralow-density proppant (the volume density is 1.02 g/cm)3). In the construction process, multiple field practices show that the pressure rise rate in unit time is 8-15 MPa/min after 22% of sand ratio enters the stratum, the sand ratio is adopted as the last sand adding stage in the last construction stage, and then displacement is carried out. Construction discharge capacity is stabilized at 14m3And/min, injecting 30-50 mesh ultra-low density proppant slug with sand ratio of 22%. At this stage, 23m of a 30 mPas solution was injected330-50 mesh ultra-low density proppant 5m3
And (3) gel breaking construction, wherein in the gel breaker of each stage of cluster fracturing fluid, the proportion of the conventional ammonium persulfate to the capsule type ammonium persulfate gel breaker is 1:1, the addition of the 1 st-stage gel breaker is 0.02%, and the subsequent step-by-step increase is 0.004%.
And (5) performing flowback and yield calculation.
By implementing the method, the over-displacement phenomenon is reduced to the minimum, the post-stress effect is improved, and the maximization of the stable yield period is realized. The well pressure has a unimpeded flow of 22.5 × 104m3The yield is improved by 12 percent compared with that of the adjacent wells on the same platform.
Although the present invention has been described in detail, modifications within the spirit and scope of the invention will be apparent to those skilled in the art. Further, it should be understood that the various aspects recited herein, portions of different embodiments, and various features recited may be combined or interchanged either in whole or in part. In the various embodiments described above, those embodiments that refer to another embodiment may be combined with other embodiments as appropriate, as will be appreciated by those skilled in the art. Furthermore, those skilled in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention.

Claims (23)

1. The staged fracturing method of the horizontal well is characterized by comprising N sand carrying fluid injection stages, wherein the volume density of a propping agent used in the Nth sand carrying fluid injection stage is smaller than that of a propping agent used in the previous N-1 sand carrying fluid injection stages, the ratio of the storage modulus to the energy consumption modulus of a fracturing fluid used in the Nth sand carrying fluid injection stage is larger than that of the fracturing fluid used in the previous N-1 sand carrying fluid injection stages, and N is a natural number larger than 1.
2. The method of claim 1, wherein the proppant used in the nth sand-carrying fluid injection stage has a bulk density of 1.2g/cm3The following.
3. The method of claim 2, wherein the proppant used in the nth sand-carrying fluid injection stage has a bulk density of 0.8 to 1.2g/cm3
4. The method of claim 2, wherein the proppant used in the Nth sand-carrying fluid injection stage is selected from the group consisting of proppant having a bulk density of 1.05 to 1.5g/cm3Low density proppant of less than 1.05g/cm bulk density3And (3) one or more of ultra-low density proppant and self-suspending proppant.
5. The method of claim 1, wherein the ratio of the storage modulus to the dissipation modulus of the fracturing fluid used in the nth sand-carrying fluid injection stage is (2.0-5.0): 1.
6. The method of claim 5, wherein the ratio of the storage modulus to the dissipation modulus of the fracturing fluid used in the Nth sand-carrying fluid injection stage is (2.5-3.0): 1.
7. The method of any one of claims 1 to 6, wherein each perforation cluster is end screenout fractured during the fracturing job.
8. The method of claim 7, wherein the fluid loss based end screenout fracturing and the fracture size based end screenout fracturing are performed simultaneously.
9. The method of claim 8, wherein the construction sand-to-fluid ratio for the end screenout fracturing based on fracture size is screened by trial and error against wellhead pressure change rate to a construction sand-to-fluid ratio that results in a wellhead pressure rise rate of 6-25 MPa/min.
10. The method as claimed in any one of claims 1 to 6, wherein during the fracturing construction, non-uniform synchronous gel breaking is used for gel breaking.
11. The method of claim 10 wherein the breaker used in each segment of the perforation cluster fracturing fluid comprises a weight ratio of 3-1: 1, designing construction parameters for alternately injecting non-capsule ammonium persulfate and capsule ammonium persulfate so as to realize the alternate distribution of the non-capsule ammonium persulfate and the capsule ammonium persulfate on a fracture height section.
12. The method of any one of claims 1 to 6, comprising conducting a pre-fracture reservoir evaluation prior to fracture construction.
13. The method of claim 12, wherein the pre-fracture reservoir evaluation comprises obtaining a brittleness index, a rock mechanics parameter, a natural fracture characteristic parameter, and a composite fluid loss coefficient.
14. The method of claim 12, wherein the geological and engineered dual-sweet-spot locations are determined based on results of pre-zonal reservoir evaluation and perforation cluster distributions are designed.
15. The method of claim 14, wherein the perforation cluster distribution is designed according to a brittleness index, and wherein each perforation segment is designed with 2-4 clusters of perforations when the brittleness index is less than 65%, and 4 or more clusters of perforations when the brittleness index is greater than 65%.
16. The method of claim 14, wherein the perforation density of the perforation clusters decreases in the direction of the wellbore and is in the range of 8-24 perforations/meter.
17. The method of claim 16, wherein the total number of perforations per perforation segment is between 45 and 75 perforations.
18. The method of claim 17, wherein the total number of perforations per perforation segment is between 50 and 70 perforations.
19. The method of claim 18, wherein the fracturing fluid displacement exceeds 15m3And in the case of/min, the total number of perforations of each perforation segment is 60-70 holes.
20. The method of any of claims 1 to 6, wherein the fracturing fluid used in the Nth sand-carrying fluid injection stage is a surfactant fracturing fluid, a clean polymer fracturing fluid, or a fiber fracturing fluid.
21. The method of any one of claims 1 to 6, wherein in the previous N-1 sand-carrying fluid injection stages, the viscosity of the fracturing fluid is between 50-100mPa.s for hypotonic and tight sandstone, carbonate and coal fracturing; for shale oil gas fracturing, the viscosity of the fracturing fluid is 2-40 mPa.s; and/or
Using 70-140 mesh and 20-40 mesh proppants for low-permeability and tight sandstone, carbonate and coal fracturing in the previous N-1 sand-carrying fluid injection stages; for shale gas fracturing, three proppants of 70-140 mesh, 40-70 mesh and 30-50 mesh are used.
22. A staged fracturing method for a horizontal well comprises the following steps:
1) obtaining brittleness index, rock mechanical parameters, natural fracture characteristic parameters and comprehensive fluid loss coefficients;
2) based on step 1), determining the position of the geological and engineering double desserts, designing perforation cluster distribution, and then perforating, wherein,
when the brittleness index is less than 65%, each perforation segment is designed with 2-4 clusters of perforation, when the brittleness index is more than 65%, each perforation segment is designed with 4-6 clusters of perforation,
the perforation density of the perforation clusters decreases progressively along the direction of the shaft and ranges from 8 to 24 holes/m,
the total number of perforations of each perforation segment is 45-75 holes;
3) pumping the pad fluid to form a gap and sequentially performing N stages of sand-carrying fluid injection, wherein,
n is a natural number of 2-5;
in the previous N-1 sand-carrying fluid injection stages, the viscosity of the fracturing fluid is 50-100mPa.s for low-permeability and compact sandstone, carbonate rock and coal rock fracturing, and the viscosity of the fracturing fluid is 2-40mPa.s for shale oil gas fracturing; and is
In the Nth sand-carrying fluid injection stage, a fracturing fluid with the ratio of the storage modulus to the energy consumption modulus of 2.0-5.0:1 is used;
in the previous N-1 sand-carrying fluid injection stages, 70-140 meshes and 20-40 meshes of proppant are used for fracturing low-permeability and tight sandstone, carbonate and coal rock, and 70-140 meshes, 40-70 meshes and 30-50 meshes of three proppants are used for fracturing shale gas; and is
In the Nth sand-carrying fluid injection stage, the sand-carrying fluid is injected by using the sand-carrying fluid with the volume density of 1.05-1.5g/cm3Low density proppant of less than 1.05g/cm bulk density3One or more proppants of the ultra-low density proppant and self-suspending proppant of (a);
4) performing replacement construction;
5) end sand-free fracturing
Performing end desanding fracturing on each section of perforation cluster, and synchronously performing end desanding fracturing based on filtration loss and end desanding fracturing based on fracture size, wherein the construction sand-liquid ratio of the end desanding fracturing based on the fracture size is screened according to the pressure change rate by a trial and error method, and the construction sand-liquid ratio of which the pressure rise rate is 6-25MPa/min is selected;
6) implementing non-uniform synchronous gel breaking
Adopting a non-uniform synchronous gel breaking method to break gel, wherein the gel breaker used by each section of perforation cluster fracturing fluid contains the following components in percentage by weight of 3-1: 1 non-capsule type ammonium persulfate and capsule type ammonium persulfate; and designing construction parameters for alternately injecting the non-capsule ammonium persulfate and the capsule ammonium persulfate so as to realize the alternate distribution of the non-capsule ammonium persulfate and the capsule ammonium persulfate on the fracture height section.
23. Use of the method of any one of claims 1 to 21 or the method of claim 22 in hypotonic and tight sandstone, carbonate, shale or coal rock horizontal well fracturing.
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