CN109958424B - Method for effectively plugging end part of hydraulic fracture - Google Patents
Method for effectively plugging end part of hydraulic fracture Download PDFInfo
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- CN109958424B CN109958424B CN201711400764.XA CN201711400764A CN109958424B CN 109958424 B CN109958424 B CN 109958424B CN 201711400764 A CN201711400764 A CN 201711400764A CN 109958424 B CN109958424 B CN 109958424B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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
- E21B43/11—Perforators; Permeators
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
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Abstract
The invention discloses a method for effectively plugging the end part of a hydraulic fracture. The method comprises the following steps: injecting the mixed particle size ultra-low density proppant and soluble fiber at the end of the crack in a mixing way; the apparent density of the proppant is 1.05-1.25g/cm 3; adopting 140-230-mesh and 70-140-mesh mixed particle size proppant; the length of the fiber is 1-2 cm; the mass ratio of the fibers to the proppant is 1: 10-1: 20. The length of the front edge of the spread proppant is equal to that of the manufactured seam, the length of the spread proppant from the seam end to the direction close to the well is 10-15m, the width of the manufactured seam is more than or equal to that of the supported seam, and the error between the width of the supported seam and the width of the manufactured seam on the corresponding length is within 10%. The invention improves the effectiveness of hydraulic fracture end plugging, enables the fracture after temporary plugging to effectively turn and extend to a far well zone, and improves the complexity and the modification volume of the main fracture in the full length range so as to solve the limitation of the prior art and realize the maximization of the reservoir production increase effect.
Description
Technical Field
The invention relates to the technical field of petroleum drilling, in particular to a method for effectively plugging the end part of a hydraulic fracture. The invention can be used for oil and gas reservoirs such as compact sandstone, shale and the like, and can be used for both vertical wells and horizontal well hydraulic fracturing.
Background
At present, no matter deep shale gas, normal pressure shale gas and compact sandstone oil and gas reservoirs are required to be effectively plugged at the end part of a fracture in hydraulic fracturing so as to greatly improve the net pressure in the fracture and promote the initiation and extension of a branch fracture. Of course, an important prerequisite for effective plugging of the fracture ends is effective control of the fracture height, which is more important especially in tight sandstone or block carbonate reservoirs. In shale oil and gas reservoirs, because of a large amount of horizontal bedding seams and texture seams, the high extension of the cracks is shielded, and only effective plugging of the ends of the cracks can be considered.
The existing commonly used fracture end plugging method mainly adopts 70-140-mesh small-particle-size propping agent, sometimes commonly uses soluble temporary plugging agent in the fracture, but temporary plugging in the fracture has uncertainty of temporary plugging position, and because the fracture volume capable of containing fracturing fluid after temporary plugging in the fracture is relatively small, in other words, the fracturing fluid and propping agent can not be injected after temporary plugging, the pressure rise amplitude can exceed the designed construction pressure limit, so that even if the fracture has turning direction, the extension range is relatively limited. In addition, the fracture before temporary plugging is difficult to have continuous injection of fracturing fluid and propping agent, so the complex fracture formed by temporary plugging exists only in the fracture zone of a middle well or a near well, the complex fracture is difficult to form in a far well, and the influence on the improvement of fracture reconstruction volume is more fatal.
Chinese patent CN105863595A proposes a whole-course temporary plugging fracturing method and application thereof, wherein temporary plugging materials in seams are added in the fracturing process for full transformation, after fracturing is completed, temporary plugging is realized by injecting temporary plugging slugs in a near well zone, and whole-course temporary plugging fracturing is realized by using the temporary plugging materials in the seams and the temporary plugging materials in the near well zone. The method is suitable for hydraulic jet fracturing transformation and thin interbed multi-section combined fracturing and flow-limiting fracturing, can simplify the fracturing process and drilling tools, guarantees construction success rate, reduces operation risks, improves transformation effects, and provides new ideas and means for horizontal well multi-section transformation. The patent realizes temporary plugging by adding temporary plugging materials in the seam and temporary plugging slugs in a near well zone, and compared with the technology that the patent does not combine effective plugging of the end part of the seam with fracturing process optimization such as seam height control technology, proppant optimization and the like, the technology provides a targeted measure technology, and has certain technical limitation.
Optimization research and application of temporary plugging fracturing process of 6-reservoir long in Wuliwan (2016 and 11 months in drilling and production process) aiming at the technical problems that the 6-reservoir long in Wuliwan is poor in pertinence and effectiveness of conventional transformation measures and rapid in water content increase and the like, the literature develops the optimization research of the temporary plugging fracturing process, optimizes the fracturing process thought and parameters, completes the optimization of parameters such as the length of a turning pressure fracture, the sand content and the adding speed of a temporary plugging agent, and simultaneously perfects to form a matched fracturing fluid system to form the temporary plugging fracturing optimization technology of 6-reservoir long in Wuliwan. The field application practice shows that the optimized temporary plugging fracturing technology has stronger pertinence and applicability, and obtains good water control and oil increasing effects. The temporary plugging fracturing technology is formed aiming at the characteristics of 6 oil reservoirs in Wuliwan, and compared with the technology which does not combine the fracture height control technology, proppant optimization and other fracturing process optimization to provide a targeted measure technology for effectively plugging the end part of a fracture, the technology has certain technical limitation.
Therefore, how to implement effective plugging at the end of the crack is very critical to improve the complexity and the modification volume of the main crack in the full length range. There is a need to develop a new technique for effectively plugging the ends of a crack to solve the above technical limitations.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for effectively plugging the end part of a hydraulic fracture. Aiming at the problem that complex fractures caused by the existing hydraulic fracturing fracture end plugging technology mainly exist in a middle well or a near well fracture zone, the effectiveness of hydraulic fracture end plugging is improved through comprehensive optimization technologies such as a fracture end height control technology, proppant type and particle size optimization, proppant injection timing and injection program optimization and the like, so that the fractures after temporary plugging can effectively turn and extend to a far well zone, the complexity and the modification volume of the main fractures in the full length range are improved, the limitation of the existing technology is solved, and the maximization of the reservoir production increasing effect is realized.
The general technical idea of the invention is as follows:
(1) the effective control of the seam height profile at the end of the seam.
Because the volume of the crack is relatively small when the crack is just initiated and extended, the extension degree of the crack height is the highest with the same volume and displacement of the fracturing fluid. In addition, during fracture propagation, the fracture fluid flow linear velocity at the end of the fracture gradually decreases due to fluid loss from the fracture fluid, and the fracture forming capability thereof, including the propagation capability over the fracture height, gradually decreases. In other words, the height of the fracture gradually decreases from the wellbore to the end of the fracture, and in an extreme case, the height of the fracture end is even decreased to 0m, so how to extend the height of the fracture close to the end of the fracture as far as possible on the premise of controlling the overall height of the fracture is particularly important for improving the effective reconstruction volume of the fracture.
For this purpose, a strategy of gradually increasing construction discharge capacity during the crack formation of the pad fluid can be adopted, and meanwhile, in the early stage of crack formation, a method of mixed injection of low-viscosity fracturing fluid and high-density small-particle-size proppant is adopted to control the excessive extension of the crack height close to the shaft, so as to prevent the excessive extension of the crack height close to the shaft from influencing the sufficient extension of the crack end during the displacement increasing process.
The construction strategy is mainly applicable to tight sandstone oil and gas reservoirs and massive carbonate oil and gas reservoirs. And may be disregarded in shales.
(2) And injecting the mixed particle size ultra-low density proppant and soluble fiber at the end part of the crack in a mixing way.
Ultra low density mixed particle size proppants are contemplated. The apparent density of the proppant is generally between 1.05 and 1.25g/cm3, and the reason for adopting the ultra-low density proppant is that the proppant is close to the density of the fracturing fluid, has better followability and better suspension property on the height of the fracture, and once the effective plugging effect is generated at the end part of the fracture, the plugging effect on the whole height of the fracture can be greatly improved. If the density of the proppant is high, even if the fracture ends are blocked, the proppant can be difficult to distribute at the top of the fracture height, so that only partial blocking of the fracture ends can be realized, and the pressure in the fracture cannot be really and effectively established. In addition, after the ultra-low density proppant is adopted, although the proppant is easy to crush under high closing stress, the crushed proppant fragments have better plugging effect on the end part of the crack, and are more beneficial to effectively realizing the end part plugging effect.
Therefore, the mixed particle size proppant of 140 meshes, 230 meshes and 70-140 meshes is adopted, and the particle bridging effect among the proppants with different particle sizes is mainly utilized, if the particle size is single, the permeability is better, and the effective plugging effect at the end part of the crack is greatly reduced. The adoption of the mixed particle size proppant is also an emergency preventive measure for preventing the proppant from being broken or having low breakage rate in case of high closure stress.
However, in order to increase the high shear of the proppant through the perforations, it is still possible to agglomerate, which maximizes the potential for effective plugging. For this purpose, soluble fibers with a length in the range of 1-2cm are used for mixing to increase the plugging effect of the proppant at the ends of the fracture. Through indoor experimental study, the mass ratio of the fibers to the proppant is 1: 10-1: 20.
(3) And optimizing the injection time and the injection program of the proppant. Ideally the length of the proppant front when it reaches the end of the fracture is exactly the designed length of the propped fracture. The adding time of the propping agent is very critical, if the adding is early, the length of the propping seam cannot reach the design expectation; on the contrary, if the time is increased later, the length of the supporting seam exceeds the design expectation. For this purpose, it can use the well-established fracture propagation simulation commercialization software, such as FracPro PT, Stimplan, Gofher, etc., to simulate the concentration profile of the proppant in the length and height of the fracture, and adjust the adding time, initial sand-liquid ratio, sand-liquid ratio step-wise increase, volume of the highest sand-liquid ratio and each sand-liquid ratio and the corresponding injection displacement, the optimized objective function is that the length of the proppant placement front is equal to the length of the fracture, and the length of the proppant placement from the fracture end to the near-well direction should be 10-15m, and the width of the proppant placement concentration is equivalent to or within 10% of the width of the fracture in the corresponding length (in this case, it is preferable that the width of the fracture is greater than the width of the proppant).
The required supporting length of the end part of the crack and the concentration requirement of the propping agent are both in consideration of the reliability and stability of the plugging of the end part of the crack, otherwise, in case of follow-up continuous injection of the fracturing fluid, the net pressure in the crack is greatly increased, if the plugging of the end part of the crack is not firm, and even propping agent migration at the plugging position of the end part of the crack occurs again, the rising process of the net pressure is stopped, the construction purpose is not expected, and even the whole fracturing construction fails.
The invention aims to provide a method for effectively plugging the end part of a hydraulic fracture.
Injecting the mixed particle size ultra-low density proppant and soluble fiber at the end of the crack in a mixing way;
the apparent density of the proppant is 1.05-1.25g/cm 3; adopting 140-230-mesh and 70-140-mesh mixed particle size proppant; the length of the fiber is 1-2 cm;
the mass ratio of the fibers to the proppant is 1: 10-1: 20.
The length of the front edge of the spread proppant is equal to that of the manufactured seam, the length of the spread proppant from the seam end to the direction close to the well is 10-15m, the width of the manufactured seam is more than or equal to that of the supported seam, and the error between the width of the supported seam and the width of the manufactured seam on the corresponding length is within 10%.
The method comprises the following steps:
(1) evaluating key reservoir parameters;
(2) the method comprises the steps of (1) geological engineering comprehensive dessert evaluation and cluster perforation position determination;
(3) optimizing a crack parameter system;
(4) optimizing fracturing construction parameters;
(5) performing perforation operation;
(6) acid pretreatment operation;
(7) performing variable-displacement seam construction on the low-viscosity fracturing fluid;
(8) injecting mixed proppant of 140 meshes, 230 meshes and 70-140 meshes for construction;
(9) fracturing injection construction of proppants with different particle sizes;
(10) and (5) replacing operation.
Among them, preferred are:
step (6), the discharge capacity of the acid injection is 1-1.5m3Min, liquid amount of 10-20m3。
After 30-40% of acid in the designed acid liquor amount enters the position close to the first cluster of perforation of the heel, the acid displacement is gradually increased by 1 time or more than 2 times; the amplitude of each displacement increase is more than 30%, but not exceeding the maximum displacement optimized by the design in the step (4).
Step (7), adopting low-viscosity slick water with the viscosity of 2-12mPa.s, and respectively taking 50%, 75% and 100% of the highest discharge capacity to carry out variable discharge capacity construction;
and (4) during each displacement construction time, according to the volume of the pad fluid optimized in the step (4), the injection amount of each stage is 30-35% of the total amount of the pad fluid.
After the construction starting liquid amount reaches 20% of the pad liquid, 70-140 parts of the pad liquid is added, and the visual density is 3.3g/cm3The high density proppant has a volume of 3-5m3(ii) a The sand-liquid ratio is 1-3-5-7%; and each sand-liquid ratio is carried out according to the equal division principle of the residual prepad liquid. Means the injection amount of the pad fluid corresponding to each sand fluid stage, for example, the injection amount of the residual pad fluid is 200m when sand feeding is started3The injection amount corresponding to the sand-liquid ratio of 1-3-5-7% is 50m3。
Step (8), injecting the mixed particle size ultra-low density proppant and soluble fiber at the end of the crack in a mixing way;
the apparent density of the proppant is 1.05-1.25g/cm 3; adopting 140-230-mesh and 70-140-mesh mixed particle size proppant; the length of the fiber is 1-2 cm;
the mass ratio of the fibers to the proppant is 1: 10-1: 20;
the volume ratio of the 140-230-mesh proppant to the 70-140-mesh proppant is (1.5-2): 1;
wellhead pressure rising speed the wellhead pressure rising speed is 0.8-1.2 MPa/min.
Step (9), adding 70-140 meshes of propping agents, 40-70 meshes of propping agents and 30-50 meshes of propping agents respectively; until finally completing the normal injection construction of all designed proppants.
The length of the front edge of the spread proppant is equal to that of the manufactured seam, the length of the spread proppant from the seam end to the direction close to the well is 10-15m, the width of the manufactured seam is more than or equal to that of the supported seam, and the error between the width of the supported seam and the width of the manufactured seam on the corresponding length is within 10%.
Step (10), injecting displacement fluid according to 110% of the current section well bore volume; and (4) adopting the highest value optimized in the step (4).
The invention can adopt the following technical scheme:
(1) evaluation of key reservoir parameters
The method comprises longitudinal and transverse distribution, lithology and whole rock mineral components, five sensitivities, physical properties, oil and gas containing property, rock mechanics and three-dimensional ground stress characteristics of a reservoir, distribution fields of the reservoir in the longitudinal direction and the transverse direction, horizontal bedding joints, high-angle natural fracture characteristics and distribution, temperature, pressure and underground fluid characteristic parameters and the like.
The method can comprehensively adopt the means of earthquake, well logging, analysis while drilling, testing, indoor testing and analysis of a pilot hole well or an adjacent well core and the like, and comprehensively balance and determine. In consideration of the dynamic and static conversion relationship of various related parameters, the parameters for general fracturing are all static parameters, and the fracturing is a quasi-static process. The dynamic and static conversion relation of various parameters can be established on the pilot hole or the adjacent well. Because the core is difficult to be obtained in the horizontal well section, the logging parameter comparison between the horizontal section and the pilot hole well or the adjacent well and the established corresponding dynamic and static conversion relation need to be compared, and the distribution profile of each relevant static parameter of the horizontal section along the horizontal shaft is determined.
(2) Geological engineering comprehensive dessert evaluation and cluster perforation position determination
On the basis of the step (1), respectively calculating the indexes of the geological dessert and the engineering dessert by using a conventional method, and then calculating a continuous curve of the comprehensive geological engineering dessert distributed along the horizontal section according to an equal weight distribution method. And then, combining the total number of the cracks (corresponding to the cluster spacing) determined in the step 3), combining the well cementation quality logging result of the horizontal shaft and considering the position of avoiding the short casing coupling, and comprehensively determining the total number of the sections. Optimization of cluster perforation positions in the segment needs to consider the limiting conditions of 2-4 clusters of perforation in the segment adopted at present, and the comprehensive dessert indexes at all the preset perforation positions are required to be equal or different within 20 percent as much as possible, especially the engineering desserts are equal or close to each other in the segment, and more importantly, the optimization is related to the problems of uniform fracture initiation and synchronous extension of cracks at a plurality of cluster perforations in the segment.
(3) Optimization of fracture parameter system
On the basis of the step (1), a fine geological model within the range of the full-seam length (generally, the full-seam length can be considered within 700 m) of the target well along the horizontal shaft and the direction vertical to the horizontal shaft is established by applying common geological modeling software PETROL. The geological model parameters are then imported into commercial software ECLIPSE commonly used for fracture yield prediction as original geological parameters needing to be input for fracture yield prediction. Then, according to an equivalent flow conductivity method (for reducing the simulation workload, after the width of the crack is amplified by a certain multiple, the permeability of the proppant in the crack is reduced in proportion, so that the product of the permeability and the flow conductivity of the crack is kept unchanged), and then, according to an orthogonal design method, simulation scheme parameters are designed, and different crack lengths, flow conductivity, crack spacing and crack length layouts (equal crack length distribution, U-shaped distribution with two ends long and a middle short, W-shaped distribution with alternate length and spindle-shaped distribution and the like) are simulated.
The above is designed for the main crack simulation scheme. The branch cracks and the micro cracks are also arranged according to the same method, but for the sake of simplicity, the length, the flow conductivity and the crack spacing of the branch cracks are 1/10 of the main cracks, the crack layout is in a simple equal crack length distribution mode, and the value of the micro cracks is 1/10 of the branch cracks. The simulation method is used for propping up the crack.
And placing the three-stage cracks into a geological model, calculating the post-pressing yield dynamics at different time, and preferably selecting a three-stage crack parameter system corresponding to the maximum post-pressing yield or the maximum economic net present value, namely the optimization result.
(4) Optimization of fracturing construction parameters
In order to obtain the fracture parameter system optimized in the step (3), mature commercial simulation software such as the FracPro PT, Stimplan, Gofher and the like is applied, different fracturing construction parameters (liquid amount, liquid amount volume ratio of fracturing liquids of different types, volume ratio of propping agents of different types and particle sizes, viscosity and injection displacement of fracturing liquids of different types, injection displacement corresponding to the fracturing liquids of different types, sand-liquid ratio, injection program design and the like) are simulated according to an orthogonal design method, and the dynamic change rule of the fracture under the different fracturing construction parameters is observed from the simulation software, and the fracturing construction parameters corresponding to the optimized fracture parameters in the step (3) are the optimization result of the fracturing construction parameters.
And optimizing fracturing construction parameters corresponding to the branch cracks and the micro cracks according to the method. Considering that the main fractures, the branch fractures and the micro fractures may exist simultaneously, other construction parameters can be accumulated except that the viscosity of the fracturing fluid cannot be accumulated.
(5) Perforating operation
And performing perforation operation by using a conventional bridge plug perforation combination method in one step. The first section of perforation is carried out by adopting a coiled tubing to carry a perforating gun without using a bridge plug. And other sections adopt a pumping method to transport the bridge plug and the perforation combined tool string. And (3) after the bridge plug reaches a preset position, setting and releasing, then lifting the perforating gun step by step to the cluster perforating position determined in the step (2), igniting and perforating. And after all the shower holes are finished, lifting up the hole tool string. And (4) pouring the acid injection process, and connecting the main fracturing injection process.
(6) Acid pretreatment operation
And (2) taking different acid types and formulas according to the pilot hole core in the step (1), carrying out acid-rock compatibility and acid dissolution rate experiments, and taking the acid type and formula with good compatibility and highest acid dissolution rate.
The discharge capacity of the acid injection is generally 1-1.5m3Min, liquid amount of 10-20m3After acid injection, the injection flow of the reverse fracturing fluid is generally low-viscosity slickwater with the viscosity of 2-12mPa.s, and the discharge capacity of the acid replacement is generally 4-5m3Min, but after the acid is fast-fed into the first shower hole position near the heel, the displacement of the acid is reduced to the previous low-displacement level of acid injection, so as to increase the acid rock reaction time and the acid pressure drop effect.
In order to increase the probability of uniform entering of acid into each cluster of perforation, when the acid enters 30-40% of the position close to the first cluster of perforation of the heel, the discharge capacity of the acid is gradually increased by 1 time or more than 2 times according to the number of the clusters of the perforation of each section. The magnitude of each displacement increase should be over 30%, but not exceed the maximum displacement optimized by the design in step (4).
(7) Low-viscosity fracturing fluid variable-displacement joint construction
According to the requirement of the idea (1), adopting low-viscosity slick water with the viscosity of 2-12mPa.s, and respectively taking the water according to the maximum discharge capacity optimized in the step (4)50%, 75% and 100% of the construction is carried out with variable displacement. And (4) injecting the pre-positioned liquid according to the optimized pre-positioned liquid volume in the step (4) according to a trisection principle in each displacement construction time. In order to increase the restraining force of the seam height extending downwards, 70-140 visual density of 3.3g/cm is required to be added in the whole process of the pad liquid (after the construction starting liquid amount reaches 20 percent of the pad liquid)3The high density proppant has a volume of 3-5m3. The continuous sand adding can be carried out, the sand-liquid ratio is executed according to 1-3-5-7%, and each sand-liquid ratio is carried out according to the equal division principle of the residual prepad liquid.
However, if the shale formation is the shale formation and the minimum horizontal principal stress is relatively close to the overlying stress, in order to avoid the restraining effect of the opening of the horizontal bedding joints on the height of the vertical joints, high-viscosity fracturing fluid with the viscosity of 60-80mpa.s is required to be adopted, a variable displacement strategy is not adopted, and a method of increasing the displacement to the designed maximum value as soon as possible is directly adopted to extend the height of the initial joints as high as possible. And high density 70-140 mesh small particle size proppant is not used.
(8) Mixed injection construction of 140-230 mesh and 70-140 mesh mixed proppant and soluble fiber
And (4) executing the main parameters according to the optimized results of the thought (2), the thought (3) and the step (4). To increase the effective plugging effect at the ends of the fractures, the volume ratio of 140-230 mesh and 70-140 mesh proppants was performed between 1.5:1 and 2: 1. The mass ratio of the fibers to the proppant is 1: 10-1: 20.
The construction parameters are simulated and need to be adjusted in real time by combining the change of the site construction pressure, the rise speed of the wellhead pressure is generally required to be 1MPa/min, the difference amplitude cannot exceed 10-20%, otherwise, the sand-liquid ratio and the injection procedure need to be adjusted in time until the rise amplitude of the wellhead pressure reaches the requirements.
(9) Fracturing injection construction of proppant with different particle sizes
On the basis that the expected requirement is met in the step (8), a pressure window of 5-10MPa can be reserved according to the requirement of wellhead pressure limiting, and under the premise, the net pressure of the crack can be continuously increased by injecting and maintaining.
Then, according to the normal sand adding procedure, 70-140 meshes of propping agents, 40-70 meshes of propping agents and 30-50 meshes of propping agents are added respectively. Until finally completing the normal injection construction of all designed proppants.
The length of the front edge of the spread proppant is equal to that of the manufactured seam, the length of the spread proppant from the seam end to the direction close to the well is 10-15m, the width of the manufactured seam is more than or equal to that of the supported seam, and the error between the width of the supported seam and the width of the manufactured seam on the corresponding length is within 10%.
(10) Replacement work
The displacement fluid is injected at 105-110% of the current wellbore volume. And (4) adopting the highest value optimized in the step (4). The viscosity of the former 30-40% displacement fluid is 60-80mPa.s, so as to increase the carrying effect of the fracturing fluid on the horizontal wellbore proppant and prevent the lower bridge of the subsequent section from being blocked. Then replacing low viscosity slickwater with viscosity of 1-3mPa.s until all the displacing liquid is injected.
(11) And (5) repeating the steps (5) to (10) for the operation of other sections until all the sections are constructed.
(12) Drilling, blocking, flowback, testing, normal production and other links are executed according to conventional processes and standards, and are not redundant.
ADVANTAGEOUS EFFECTS OF INVENTION
Compared with the conventional hydraulic fracturing technology, the invention provides a brand-new effective plugging technology for the end part of the fracturing fracture, a single small-particle-size propping agent or a temporary plugging agent in a soluble fracture is not used for plugging in the fracturing process, and on the basis of reservoir parameter evaluation, the effectiveness of plugging of the end part of the hydraulic fracture is improved through comprehensive optimization technologies such as a fracture end part seam height control technology, propping agent type and particle size optimization, propping agent injection time and injection program optimization and the like.
The method can effectively improve the effectiveness of hydraulic fracture end plugging, enables the fracture after temporary plugging to effectively turn and extend to a far well zone, improves the complexity and the modification volume of the main fracture within the full length range, enhances the supply capacity of the fracture to an oil-gas seepage channel, and maximally excavates the yield-increasing capacity of a reservoir.
The site operation also has operability, the fracturing fluid, the propping agent and the like are prepared in advance, and different construction discharge capacities can generally meet the requirements.
Detailed Description
The present invention will be further described with reference to the following examples.
Examples
And the lithology of the target interval of the well A is feldspar sandstone, and a natural crack develops relatively. The fracturing well section of the target stratum is 3537.2-4142.0m, the average Young modulus of the reservoir is 33.4GPa, and the average Poisson ratio is 0.24; the temperature of the target layer was 132 ℃. In order to know the oil content and the productivity of the target layer and carry out the next exploration and evaluation work on the block, the fracturing scheme design and the field pilot test of the well are carried out by taking the process method provided by the patent as reference and combining the actual situation of the well, and the specific implementation method and the effect are as follows:
(1) evaluating reservoir parameters: according to earthquake, geology, well logging and core test data, the lithology of a target interval is feldspar sandstone, the clay mineral content is 12.6-38.7%, and the average content is 25.3%; the content of siliceous minerals is 18.9-54.3%, and the average content is 38.4%; the content of carbonate minerals is 7.2-34.6%, and the average content is 12.7%. The oil-gas content is gas content, cracks mainly develop in mudstone, and the development degree of the cracks in the sandstone is relatively low; the high-angle natural cracks are underdeveloped and meet horizontal layer arrangement; the reservoir has the characteristics of weak speed sensitivity, weak-medium acid sensitivity, weak-medium water sensitivity and weak-medium stress sensitivity; the average Young modulus of the reservoir is 33.4GPa, the average Poisson ratio is 0.24, and the tensile strength is 11.3-17.6 MPa; maximum horizontal principal stress 96.4-98.5MPa, minimum horizontal principal stress: 77.9-79.2MPa, and the temperature of the target layer is 132 ℃.
(2) And (3) geological engineering comprehensive dessert evaluation and cluster perforation position determination: and (3) according to the parameter evaluation in the step (1), combining the adjacent well data and PETREL geological modeling software, calculating the spread range of the hydraulic fractures of the geological dessert and the engineering dessert along the horizontal segment and the transverse direction of the horizontal segment, further obtaining the comprehensive dessert, and determining the position of each cluster of perforation of each segment. The well is divided into 4 sections for fracturing, and each section is divided into 2-3 clusters.
(3) Optimizing a crack parameter system: through the simulation calculation of an orthogonal method, the equal slit length distribution is determined, the half slit length is 220-; fracturing into 4 sections, 2 clusters in each section of 1-2 sections, 3 clusters in each section of 3-4 sections, and the cluster spacing is 15-20 m.
(4) Optimizing fracturing construction parameters: according toAnd performing orthogonal simulation calculation by GOFHER software to determine each construction parameter. Wherein the single-stage construction liquid amount is 1000-350-60m of supported dose3Construction displacement of 2-10m3And/min, selecting a glue solution, a low-viscosity slippery water and a high-viscosity slippery water as the fracturing fluid, wherein the viscosity of the glue solution is 50-60mPa & s, the viscosity of the low-viscosity slippery water is 2-5mPa & s, the viscosity of the high-viscosity slippery water is about 30mPa & s, and the propping agents are 140-230 meshes, 70-140 meshes, 40-70 meshes and 30-50 meshes. The aperture of the perforation is selected to be 13.9mm primarily, and the hole density is 16 holes/m.
(5) Perforating: the first section of perforation is carried out by adopting a coiled tubing to carry a perforating gun without using a bridge plug. And other sections adopt a pumping method to transport the bridge plug and the perforation combined tool string.
(6) Acid pretreatment operation: according to compatibility and acid dissolution rate experiments, hydrochloric acid is selected as a pretreatment liquid, the formula is 15% of HCl, 2.0% of high-temperature corrosion inhibitor, 1.0% of cleanup additive and 1.0% of iron ion stabilizer, and the dosage of each stage is 15m3. 1, 2 first 1.5m3Permin displacement injection 15m3Acid liquor, the reverse fracturing fluid injection process is performed by firstly using 5m3Permin displacement injection 5m3Fracturing fluid, again at 7m3Permin displacement injection 10m3A fracturing fluid; the 3 rd and 4 th sections are firstly 1.5m3Permin displacement injection 15m3Acid liquor, the reverse fracturing fluid injection process is performed by firstly using 5m3Permin displacement injection 5m3Fracturing fluid, again at 7m3Permin displacement injection 5m3Fracturing fluid, again at 9m3Permin displacement injection 5m3And (4) fracturing fluid.
(7) The low-viscosity fracturing fluid variable-displacement seam construction: the dosage of the low-viscosity fracturing fluid in the 1 st and 2 nd stages is 210m3At a displacement of 5m respectively3/min、7.5m3/min、10m3Min injection 70m3A low viscosity fracturing fluid; the dosage of the low-viscosity fracturing fluid in the 3 rd and 4 th sections is 240m3At a displacement of 5m respectively3/min、7.5m3/min、10m3Min injection 80m3A low viscosity fracturing fluid.
After the construction starting liquid amount reaches 20% of the pad liquid, 70-140 parts of the pad liquid is added, and the visual density is 3.4g/cm3High density proppant of 4m3(ii) a The sand-liquid ratio is 1-3-5-7%; each sand-liquid ratio is as followsThe rest pre-liquid is equally divided.
(8) Mixed injection construction of 140-230 mesh and 70-140 mesh mixed proppant and soluble fiber
The dosages of the 140-mesh and 230-mesh and 70-140-mesh proppants in the step are respectively 5m3、3m3The sand-liquid ratio is 3 percent, and the injection discharge capacity is 5m3And/min. The fiber length was 1.5cm and the amount added was 640 kg.
Apparent density of proppant 1.2g/cm3(ii) a The mass ratio of fibers to proppant was 1: 15.
(9) Fracturing injection construction of proppant with different particle sizes
The dosages of 70-140 meshes, 40-70 meshes and 30-50 meshes of propping agents in the step are respectively 5m3、22m3、25m3The sand-liquid ratio of 70-140 meshes of proppant stage is 5-7-9-11%, and the injection displacement is 5m3Min; the sand-liquid ratio of 40-70 mesh proppant stage is 8-12-16-20%, and the injection displacement is 5-8m3Min; the sand-liquid ratio of the 30-50 mesh proppant stage is 16-20-24%, and the injection displacement is 8-10m3/min。
The length of the laying front edge of the propping agent is equal to that of the seam, the length of the laying front edge of the propping agent from the seam end to the direction close to the well is 12.2m, the width of the seam is more than or equal to that of the supporting seam, and the error between the width of the supporting seam and the width of the seam on the corresponding length is 8.6%.
(10) Replacement operation: the total liquid volume of the displacement liquid is 150m3First, 10m350 m/min displacement3And (4) replacing the high-viscosity slick water with the low-viscosity slick water until the replacement is finished.
(11) Drilling, blocking, flowback, testing, normal production and other links are executed according to conventional processes and standards, and are not redundant.
The well is subjected to fracturing construction according to the steps, and the site construction process is successful. The gas production profile test result after the well pressure is combined, and the fact that the fracture after the well pressure is longer in fracture length, and the fracture complexity and the modification volume are larger compared with the fracture generated by the adjacent well in the same-specification die fracturing is verified. The well pressure has good effect, and the daily oil gas yield is 6.5 multiplied by 10 in the early stage after the well pressure is increased4m3A half-year-later daily yield of 3.0X 104m3About/d is superior toAnd the adjacent well has the same layer effect.
Pilot experiments through this well demonstrated: by using the process method provided by the patent for reference, the daily gas production rate at the initial stage after the fracturing reaches about 2 times of that of an adjacent well, the yield after the fracturing is decreased gradually and is obviously slower than that of the adjacent well or an adjacent block, the stable yield after the fracturing and the effective period are obviously increased, the obvious oil increasing effect is obtained, and the fracturing transformation effect of the reservoir is improved.
Claims (7)
1. A method of achieving effective plugging of hydraulic fracture ends, the method comprising:
(1) evaluating key reservoir parameters;
(2) the method comprises the steps of (1) geological engineering comprehensive dessert evaluation and cluster perforation position determination;
(3) optimizing a crack parameter system;
(4) optimizing fracturing construction parameters;
(5) performing perforation operation;
(6) acid pretreatment operation;
(7) the construction of variable-displacement seam making of low-viscosity fracturing fluid or the construction of large displacement of high-viscosity fracturing fluid;
(8) mixed proppant and soluble fiber of 140 meshes 230 and 70 meshes 140 meshes are mixed and injected for construction;
injecting the mixed particle size ultra-low density proppant and soluble fiber at the end of the crack in a mixing way;
the apparent density of the proppant is 1.05-1.25g/cm 3; adopting 140-230-mesh and 70-140-mesh mixed particle size proppant; the length of the fiber is 1-2 cm; the volume ratio of the 140-230-mesh proppant to the 70-140-mesh proppant is (1.5-2): 1; the mass ratio of the fibers to the proppant is 1: 10-1: 20;
the length of the front edge of the spread proppant is equal to that of the manufactured seam, the length of the spread proppant from the seam end to the direction close to the well is 10-15m, the width of the manufactured seam is more than or equal to that of the supported seam, and the error between the width of the supported seam and the width of the manufactured seam on the corresponding length is within 10%;
the pressure rising speed of the well mouth is 0.8-1.2 MPa/min;
(9) fracturing injection construction of proppants with different particle sizes;
(10) and (5) replacing operation.
2. A method of effecting effective hydraulic fracture end plugging according to claim 1 wherein:
step (6), the discharge capacity of the acid injection is 1-1.5m3Min, liquid amount of 10-20m3。
3. A method of effecting effective hydraulic fracture end plugging according to claim 2 wherein:
after 30-40% of acid liquid amount is designed to enter a first shower hole position close to a heel, the acid displacement is gradually increased for more than 2 times; the amplitude of each displacement increase is more than 30%, but not exceeding the maximum displacement optimized in the step (4).
4. A method of effecting effective hydraulic fracture end plugging according to claim 1 wherein:
step (7), adopting low-viscosity slick water with the viscosity of 2-12mPa.s, and respectively taking 50%, 75% and 100% of the highest discharge capacity to carry out variable discharge capacity construction;
and (4) during each displacement construction time, according to the volume of the pad fluid optimized in the step (4), the injection amount of each stage is 30-35% of the total amount of the pad fluid.
5. A method of effecting effective hydraulic fracture end plugging according to claim 4 wherein:
after the construction starting liquid amount reaches 20% of the pad liquid, 70-140 parts of the pad liquid is added, and the visual density is 3.3g/cm3The high density proppant has a volume of 3-5m3(ii) a The sand-liquid ratio is 1-3-5-7%; and each sand-liquid ratio is carried out according to the equal division principle of the residual prepad liquid.
6. A method of effecting effective hydraulic fracture end plugging according to claim 1 wherein:
step (9), adding 70-140 meshes of propping agents, 40-70 meshes of propping agents and 30-50 meshes of propping agents according to the design of the step (4); until finally completing the normal injection construction of all designed proppants.
7. A method of effecting effective hydraulic fracture end plugging according to claim 1 wherein:
step (10), injecting displacement fluid according to 110% of the current section well bore volume; and (4) adopting the highest value optimized in the step (4).
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| CN112253066B (en) * | 2019-07-03 | 2023-03-24 | 中国石油化工股份有限公司 | Method for improving fracture complexity and transformation volume of deep shale gas |
| CN112253074B (en) * | 2019-07-22 | 2022-11-29 | 中国石油化工股份有限公司 | Method for improving bridge plug pumping efficiency by deep horizontal well fracturing |
| CN112343569B (en) * | 2019-08-06 | 2023-02-28 | 中国石油化工股份有限公司 | Horizontal well fracturing method for promoting multiple clusters of fractures by multiple acid injection and temporary plugging |
| CN113513295B (en) * | 2020-04-10 | 2023-06-13 | 中国石油化工股份有限公司 | Method for improving uniform extension and support of multi-cluster cracks in section |
| CN113530513B (en) * | 2020-04-22 | 2023-02-28 | 中国石油化工股份有限公司 | Fracturing method for graded support of proppants with different particle sizes in multi-scale fracture |
| CN111485864B (en) * | 2020-04-30 | 2022-08-30 | 中国石油天然气股份有限公司 | Hydraulic fracturing method for long-acting sealing of high-angle fracture |
| CN111963157B (en) * | 2020-07-14 | 2023-08-22 | 中国石油天然气股份有限公司 | Perforation parameter optimization method for improving horizontal well segmentation multi-cluster receiving efficiency |
| CN114427425B (en) * | 2020-09-16 | 2024-08-02 | 中国石油化工股份有限公司 | Thin inter-layer penetrating layer fracturing method and application thereof |
| CN114427417B (en) * | 2020-09-24 | 2024-07-05 | 中国石油化工股份有限公司 | Multilayer reservoir fracturing method with large stress difference and application |
| CN113356826B (en) * | 2021-07-08 | 2022-02-11 | 西南石油大学 | Moderate sand adding and pressure increasing acid fracturing method for improving fracture-cavity reservoir transformation effect |
| CN113653481B (en) * | 2021-09-14 | 2023-02-03 | 中国石油大学(华东) | Channel fracturing method based on self-suspension coated quartz sand |
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