CN115370342A - Less-liquid and multi-sand fracturing method suitable for normal-pressure shale gas encryption well - Google Patents
Less-liquid and multi-sand fracturing method suitable for normal-pressure shale gas encryption well Download PDFInfo
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- 239000003795 chemical substances by application Substances 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 239000006004 Quartz sand Substances 0.000 claims description 11
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- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
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- 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 less-liquid multi-sand fracturing method suitable for an atmospheric shale gas encrypted well. It comprises the following steps: A. evaluating key shale gas reservoir parameters; B. determining a perforation position and performing perforation operation; C. optimizing fracture parameters and main parameters of the fracturing process; D. performing acid pretreatment operation; E. high-displacement front low-viscosity fracturing fluid for fracture making; F. continuously adding sand into the multi-stage variable parameter mixed proppant; G. controlling according to the pressure fluctuation characteristics; H. and performing replacement operation, and performing residual section fracturing construction. It has the following effects: the fracturing fluid flow rate is increased, the fracturing fluid consumption is reduced, the sand adding is increased, the sand laying efficiency, the fracture forming effect and the complexity index of a fracture system are greatly improved, the fracturing modification effect of an encrypted well of the normal-pressure shale gas reservoir is effectively improved, and the yield increasing and stabilizing effects after fracturing are improved.
Description
Technical Field
The invention relates to a less-liquid multi-sand fracturing method suitable for an atmospheric shale gas encryption well, and belongs to the technical field of oil exploitation.
Background
The encrypted well is complicated with the adjacent well spatial relationship in earlier stage, presses and scurries the possibility highly, has goaf leakage, the asymmetric condition in crack, and the regional internal reserve volume does not fully utilize, and has passed through the production of longer time after the adjacent well fracturing, compares with the initial condition, and the region that encrypted well passed through, the gas content reduces by a wide margin, and formation pressure also reduces by a wide margin, consequently, encrypted well fracturing wants to gain breakthrough, and the degree of difficulty is bigger.
The main reasons are as follows: firstly, after the adjacent well is pressed, a large amount of shale gas is produced, so that large-area depletion of formation pressure is caused, the reduction of the formation pressure, the reduction of ground stress and the reduction of effective permeability are caused, and a better effect can be obtained only by using a more effective seepage channel; second, after the adjacent well is pressed, the adjacent well is produced for a long time, induced stress reduction effect caused by fracture and production is caused, two-directional horizontal stress difference is reduced, the stress tends to be isotropic, a main-oriented extension seam is not easily formed in the fracture initiation direction and the subsequent extension process of the fracture, a complex seam which is easily formed in the adjacent well zone is formed, small-scale fractures and seam lines cannot be effectively filled and supported, and the complexity degree of the fracture and the stable production effect after the fracture are reduced.
The burial depth of the normal-pressure shale gas reservoir ranges from 500 meters to 5000 meters, the change of the burial depth of the reservoir is large, and the particle size, sand-liquid ratio and sand adding amount of the propping agent are difficult to be completely matched with the multi-scale fracture. The sand adding procedure is hastily promoted, and early sand blocking can be induced, but the slug type sand adding is too conservative, so that the utilization rate of the crack forming volume is low, and the effective crack transformation volume is difficult to improve. The effective reconstruction volume of the fracture has short maintenance time or high reduction rate, the core of the effective reconstruction volume of the fracture is that the fracture conductivity caused by low sand laying concentration is low, and the fracture conductivity is reduced more seriously due to the crushing and embedding of the propping agent under the condition of high closing stress.
Therefore, a new fracturing method for the normal-pressure shale gas encrypted well is needed.
Disclosure of Invention
The invention aims to provide a less-liquid multi-sand fracturing method which is suitable for an atmospheric shale gas encryption well and can effectively improve the sand laying concentration and the supporting effect of a crack and further improve the development and transformation effects of an atmospheric shale reservoir.
In order to solve the technical problems, the less-liquid and more-sand fracturing method applicable to the normal-pressure shale gas encryption well comprises the following steps of:
A. evaluating key shale gas reservoir parameters;
B. determining a perforation position and performing perforation operation:
projecting the borehole trajectory and the perforation position of the adjacent well and the geodetic coordinates of the borehole trajectory of the encrypted well, measuring the linear distance of a connecting line between the encrypted well and the adjacent well on a projection plane, and performing encrypted perforation on the encrypted well at the position corresponding to the bridge plug of the adjacent well;
C. simulating fracture parameters, and determining main parameters of the fracturing process;
D. acid pretreatment operation: in the operation process, the acid consumption of each section is 10-20m 3 Discharge capacity of 1-2m 3 /min；
E. Leading low-viscosity fracturing fluid to carry out high-displacement crack formation;
F. continuously adding sand into the multi-stage variable parameter mixed proppant;
G. controlling according to the pressure fluctuation characteristics;
H. and performing replacement operation, and performing the rest section of fracturing construction.
And further, in the step C, fracturing key parameters such as total liquid amount, total propping agent amount, construction displacement and liquid viscosity required by single-stage fracturing are determined by utilizing shale gas reservoir parameter data to use software simulation and taking the optimal joint length and flow conductivity as optimization targets.
And furthermore, in the step E, the salt-resistant and viscosity-changing integrated fracturing fluid is adopted and is prepared by adding an emulsion type thickening agent into water, the viscosity is adjusted in real time, the resistance reduction rate is greater than 70%, and the surface tension is less than 30mN/m.
And further, in the step E, a pad fluid stage is pumped, the high discharge capacity is quickly increased under the condition of casing pressure limitation, the pad fluid adopts low-viscosity slick water to carry out early-stage crack formation and fracturing construction, the viscosity is 9-12mpa · s, and the pad fluid volume is 3-4 times of the wellbore volume fluid volume.
And further, in the step F, performing staged fracturing construction on the reservoir by adopting a multistage variable parameter mixed sand adding one-stage continuous sand adding mode.
And furthermore, in the step F, the initial sand-liquid ratio is 9-12%, and according to the wellhead extension pressure condition: when the extension pressure of the well mouth is less than or equal to 68MPa, the sand is added when the initial sand ratio is 11-12%; when the extension pressure of the well mouth is more than 68MPa, the sand is added when the initial sand ratio is 8-10%; the sand-liquid ratio is increased in a stepwise manner, the increase range of the sand-liquid ratio is not limited to 1% every time, and the sand-liquid ratio is continuously increased until the total sand amount of the section is injected.
Furthermore, in the step F, the sand carrying fluid amount of each sand-fluid ratio is 1.5 times of the volume of the shaft, and the pressure condition of the proppant after entering the stratum is observed; if the pressure is stable, continuously increasing the sand-liquid ratio; when the pressure rises slightly, the sand-liquid ratio is continuously increased until the current sand-liquid ratio is stable, and then the sand-liquid ratio is increased after the pressure is stable.
Still further, in the step F, 70/140 mesh, 40/70 mesh, 30/50 mesh and 20/40 mesh proppants are adopted as the proppants; wherein, the type of the propping agent can be quartz sand or ceramsite;
and furthermore, in the step F, the width of a seam formed in the radial direction of the shaft in the fracturing process is changed from wide to narrow, and the multi-stage variable parameter mixing continuous sand adding mode selects multi-stage variable parameter mixing sand adding of two or three particle size proppants.
Furthermore, in the step G, when the rising speed of the wellhead pressure is less than or equal to 3.0MPa/min, the volume of the sand-carrying liquid under the sand-liquid ratio is increased, the pressure change trend is observed, and after the pressure is stable, sand is continuously added according to the step sand-extracting liquid ratio; when the pressure rise speed of the well mouth is more than 3MPa/min, a small amount of medium-high viscosity slippery water is adopted to flush and treat the sand plug, the height of the sand bank at the seam mouth is reduced, after the pressure is stable, the low viscosity slippery water is recovered to carry sand to make the seam, and the step sand-liquid ratio is continuously increased.
And further, in the step H, the displacement is 2 times of the volume of the well bore, and 20m is pumped and injected firstly 3 The viscosity of the medium-high viscosity slickwater fracturing fluid is 20-25mPa.s, settled sand in a shaft is cleaned, a lower pumping bridge plug perforating tool is prevented from being blocked, and the residual displacement fluid is still replaced by low-viscosity slickwater with the low viscosity of 9-12mPa.s until 2 times of shaft volume fluid is injected.
The invention has the following effects:
(1) The method adopts a multi-stage variable parameter proppant mixing one-stage continuous high sand ratio sand adding technology, fully considers the adding time, the particle size, the sand-liquid ratio and the sand amount of the proppant in the crack making process, realizes the aim that the crack making spaces with different scales can be filled with the proppant in a saturated mode, simultaneously keeps the high sand ratio sand adding to play a role of temporary blocking in the crack, promotes the net pressure in the main crack to rise, realizes the crack turning and further improves the complexity of the crack, adopts a particle size combination high sand-liquid ratio construction method, continuously adds the sand in a tentative mode, improves the sand-liquid ratio under the condition of avoiding sand blocking, reduces the using amount of fracturing liquid, realizes the efficient fracturing with less liquid injection and more sand adding, greatly improves the sand laying efficiency, the crack making effect and the complexity index of a crack system, effectively improves the yield increasing and stabilizing effect after the encrypted well pressure of the normal-pressure shale gas reservoir, and realizes cost reduction and efficiency improvement.
(2) Compared with the conventional slug type sand adding fracturing transformation, the length of a propping agent supporting crack can be increased by more than 12%, the sand adding strength can be increased by more than 30%, the liquid consumption is saved by more than 10%, the crack flow conductivity and the effective supporting crack volume are improved, the damage to a reservoir caused by the soaking of fracturing liquid is reduced, and the influence on the production of an adjacent well caused by the fact that a pressure string is communicated with an adjacent well seam network is avoided.
(3) The whole fracturing method is simple and easy to implement, controllable in cost and strong in operability, improves the development and modification effects of the normal-pressure shale reservoir stratum infilled well, can meet the requirements of the shale oil-gas well on improving the fracturing construction success rate, is remarkable in application effect, and has a very wide application prospect.
Drawings
FIG. 1 is a plot of a sand fracturing stage for field application of the present invention.
Detailed Description
The method for fracturing the encrypted well in the normal-pressure shale gas reservoir with less liquid and more sand according to the invention is further described in detail with reference to the attached drawings and the specific implementation mode.
As shown in the figure, the less-liquid and more-sand fracturing method applicable to the normal-pressure shale gas reservoir encrypted well comprises the following steps of:
A. evaluating key shale gas reservoir parameters;
the reservoir parameter evaluation comprises lithology parameters, physical properties (including porosity and permeability) parameters, rock mechanics parameters, crustal stress and the like of the normal-pressure shale gas reservoir, natural fracture development characteristics and bedding joints (including high-angle natural fractures and horizontal texture joints).
The conventional evaluation means of the reservoir can adopt methods such as well logging, well testing, core experiment and the like, and the evaluation of natural cracks and bedding cracks is carried out by methods such as core slice, CT scanning electron microscope, FMI imaging well logging and the like besides visually observing the core by naked eyes. The specific operations of conventional evaluation means of reservoir and evaluation means of natural fractures and bedding joints are known to those skilled in the art and are not described herein.
B. Determining a perforation position and performing perforation operation:
in order to improve the stratum reserve utilization rate, the planar three-dimensional position relation and the fracturing parameters of adjacent old well tracks are analyzed. Projecting the borehole tracks and perforation positions of adjacent wells and geodetic coordinates of the borehole tracks of the encrypted wells, measuring the linear distance of a connecting line between the encrypted wells and the adjacent wells on a projection plane, performing encrypted perforation on the positions, corresponding to bridge plugs of the adjacent wells, on the encrypted wells, preferably performing perforation at positions with high gas logging, low gamma, low drilling time and low stress, and optimizing the perforation positions by combining gamma and gas logging data to achieve the purpose of refining transformation;
for example: the perforation can be densely arranged on the position of the encrypted well relative to the position 40m above and below the old well bridge plug, the perforation is arranged in a staggered mode with the old well perforation position, and meanwhile, the perforation is densely arranged on the high gas logging display section. Comprehensively considering the factors as the basis for selecting the perforation position.
The single section adopts 6-8 clusters of perforation, 0.4-0.5 m/cluster. The number of each cluster of holes in the 6 clusters of perforated intervals from bottom to top is 6 holes (bottom 2 clusters) -5 holes (middle 2 clusters) -4 holes (top 2 clusters), and the total number of the holes is 30; the number of holes of each cluster of the 8 clusters of perforation layers is from bottom to top, and the number of the holes is from 5 holes (bottom 2 clusters) -4 holes (middle 4 clusters) -3 holes (top 2 clusters), and the total number of the holes is 32. And the aperture of the large-aperture bullet hole is 16mm, so that the transformation degree of a near wellbore area is improved.
C. Simulating fracture parameters, and determining main parameters of the fracturing process, wherein the method comprises the following specific steps:
the method comprises the steps of utilizing the existing shale gas reservoir parameter data to simulate by using professional software, and determining the fracturing key parameters such as total liquid amount, total propping agent amount, construction discharge amount and liquid viscosity required by single-stage fracturing by taking the optimal seam length and flow conductivity as targets; optimizing the fracturing key parameters of the normal-pressure shale gas encrypted well: the discharge capacity is 15-17m 3 M; sand adding strength of 2-2.2m 3 (m), injection strength of 25-30m 3 M, the comprehensive sand-liquid ratio is 10-12%;
specifically, on the basis of reservoir parameter evaluation in the step A, a geological model is established by adopting modeling software, different crack lengths, flow conductivity, crack layout and the like are set, and a crack parameter system with relatively highest final yield is simulated. On this basis, mature fracture propagation simulation software (such as Fracpro PT, meyer or GOFHER) is applied to simulate the pumping process in one fracturing section, so as to obtain the fracture propagation distribution conditions corresponding to different pumping stages and main process parameters required for realizing the fracture parameters, including total fracturing fluid amount, construction displacement, propping agent amount and the like.
D. Acid pretreatment operation: in the process of operation, hydrochloric acid formula or rare earth acid formula can be adopted, and the acid consumption of each section is 10-20m 3 Discharge capacity of 1-2m 3 Min; according to the test before and after the acid dissolution rate test of the rock core, the pretreatment is preferably carried out by 15 percent hydrochloric acidSo as to reduce the fracture pressure and improve the seepage capability of the near-wellbore zone fracture.
E. High-displacement front low-viscosity fracturing fluid crack formation; the fracturing fluid can be prepared by adding an emulsion type thickening agent into water, and more preferably, the fracturing fluid can be mixed with a high-salinity flowback fluid after the adjacent well is pressed and then is injected with a sand pump; adjusting the viscosity in real time, wherein the resistance reduction rate is more than 70 percent, and the surface tension is less than 30mN/m; the pad fluid adopts low-viscosity slickwater to carry out early-stage crack-making fracturing construction, the viscosity is 9-12mpa · s, the amount of pad fluid liquid injected by a pump is 3-4 times of the volume of a shaft, the high displacement is quickly increased under the condition of sleeve pressure limitation, and the pad fluid amount is injected by the pump to carry out next-stage low-viscosity slickwater sand-carrying construction.
Specifically, pumping low-viscosity slickwater according to the key parameters determined in the step C, and performing construction injection under a pressure-limiting rapid displacement-increasing strategy to form high pressure difference, open a plurality of perforation clusters and establish crack channels, wherein the low-viscosity slickwater is preferably selected and prepared by adding an anti-salt integrated emulsion type thickening agent into fracturing fluid as described above; the used salt-resistant integrated emulsion fracturing fluid can be used with a flowback fluid preparation of a peripheral drainage and production well, the addition concentration of an emulsion thickening agent is 0.10-0.13%, the viscosity is 9-12mpa · s, and low-viscosity slick water can communicate and expand a micro-fracture system of a matrix to the maximum extent.
F. The width of a seam formed in the radial direction of a shaft in the fracturing process is narrowed from width, multi-stage variable parameter mixed proppant is adopted for continuously adding sand, and preferably, a multi-stage variable parameter mixed sand one-stage continuous sand adding mode of two or three particle size proppants can be adopted for performing staged fracturing construction on a reservoir stratum.
The continuous sand adding mode is a one-stage continuous sand adding mode, the initial sand-liquid ratio is gradually increased to the designed highest sand-liquid ratio, and then the sand adding with the high sand-liquid ratio is kept until the fracturing injection of the total designed sand amount of the stage is completed; the initial sand-liquid ratio refers to the lowest sand-liquid ratio of the pump injection design; the method adopts the mixed injection of two or three or more kinds of particle size proppants to realize the multi-stage parameter-varying mixed sand addition of the two or three kinds of particle size proppants;
specifically, in an atmospheric shale gas fracturing embodiment, a five-stage variation of two particle size proppants is preferred with sand (70/140 mesh, 40/70 mesh proppant): the volume ratio of 70/140 mesh to 40/70 mesh = 1; wherein 70-140 mesh proppant accounts for 50-60%, and 40-70 mesh proppant accounts for 40-50%; the 70/140 mesh proppant contains 70/140 mesh quartz sand and 70/140 mesh ceramsite, and the 40/70 mesh proppant contains 40/70 mesh quartz sand and 40/70 mesh ultra-low-density ceramsite; of course, it is more preferred to use a six-stage variation of three particle size proppants mixed with sand: 70/140 mesh, 40/70 mesh, 30/50 mesh volume ratio = 1; wherein, 70-140 mesh proppant accounts for 20-30%,40-70 mesh proppant accounts for 40-50%,30/50 mesh proppant accounts for 20-30%, sand-eating capacity of cracks in different pump injection stages is explored, the aims of rapid sand extraction ratio, less liquid consumption and more sand addition are achieved, smooth fracturing construction is ensured, and construction cost is reduced;
taking one of the above data as an example: in the specific embodiment of normal pressure shale gas fracturing, 70/140 mesh proppant is added firstly, and the sand injection amount of a pump is 30 percent of the total sand amount of a single section; the construction pressure stable switching proppant is a mixed proppant (volume ratio is 2; the construction pressure stable switching proppant is 70/140 meshes and 40/70 meshes of mixed proppant (volume ratio is 1; the construction pressure is stably switched to 70/140-mesh proppant and 40/70-mesh mixed proppant (volume ratio is 1; the construction pressure stably switches the propping agent to 40/70 mesh propping agent, the pump sand injection amount is 10% of the single-section total sand amount, and the single-section sand adding amount is completed. Wherein the dosage of the 70/140 mesh proppant is 50-60% of the volume dosage of the total proppant, and the dosage of the 40/70 mesh proppant is 40-50% of the volume dosage of the total proppant.
During construction, the initial sand-liquid ratio is 9-12%, and according to the wellhead extension pressure condition: when the extension pressure of the well mouth is less than or equal to 68MPa, the sand is added when the initial sand ratio is 11-12%; when the extension pressure of the well mouth is more than 68MPa, the sand is added when the initial sand ratio is 8-10%; the sand-liquid ratio is increased in a step-by-step mode, the increasing range of the sand-liquid ratio is not limited to 1% every time, and sand adding is continuously performed until the injection of the total sand amount of the section of design is completed.
The sand carrying fluid amount of each sand-fluid ratio is 1.5 times of the volume of the shaft, and the pressure condition of the propping agent entering the stratum is observed; if the pressure is stable, continuously increasing the sand-liquid ratio; when the pressure rises slightly, the sand-liquid ratio is continuously increased until the current sand-liquid ratio is stable, and then the sand-liquid ratio is increased after the pressure is stable.
G. The method is controlled according to the pressure fluctuation characteristics and comprises the following specific steps:
when the pressure rising speed of the well mouth is less than or equal to 3MPa/min, increasing the volume of the sand carrying liquid under the sand-liquid ratio, observing the pressure change trend, and continuously adding sand in the stepped sand-liquid ratio after the pressure is stable; when the pressure rise speed of the well mouth is more than 3MPa/min, a small amount of medium-high viscosity slick water is adopted to flush and treat the sand plug, the height of the sand bank at the seam mouth is reduced, after the pressure is stable, the low viscosity slick water sand carrying and seam making is recovered, and the sand is continuously added in the step sand-extracting liquid ratio; if the pressure continues to rise, reducing the sand-liquid ratio by 1-2% and adding sand, recovering low-viscosity slickwater to carry sand and make a seam after the pressure is stable, and continuously adding sand according to the stepped sand-liquid ratio; by adopting a particle size combination high sand-liquid ratio construction method, sand is added tentatively continuously, the final sand-liquid ratio is improved under the condition of avoiding sand blocking, and less liquid injection and more sand addition are realized.
H. And performing replacement operation, and performing residual section fracturing construction. During specific construction, the displacement is 2 times of the well bore volume, and 20m is pumped firstly 3 The viscosity of the medium-high viscosity slickwater fracturing fluid is 20-25mPa.s, settled sand in a shaft is cleaned, a lower pumping bridge plug perforating tool is prevented from being blocked, and the residual displacement fluid is still replaced by low-viscosity slickwater with the low viscosity of 9-12mPa.s until 2 times of shaft volume fluid is injected.
The effect of the normal-pressure shale gas encryption well A (with the vertical depth of 3100m and the horizontal length of 2133 m) in south China Chongqing is verified as follows:
the horizontal section space distribution condition of the A well and the adjacent B well is as follows: the distance between the A well and the adjacent B well is 348-355m in plane and 369-407m in space; the space and plane distances between the well and other adjacent wells are larger than 150m. The fracturing method provided by the invention is adopted to carry out volume fracturing on the well A, and the transformation concept of staggered variable-density perforation, liquid control and sand extraction and high-strength sand addition is adopted to carry out transformation, and the method comprises the following steps.
Step 1, carrying out fine evaluation on natural fractures and bedding fractures of the shale reservoir of the well A and the peripheral adjacent wells. Parameters such as reservoir lithology, physical properties, rock mechanics, ground stress profile and the like are accurately evaluated through well logging, well testing data, core data and the like, and the method is used for designing a fracturing scheme. The reservoir lithology of the well A is gray black carbonaceous shale, the porosity is 4.1%, the elastic modulus is 30GPa, the Poisson ratio is 0.22, and the pressure coefficient is 1.0. The high-permeability seam does not grow, and the high-permeability seam grows better.
Step 2, projecting the borehole trajectory of the well A, the borehole trajectory of the well B of the adjacent well and geodetic coordinates of perforation positions, carrying out encrypted perforation in the range of 40 meters above and below the bridge plug position of the well A relative to the well B of the adjacent well, distributing holes in a staggered manner with the perforation positions of the well B of the adjacent well, and optimally adjusting the perforation positions by combining data such as gamma, gas measurement, drilling time and the like to achieve the purpose of fine modification;
step 3, optimizing fracturing construction parameters by means of Meyer simulation, and determining total pumping liquid amount 1690m of the best single-section fracture expansion of the A well according to fracture parameter simulation 3 Total sand amount of 160m per section 3 The viscosity of the slickwater is 9-12mPa.s, and the injection displacement is 15-17m 3 /min。
And 4, performing the site fracturing construction of the well A based on the construction parameters in the step 3.
1) Acid injection 10m 3 Discharge capacity of 1.5m 3 Permin, then pumping and injecting front low-viscosity fracturing fluid for 200m 3 。
2) Preparing sand adding, starting to add 70/140-mesh quartz sand with 9% of initial sand-liquid ratio according to the construction extension pressure of 69MPa, pumping 1.5 times of shaft volume, observing stable pressure, continuously extracting 10% -11% -12% -13% of sand-liquid ratio, keeping the sand-liquid ratio of 14% until 70/140-mesh quartz sand is added, wherein the total amount of 70/140-mesh quartz sand is 30% of the total amount of single-section sand;
the observation pressure is relatively stable, the combination of the proppant is switched into quartz sand (the volume ratio is 2;
the observation pressure is relatively stable, the proppant combination is switched to 70/140 meshes and 40/70 meshes of quartz sand (the volume ratio is 1);
observing that the pressure is relatively stable, switching the proppant combination into 70/140-mesh and 40/70-mesh quartz sand (the volume ratio is 1: 2), wherein the sand-liquid ratio is 18%, the extended pressure fluctuation is less than 3MPa/min, continuing to extract the sand-liquid ratio to 19%, and the pressure is relatively stable until the total amount of injected quartz sand is 90% of the total sand amount of a single section;
and (4) observing that the pressure is relatively stable, switching the propping agent into 40/70-mesh ceramsite, and controlling the sand-liquid ratio to be 19%, wherein the pressure is relatively stable until the total sand adding amount of the section is finished.
And 5, replacing the low-viscosity fracturing fluid with twice of the volume of the shaft to finish the fracturing construction of the section, and pumping the bridge plug for staged perforation to finish the fracturing construction of the rest section.
By adopting the fracturing method provided by the invention to perform fracturing reconstruction construction on the well A, the well A finishes 27 sections of fracturing altogether, the average section length is 79.18m, the total injected formation liquid amount is 48614.6m3, and the sand addition amount is 5547.9m3. Average single liquid volume 1800.91m 3 Average single-segment sand amount of 205.5m 3 Average sand addition per meter of 2.6m 3 M, average liquid consumption per meter 22.7m 3 The comprehensive sand-liquid ratio is 12.36 percent.
The fracturing section length of the adjacent well B well is 1900m, the fracturing is divided into 27 sections, the average section length is 70.4m, and the total construction liquid amount is 53823.5m 3 Total sand amount 3534.13m 3 Average single-stage liquid volume 1993.5m 3 Average liquid consumption per meter of 28.33m 3 Average single-segment sand amount of 130.9m 3 Average sand addition per meter of 1.86m 3 The comprehensive sand-liquid ratio of the whole well is 6.57 percent,
combining software simulation to obtain that the length of a half seam of a propping fracture of the well A fracturing propping agent reaches 138m, and the seam height is 25m; the B well fracturing propping agent propped fracture has a half-fracture length of 120m and a fracture height of 26m. Compared with an adjacent well B, the well A has the advantages that the length of a propping crack of the propping agent is improved by 15%, the sand adding strength is improved by 39%, and the liquid consumption is saved by 10.1%. The application of the scheme of the invention increases the effective supporting seam length of the propping agent, reduces the injection amount of the fracturing fluid, improves the sand adding strength, improves the fracture flow conductivity and the effective supporting fracture volume, and simultaneously avoids the influence of the pressure string on the adjacent well seam network to the production of the adjacent well.
The unimpeded flow rate after the well pressure A reaches 25.23 multiplied by 10 4 m 3 Daily gas production of 5.5X 10 4 m 3 And d is 2.2 times of the daily gas production of the adjacent well B, and remarkable economic benefit is obtained. According to construction parameters and production conditions, evaluation and analysis are carried out on the well A after pressing, and results show that the actual volume seam forming effect is ideal, the proppant laying efficiency is high, and the estimated stable production time is long.
It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make modifications, alterations, additions or substitutions within the spirit and scope of the present invention.
Claims (11)
1. A less-liquid and more-sand fracturing method suitable for an atmospheric shale gas encrypted well is characterized by comprising the following steps of:
A. evaluating key shale gas reservoir parameters;
B. determining a perforation position and performing perforation operation:
projecting the borehole trajectory and the perforation position of the adjacent well and the geodetic coordinates of the borehole trajectory of the encrypted well, measuring the linear distance of a connecting line between the encrypted well and the adjacent well on a projection plane, and performing encrypted perforation on the encrypted well at the position corresponding to the bridge plug of the adjacent well;
C. simulating fracture parameters, and determining main parameters of the fracturing process;
D. acid pretreatment operation: in the operation process, the acid consumption of each section is 10-20m 3 Discharge capacity of 1-2m 3 /min；
E. Leading low-viscosity fracturing fluid to carry out high-displacement crack formation;
F. continuously adding sand into the multi-stage variable parameter mixed proppant;
G. controlling according to the pressure fluctuation characteristics;
H. and performing replacement operation, and performing residual section fracturing construction.
2. The few-fluid and many-sand fracturing method suitable for the normal-pressure shale gas encrypted well according to claim 1, characterized by comprising the following steps: and C, simulating by using software by using shale gas reservoir parameter data, and determining fracturing key parameters such as total liquid amount, total propping agent amount, construction discharge amount and liquid viscosity required by single-stage fracturing by taking the optimal joint length and flow conductivity as optimization targets.
3. The low-fluid high-sand fracturing method suitable for the atmospheric shale gas encrypted well according to claim 1, characterized in that: in the step E, the salt-resistant and viscosity-variable integrated fracturing fluid is adopted and prepared by adding an emulsion type thickening agent into water, the viscosity is adjusted in real time, the resistance reduction rate is greater than 70%, and the surface tension is less than 30mN/m.
4. The few-fluid and many-sand fracturing method suitable for the normal-pressure shale gas encrypted well according to claim 1, characterized by comprising the following steps: and E, in the stage of pumping the pad fluid, rapidly increasing the pad fluid to high discharge capacity under the condition of casing pressure limitation, wherein the pad fluid adopts low-viscosity slickwater to carry out early crack formation and fracturing construction, the viscosity is 9-12mpa · s, and the pad fluid quantity is 3-4 times of the wellbore volume fluid quantity.
5. The low-fluid high-sand fracturing method suitable for the atmospheric shale gas encrypted well according to claim 1, characterized in that: and F, performing staged fracturing construction on the reservoir by adopting a multistage variable parameter mixed sand adding one-stage continuous sand adding mode.
6. The low-fluid high-sand fracturing method suitable for the atmospheric shale gas encrypted well according to claim 1, characterized in that: in the step F, the initial sand-liquid ratio is 9-12%, and according to the wellhead extension pressure condition: when the extension pressure of the well mouth is less than or equal to 68MPa, the sand is added when the initial sand ratio is 11-12%; when the extension pressure of the well mouth is more than 68MPa, the sand is added when the initial sand ratio is 9-10%; the sand-liquid ratio is increased in a stepwise manner, the increase range of the sand-liquid ratio is not limited to 1% every time, and the sand-liquid ratio is continuously increased until the total sand amount of the section is injected.
7. The few-fluid and many-sand fracturing method suitable for the normal-pressure shale gas encrypted well according to claim 1, characterized by comprising the following steps: in the step F, the sand carrying fluid amount of each sand-fluid ratio is 1.5 times of the volume of the shaft, and the pressure condition of the propping agent entering the stratum is observed; if the pressure is stable, the sand-liquid ratio is continuously increased; when the pressure rises slightly, the sand-liquid ratio is continuously increased until the current sand-liquid ratio is stable, and then the sand-liquid ratio is increased after the pressure is stable.
8. The few-fluid and many-sand fracturing method suitable for the normal-pressure shale gas encrypted well according to claim 1, characterized by comprising the following steps: in the step F, 70/140 meshes, 40/70 meshes, 30/50 meshes and 20/40 meshes of propping agents are adopted; the proppant is quartz sand or ultra-low density ceramsite.
9. The few-fluid and many-sand fracturing method suitable for the normal-pressure shale gas encrypted well according to claim 1, characterized by comprising the following steps: in the step F, the width of a seam formed in the radial direction of the shaft in the fracturing process is narrowed, and the multi-stage variable parameter mixing sand adding of two or three particle size proppants is selected.
10. The low-fluid high-sand fracturing method suitable for the atmospheric shale gas encrypted well according to claim 1, characterized in that: in the step G, when the rising speed of the wellhead pressure is less than or equal to 3.0MPa/min, the volume of the sand-carrying liquid under the sand-liquid ratio is increased, the pressure change trend is observed, and after the pressure is stable, sand is continuously added according to the step sand-extracting liquid ratio; when the pressure rise speed of the well mouth is more than 3MPa/min, a small amount of medium-high viscosity slippery water is adopted to flush and treat the sand plug, the height of the sand bank at the seam mouth is reduced, after the pressure is stable, the low viscosity slippery water is recovered to carry sand to make the seam, and the step sand-liquid ratio is continuously increased.
11. The low-fluid high-sand fracturing method suitable for the atmospheric shale gas encrypted well according to claim 1, characterized in that: in the step H, the displacement is 2 times of the well bore volume, and 20m is pumped firstly 3 Medium-high viscosity slickwater fracturingAnd (3) cleaning settled sand in the shaft to prevent the lower-section pumping bridge plug perforation tool from being blocked, and replacing the residual displacement liquid by using low-viscosity slick water with the low viscosity of 9-12mPa.s until 2 times of shaft capacity liquid is injected.
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