CN114427424A - Deep oil and gas reservoir directional fracturing method and application - Google Patents
Deep oil and gas reservoir directional fracturing method and application Download PDFInfo
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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
- E21B43/261—Separate steps of (1) cementing, plugging or consolidating and (2) fracturing or attacking the formation
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Abstract
The invention discloses a directional fracturing method for a deep oil-gas reservoir and application thereof. The method comprises the following steps: the stress direction is changed by multiple temporary plugging and steering, the induced stress field of the formed crack and the mutual superposition principle are utilized, and then the steering angle is controlled, so that the crack extends towards the required direction, the complexity of the crack is improved, and the reconstruction volume of the crack is enlarged. The method of the invention leads the crack to extend towards the direction parallel to the maximum main stress direction by controlling the stress transition and the steering angle, forms a complex crack after a plurality of times of temporary blocking and steering, and effectively improves the yield. The method is simple and easy to implement and does not need complex tools and materials for forming complex seams of deep oil and gas reservoirs.
Description
Technical Field
The invention relates to the technical field of fracturing modification of shale, sandstone and carbonate oil and gas reservoirs, in particular to a directional fracturing method of a deep oil and gas reservoir and application thereof.
Background
At present, with the continuous deepening of the exploration and development process, shale, sandstone or carbonate rock face the reservoir transformation challenges of larger burial depth, larger stress and higher temperature, and face a series of technical problems in the fracturing process: (1) with the increase of the buried depth, the friction resistance and the construction pressure of a shaft in the construction process are increased, so that the construction discharge capacity is low, and the large-discharge-volume fracturing operation cannot be carried out; (2) along with the increase of the burial depth, the Young modulus of the reservoir rock is increased, the plastic characteristic is enhanced due to the increase of the temperature, so that the fracture initiation pressure is large, the fracture forming width is narrow, the sand adding is difficult, and the sand-liquid ratio is difficult to improve; (3) the structural stress is increased, the difference of the two-direction horizontal stress is increased, and the complexity and the transformation volume of the crack are relatively limited; (4) the dual influence of the flow conductivity of the crack on high closing stress and plastic embedding can be quickly reduced even to zero, so that the limited crack transformation volume is also quickly reduced. Therefore, the yield after pressure of deep hydrocarbon reservoirs is low and the decline is fast, and economic development benefits are difficult to achieve generally.
Therefore, on the basis of the original conventional fracturing, the fracture modification volume and the flow conductivity are increased, and the fracture is extended towards a required direction. In particular, carbonate hydrocarbon reservoirs sometimes require hydraulic fractures to extend in a certain direction to communicate with highly hydrocarbon-bearing fracture-cavity bodies; for sandstone oil and gas reservoirs, such as the natural extension direction of a hydraulic fracture extending towards the direction that a sand body becomes thinner or oil and gas are poor, the extension direction of the hydraulic fracture needs to be changed so as to increase the oil and gas yield after pressurization to the maximum extent; in the case of shale, hydraulic fractures of other extension directions are required in addition to the natural extension direction of the hydraulic fractures to increase the reconstruction volume of the fractures. Therefore, directional design techniques for fracture propagation direction are required, whether sandstone, carbonate, or shale.
Chinese patent CN105041287A discloses a fiber temporary plugging steering fracturing method for improving the productivity of a low-permeability tight sandstone oil-gas well, wherein a fracturing method for temporary plugging steering by adding fibers is provided, clean fracturing fluid is used as working fluid, a fiber temporary plugging agent is added at a sand-carrying fluid stage to plug the end part of a crack, construction is carried out when the crack is successfully steered to a fracturing stage, construction pressure is monitored in real time, and whether the crack has the occurrence rate is judged to steer the crack according to the change of the construction pressure. If the pressure rapidly rises and the rising pressure is larger than the stress difference between the maximum horizontal main stress and the minimum horizontal main stress, the original crack is judged to realize plugging, a new steering crack is generated, the next construction can be carried out, and otherwise, the fiber and the propping agent are continuously injected in a mixing manner for secondary plugging. The patent only provides a fiber temporary plugging agent, and does not relate to how to apply induced stress, how to perform multiple temporary plugging steering, and how to control a stress steering area and a steering angle to enable a crack to directionally extend.
Chinese patent CN107100607A discloses a temporary blocking steering fracturing method. The high-strength water-soluble (oil-soluble) temporary plugging agent is pumped into the stratum to plug the former cracks, force the fluid to turn and press new cracks to complicate the crack shape, and the short fiber net is injected first and then the large-particle temporary plugging agent and the powdery temporary plugging agent are injected. Compared with other patents, the patent also adopts the temporary plugging agents with different grain diameters to carry out crack diversion, and does not relate to how to directionally extend the cracks by utilizing induced stress, a stress diversion area, a diversion angle and the like.
Chinese patent CN109458168A discloses a composite temporary plugging diversion fracturing method for improving the productivity of a sandstone reservoir gas well. The composite temporary plugging agent is different from a fiber temporary plugging agent and a chemical temporary plugging agent, and mainly comprises a foam temporary plugging agent and the fiber temporary plugging agent, wherein the dosage of the fiber temporary plugging agent is 3 per mill of the mass fraction of the foam temporary plugging agent, the temporary plugging method requires that the stress difference between the maximum horizontal main stress and the minimum horizontal main stress is 6-10 MPa, reservoir microcracks develop, the rock brittleness coefficient is 0.33-0.42, and the stress difference of a storage interlayer is more than 6 MPa. The patent still only mentions the temporary plugging steering by using the temporary plugging agent, and still does not relate to how to directionally extend the crack by using induced stress, a stress steering area, a steering angle and the like.
Chinese patent CN109826607A discloses a novel temporary plugging diversion fracturing method. And carrying out dense perforation by using bullets with equal apertures to obtain uniform apertures. And then injecting the temporary plugging agent into the same perforation section for three times, wherein the temporary plugging agent with small particle size is injected by carrying low-discharge low-viscosity fracturing fluid, the temporary plugging agent with large particle size is injected by carrying high-discharge high-viscosity fracturing fluid after the injection of the temporary plugging agent with small particle size is finished, and the temporary plugging agent with small particle size is finally injected by carrying high-discharge low-viscosity fracturing fluid. The patent still does not address how to directionally propagate the fracture using induced stresses, stress-deflecting zones, and deflection angles, among others.
Chinese patent CN101498210A discloses a coalbed methane slim hole hydraulic jet directional fracturing production increasing method. On the basis of directional slim-hole hydraulic jet, active water is used for sand adding and fracturing, the jet direction is controlled to be at a position with a certain included angle of 30-45 degrees with the maximum horizontal stress direction, and a horizontal hole with a certain length of 50-100 m is directly jetted at 1 inch, and then the active water sand adding and fracturing is matched with the active water sand adding and fracturing of a conventional coal bed gas well; according to geological measurement, acquiring a local larger horizontal stress direction, and carrying out construction design; preparing the hydraulic spraying device according to requirements, and performing hydraulic spraying operation after the material. The method solves the problems of uncontrollable fracture trend, small reservoir transformation volume and poor yield increasing effect in the prior art. The patent mainly realizes the problem of the initial fracture initiation direction through radial horizontal well hydraulic jet drilling, but the fracture finally develops along the direction of the parallel maximum horizontal principal stress after extending for a certain distance, and how to control the subsequent fracture extension is not related.
Chinese patent CN102777162A discloses a directional fracturing device for horizontal wells. The horizontal well directional fracturing device is provided, the horizontal well directional fracturing is realized, the direction and the direction of fracturing transformation are selected in a targeted manner, the water layer direction or the extending direction of a water injection waterline can be avoided, the oil displacement area is increased, and the water breakthrough period of the horizontal well is prolonged. The problem that the periphery of a conventional fractured and transformed fractured rock shaft is uniformly arranged is solved. There is no reference to how complex cracks are formed and steering is temporarily stopped.
The above patents all describe fracture diversion by using temporary plugging agent or fiber temporary plugging method to increase fracture complexity and achieve certain effect, and the related patents mainly reflect on the type of temporary plugging agent, but there is no reference in all documents and patents on how to achieve directional fracture extension.
The directional fracturing patents and documents mainly focus on directional generating devices, and do not relate to a directional fracturing method and process. Therefore, there is a need to develop a new hydraulic fracture orientation design technique to solve the above limitations.
Disclosure of Invention
The deep oil and gas reservoir often makes the fracture that forms be single main fracture because of buried depth, stress height, temperature height, and the transformation volume is limited for the initial stage output after pressing is low, and the steady production period is short, and most deep oil and gas reservoirs hardly obtain economic effective development. In order to solve the problems in the prior art, the invention provides a deep oil-gas reservoir directional fracturing method and application. The stress direction is changed by multiple temporary plugging and steering, the induced stress field of the formed crack and the mutual superposition principle are utilized, and then the steering angle is controlled, so that the crack extends towards the required direction, the complexity of the crack is improved, and the reconstruction volume of the crack is enlarged. The method is simple and easy to implement, does not need complex tools and materials, achieves the purpose of volume fracturing, and improves the post-fracturing effect.
The invention aims to provide a directional fracturing method for a deep oil and gas reservoir.
The stress direction is changed by multiple temporary plugging and steering, the induced stress field of the formed crack and the mutual superposition principle are utilized, and then the steering angle is controlled, so that the crack extends towards the required direction, the complexity of the crack is improved, and the reconstruction volume of the crack is enlarged.
The method comprises the following steps:
1) evaluation of key reservoir parameters
2) Geological dessert and engineered dessert calculation and perforation location determination
3) Optimization of fracture parameters
4) Fracturing construction parameter optimization
5) Perforating operation
6) Acid pretreatment operation
7) First crack fracturing construction
8) Temporary plugging construction for first crack
9) Calculation of the second crack steering angle
10) Second crack fracturing construction
11) Temporary plugging construction for second crack
12) Calculation of the third crack steering Angle
13) And (4) performing fracturing construction and temporary plugging from a third crack to a penultimate crack, referring to the steps 7) to 7)
12)
14) Calculating the pump stopping time before the last crack is constructed
15) Final main crack fracturing construction
16) And (5) replacing operation.
In a preferred embodiment of the present invention,
and 5), within 3-5 m of single-layer perforation of the vertical well, the length of single-section perforation of the horizontal section is 2-4 m, and the length of each cluster of perforation is 0.5-1 m.
In a preferred embodiment of the present invention,
step 6) of the above-described steps,
acid pretreatment: the acid strength for the vertical well is 1-2m3The acid strength of a/m reservoir and a horizontal well is 0.1-0.3 m3A/m reservoir.
The discharge amount of acid is 1-2m3/min。
In a preferred embodiment of the present invention,
step 7) of the above-described steps,
performing fracturing construction on the first crack, wherein the viscosity of the slickwater is 2-3 mPa.s; and/or the presence of a gas in the gas,
and (3) measuring the liquid amount to be 3-5% of the total liquid amount in the step 4), and measuring the maximum discharge amount optimized in the step 4).
In a preferred embodiment of the present invention,
step 8) of the above-described steps,
the particle size of the temporary plugging agent is 30-60% of the average value of the width of the crack, and/or,
the construction sand-liquid ratio is 2-3-4%, and the volume of the sand-carrying liquid in each stage is 5-10 m3(ii) a Keeping the rising speed of the bottom hole pressure within the range of 2-3 MPa/min;
after the temporary plugging agent is added, 1-2m of the temporary plugging agent is added3And 2-3 mPa.s of slickwater for replacement.
In a preferred embodiment of the present invention,
step 9) of the above-described steps,
in the stress turning area, the crack initiation position of the second crack is vertical to the first crack, and after the second crack passes through the stress turning area, the crack in the non-stress turning area turns to the direction of the first crack.
In a preferred embodiment of the present invention,
step 10) of the above-described method,
performing second crack fracturing construction, wherein the viscosity of the slickwater is 20-30 mPa.s, and/or,
and (3) measuring 6-10% of the total liquid amount in the step 4), and measuring the maximum discharge amount optimized in the step 4).
In a preferred embodiment of the present invention,
step 11) of the above-described steps,
the particle size of the temporary plugging agent is 30-60% of the average value of the width of the crack, and/or,
the construction sand liquid ratio is 3-5-7%, and the volume of the sand carrying liquid in each stage is 5-10 m3；
Keeping the rising speed of the bottom hole pressure within the range of 2-3 MPa/min;
after the temporary plugging agent is added, 1-2m of the temporary plugging agent is added3Replacing with 20-30 mPa.s of slickwater.
In a preferred embodiment of the present invention,
step 12) of the above-described method,
in the stress turning area, the crack initiation position of the third crack is vertical to the second crack, and after the third crack passes through the stress turning area, the crack in the non-stress turning area turns to the direction of the second crack.
In a preferred embodiment of the present invention,
step 13) of the above-described steps,
constructing and temporarily blocking a third crack to a penultimate crack, and referring to steps 7) to 12);
wherein,
the viscosity of the slickwater is 40-50 mPa.s; measuring the liquid amount to be 10-15% of the total liquid amount in the step 4); measuring the optimized highest displacement in the step 4);
the construction sand-liquid ratio is 5-7-9%, and the volume of the sand-carrying liquid in each stage is 5-10 m3；
Keeping the rising speed of the bottom hole pressure within the range of 2-3 MPa/min in the temporary plugging construction process;
after the temporary plugging agent is added, 1-2m of the temporary plugging agent is added3Replacing the slickwater with 40-50 mPa.s;
in a preferred embodiment of the present invention,
step 14) of the above-described steps,
and calculating the superposition effect of the induced stresses of different cracks, then calculating the steering angle of the last crack, and calculating the decrement values of the induced stresses under different pump stopping times if the steering angle exceeds the expected directional direction, thereby determining the pause time before the construction of the last crack.
The pump stopping time is generally 20-30 min;
in a preferred embodiment of the present invention,
step 15) of the above-described steps,
and performing seam making and sand adding construction based on the fracturing construction parameters optimized in the step 4).
In a preferred embodiment of the present invention,
step 16) of the operation,
a vertical well, which is displaced by 100% of the volume of the well bore and is displaced by slick water with the viscosity of 2-3 mPa.s;
the horizontal well is displaced according to 105-110% of the volume of the shaft, the first 40% is displaced by using slick water with the viscosity of 40-60 mPa.s, and then the slick water with the viscosity of 2-3 mPa.s is used for continuous displacement;
the displacement is the highest displacement optimized in the step 4).
The second purpose of the invention is to provide the application of the method in oil recovery.
The idea of the invention is as follows:
1) firstly, an induced stress field is formed by utilizing the induced stress effect existing in single fracture fracturing. Although the deep layer is formed, the induced stress propagation distance caused by strong plasticity is small, and the induced stress is relatively small due to the narrow width of the seam formed by the deep layer. Therefore, even if the method of temporary plugging in the crack is adopted to improve the net pressure in the crack and the corresponding induced stress, the pressure window (the difference value between the designed pressure limit of the well head and the construction pressure) is relatively small due to the pressure limit of the well head, so the induced stress generated by the fracturing of a single crack is relatively small, the propagation distance is relatively small, the influence on the steering of the crack is small, and the initial induced stress value is provided for the superposition of the induced stress in the later period.
It is particularly noted that if fracture diversion is to be achieved, diversion of subsequent fractures will only be meaningful if the difference in induced stresses in the induced stress zones (the difference between the induced stress at the minimum level of principal stress and the induced stress at the maximum level of principal stress, in general, the induced stress at the minimum level of principal stress is much greater than the induced stress at the maximum level of principal stress) is greater than or equal to the original level stress difference (which may be referred to as a stress diversion zone, and other non-stress diversion zones that have induced stresses but do not achieve diversion effects). Otherwise, stress steering can be realized only after a plurality of induced stresses of the non-stress steering areas of a plurality of subsequent cracks are superposed.
2) The temporary plugging forms the superposition effect of induced stress, realizes a plurality of cracks in different directions, and guides the direction of a new crack to an expected specific direction. The induced stress of each crack should propagate relatively far enough for the induced stress of the multiple cracks to have such a large effect. Therefore, temporary plugging in the crack or temporary plugging at the end part of the crack is considered during construction of each crack, even if the bottom of the well is increased by 2-3 MPa due to temporary plugging of each crack, the superposition effect of induced stress increased by a plurality of cracks is considerable. The method for temporary blocking in the cracks or at the ends is relatively mature, and a soluble temporary blocking agent can be used, but the particle diameter and construction concentration of the temporary blocking agent are matched with the crack forming width of each crack.
In order to ensure that the subsequent cracks can be continuously initiated and extended from different directions, 1-2m is carried out after the addition of the temporary plugging agent is finished each time3The slick water displacement ensures that the maximum particles of the temporary plugging agent have a certain distance, such as 1-2m, from the holes, so that when a plurality of subsequent cracks turn, new cracks are initiated and extended at the same hole positions basically.
3) The calculation and control technology of the crack initiation angle of the stress steering zone is crucial. The superposition effect of the induced stress consists of two parts, wherein one part is the induced stress formed by increasing the net pressure formed by temporary plugging of the end of the same crack, and the other part is the induced stress formed by initiating and extending different cracks. In the stress steering area, the steering angle of a newly formed steering crack needs to be accurately controlled, the length of the steering crack can be longer, the complexity of the crack is increased, and the crack initiation angle of the stress steering area is mainly controlled by the magnitude of induced stress.
In the stress deflecting region, the induced stresses are different at each point in the deflecting region, and particularly the induced stresses in the direction of the minimum horizontal principal stress and the direction of the maximum horizontal principal stress are different. Resulting in a new minimum and maximum level principal stress being superimposed at each final point that is different. Thus, the direction of the maximum principal stress at each point within the turning zone varies in real time and is different.
The direction of maximum principal stress of such a change can be calculated accurately. However, in order to increase the extension of the turning crack and to precisely control the turning angle, the induced stress of each crack at an early stage may be suitably low. The turning angle of the new turning crack in the turning zone can be relatively low, which is beneficial to extend the crack more in the turning zone, otherwise, if the turning angle is relatively large in the early period, the orientation angle is not easy to be accurately controlled, and the turning crack can rapidly pass through the turning zone, and then the crack direction rapidly returns to the original maximum horizontal principal stress direction.
If the steering angle of the crack before the final fracturing exceeds the expected value, the method is to wait for a period of time properly so as to utilize the reducing effect of the width reduction on the induced stress when the crack is closed. As for the optimization of the specific waiting time, the simulation determination can be made based on the commonly used commercial simulation software ABAQUS.
It is worth noting that in the calculation of one or more fracture-induced stresses, the implicit precondition is that the fracture height of each fracture is comparable and all passes through the effective thickness of the reservoir. Otherwise, even if so-called directional fracturing is achieved, the fracture height may cover only part of the reservoir thickness, and in reservoirs with unconnectorized fracture heights, the goal of directional reformation is not really achieved.
The invention can adopt the following technical scheme:
1) evaluation of key reservoir parameters
The parameters related to the crack propagation and stress simulation mainly comprise lithology, physical properties, rock mechanical parameters, three-dimensional ground stress parameters, natural cracks, horizontal bedding crack characteristics and the like.
The method comprehensively applies means such as logging, well testing, target stratum rock core indoor test analysis and the like. The above parameters can be obtained by testing and analyzing the core of the target layer. However, considering that the coring cost is relatively high, the parameters can be generally obtained through logging, a conversion relation between dynamic and static parameters can be established between the target layer core indoor test parameters and the logging parameters, and the static parameters of the non-coring section (the general target layer core test result) can be obtained from the logging interpretation result of the corresponding section and the established conversion relation.
2) Geological dessert and engineered dessert calculation and perforation location determination
On the basis of the step 1), respectively calculating the geological dessert and the engineering dessert according to a conventional method, and further obtaining a final comprehensive dessert index by an equal weight method. And (4) sequencing all the comprehensive dessert indexes of the target layer from high to low by taking 1-2m as a calculation point. For a vertical well, the thickness of a single perforation layer is within 50m, and for a horizontal well, the length of a single section is generally 50-100 m (the specific optimization result can refer to the seam spacing optimization result in the step 3). The difference between the highest index and the lowest index of each synthetic dessert in the general section is within 20 percent. The specific perforation locations may be considered to be predominantly evenly distributed within the segment. In addition, the comprehensive balance and determination of the cementing quality of the target interval and the position of the casing coupling are required.
3) Optimization of fracture parameters
Based on the parameters in the step 1), a common geological modeling software PETREL is applied to establish a fine geological model of a target well layer, then the result is led into a common ECLIPSE software for fracturing well yield prediction, an orthogonal design method is applied to simulate the yield dynamics under different seam lengths, flow conductivity and seam intervals, and therefore the optimal fracture parameter system is obtained when the yield after pressing is relatively maximum or the economic net present value is maximum.
The direction of the optimized crack is the intended direction of orientation.
4) Fracturing construction parameter optimization
The method is characterized in that commercial simulation software commonly used for fracturing design, such as Frac PROPT, STIMPLAN, GOHFER and the like, is applied to simulate the fracture geometric dimension and the flow conductivity dynamic change rule under different fracturing construction parameter conditions (discharge capacity, viscosity, fracturing fluid amount corresponding to different viscosities, proppant amount, the proportion of proppants with different particle sizes, sand-fluid ratio, injection programs with different sand-fluid ratios and the like) according to an orthogonal design method. Thereby determining the fracturing construction parameter combination capable of obtaining the optimized fracture parameter system in the step 3).
The fracturing construction parameters correspond to the fracture parameter system optimized in the step 3). In fact, before this construction, there are also a plurality of constructions, corresponding to a plurality of fracture systems of the previous stage. However, the proppant is not added to the early stage of fracture, and the length of the seam is not 100% of the design value of the last fracture, for example, the length of some seams is only 20%, some 40%, some 60% and the like of the design value. Generally, 100% of fracturing fluid for fracture formation occupies 20-30% of the total operation, the proportion of 60% of fracturing fluid for fracture formation is about 10-15%, the proportion of 40% of fracturing fluid for fracture formation is about 6-10%, and the proportion of 20% of fracturing fluid for fracture formation is about 3-5%. The smaller the length of the fracture, the smaller the proportion of the fracturing fluid amount of the fracture, and the faster the fracture extends at the early stage, the slower the fracture extends backward. The length of the fracture making in the early stage may be more than 2-3 times of the length of the fracture making in the middle and later stages by the same fracturing fluid amount.
5) Perforating operation
The length of a single-section perforation of a horizontal section is generally 2-4 m, and the length of each cluster of perforations is 0.5-1 m. Other parameters are executed according to conventional parameters, such as spiral perforation, the hole density is 12-20 holes/meter, and the hole diameter is generally more than 9.5 mm.
6) Acid pretreatment operation
The acid type and the formula are determined by comprehensively balancing based on the compatibility and the acid rock corrosion rate experiment result of the target layer rock core in the step 1). The acid strength of the acid pretreatment is generally 1-2m of that of a vertical well3The acid strength of the horizontal well is 0.1-0.3 m3/m。
7) First crack fracturing construction
The first crack is constructed, the viscosity is the lowest, generally 2-3 mPa.s, the liquid amount is generally 3-5% of the total liquid amount in the step 4), the maximum discharge amount optimized in the step 4) is obtained, and the discharge amount extraction time can be slow, for example, 3-4 min.
8) Temporary plugging construction for first crack
On the basis of the step 7), simulating the parameters of the first crack, such as length, width, height and the like, particularly the height of the crack, which must penetrate through the thickness of the whole reservoir based on the fracturing design software mentioned in the step 4). Then, according to the simulation result of the seam width, the average value of 30-60% of the seam width is taken as the particle size of the temporary plugging agent, the construction sand-liquid ratio is 2-3-4%, and the volume of the sand-carrying liquid in each stage is generally 5-10 m3. The specific sand-liquid ratio and the volume of each section of sand-liquid ratio can be adjusted in real time according to the rising speed of the bottom hole pressure of 2-3 MPa/min, and the temporary plugging position of the temporary plugging agent is relatively close to the well casing.
Finally, after the temporary plugging agent is added, adding 1-2m32 to 3 mPa.s. slipperyAnd (5) draining for replacement.
9) Calculation of the second crack steering angle
And based on the idea 3) calculating method, calculating the range of a stress turning area and a non-turning area generated by the first crack. In the stress turning area, the crack initiation position of the second crack is vertical to the first crack, and after the second crack passes through the stress turning area, the crack in the non-stress turning area slowly turns to the direction of the first crack.
10) Second crack fracturing construction
And (3) constructing the second crack, wherein the viscosity is properly increased and is generally 20-30 mPa.s, the liquid amount is generally 6-10% of the total liquid amount in the step 4), and the maximum discharge amount optimized in the step 4) is adopted. The time for lifting the volume can be relatively short, such as 2-3 min.
11) Temporary plugging construction for second crack
On the basis of the step 10), simulating the parameters of the second crack, such as length, width, height and the like, particularly the height of the crack, of the second crack, which must penetrate through the thickness of the whole reservoir, based on the fracturing design software mentioned in the step 4). Then, according to the simulation result of the seam width, the average value of 30-60% of the seam width is taken as the particle size of the temporary plugging agent, the construction sand-liquid ratio is 3-5-7%, and the volume of the sand-carrying liquid in each stage is generally 5-10 m 3. The specific sand-liquid ratio and the volume of each section of sand-liquid ratio can be adjusted in real time according to the rising speed of the bottom hole pressure of 2-3 MPa/min, and the temporary plugging position of the temporary plugging agent is relatively close to the well casing.
And finally, after the temporary plugging agent is added, adding 20-30 mPa.s of 1-2m 3 slickwater for replacement.
12) Calculation of the third crack steering Angle
And based on the idea 3) calculating method, calculating the range of a stress turning area and a non-turning area generated by the second crack. In the stress turning area, the crack initiation position of the third crack is vertical to the second crack, and after the third crack passes through the stress turning area, the crack in the non-stress turning area slowly turns to the direction of the second crack.
13) And (3) performing fracturing construction and temporary plugging from the third crack to the penultimate crack, referring to the steps 7) to 12)
14) Calculation of the pause time before the last crack construction
And calculating the superposition effect of different crack induced stresses based on the idea of the idea 3). And then calculating the steering angle of the last crack, if the steering angle exceeds the expected directional direction, calculating the reduction values of the induced stress under different pump stopping times, and determining the pause time before the construction of the last crack.
15) Final main crack fracturing construction
And (4) performing joint making and sand adding construction based on the optimized fracturing construction parameters in the step 4), including liquid amount, supporting agent amount, viscosity, sand-liquid ratio and the like in the joint making and sand carrying stages.
16) Replacement work
If the well is a vertical well, the displacement is carried out according to 100 percent of the volume of the well, and the displacement is carried out by using low-viscosity slick water with the viscosity of 2-3 mPa.s.
If the horizontal well is used, replacing according to 105-110% of the volume of the well, replacing the first 40% with viscosity of 40-60 mPa.s, and continuing replacing with viscosity of 2-3 mPa.s. The displacement is the highest displacement optimized in the step 4).
17) And if the fracturing is horizontal well staged fracturing, other staged fracturing construction is carried out, and the steps 5) to the step 16) are repeated.
18) Drilling plugging, flowback, testing, production, etc., are performed with reference to conventional procedures and parameters, which are not redundant.
ADVANTAGEOUS EFFECTS OF INVENTION
The design method for the directional fracturing of the deep oil and gas reservoir changes the stress direction by multiple temporary plugging and steering, utilizes the induced stress field of the formed crack and the mutual superposition principle, leads the crack to extend towards the direction parallel to the maximum main stress direction by controlling the stress transition and steering angle, forms a complex crack after multiple temporary plugging and steering and enlarges the reconstruction volume of the crack. The method is simple and easy to implement and does not need complex tools and materials for forming complex seams of deep oil and gas reservoirs.
Detailed Description
While the present invention will be described in detail with reference to the following examples, it should be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the present invention.
Example 1
The X well is a sidetrack horizontal well, the slant depth is 3336m, the vertical depth is 2233.68m, and the horizontal section is 966.32 m. Well drilling and completion adopt
The casing with the wall thickness of 12.34mm is completed, and the internal pressure resistance of the casing is 117.3 MPa. The well co-drilling is displayed by different levels of oil and gas in the layer of 301 m/22. Comprehensively predicting the pressure coefficient of the Toosendanmaxi group-Shandongtao Orotu Wufeng group to be 1.25-1.40, and the formation temperature in the middle of the reservoir to be about 81 ℃. The porosity of the reservoir layer of the well is 1.22 percent at the minimum and 4.15 percent at the maximum, and the average value is 2.83 percent; the permeability is minimum 0.004md, maximum 309.93md, average value 16.139 md. The content of clay minerals is minimum 15%, maximum 70%, and average value is 45.1%. The brittle mineral content was minimum 21%, maximum 81%, average 48.7%, dominated by quartz, 32.7%, followed by feldspar 5.9%, calcite 5.9%.
The well is implemented specifically as follows:
1) evaluation of key reservoir parameters
The rock mechanical experiment, logging explanation, pilot hole core experiment and other tests and calculations are carried out to obtain the characteristics of lithology, rock and ore characteristics, physical properties, sensitivity, rock mechanical parameters, three-dimensional ground stress parameters, horizontal bedding joints, high-angle natural crack development conditions, temperature, pressure, underground oil, gas and water characteristics and the like.
2) Calculation of geological and engineered desserts and determination of segment cluster locations
Respectively calculating the geological dessert and the engineering dessert according to a conventional method, and then calculating the comprehensive dessert indexes according to an equal weight method. And avoiding the stratum with poor gas-bearing property, and performing effective fracturing construction on the horizontal well section of the shale in 12 sections. 2-3 clusters of perforation are formed in each section, each cluster is about 1.5m, 89mm gun 102 bullets are used for perforation, the hole density is 16 holes/m, the phase is 60 degrees, and the perforation aperture is more than 12 mm. The perforation position is selected to perforate at favorable positions such as higher TOC in the middle of each stage, high crack development, porosity and permeability, small stress difference, good gas detection display and the like.
3) Optimization of fracture parameters
On the basis of the step 1), PETREL geological modeling software is used, and then model result parameters are led into commercial simulation software ECLIPSE commonly used for yield prediction after fracturing well pressure. The optimized crack support half-crack length is about 280m, and a better production effect can be obtained.
4) Fracturing construction parameter optimization
MEYER software is adopted to simulate the dynamic change rule of the fracture under different fracturing construction parameters, the W-shaped seam distribution mode is adopted for the well, and the average liquid amount of each section is 1600m3～1800m3Sand addition scale of 60m3～80m3Construction displacement of 12m3/min～16m3/min。
5) Lower bridge plug and shower hole operation
Based on the optimized segment cluster position in the step 2), the first segment does not go down a bridge plug, and an oil pipe or a continuous oil pipe carries a perforating gun to carry out perforating operation.
6) Acid pretreatment operation
Based on the pilot hole core obtained in the step 1), compatibility and acid dissolution rate experiments under different acid types and formulas are carried out indoors, and the acid type and the formula with good compatibility and relatively highest acid dissolution rate are preferably selected.
First-stage fracturing co-injection acid 20m3The discharge capacity of acid injection is 1.5m3Min, after acid injection, the discharge capacity of the acid substitute is increased to 3m3And/min. When acid liquor enters 40% of the first cluster of cracks close to the heel, the discharge capacity is increased to 6m3And/min until all acid liquor is injected.
7) First crack fracturing construction and temporary plugging
Construction is carried out by adopting slickwater with viscosity of 3mPa, and the construction discharge capacity is increased to the maximum discharge capacity within 3-4 minutes: 8m3/min～10m3/min～12m3/min～16m3Min; shared slickwater 80m3Then injecting a temporary plugging agent with the particle size of 140-200 meshes, the construction sand-liquid ratio of 2% -3% -4%, and the volume of the sand-carrying liquid in each stage is 50m3Left and right, with slick water 150m3. Keeping the rising speed of the bottom hole pressure within the range of 2-3 MPa/min, and adopting 2m after the temporary plugging agent is added3Displacing with slickwater of viscosity 3 mPa.s.
8) Second crack construction
After the first crack is fractured and replaced, high-viscosity slickwater with the viscosity of 28mPa.s is adopted for construction, and the construction discharge capacity is 16m3And/min. Shared slick water of 150m3；
Then injecting a temporary plugging agent with the particle size of 140-200 meshes and the construction sand-liquid ratio of 3% -5% -7%, wherein the volume of the sand-carrying liquid in each stage is 50m3Left and right, with slick water 150m3Keeping the rising speed of the bottom hole pressure within the range of 2-3 MPa/min; after the temporary plugging agent is added, slickwater with viscosity of 28mPa.s is adopted for 2m3And performing displacement.
9) Calculation of Pump off time before last crack construction
And calculating the superposition effect of different crack induced stresses based on the idea of the idea 3). And then calculating the steering angle of the last crack, if the steering angle exceeds the expected directional direction, calculating the decrement value of the induced stress under different pump stopping time, and determining the pump stopping time 20min before the construction of the last crack.
10) Final main crack fracturing construction
And (3) after the two cracks are subjected to steering construction, constructing the last main crack, and performing crack making and sand adding construction according to the fracturing construction parameters optimized in the step 4), including the liquid amount, the supporting agent amount, the viscosity, the sand-liquid ratio and the like of the crack making and sand carrying stages. The construction is carried out by adopting slickwater with the viscosity of 55mPa.s at the stage, and the construction discharge capacity is 16m3The construction sand-liquid ratio is 5 to 7 to 9 to 11 to 13 to 15 percent, and the using amount of the sand-liquid ratio slickwater in each stage is 200m3Sharing a slickwater of 1200m3Adding 70-100 mesh ceramsite 48m3Adding 30m of 40-70 mesh ceramsite3Total addition of sand 78m3。
11) Replacement work
High-viscosity slickwater 1 with the displacement viscosity of 55mPa.s accounting for 110 percent of the volume of the 1 st section of well bore0m3. Then replacing with low viscosity slick water with viscosity of 3mPa.s, and continuously replacing for 33m3When the construction is finished, the displacement of the replacement construction is 16m3/min。
12) And (5) performing other fracturing construction stages, and repeating the steps 5) to 11).
13) Drilling plugging, flowback, testing, production, etc., are performed with reference to conventional procedures and parameters, which are not redundant.
The fracturing construction of the well according to the invention obtains good after-fracturing effect after fracturing, the initial gas production after the well fracturing reaches 15 ten thousand square/day, and compared with an adjacent well, the yield is improved by 33%.
Example 2
The Y well is a compact sandstone horizontal well in an Ordos basin, and has a slant depth of 2732m, a vertical depth of 1833.68m and a horizontal section length of 921.4 m. Well drilling and completion adopt
The well was completed with a casing having a wall thickness of 6.354mm and having an internal pressure resistance of 73.7 MPa. The well co-drilling meets 608.2m/3 layers of gas bearing display of different grades. Comprehensively predicting the pressure coefficient of the rock-feeding box group to be 0.98-1.05, and the temperature of the stratum in the middle of the reservoir to be about 51 ℃. The porosity of the well reservoir is 3.22 percent at minimum and 12.15 percent at maximum, and the average value is 7.83 percent; the permeability is minimum 0.1md and maximum 12.4md, with an average value of 3.22 md. The clay mineral content is minimum 3.9%, maximum 78%, and average 25.1%. The brittle mineral content was minimum 21%, maximum 89%, average 58.7%, dominated by quartz, 62.7%, followed by feldspar 5.9%, calcite 7.2%.
The well is implemented specifically as follows:
1) evaluation of key reservoir parameters
The rock mechanical experiment, logging explanation, pilot hole core experiment and other tests and calculations are carried out to obtain the characteristics of lithology, rock and ore characteristics, physical properties, sensitivity, rock mechanical parameters, three-dimensional ground stress parameters, horizontal bedding joints, high-angle natural crack development conditions, temperature, pressure, underground oil, gas and water characteristics and the like.
2) Calculation of geological and engineered desserts and determination of segment cluster locations
Respectively calculating the geological dessert and the engineering dessert according to a conventional method, and then calculating the comprehensive dessert indexes according to an equal weight method. And avoiding the layer section with poor gas-bearing property, and effectively performing 9-section fracturing construction on the horizontal well section of the sandstone. 2-3 clusters of perforation are formed in each section, each cluster is 1.0m, 89 bullets with the diameter of 73mm are adopted for perforation, the hole density is 16 holes/m, the phase is 60 degrees, and the perforation aperture is more than 12 mm. The perforation position is selected to perforate at favorable positions such as higher TOC in the middle of each stage, high crack development, porosity and permeability, small stress difference, good gas detection display and the like.
3) Optimization of fracture parameters
On the basis of the step 1), PETREL geological modeling software is used, and then model result parameters are led into commercial simulation software ECLIPSE commonly used for yield prediction after fracturing well pressure. The optimized crack support half-crack length is about 180m, and a better production effect can be obtained.
4) Fracturing construction parameter optimization
MEYER software is adopted to simulate the dynamic change rule of the fracture under different fracturing construction parameters, the W-shaped seam distribution mode is adopted for the well, and the average liquid volume of each section is 600m3～800m3Sand addition scale of 50m3～70m3Construction displacement of 8m3/min～12m3/min。
5) Lower bridge plug and shower hole operation
And (3) carrying a perforating gun by the continuous oil pipe to perform perforating operation on the first section without putting a bridge plug on the basis of the optimized section cluster position in the step 2).
6) Acid pretreatment operation
Based on the pilot hole core obtained in the step 1), compatibility and acid dissolution rate experiments under different acid types and formulas are carried out indoors, and the acid type and the formula with good compatibility and relatively highest acid dissolution rate are preferably selected.
Acid co-injection 10m for first stage fracturing3The discharge capacity of acid injection is 1.0m3Min, after acid injection, the discharge capacity of the acid substitute is increased to 2m3And/min. When acid liquor enters 50% of the first cluster of cracks close to the heel, the discharge capacity is increased to 8m3And/min until all acid liquor is injected.
7) First crack fracturing construction and temporary plugging
Construction is carried out by adopting slick water with viscosity of 2mPa.s, and the highest discharge capacity is increased within 2-3 minutes: 8m3/min～10m3/min～12m3Min; shared slickwater 120m3Then injecting a temporary plugging agent with the particle size of 140-200 meshes, the construction sand-liquid ratio of 2% -3% -4%, and the volume of the sand-carrying liquid in each stage is 30m3Using slick water of 90m3. Keeping the rising speed of the bottom hole pressure within the range of 2-3 MPa/min, and adopting 2m after the temporary plugging agent is added3Displacement with slickwater of viscosity 2 mpa.s.
8) Second crack construction
After the first crack is fractured and replaced, high-viscosity slickwater with the viscosity of 24mPa.s is adopted for construction, and the construction discharge capacity is 12m3And/min. Shared slickwater 80m3；
Then injecting a temporary plugging agent with the particle size of 140-200 meshes and the construction sand-liquid ratio of 3% -5% -7%, wherein the volume of the sand-carrying liquid in each stage is 30m3Left and right, with slick water 90m3Keeping the rising speed of the bottom hole pressure within the range of 2-3 MPa/min; after the temporary plugging agent is added, slickwater with viscosity of 24mPa.s is adopted for 2m3And performing displacement.
9) Calculation of Pump off time before last crack construction
And calculating the superposition effect of different crack induced stresses based on the idea of the idea 3). And then calculating the steering angle of the last crack, if the steering angle exceeds the expected directional direction, calculating the decrement value of the induced stress under different pump stopping time, and determining the pump stopping time 25min before the construction of the last crack.
10) Final main crack fracturing construction
And (3) after the two cracks are subjected to steering construction, constructing the last main crack, and performing crack making and sand adding construction according to the fracturing construction parameters optimized in the step 4), including the liquid amount, the supporting agent amount, the viscosity, the sand-liquid ratio and the like of the crack making and sand carrying stages. The construction is carried out by adopting linear glue with the viscosity of 45mPa.s at the stage, and the construction discharge capacity is 12m3The construction sand-liquid ratio is 8 to 12 to 16 to 20 to 24 to 28 percent per minThe consumption of the stage sand-liquid ratio linear glue is 50m3Sharing a linear glue 300m3Adding 70-100 mesh ceramsite with the particle size of 18m3Adding 34m of 40-70 meshes of ceramsite3Total addition of sand 52m3。
11) Replacement work
The displacement viscosity of the 1 st section of the shaft is 45mPa.s linear glue 10m according to the volume of 110 percent3. Then replacing with low-viscosity slick water with viscosity of 3mPa.s to continuously replace for 13m3When the construction is finished, the displacement of the replacement construction is 12m3/min。
12) And (5) performing other fracturing construction stages, and repeating the steps 5) to 11).
13) Drilling plugging, flowback, testing, production, etc., are performed with reference to conventional procedures and parameters, which are not redundant.
The fracturing construction of the well according to the invention obtains good post-fracturing effect after fracturing, the initial gas production after the well fracturing reaches 17 ten thousand square/day, and compared with an adjacent well, the yield is improved by 67%.
Claims (15)
1. A method of directional fracturing of a deep hydrocarbon reservoir, the method comprising:
the stress direction is changed by multiple temporary plugging and steering, the induced stress field of the formed crack and the mutual superposition principle are utilized, and then the steering angle is controlled, so that the crack extends towards the required direction, the complexity of the crack is improved, and the reconstruction volume of the crack is enlarged.
2. The directional fracturing method according to claim 1, characterized in that it comprises:
1) evaluation of key reservoir parameters
2) Geological dessert and engineered dessert calculation and perforation location determination
3) Optimization of fracture parameters
4) Fracturing construction parameter optimization
5) Perforating operation
6) Acid pretreatment operation
7) First crack fracturing construction
8) Temporary plugging construction for first crack
9) Calculation of the second crack steering angle
10) Second crack fracturing construction
11) Temporary plugging construction for second crack
12) Calculation of the third crack steering Angle
13) And (3) performing fracturing construction and temporary plugging from the third crack to the penultimate crack, referring to the steps 7) to 12)
14) Calculating the pump stopping time before the last crack is constructed
15) Final main crack fracturing construction
16) And (5) replacing operation.
3. The directional fracturing method of claim 2, wherein:
and 5), within 3-5 m of single-layer perforation of the vertical well, the length of single-section perforation of the horizontal section is 2-4 m, and the length of each cluster of perforation is 0.5-1 m.
4. The directional fracturing method of claim 2, wherein:
step 6) of the above-described steps,
acid pretreatment: the strength of the acid used for the vertical well is 1-2m3The acid strength of a/m reservoir and a horizontal well is 0.1-0.3 m3A/m reservoir; and/or the presence of a gas in the gas,
the discharge amount of acid is 1-2m3/min。
5. The directional fracturing method of claim 2, wherein:
step 7) of the above-described steps,
performing fracturing construction on the first crack, wherein the viscosity of the slickwater is 2-3 mPa.s; and/or the presence of a gas in the gas,
and (3) measuring the liquid amount to be 3-5% of the total liquid amount in the step 4), and measuring the maximum discharge amount optimized in the step 4).
6. The directional fracturing method of claim 2, wherein:
step 8) of the above-described steps,
the particle size of the temporary plugging agent is 30-60% of the average value of the width of the crack, and/or,
the construction sand-liquid ratio is 2-3-4%, and the volume of the sand-carrying liquid in each stage is 5-10 m3(ii) a Keeping the rising speed of the bottom hole pressure within the range of 2-3 MPa/min;
after the temporary plugging agent is added, 1-2m of the temporary plugging agent is added3And 2-3 mPa.s of slickwater for replacement.
7. The directional fracturing method of claim 2, wherein:
step 9) of the above-described steps,
in the stress turning area, the crack initiation position of the second crack is vertical to the first crack, and after the second crack passes through the stress turning area, the crack in the non-stress turning area turns to the direction of the first crack.
8. The directional fracturing method of claim 2, wherein:
step 10) of the above-described method,
performing second crack fracturing construction, wherein the viscosity of the slickwater is 20-30 mPa.s, and/or,
and (3) measuring 6-10% of the total liquid amount in the step 4), and measuring the maximum discharge amount optimized in the step 4).
9. The directional fracturing method of claim 2, wherein:
step 11) of the above-described steps,
the particle size of the temporary plugging agent is 30-60% of the average value of the width of the crack, and/or,
the construction sand liquid ratio is 3-5-7%, and the volume of the sand carrying liquid in each stage is 5-10 m3；
Keeping the rising speed of the bottom hole pressure within the range of 2-3 MPa/min;
after the temporary plugging agent is added, 1-2m of the temporary plugging agent is added3Replacing with 20-30 mPa.s of slickwater.
10. The directional fracturing method of claim 2, wherein:
step 12) of the above-described method,
in the stress turning area, the crack initiation position of the third crack is vertical to the second crack, and after the third crack passes through the stress turning area, the crack in the non-stress turning area turns to the direction of the second crack.
11. The directional fracturing method of claim 2, wherein:
step 13) of the above-described steps,
performing fracturing construction and temporary plugging from a third crack to a penultimate crack, referring to steps 7) to 12);
wherein,
the viscosity of the slickwater is 40-50 mPa.s; measuring the liquid amount to be 10-15% of the total liquid amount in the step 4); measuring the optimized highest displacement in the step 4);
the construction sand-liquid ratio is 5-7-9%, and the volume of the sand-carrying liquid in each stage is 5-10 m3；
Keeping the rising speed of the bottom hole pressure within the range of 2-3 MPa/min in the temporary plugging construction process;
after the temporary plugging agent is added, 1-2m of the temporary plugging agent is added3Replacing with 40-50mPa.s of slickwater.
12. The directional fracturing method of claim 2, wherein:
step 14), the pump stopping time is 20-30 min.
13. The directional fracturing method of claim 2, wherein:
step 15) of the above-described steps,
and performing seam making and sand adding construction based on the fracturing construction parameters optimized in the step 4).
14. The directional fracturing method of claim 2, wherein:
step 16) of the operation,
a vertical well, which is displaced by 100% of the volume of the well bore and is displaced by slick water with the viscosity of 2-3 mPa.s;
the horizontal well is displaced according to 105-110% of the volume of the shaft, the first 40% is displaced by using slick water with the viscosity of 40-60 mPa.s, and then the slick water with the viscosity of 2-3 mPa.s is used for continuous displacement;
the displacement is the highest displacement optimized in the step 4).
15. Use of a method according to any one of claims 1 to 14 in oil recovery.
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