CN111911127B - Fracturing sand adding method - Google Patents
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- CN111911127B CN111911127B CN201910375827.3A CN201910375827A CN111911127B CN 111911127 B CN111911127 B CN 111911127B CN 201910375827 A CN201910375827 A CN 201910375827A CN 111911127 B CN111911127 B CN 111911127B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
Abstract
The invention provides a fracturing sand adding method, which comprises the following steps: s1, pretreating a reservoir by using acid liquor, and then sequentially injecting low-viscosity fracturing fluid slick water and high-viscosity fracturing fluid; s2, injecting slick water fracturing fluid carrying small-particle-size propping agent in a slug mode; s3, injecting slick water fracturing fluid carrying small-particle-size proppant and slick water fracturing fluid carrying medium-particle-size proppant in a slug mode to perform reverse bench type sand adding, wherein in each slug period, firstly injecting slick water fracturing fluid carrying small-particle-size proppant and then injecting slick water fracturing fluid carrying medium-particle-size proppant in a tail-tracking mode; s4, injecting a slickwater fracturing fluid carrying medium-grain-size propping agent in a long-section plug manner; s5, continuously injecting slickwater fracturing fluid carrying large-particle-size propping agent; and S6, replacing by using fracturing fluid. The method provided by the invention can effectively improve the flow conductivity of the crack and ensure the fracturing effect of the deep high-stress reservoir.
Description
Technical Field
The invention relates to a fracturing sand adding method.
Background
At present, no matter shale, sandstone or pore type carbonate oil and gas reservoirs, hydraulic sand fracturing technology is adopted. However, as the exploration and development process deepens, the burial depth becomes deeper and deeper, so that the construction pressure of a wellhead is greatly increased, and the injection displacement is correspondingly reduced, so that the three-dimensional geometric size of a fractured fracture is relatively small, and great difficulty is brought to smooth addition of a propping agent. At present, the conventional proppant slug technology is widely adopted on site, namely, before formal sand adding, in order to polish the bending friction of a near-wellbore fracture, or in order to obtain the pressure response characteristic after tentative sand adding, a proppant with a relatively low sand-liquid ratio and a relatively small grain size is injected by using a relatively small sand-carrying liquid amount (generally adopting half or one wellbore volume), and the pressure response characteristic of a wellhead after the proppant enters a stratum until the whole proppant slug enters the fracture is closely observed, if the pressure does not obviously rise, the sand-liquid ratio, the grain size or the slug amount designed for the proppant slug is conservative compared with the actual requirement; otherwise, the sand is accelerated, and early sand blockage can be caused. The optimal situation is that a certain pressure rise is provided, so that the grinding effect is good. Therefore, the construction injection program can be adjusted in real time, and normal operation of main fracturing construction is guaranteed.
On the basis of the proppant slug technology, in order to further increase the construction efficiency, a bench type proppant slug technology is developed, namely, in the process of injecting the proppant slug with a certain sand-to-liquid ratio, the higher sand-to-liquid ratio of the next proppant slug is moved out by 20-30m in advance 3 And then, after-tracking injection is carried out, because the sand-liquid ratio of the after-tracking injection is relatively high and the liquid amount is relatively small, the shape of the fracturing construction comprehensive curve of the sand-liquid ratio changing along with time is similar to a bench (see the attached drawing 1), so that the technology is called as bench type proppant slug technology, and sometimes is called as bench type sand adding for short. The technology has good effect in field application and is adopted and applied on a large scale.Proppants in fracturing are generally classified into three categories: small-particle size proppant (also called powder pottery, generally with a diameter range of 70-140 meshes or 80-120 meshes), medium-particle size proppant (also called medium sand, generally with a diameter range of 40-70 meshes) and large-particle size proppant (also called coarse sand, generally with a diameter range of 30-50 meshes). The proppant injection sequence was: small-particle size proppant-medium-particle size proppant-large-particle size proppant.
However, the bench type sand adding also has technical limitations, when a deep high-stress reservoir fractures, if the bench type sand-liquid ratio section which is traced back enters the stratum, the sand-liquid ratio is still sensitive, the pressure of a well head rises obviously, even if the same bench type sand-liquid ratio is injected again, the sensitivity is still very high after the sand enters the stratum, the pressure of the well head is high, the injection of the propping agent with medium and large particle sizes into a shaft and a crack is extremely difficult, and the fracturing effect of the deep high-stress reservoir is also directly influenced.
Therefore, research and exploration of a new sand adding technology are needed, which can reduce the injection pressure of the propping agent, improve the three-dimensional geometric size and the fracturing modification volume of the fracture and ensure the successful fracturing of the deep high-stress reservoir.
Disclosure of Invention
In order to solve the problems in the existing sand adding technology, the invention provides a novel fracturing sand adding technology, which utilizes the characteristics that the flow following property of medium-particle-size propping agent and fracturing fluid and the impact force on a fracture wall are superior to those of small-particle-size propping agent, after the slippery water carrying the small-particle-size propping agent is injected for many times, the slippery water carrying the medium-particle-size propping agent, the ratio of which is about half of that of the slippery water carrying the small-particle-size propping agent, is added, so as to form directional bench sand adding, under the premise of ensuring that the total fracture resistance of the propping agent is equivalent, the grinding effect on the bending part of a near-wellbore fracture is improved, the fatigue damage effect on the rock of the fracture wall is increased, the crack width is increased, the sensitivity of the crack on the construction sand ratio is gradually reduced, the difficult problems that the well mouth pressure is too high and the medium-particle-size propping agent and the large-particle-size propping agent are injected when a deep high-stress reservoir is fractured are solved, the three-dimensional geometric size and the fracturing volume is increased, the fracture conductivity of the crack is improved, and the high-stress deep reservoir is ensured.
According to a first aspect of the present invention, there is provided a method of frac sanding comprising the sequential steps of:
s1, pretreating a reservoir by using acid liquor, and sequentially injecting low-viscosity slick water and high-viscosity fracturing fluid into the reservoir after acid liquor pretreatment;
s2, injecting slick water carrying small-particle size proppant in a slug mode;
s3, injecting slick water carrying small-particle size proppant and slick water carrying medium-particle size proppant in a slug type manner to perform reverse bench type sand adding, and in each slug period, injecting slick water carrying small-particle size proppant firstly and then injecting slick water carrying medium-particle size proppant after tracing;
s4, injecting slick water carrying the medium-particle-size propping agent in a long-segment plug manner;
s5, continuously injecting slick water carrying the proppant with large particle size;
and S6, replacing by using the fracturing fluid.
And S3, injecting slick water carrying small-particle size propping agent and slick water carrying medium-particle size propping agent in a slug type for reverse bench type sand adding, and injecting slick water carrying small-particle size propping agent first and then injecting slick water carrying medium-particle size propping agent in a tail tracking manner in each slug period.
The fracturing sand adding method adopts a reverse bench to add sand, namely, the sand-liquid ratio after the sand is not increased but reduced. If the proppant with the same particle size is injected, the polishing effect is not good, and in order to improve the polishing effect, the particle size of the proppant to be traced needs to be increased. It is contemplated that the currently used small particle size proppant slugs are typically 70-140 mesh or 80-120 mesh in size, while medium particle size proppants are typically 40-70 mesh in size. If the small-particle size proppant is changed to the medium-particle size proppant during the back-up, the particle size of the proppant is doubled, and if the back-up medium-particle size proppant still maintains the original sand-liquid ratio or is further increased, larger sand blocking is induced. Therefore, it is necessary to reduce the sand-to-fluid ratio of the trailing medium-particle-size proppant.
According to a preferred embodiment of the present invention, in step S3, the sand-to-fluid ratio of the fracturing fluid carrying the medium-particle-size proppant is 50% -60% of the sand-to-fluid ratio of the fracturing fluid carrying the small-particle-size proppant in each slug period, preferably, 15-30m after injecting the slickwater carrying the small-particle-size proppant in each slug period 3 Carrying medium particle size proppant. In the step, the small-particle size propping agent and the medium-particle size propping agent are used for interactive polishing, so that the fatigue damage effect on the rock on the fracture wall is increased, the fracture width is increased, and the injection amount of the medium-particle size propping agent is increased.
According to a preferred embodiment of the present invention, the small particle size proppant has a particle size of 70 to 140 mesh, preferably 80 to 120 mesh; and/or the presence of a gas in the atmosphere,
the particle size of the medium-particle size proppant is 40-70 meshes; and/or the presence of a gas in the gas,
the particle size of the large-particle size proppant is 30-50 meshes.
According to the preferred embodiment of the invention, before the step S1, the method further comprises evaluating parameters of a reservoir before fracturing, optimizing fracture parameters and fracturing construction parameters according to the obtained reservoir parameters, and lowering the staged fracturing string.
Preferably, the reservoir parameters include one or more of closure stress, near-wellbore fracture bending friction, rock mechanics parameters, and integrated fluid loss parameters.
According to a preferred embodiment of the invention, ECLIPSE is used for fracture parameter optimization. The crack parameters are optimal in crack distance, crack half-length, flow conductivity and the like.
According to a preferred embodiment of the present invention, fracture construction parameter optimization is performed using one or more of Fracpro PT, GOFHER and STimplan. Preferably, the fracturing construction parameters comprise discharge capacity, single-stage fracturing fluid dosage, single-stage proppant dosage, proppant particle size, slickwater viscosity and the like.
According to a preferred embodiment of the present invention, in step S2, the sand-liquid ratio of the slickwater carrying the small-particle size proppant is increased stepwise from 1% to 4% with an increase of 1% -2%. For example, in step S2, slug injection may be performed sequentially with slick water carrying small particle size proppant at a sand to fluid ratio of 1-2-3-4%. By adopting the method, the bending friction resistance of the near-wellbore fracture can be polished, and the pressure response characteristic after sand adding is tentatively performed.
According to a preferred embodiment of the present invention, in step S2, the injection amount of slickwater carrying small particle size proppant is 50% -100% of the wellbore volume in each slug period; and/or the injection amount of the spacer fluid is 50-100% of the well bore volume.
According to a preferred embodiment of the present invention, in step S2, the injection displacement of the slickwater carrying the small particle size proppant is 70-90%, preferably 80% of the maximum displacement.
According to a preferred embodiment of the present invention, in step S2, the slickwater is low-viscosity slickwater with viscosity of 1-3mPa · S.
According to a preferred embodiment of the invention, in step S2, after injection of the slickwater carrying small particle size proppant with lower sand to fluid ratio, if there is no significant pressure rise (2 MPa pressure rise is a significant rise in 5 minutes, less than 2MPa pressure rise is no significant rise), then 15-30m after injection of the slug 3 In the volume, the slick water carrying the proppant with small grain diameter and higher sand-to-fluid ratio can be injected, namely bench type sand adding is carried out in advance.
According to a preferred embodiment of the present invention, in step S3, after injecting slickwater carrying small particle size proppant, 15-30m is injected 3 Carrying medium particle size proppant. The process of injecting slickwater carrying proppant with medium particle size after injecting slickwater carrying proppant with small particle size can also be called reverse bench type sand adding. In general, in the reverse bench-type sanding process in step S3, the ratio of the sand-to-fluid ratio of the fracturing fluid carrying medium-particle-size proppant to the sand-to-fluid ratio of the fracturing fluid carrying small-particle-size proppant to be chased is larger in the later slug period, so that the medium-particle-size proppant can be increased to the fracture near the wellborePolishing effect of the seam bending part.
The flow following of the medium-particle size proppant and the fracturing fluid is better than that of the small-particle size proppant, because the medium-particle size proppant has larger particle size and stronger impact force on the fracture wall. Either the small or medium particle size proppant is used for polishing, and if only one of them is used, the polishing effect is not optimal. After the small-particle size propping agent and the medium-particle size propping agent are interactively polished, the variable-strength fatigue damage effect (due to different polishing force) is equivalently performed on the rock of the fracture wall, and the fracture width is inevitably increased as long as the fatigue damage frequency is high enough. Therefore, the number of steps for the reverse bench-type sanding process cannot be too small. Preferably, step S4 comprises at least 3 slug periods.
According to a preferred embodiment of the invention, in step S4, the sand-to-fluid ratio of the slickwater carrying the medium-sized proppant is increased stepwise from 3% to 10-14% with an increase of 1% -2%.
According to a preferred embodiment of the invention, in step S4, the injection amount of slickwater per sand to liquid ratio is 80-100%, preferably 100%, of the wellbore volume in each slug period;
preferably, the spacer fluid is injected in an amount of 100% to 150% of the wellbore volume.
According to a preferred embodiment of the invention, in step S4, the injection displacement is 90% -100% of the maximum displacement.
According to a preferred embodiment of the present invention, in step S4, in order to ensure a good sand-carrying effect, the slickwater is medium-viscosity slickwater with a viscosity of 9-12mPa · S.
According to a preferred embodiment of the present invention, in step S5, the sand-fluid ratio of the slickwater carrying the large-particle size proppant is increased stepwise from 10% to 18% with an increase of 1% -3%.
According to a preferred embodiment of the present invention, in step S5, the slickwater carrying the proppant with large particle size is injected in an amount of 20-30% of the wellbore volume per sand to fluid ratio.
According to a preferred embodiment of the present invention, in step S5, the injection displacement of slickwater carrying proppant with large particle size is 90% -100% of the maximum displacement.
According to a preferred embodiment of the present invention, in step S5, the high-viscosity slickwater having a viscosity of 15 to 20mPa · S is used as the slickwater.
According to the preferred embodiment of the invention, in step S6, the amount of the fracturing fluid in the displacement stage is 110-130% of the volume of the well bore, and preferably, the high-viscosity fracturing fluid of 30-40mPa & S is used for reducing the sand setting effect of the horizontal well bore, and then the low-viscosity slickwater of 1-3mPa & S is used for displacement; preferably, the volume of the high viscosity fracturing fluid is 25% to 35%, preferably 30%, of the total volume of the fracturing fluid used in step S5.
According to a preferred embodiment of the invention, in step S1, the pretreatment of the reservoir with an acid solution is generally carried out using industrial hydrochloric acid, in an amount of 10-20m 3 。
According to a preferred embodiment of the invention, in step S1, the low-viscosity slickwater has a viscosity of 1-3 mPa.s and is used in an amount of 50-100m 3 With a delivery volume of from 2m 3 The/min is gradually increased to 50-70%, preferably 60% of the maximum displacement. Preferably, the displacement is in the range of 2-4m 3 The amplification of/min is increased in a step-like manner.
According to a preferred embodiment of the present invention, the high viscosity fracturing fluid has a viscosity of 30 to 40 mPas in an amount of 10 to 30m in step S1 3 Displacement per cluster of cracks from 4m 3 The/min is gradually increased to 70-90%, preferably 80% of the maximum displacement. Preferably, the displacement is in the range of 2-4m 3 The amplification of/min is increased in a step-shaped manner.
According to the preferred embodiment of the invention, in the process of lowering the segmented fracturing string, the completion of the casing is carried out by adopting a bridge plug perforation combination mode; and during open hole well completion, a lower open hole packer and a multistage sliding sleeve subsection mode are adopted.
The invention also provides application of the method in deep high-stress reservoir fracturing.
By adopting the method provided by the invention, after the medium-particle-size propping agent is traced back and the sand-liquid ratio is properly reduced, the polishing effect on the crack bending part close to the well casing is enhanced on the premise of ensuring that the total crack entering resistance of the propping agent is equivalent, because the particle diameter of the medium-particle-size propping agent is almost doubled, the inertia force carried by slickwater is also almost doubled, and the polishing effect on the crack bending part close to the well casing is greatly increased. In addition, the medium-particle size proppant has better flow following with the fracturing fluid than the small-particle size proppant because the medium-particle size proppant has larger particle size and stronger impact force on the fracture wall. Either sanding with powder Tao Damo or with medium particle size proppant, if only one is done, the sanding effect will not be optimal. After the small-particle-size propping agent and the medium-particle-size propping agent are interactively polished, the method is equivalent to performing strength-variable fatigue failure on the rock of the fracture wall (due to different polishing forces), and the fracture width is inevitably increased as long as the frequency of the fatigue failure is high enough. After the polishing effect is increased, the width of the crack can be correspondingly increased, so that the sensitivity of the crack to the construction sand-liquid ratio is gradually reduced along with the subsequent repeated reverse bench type sand adding. And then, the reverse bench type sand adding is carried out by using a higher sand-liquid ratio, so that the grinding effect is better, the whole width of the crack can also become larger, the sensitivity to the subsequent sand-liquid ratio can also be gradually reduced, and finally, the construction difficulty is basically not different between a deep high-stress reservoir and medium-depth oil and gas reservoir fracturing.
The fracturing method of the invention utilizes the characteristic that the flow following property of medium-particle size propping agent and fracturing fluid and the impact force to the fracture wall are superior to those of small-particle size propping agent, and after the small-particle size propping agent is injected for many times, medium-particle size propping agent with only half of the sand-liquid ratio is added in a back-end-up manner to form a reverse bench sand adding mode, so that the injection amount of the medium-particle size propping agent is increased, the polishing effect on the bending part of the near-wellbore fracture is improved on the premise of ensuring that the overall fracture resistance of the propping agent is equivalent, the fatigue damage effect on the rock of the fracture wall is increased, the fracture width is increased, the sensitivity of the fracture to the construction sand-liquid ratio is gradually reduced, the problems of overhigh well head pressure and high injection difficulty of the medium-particle size and large-particle size propping agent during the fracturing of a high-stress reservoir are solved, the three-dimensional geometric size and the fracturing modification volume of the fracture are increased, the fracture conductivity is improved, and the fracturing effect of the high-stress reservoir is ensured.
Drawings
FIG. 1 is a schematic illustration of "bench" sanding;
FIG. 2 is a schematic view of an inverted "bench" style sanding.
Detailed Description
The present invention will be described in detail with reference to examples, but the present invention is not limited to the examples.
A fracturing sand adding method comprises the following steps:
1) Evaluation of pre-stress reservoir parameters
The reservoir parameters comprise parameters such as closing stress, near-wellbore fracture bending friction, rock mechanics parameters and comprehensive fluid loss. And injecting and explaining by adopting a small-scale test fracturing technology when the parameters of the reservoir before fracturing are evaluated. In order to obtain stratum-related parameters as soon as possible, low-viscosity slickwater with the viscosity of 1-2mPa & s is used for injection. And (4) carrying out step-up displacement and step-down displacement tests according to a conventional method, and stopping the pump for about 60 min.
2) Crack parameter optimization and construction parameter optimization
And (3) performing fracture parameter optimization by using common commercial software ECLIPSE for predicting the yield of the fractured well, and performing optimization of fracturing construction parameters by using common commercial simulation software for fracturing design optimization, such as Fracpro PT, GOFHER, STImplan and the like.
3) Lower staged fracturing string
When casing is completed, the operation of perforating the bridge plug is generally adopted. The first section does not lower the bridge plug, and uses coiled tubing to carry perforating gun, and the other sections adopt pumping mode to lower the bridge plug and perforating gun. After the bridge plug seat is sealed, the bridge plug is released, and the perforating gun is lifted up one by one to perform perforation. And finally, releasing the hand and lifting the perforating pipe string.
During an open hole well completion mode, a common open hole packer and a multi-stage sliding sleeve are used for subsection operation. After the pipe column is put in place, all stages of packers are set together, and then the sliding sleeve is opened by throwing balls step by step for construction.
4) Acid pretreatment operation
Generally, industrial hydrochloric acid is adopted, and the dosage is 10-20m 3 . Generally in the acid replacementThe discharge capacity is properly improved in the midway, and the balanced acid feeding and the balanced rupture of each cluster of perforation are ensured.
5) Low viscosity slickwater isolation operations
Generally, 50-100m is adopted 3 Low viscosity slickwater (viscosity 1-3 mPa.s) and step-by-step increase of discharge capacity from 2-4-6m 3 The/min always refers to about 60% of the maximum displacement of the design. The low-viscosity slick water and low-displacement combined injection also ensure that the pressure gradient in the horizontal shaft is reduced and the balanced extension of each cluster of cracks is ensured.
6) High-viscosity fracturing fluid moderate-displacement injection construction
Generally, high-viscosity fracturing fluid base fluid with the viscosity of 30-40 mPas is adopted for injection, and the fluid amount is generally 10-30m per cluster of cracks 3 The discharge capacity is generally from 4-6-8m 3 The/min is increased to about 80% of the design maximum.
7) Slash water section plug type injection operation carrying small-particle-size propping agent
And (3) carrying out slug injection by sequentially adopting 1-2-3-4% of sand-liquid ratio, wherein the particle size of the propping agent is 70-140 meshes, preferably 80-120 meshes, and the volume of the slick water carrying the propping agent and the volume of the spacer fluid of each propping agent slug are 0.5-1 shaft volume. And performing section-by-section polishing by using low-viscosity slickwater with the viscosity of 1-3mPa & s, wherein the polishing effect is better than that of the high-viscosity fracturing fluid. If a slickwater carrying small-particle size proppant with a sand-to-fluid ratio of 1% is used and no obvious pressure rise characteristic is used after injection, the rest 15-30m in the section can be used 3 And injecting the subsequent slickwater carrying the proppant with small particle size into the sand-liquid ratio (2%) in advance in volume, namely adding sand in an bench mode in advance. Similarly, other sand-to-liquid ratio sections are created in the same way. But if the pressure rise is obvious, the proppant slug can be polished again by repeating the polishing in the sensitive sand-to-fluid ratio section and even reducing the sand-to-fluid ratio by one again. The injection displacement is still typically maintained at 80% of the maximum displacement.
8) Reverse bench type sand adding operation
After the small-particle size proppant is injected in a plug mode, the flowing following property of the medium-particle size proppant and the fracturing fluid and the characteristic that the impact force on the fracture wall are superior to those of the small-particle size proppant are utilizedOn the premise of ensuring that the total joint-entering resistance of the propping agent is equivalent, the polishing effect on the bending part of the near-wellbore crack is improved, and the fatigue damage effect on the rock of the crack wall is increased, so that the crack width is increased, and the sensitivity of the crack to the construction sand-liquid ratio is gradually reduced. For example, after 6% of small-particle size proppant, 3% of medium-particle size proppant (the particle size of the medium-particle size proppant is generally 40-70 meshes) is added, and the liquid amount of the medium-particle size proppant is generally 15-30m 3 . If the pressure response characteristic is not obvious, the sand-liquid ratio of the fracturing fluid carrying the small-particle-size proppant and the fracturing fluid carrying the medium-particle-size proppant can be normally increased for injection when the next reverse bench type sand adding is carried out. And the more backward injection, the ratio of the sand-liquid ratio of the slickwater carrying the medium-particle-size propping agent to the sand-liquid ratio of the slickwater carrying the small-particle-size propping agent can exceed 50 percent and even reach 60 percent so as to increase the polishing effect of the medium-particle-size propping agent on the bent part of the near-well casing crack. The slippery water still adopts low-viscosity slippery water with the viscosity of 1-3 mPas. The injection displacement is still typically maintained at 80% of the maximum displacement.
9) Slubby water long slug injection with medium particle size proppant
After the reverse bench type sand adding, long-section plug construction of medium-particle-size propping agent can be carried out, such as injection construction with 3-4-5-6%, 7-8-9-10% and 10-12-13-14% of even higher sand-liquid ratio. The slickwater injection of the medium particle size proppant per sand to fluid ratio can be 1 wellbore volume. The long plug injection may be 1-1.5 wellbore volumes of spacer fluid, taking into account the risk of long plug injection. In consideration of increasing the sand carrying effect, the slickwater adopts the slickwater with medium viscosity of 9-12 mPas. The injection displacement is still typically maintained at 100% of the maximum displacement.
10 Continuous injection of slickwater carrying large particle size proppant
The particle size of the propping agent is generally 30-50 meshes, the fracturing fluid generally adopts high-viscosity slickwater, the viscosity is generally 15-20 mPa.s, a continuous sand adding mode is adopted, the sand-fluid ratio is generally 10-12-14-16-18%, the volume of the slickwater carrying the propping agent with large particle size in each sand-fluid ratio is generally 20-30%, and the injection displacement is generally kept to be 100% of the maximum displacement.
11 Replacement operation
And (3) performing proper over-displacement according to 110-130% of the volume of the current section of the shaft, adopting high-viscosity fracturing fluid of 30-40 mPa.s to reduce the sand setting effect of the horizontal shaft, and then replacing with low-viscosity slick water of 1-3 mPa.s, wherein the using amount of the high-viscosity fracturing fluid of 30-40 mPa.s is 30% of the volume of the displacement fluid. The displacement is taken to be the maximum value of the design.
12 And) other sections are operated, and the steps 3) to 10) are repeated until all the sections are constructed.
13 Drilling plug after pressing (open hole string can be ignored), testing, normal production and the like, and the method is executed according to conventional processes and parameters.
Example 1
The invention is applied to the construction of fracturing and improving the volume of a certain well in the south of the east of Chuannan, and the well has the vertical depth of 3895m, the inclined depth of 4992m and the horizontal section of 1496m. The method provided by the invention is used for carrying out optimization design, and the steps and the results are as follows:
1) Carrying out a small pressure test on the first section, explaining the minimum horizontal main stress of 85MPa and the bending friction resistance of the near-wellbore crack of 4-8 MPa; the evaluation of the key reservoir parameters of the well logging interpretation shale proves that the well has good shale development and good static indexes;
2) And (3) optimizing by adopting ECLIPSE software to obtain the optimal fracture parameters of the long-term yield after pressing: the optimal gap distance is 16-22m, the half length of the crack is 260-300m, and the flow conductivity is 20-35 mD.m;
and (3) simulating by adopting GOFHER software to obtain construction parameters of the optimal crack form: the discharge capacity is 14-16 m 3 Permin, the dosage of the single-stage fracturing fluid is 1900-2100m 3 Single stage supported dose of 60m 3 -80m 3 The particle size of the propping agent is 70-140 meshes, 40-70 meshes and 30-50 meshes, and the viscosity of the three kinds of slickwater are respectively 1-3 mPa.s of low viscosity, 9-12 mPa.s of medium viscosity, 15-20 mPa.s of high viscosity and 30-40 mPa.s of glue solution.
3) Carrying out perforating operation by adopting a bridge plug perforating combination method;
4) Pretreating with acid liquor;
5) Step lift displacement (2-4-6-8 m) 3 Min) injection of 30m 3 Sliding water, then ascending the displacement in steps (4-6-8-10-12 m) 3 Min) injection 80m 3 Glue solution;
6) The slickwater carrying small-particle-size propping agent is injected in a plug mode, the slickwater carrying 80-120 meshes of propping agent is injected in a plug mode by adopting 1-3mPa & s low-viscosity slickwater, and the thickness of the slickwater is 12m 3 The displacement of the fracturing fluid per slug period is that slickwater carrying 80-120 meshes of propping agent is injected in a slug-type mode in sequence, the sand-liquid ratio of low-viscosity slickwater carrying small-particle-size propping agent in 3 slug periods is 2%, 4% and 6% in sequence, wherein the volume of fracturing fluid in each slug period is 50m 3 The volume of the spacer fluid is 40m 3 ；
7) Continuously injecting 3 reverse bench type sand adding slugs, in each slug period of the stage, after injecting the slick water carrying the small-particle-size proppant, adding the slick water carrying the medium-particle-size proppant after tail-tracking, wherein the sand-liquid ratio of the slick water carrying the medium-particle-size proppant is half of the sand-liquid ratio of the slick water carrying the small-particle-size proppant,
in the stage, 3 slugs are injected periodically, and the slickwater with the small-particle size proppant sequentially comprises the following components: slickwater carrying 6% of 70-140 mesh proppant and tailing slickwater carrying 3% of 40-70 mesh proppant (6-70-140 mesh + 3-40-70 mesh), slickwater carrying 8% of 70-140 mesh proppant and tailing slickwater carrying 5% of 40-70 mesh proppant (8-70-140 mesh + 5-40-70 mesh), slickwater carrying 10% of 70-140 mesh proppant and tailing slickwater carrying 6% of 40-70 mesh proppant (10%70-140 mesh + 6-40-70 mesh), injection amount of slickwater carrying powder pottery and injection amount of slickwater carrying middlings were 30m each 3 And 20m 3 The amount of the spacer liquid is 50m 3 ；
8) Injecting slickwater carrying medium-particle size propping agent (40-70 meshes) into the water, changing the slickwater into medium-viscosity slickwater with the viscosity of 9-12 mPa.s, and increasing the discharge to 15-16 m 3 Min, volume of slick water carrying medium-particle size proppant and the amount of insulating liquid in each slug period are both 50m 3 The sand-liquid ratio of the slickwater carrying the medium-particle-size propping agent is 3-4-5-6% (the 4 sand-liquid ratio is continuously added with sand), 4-5-6-7% (the 4 sand-liquid ratio is continuously added with sand), 5-6-7-8% (the 4 sand-liquid ratio is continuously added with sand), 6-7-8-9% (the 4 sand-liquid ratio is continuously added with sand) and 7-8-9-10% (the 4 sand-liquid ratio is continuously added with sand) in sequenceMore than continuous sand adding), 8-9-10-11% (the 4 sand liquids are more than continuous sand adding), 9-10-11-12% (the 4 sand liquids are more than continuous sand adding), 10-11-12-13% (the 4 sand liquids are more than continuous sand adding), 11-12-13-14% (the 4 sand liquids are more than continuous sand adding), 12-13-14-15% (the 4 sand liquids are more than continuous sand adding), 13-14-15-16% (the 4 sand liquids are more than continuous sand adding);
9) Continuously injecting fracturing fluid carrying large-particle-size propping agent (30-50 meshes), wherein the fracturing fluid is changed into high-viscosity slickwater with the viscosity of 15-20 mPa.s, and the total injection amount is 60m 3 Carrying coarse sand (30-50 meshes) in a fracturing fluid, wherein the sand-liquid ratio of the fracturing fluid is 10-12-14-16-18% in sequence;
10 Using 20 m) 3 High viscosity glue and 45m 3 Displacing with low-viscosity slippery water.
11 Repeating the steps to complete the rest of the fracturing construction. And after fracturing is finished, performing flowback, test production and formal commissioning according to a conventional process.
By implementing the invention, the unimpeded flow rate after the well pressure reaches 20.5 multiplied by 10 4 m 3 And a better fracturing effect is obtained.
It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. Modifications may be made to the invention as defined within the scope of the claims and modifications may be made without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.
Claims (17)
1. A method of frac sanding comprising the sequential steps of:
s1, pretreating a reservoir by using acid liquor, and sequentially injecting low-viscosity slick water and high-viscosity fracturing fluid into the reservoir pretreated by using the acid liquor;
s2, injecting slick water carrying small-particle-size proppant in a slug mode;
s3, injecting slick water carrying small-particle size proppant and slick water carrying medium-particle size proppant in a slug type manner to perform reverse bench type sand adding, wherein in each slug period, firstly injecting slick water carrying small-particle size proppant and then injecting slick water carrying medium-particle size proppant in a tail-tracking manner;
s4, injecting slick water carrying the medium-particle-size propping agent in a long-segment plug manner;
s5, continuously injecting slick water carrying the large-particle size propping agent;
s6, replacing by using fracturing fluid;
in step S3, in each slug period, the sand-to-fluid ratio of the slickwater carrying the medium particle size proppant is 50% -60% of the sand-to-fluid ratio of the slickwater carrying the small particle size proppant.
2. The method as claimed in claim 1, wherein in step S3, after injection of the slickwater carrying the small particle size proppant, 15-30m of the slickwater is injected in each slug cycle 3 Carrying medium particle size proppant.
3. The method of claim 2, wherein step S3 comprises at least 3 slug cycles.
4. The method of any one of claims 1-3, wherein the small particle size proppant has a particle size of 70-140 mesh; and/or the presence of a gas in the gas,
the particle size of the medium-particle size proppant is 40-70 meshes; and/or the presence of a gas in the gas,
the particle size of the large-particle size proppant is 30-50 meshes.
5. The method of claim 4, wherein the small particle size proppant has a particle size of 80-120 mesh.
6. The method according to any one of claims 1-3, wherein before step S1, the method further comprises evaluating reservoir parameters before fracturing, optimizing fracture parameters and optimizing fracturing construction parameters according to the obtained reservoir parameters, and lowering the staged fracturing string.
7. The method of claim 6, wherein the reservoir parameters comprise one or more of closure stress, near-wellbore fracture bending friction, rock mechanics parameters, and synthetic fluid loss parameters; and/or performing fracture parameter optimization using ECLIPSE, and/or performing fracture construction parameter optimization using one or more of Fracpro PT, GOFHER, and STimplan.
8. The method according to any one of claims 1-3, wherein in step S2, the sand-to-fluid ratio of the slickwater carrying the small particle size proppant is increased stepwise from 1% to 4% with an increase of 1% -2%; and/or the presence of a gas in the gas,
in each slug period, the injection amount of slickwater carrying the small-particle size proppant is 50% -100% of the volume of the shaft; and/or the injection amount of the spacer fluid is 50-100% of the volume of the well bore; and/or the presence of a gas in the gas,
the injection displacement is 70-90% of the maximum displacement; and/or the presence of a gas in the atmosphere,
the slippery water is low-viscosity slippery water with the viscosity of 1-3mPa & s.
9. The method of claim 8, wherein in step S2, the injection displacement is 80% of the maximum displacement.
10. The method according to any one of claims 1-3, wherein in step S4, the sand-to-fluid ratio of the slickwater carrying the medium-sized proppant is increased stepwise from 3% to 10-14% with an increase of 1% -2%; and/or the presence of a gas in the gas,
in each slug period, the injection amount of slickwater carrying medium-particle size proppant in each sand-liquid ratio is 80-100% of the volume of a well bore; and/or the injection amount of the spacer fluid is 100-150% of the volume of the well bore; and/or the presence of a gas in the gas,
the injection displacement is 90% -100% of the maximum displacement; and/or the presence of a gas in the gas,
the slippery water has a medium viscosity of 9-12 mPas.
11. The method of claim 10 wherein in step S4, slickwater with medium particle size proppant is injected at each sand to fluid ratio at 100% of the wellbore volume.
12. The method according to any one of claims 1 to 3, wherein in step S5, the sand-to-fluid ratio of slickwater carrying large particle size proppant is increased stepwise from 10% to 18% with an increase of 1% to 3%; and/or the presence of a gas in the gas,
the injection amount of the slickwater carrying the large-particle size proppant in each sand-liquid ratio is 20-30% of the volume of the well bore; and/or the presence of a gas in the gas,
the injection displacement is 90% -100% of the maximum displacement; and/or the presence of a gas in the gas,
the slippery water is high-viscosity slippery water with the viscosity of 15-20mPa & s.
13. The method of any one of claims 1-3, wherein in step S6 the amount of fracturing fluid used is 110-130% of the wellbore volume.
14. The method of claim 13, wherein the high viscosity fracturing fluid of 30-40 mPa-s is used to reduce the sand setting effect of the horizontal wellbore during displacement, followed by displacement with low viscosity slickwater of 1-3 mPa-s.
15. The method of claim 13, wherein the volume of the high viscosity fracturing fluid is 25% to 35% of the total volume of the fracturing fluid used in step S6.
16. The method according to any one of claims 1 to 3, wherein in step S1 the low viscosity slickwater has a viscosity of 1 to 3mPa S and is used in an amount of 50 to 100m 3 With a displacement of from 2m 3 The/min is gradually increased to 50-70% of the maximum discharge capacity;
the high-viscosity fracturing fluid has viscosity of 30-40mPa · s and dosage of 10-30m 3 Displacement per cluster of cracks from 4m 3 The/min is gradually increased to 70-90% of the maximum discharge capacity.
17. Use of the method of any one of claims 1 to 16 in deep high stress reservoir fracturing.
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| CN113216923A (en) * | 2021-05-19 | 2021-08-06 | 西南石油大学 | Shale gas fracturing crack-making and sand-adding alternating process for improving supporting effect of crack net |
| CN113445982A (en) * | 2021-08-09 | 2021-09-28 | 中国石油天然气股份有限公司 | Rapid flowback segmented multi-cluster uniform fracturing method suitable for tight sandstone |
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