CN117404066A - Fracturing method for reinforced joint net of deep coal bed gas horizontal well reservoir - Google Patents
Fracturing method for reinforced joint net of deep coal bed gas horizontal well reservoir Download PDFInfo
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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
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- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
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Abstract
The invention relates to a fracturing method of a reinforced joint net for deep coal bed gas horizontal well reservoirs, which comprises the following steps of (1) dividing the same reservoir into a plurality of fracturing areas according to different geological properties of coal bed gas for the same deep reservoir, wherein at least one well platform is arranged in one fracturing area, and the well platform comprises at least two horizontal wells; (2) setting the position of the horizontal well, and then drilling the well; (3) Different wellheads in the same fracturing area are not constructed simultaneously, and the construction is needed to be sequentially performed according to the sequence; and (3) alternately perforating and fracturing different wells in sequence for the same well platform, perforating the next well after perforating the last well, fracturing the last well at the same time, and discharging fracturing fluid uniformly after all wells of the same well platform are fractured. The invention adopts the mode of alternately perforating and fracturing a plurality of wells and then uniformly discharging liquid, so that the deep reservoir is easier to generate cracks during fracturing and communicated with the fractured cracks, thereby forming a complex seam net scale.
Description
Technical Field
The invention belongs to the technical field of fracturing of coal-bed gas well reservoirs, and particularly relates to a fracturing method of a reinforced joint net for a deep coal-bed gas horizontal well reservoir.
Background
Reservoir seepage capability is a key property of deep coal-bed gas well exploration and development. The seepage capability of the target reservoir is improved to the greatest extent, and the method is very necessary and beneficial to analysis and seepage of later-stage coalbed methane and improvement of single-well gas production effect. At present, the limit volume fracturing technology of ultra-large, ultra-dense and fully-supported volume fracture network is mainly adopted for the deep reservoir pressure transformation method of 1500m in China, and the seepage transformation of the target reservoir is carried out by continuously increasing the fracturing construction parameters, so that the permeability of the reservoir is improved. However, this approach also has some problems: (1) The larger the fracturing scale is, the larger the influence on the inter-well interference generated by adjacent wells is, and particularly, the well kick and overflow adjacent to the well being drilled are easy to occur when the drilling operation of the adjacent well platform is being constructed or the produced drainage well is put into production; or, the casing is broken, deformed or crushed; or the conditions of gas production reduction, water production increase, well bench pressure fluctuation and the like of the drainage and production wells finally cause that some deployment wells cannot carry out later fracturing production; (2) After the fracturing construction parameters reach the set maximum scale value, the reservoir seepage capability can not be improved by increasing the fracturing construction parameters.
Disclosure of Invention
In view of the above problems, the present invention provides a fracturing method for a reinforced fracture network of a deep coal bed gas horizontal well reservoir, wherein for a plurality of vertical shafts (vertical wells or cluster wells) or a plurality of horizontal wells, the conventional fracturing is to fracture a first well and discharge pressure fluid, and then fracture a next well until a plurality of wells of a well platform are fractured next to each other; according to the invention, a mode of sequentially alternately perforating and fracturing is adopted for a plurality of wells, and then liquid is discharged uniformly, so that cracks are more easily generated in deep stratum during fracturing, the cracks and the cracks after fracturing are communicated, the volume is expanded and reformed to the maximum extent, the inter-crack interference is enhanced, thereby forming a complex seam net scale and improving the effect of ultra-large-volume fracturing.
The fracturing method for the reinforced joint net of the deep coal bed gas horizontal well reservoir comprises the following steps of:
(1) For the deep reservoir of the same layer, dividing the same reservoir into a plurality of fracturing areas according to different geological properties of coalbed methane, wherein at least one well platform is arranged in one fracturing area, and comprises at least two vertical shafts or two horizontal wells;
(2) Setting the position of a vertical shaft or a horizontal well, and then drilling a well;
(3) Different wellheads in the same fracturing area are not constructed simultaneously, and the construction is needed to be sequentially performed according to the sequence;
and (3) alternately perforating and fracturing different wells in sequence for the same well platform, perforating the next well after perforating the last well, simultaneously fracturing the last well, temporarily discharging no liquid after all wells of the same well platform are completely fractured, perforating and fracturing other well platforms in the same fracturing area according to the method until all well platforms in the fracturing area are completely perforated and fractured, and uniformly discharging fracturing fluid of all well platforms.
Optionally, in the step (1), the geological properties of the coalbed methane include geological conditions and geological features, specifically including geological structure, hydrologic conditions, gas content of the coalbed, permeability, burial depth and thickness, and avoiding faults in the same fracturing area; the geological conditions and the geological features of the same fracturing area are the same or similar.
In order to avoid the mutual interference of different wellheads, the invention divides adjacent areas with similar or same coalbed methane geological properties into the same fracturing area, and well pattern spacing is properly increased among different fracturing areas so as to effectively avoid the mutual interference among construction and production such as drilling, fracturing, drainage and the like.
Further optionally, in step (1), the spacing of wells between different fracturing zones is greater than 4 times the maximum fracture length of the region where the deep reservoir is located, so as to avoid mutual interference of different wells;
and (3) carrying out theoretical calculation by adopting a mathematical model and test data due to the difference of parameters such as ground stress, coal quality, porosity, permeability, rock mechanics and the like in different areas, and obtaining the maximum crack length of the area corresponding to the deep reservoir by combining microseism monitoring.
Optionally, in the step (2), the surface factors, the underground factors and the influence of drilling engineering conditions need to be considered, and the coordinates of a well platform are adjusted according to the actual condition of the land, so that the target positions of different wells are optimized; for a vertical shaft, the occurrence of the collision prevention problem of a drilling well hole needs to be considered, and proper drilling construction positions and sequences are designed.
Optionally, in step (2), top wellheads of a plurality of vertical shafts of the same wellstand are in the range of the wellstand, the vertical shafts comprise two forms of vertical shafts and cluster wells, and the vertical shafts vertically enter the deep reservoir downwards; the cluster wells are inclined downwards into the deep reservoir, and a plurality of cluster wells on the same well platform are in a divergent shape and are inclined outwards in a direction away from each other.
Optionally, in the step (2), the vertical sections of the plurality of horizontal wells of the same well platform are divergent, inclined outwards in a direction away from each other, and the horizontal sections of the plurality of horizontal wells are arranged in parallel and at the same or similar depth positions, and the horizontal sections extend in a direction away from the corresponding vertical sections;
and a plurality of fracturing sections are arranged along the length direction of the horizontal sections and are used for perforation and fracturing operation.
Alternatively, in step (3), wells of different fracture zones may be simultaneously fracture-constructed.
Optionally, in the step (3), for the same well platform including a plurality of vertical wells, a volumetric fracturing method is adopted, and the method specifically includes the following steps:
(a) Carrying out perforation operation of a target reservoir by the vertical shaft I;
(b) After the perforation of the first vertical shaft is completed, the perforation equipment is moved into the second vertical shaft, the perforation operation of the second vertical shaft is carried out, and meanwhile, the first vertical shaft carries out the fracturing operation of the target reservoir;
(c) After the perforation of the second vertical shaft is completed, the perforation equipment is moved into the next vertical shaft, the perforation operation of the next vertical shaft is carried out, after the first vertical shaft is fractured, liquid is not discharged temporarily, and meanwhile, the second vertical shaft carries out the fracturing operation of the target reservoir;
according to the construction method and the construction sequence, a plurality of vertical shafts are perforated and fractured in sequence, and no liquid is discharged;
(d) After all wells of other well platforms in the same fracturing area are perforated and fractured, uniformly discharging fracturing fluid from all vertical shafts in the fracturing area.
Optionally, in step (3), for the same well platform including a plurality of horizontal wells, each horizontal well has respective perforation equipment and fracturing equipment, is equipped with a plurality of fracturing sections in each horizontal well, and a plurality of fracturing sections evenly set up along the length direction of horizontal well, adopts the volume fracturing method, specifically includes the following steps:
(i) Carrying out perforation operation of a target reservoir in a fracturing section I of a horizontal well I;
(ii) After the perforation of the first fracturing section of the horizontal well is completed, the first fracturing section of the horizontal well performs perforation operation, and meanwhile, the first fracturing section of the horizontal well performs fracturing operation of a target reservoir;
(iii) After the perforation of the first fracturing section of the second horizontal well is completed, perforating operation is carried out on the first fracturing section of the next horizontal well, liquid is not discharged temporarily after the first fracturing section of the first horizontal well is completely fractured, and fracturing operation is carried out on the first fracturing section of the second horizontal well;
(iv) After the perforation of the first fracturing stage of the next horizontal well in the step (iii) is completed, perforating operation is carried out on the first fracturing stage of the next horizontal well, after the first fracturing stage of the second horizontal well is completely fractured, liquid is not discharged temporarily, and fracturing operation is carried out on the first fracturing stage of the next horizontal well;
according to the construction method and the construction sequence, perforating and fracturing the first fracturing sections of a plurality of horizontal wells in sequence, and discharging no liquid;
(v) According to the construction method and the construction sequence, perforating and fracturing the second fracturing sections of the plurality of horizontal wells in sequence, and discharging no liquid;
(vii) According to the construction method and the construction sequence, a plurality of fracturing sections of a plurality of horizontal wells are perforated and fractured in sequence, and no liquid is discharged;
(viii) After the last fracturing section of the last horizontal well of the well platform is fractured, all the horizontal wells of the well platform are not discharged;
and after the last fracturing sections of the last horizontal wells of other wellheads in the same fracturing area are fractured, uniformly discharging fracturing fluid from all fracturing sections of all horizontal wells in the fracturing area.
In the same horizontal well, the more far away from the fracturing section of the well platform, the earlier fracturing is performed.
Optionally, in the step (3), after the volume fracturing is finished, the fracturing fluid in the reservoir is discharged back out of the reservoir by adopting a liquid discharge method, and then lifting equipment is installed, so that the production test of the coal mining layer gas is started.
Optionally, in the step (3), the vertical shaft adopts a directional perforation mode, and the horizontal well adopts a cluster perforation mode; perforation direction is conventional in the art.
Optionally, the perforation density of the vertical or horizontal well fracture is determined by the following formula:
wherein W is pm Perforation density, number/m; p (P) Eyelet hole Pressure lost to perforation frictionLowering the pressure of MPa; ρ is the density of the fracturing fluid, kg/m 3 ；S t Is the surface coefficient of well completion, dimensionless; q is the discharge capacity of fracturing fluid, m 3 /min；C d The flow coefficient of the fracturing fluid is conveyed to a pump, and the pump is dimensionless; d is the aperture of the perforation, mm; h is a p The firing thickness, m, of the perforation.
The P is Eyelet hole Is determined by the following formula:
P eyelet hole ＝P Rupture of -P Stratum layer
Wherein P is Rupture of The fracture pressure of the target reservoir, MPa; p (P) Stratum layer The rock fracture pressure, MPa, for the target reservoir.
The S is t Is determined by the following formula:
S t ＝S bf +S P +S al +S z
wherein S is bf Skin factor for a partially ejected formation; s is S p Is perforation skin coefficient; s is S al Is the skin coefficient of well deviation; s is S z The special skin coefficient of the fracturing method is obtained; the above parameters are dimensionless.
The S is z Is determined by the following formula:
wherein K is the permeability of the target reservoir, mD; p (P) s The pressure of the stratum which is adjacent to the nearest well and is not discharged after fracturing is carried out is MPa; p (P) wf Is the formation pressure around the outside of the wellbore, MPa; mu is the viscosity of the fracturing fluid and mPa.S.
According to the method, through the division of the fracturing areas of the deep reservoir, larger well spacing intervals are designed among different fracturing areas, and in the same fracturing area, the alternate perforation and fracturing operation method in the step (3) is designed, so that the mutual interference of different wells in the conventional production process of drilling, fracturing and drainage cross operation is effectively avoided.
The multi-well alternate perforation and fracturing and temporary drainage mode of the step (3) ensures that the reservoir is always in a higher pressure state, the irregular steering of the reservoir cracks is promoted, the hooking between the cracks is further enhanced, a larger and more complex seam net is produced, the maximized communication of the reservoir cracks and pores is realized, the permeability of the reservoir is increased, the gas production of the well is improved, the fracturing cost is reduced, and the construction and production period is shortened.
The method in the step (3) is matched with the current limit volume fracturing technology, so that the seepage condition of the reservoir can be improved maximally, the production of coal bed gas is facilitated, and the gas production effect of a deployment well is improved.
Drawings
FIG. 1 is a schematic process flow diagram of the fracturing method of example 1;
FIG. 2 is a schematic process flow diagram of the fracturing method of example 2;
fig. 3 is a graph showing the effect of example 2 after fracturing.
Detailed Description
Example 1
The fracturing method for the reinforced joint net of the deep coal bed gas horizontal well reservoir provided by the embodiment comprises the following steps:
(1) For the deep reservoir of the same layer, dividing the same reservoir into a plurality of fracturing areas according to different geological properties of coalbed methane, wherein two wellheads are arranged in one fracturing area, and one wellhead comprises four cluster wells;
(2) Setting the positions of four cluster wells, and then drilling a well;
(3) Different wellheads in the same fracturing area are not constructed simultaneously, and the construction is needed to be sequentially performed according to the sequence;
and (3) alternately perforating and fracturing four cluster wells on the same well platform in sequence, perforating the last well, perforating the next well again, fracturing the last well, perforating and fracturing the other well platform in the same fracturing area according to the method after the four cluster wells on the same well platform are completely fractured, and uniformly discharging fracturing fluid of all wells again until all cluster wells on the two well platforms are completely perforated and fractured.
In the step (1), the geological properties of the coalbed methane comprise geological conditions and geological features, and specifically comprise geological structures, hydrologic conditions, gas content of the coalbed, permeability, burial depth and thickness, and no (i.e. avoiding) faults exist in the same fracturing area; the geological conditions and the geological features of the same fracturing area are the same or similar.
In the step (1), the interval between wells in different fracturing areas is 5 times of the maximum fracture length of the region where the deep reservoir is located, so that the mutual interference of different wells is avoided;
in the embodiment, according to the ground stress, coal quality, porosity, permeability and rock mechanical parameters of the region, the theoretical calculation of the fracture length is performed by adopting fracture simulation software (such as Gohfer, meyer, fracpro-PT), and the maximum fracture length of the region where the deep reservoir is located in the embodiment is obtained by combining microseism fracture monitoring (refer to hydraulic fracturing microseism fracture monitoring technology and application thereof, ("broken block oil and gas field, 2013,20 (05): 644-648.)).
In the step (2), the influence of surface factors, underground factors and drilling engineering conditions is required to be considered, the coordinates of a well platform are adjusted according to actual land characterization conditions, and the target positions of different wells are optimized; for a cluster well, proper drilling construction positions and sequences need to be designed in consideration of the occurrence of the collision prevention problem of a drilling well.
The top wellheads of four cluster wells of the same wellstand are in the range of the wellstand, the cluster wells incline downwards into the deep reservoir, and the four cluster wells of the same wellstand are in a divergent shape, incline outwards in the directions away from each other. The maximum well inclination angle is controlled within 35 DEG, and the building slope is smaller than 3 DEG/30 m
In the step (3), the embodiment adopts a volume fracturing method, which specifically comprises the following steps:
(a) Performing perforation operation of a target reservoir by the cluster well I;
(b) After the first cluster well is perforated, the perforating equipment is moved into the second cluster well to perform perforation operation of the second cluster well, and meanwhile, the first cluster well performs fracturing operation of the target reservoir;
(c) After the second cluster well is perforated, the perforating equipment is moved into a third cluster well to perform perforation operation of the third cluster well, after the first cluster well is fractured, liquid is not discharged temporarily, and meanwhile, the second cluster well performs fracturing operation of a target reservoir;
(d) After the third perforation of the cluster well is completed, the perforation equipment is moved into the fourth cluster well to perform perforation operation of the fourth cluster well, after the second cluster well is completely fractured, liquid is not discharged temporarily, and meanwhile, the third cluster well performs fracturing operation of a target reservoir;
(e) After the four perforations of the cluster well are completed, the perforations are all completed; after the fracturing of the cluster well III is finished, the fluid is not discharged temporarily, meanwhile, the fracturing operation of the target reservoir is carried out on the cluster well IV, and after the fracturing is finished, the fluid is not discharged temporarily for four cluster wells;
and carrying out perforation and fracturing of four cluster wells of the next well platform, and uniformly discharging the fracturing fluid after the last cluster well of the second well platform is completely fractured according to the method.
The cluster well adopts a directional perforation mode, and is perforated downwards along the shaft in a spiral way, and the perforation density is fixed to be 14 holes/meter.
After fracturing, the fracturing fluid in the reservoir is discharged back out of the reservoir by adopting an open flow liquid discharge method, lifting equipment is installed, and the production test is started to extract the coal seam gas.
Comparative example 1
The fracturing method of the reinforced joint net for the deep coal bed methane horizontal well reservoir provided by the comparative example is the same as that of the embodiment 1, and is characterized in that in the step (3), the fracturing is performed after the vertical shaft is perforated, and then the liquid is discharged; then perforating, fracturing and draining the liquid of the second vertical shaft; then perforating, fracturing and draining of the vertical shaft III are carried out; then perforating, fracturing and draining the liquid in the fourth vertical shaft.
Example 2
The fracturing method of the reinforced joint net for the deep coal bed gas horizontal well reservoir provided by the embodiment is the same as that of the embodiment 1, and is characterized in that (1) for the same deep reservoir, the same reservoir is divided into a plurality of fracturing areas according to different geological properties of coal bed gas, one well platform is arranged in one fracturing area, and the one well platform comprises two horizontal wells; (2) Setting the positions of a well table and a horizontal section of 2 horizontal wells, and drilling.
In the step (2), the vertical sections of the two horizontal wells are divergent, inclined outwards in a direction away from each other, and the horizontal sections of the horizontal wells are arranged in parallel and positioned at the same depth position, and extend in a direction away from the corresponding vertical sections; the well depth of the two horizontal wells is 1625.90 meters, and the length of the horizontal section is 1550m;
six fracturing sections are provided along the length of the horizontal sections for perforating and fracturing operations.
In the step (3), 2 horizontal wells are provided with respective perforating equipment and fracturing equipment, the perforating and fracturing equipment are alternately used, six fracturing sections are uniformly arranged along the length direction of the horizontal wells, and a volume fracturing method is adopted, and specifically comprises the following steps:
(i) Carrying out perforation operation of a target reservoir in a fracturing section I of a horizontal well I;
(ii) After the perforation of the first fracturing section of the horizontal well is completed, carrying out fracturing operation on the first fracturing section of the horizontal well, and carrying out perforation operation on the first fracturing section of the horizontal well;
the first fracturing section of the first horizontal well is completely fractured, liquid is not discharged after fracturing, and the first fracturing section is sealed;
(iii) After the first fracturing section of the second horizontal well is perforated, carrying out fracturing operation on the first fracturing section of the second horizontal well, and simultaneously carrying out perforation operation on the second fracturing section of the first horizontal well;
the first fracturing section of the second horizontal well is completely fractured, liquid is not discharged after fracturing, and the second fracturing section is sealed;
(iv) After the second fracturing section of the first horizontal well is perforated, carrying out fracturing operation on the second fracturing section of the first horizontal well, and simultaneously carrying out perforation operation on the second fracturing section of the second horizontal well;
the second fracturing of the fracturing section of the first horizontal well is completed, liquid is not discharged after fracturing, and the fracturing section is sealed;
(v) After the second fracturing section of the horizontal well is perforated, carrying out fracturing operation on the second fracturing section of the horizontal well, and simultaneously carrying out perforation operation on the third fracturing section of the horizontal well;
the second fracturing section of the horizontal well is completely fractured, no liquid is discharged after fracturing, and the second fracturing section is sealed;
(vi) After the third fracturing section of the first horizontal well is perforated, the third fracturing section of the first horizontal well performs fracturing operation, and simultaneously, the third fracturing section of the second horizontal well performs perforation operation;
the third fracturing of the fracturing section of the first horizontal well is completed, liquid is not discharged after fracturing, and the third fracturing section is sealed;
(vii) After the third fracturing section of the second horizontal well is perforated, the third fracturing section of the second horizontal well performs fracturing operation, and simultaneously, the fourth fracturing section of the first horizontal well performs perforation operation;
the third fracturing of the fracturing section of the second horizontal well is completed, liquid is not discharged after fracturing, and the third horizontal well is sealed;
(viii) After the perforation of the fracturing section IV of the horizontal well I is completed, carrying out fracturing operation on the fracturing section IV of the horizontal well I, and simultaneously carrying out perforation operation on the fracturing section IV of the horizontal well II;
the fourth fracturing of the first fracturing section of the horizontal well is completed, liquid is not discharged after fracturing, and the section is sealed;
(ix) After the fourth fracturing section of the second horizontal well is perforated, the fourth fracturing section of the second horizontal well performs fracturing operation, and meanwhile, the fifth fracturing section of the first horizontal well performs perforation operation;
the fourth fracturing of the fracturing section of the second horizontal well is completed, liquid is not discharged after fracturing, and the section is sealed;
(x) After the perforation of the fracturing section five of the horizontal well I is finished, carrying out fracturing operation on the fracturing section five of the horizontal well I, and simultaneously carrying out perforation operation on the fracturing section five of the horizontal well II;
the fourth fracturing of the first fracturing section of the horizontal well is completed, liquid is not discharged after fracturing, and the section is sealed;
(xi) After the fifth fracturing section of the second horizontal well is perforated, the fifth fracturing section of the second horizontal well is subjected to fracturing operation, and meanwhile, the sixth fracturing section of the first horizontal well is perforated;
the fifth fracturing of the fracturing section of the second horizontal well is completed, liquid is not discharged after fracturing, and the fracturing section is sealed;
(xii) After the perforation of the fracturing segment six of the horizontal well I is completed, carrying out fracturing operation on the fracturing segment six of the horizontal well I, and simultaneously carrying out perforation operation on the fracturing segment six of the horizontal well II;
the six fracturing of the fracturing section of the first horizontal well is completed, and no liquid is discharged after fracturing;
(10-x) after the completion of perforation of the fracturing segment six of the horizontal well II, carrying out fracturing operation on the fracturing segment six of the horizontal well II;
after fracturing is completed, uniformly discharging fracturing fluid in the 2 horizontal well reservoirs by using an open flow drainage method, installing lifting equipment, and starting pumping and production test coal mining layer gas.
In the same horizontal well, the more far away from the fracturing section of the well platform of the horizontal well, the earlier fracturing is performed.
The horizontal well adopts a cluster perforation mode, and perforation density is fixed to be 20 holes/meter along the spiral perforation of the shaft.
Example 3
The provided fracturing method for the reinforced slotted network of the deep coal bed gas horizontal well reservoir is the same as in the embodiment 1, wherein the perforation density of the vertical shaft is determined by the following formula:
wherein W is pm Perforation density, number/m; p (P) Eyelet hole Pressure drop, MPa, of friction loss for perforations; ρ is the density of the fracturing fluid, kg/m 3 ；S t Is the surface coefficient of well completion, dimensionless; q is the discharge capacity of fracturing fluid, m 3 /min；C d The flow coefficient of the fracturing fluid is conveyed to a pump, and the pump is dimensionless; d is the aperture of the perforation, mm; h is a p The firing thickness, m, of the perforation.
The P is Eyelet hole Is determined by the following formula:
P eyelet hole ＝P Rupture of -P Stratum layer
Wherein P is Rupture of The fracture pressure of the target reservoir, MPa; p (P) Stratum layer The rock fracture pressure, MPa, for the target reservoir.
The S is t Is determined by the following formula:
S t ＝S bf +S P +S al +S z
wherein S is bf Skin factor for a partially ejected formation; s is S p Is perforation skin coefficient; s is S al Is the skin coefficient of well deviation; s is S z The special skin coefficient of the fracturing method is obtained; the above parameters are dimensionless.
The S is z Is determined by the following formula:
wherein, the permeability of the K target reservoir, mD; p (P) s The pressure of the stratum which is adjacent to the nearest well and is not discharged after fracturing is carried out is MPa; p (P) wf Is the pressure near the shaft, MPa; mu is the viscosity of the fracturing fluid and mPa.S.
Table 1 parameters and calculation results of example 3
| P s | 35 | μ | 62 |
| P wf | 8.25 | ρ | 1.22 |
| h p | 0.6 | Q | 5 |
| K | 1.5 | C d | 0.5 |
| S z | 0.48771 | d | 4 |
| S bf | 0.35 | P Eyelet hole | 0.29981 |
| S p | 2.323 | P Stratum layer | 32.5 |
| S al | 0.72 | P Rupture of | 32.79981 |
| S t | 3.88 | W pm | 16 |
。
After fracturing is completed and liquid is discharged, the exploitation amount of coal bed gas is compared, and the gas production amounts of the embodiment 1, the comparative example 1 and the embodiment 3 are 2146m respectively 3 /d、1280m 3 /d and 2258m 3 /d。
Therefore, the fracturing method provided by the invention can strengthen the staggered complexity degree of the fracture net of the fracture, further remarkably improve the gas production, and simultaneously can quickly and accurately obtain a more suitable value of the perforation density by being matched with the perforation density determining method.
Claims (6)
1. The fracturing method of the reinforced joint net for the deep coal bed gas horizontal well reservoir is characterized by comprising the following steps of:
(1) For the deep reservoir of the same layer, dividing the same reservoir into a plurality of fracturing areas according to different geological properties of coalbed methane, wherein at least one well platform is arranged in one fracturing area, and comprises at least two horizontal wells;
(2) Setting the position of a horizontal well, and then drilling a well;
(3) Different wellheads in the same fracturing area are not constructed simultaneously, and the construction is needed to be sequentially performed according to the sequence;
for the same well platform, alternately perforating and fracturing different wells in sequence, perforating the last well, perforating the next well again, fracturing the last well at the same time, temporarily discharging no liquid after all wells of the same well platform are completely fractured, perforating and fracturing other well platforms in the same fracturing area according to the method until all well platforms in the fracturing area are completely perforated and fractured, and uniformly discharging fracturing fluid of all well platforms again;
in the step (2), the vertical sections of a plurality of horizontal wells of the same well platform are divergent, inclined outwards in a direction away from each other, and the horizontal sections of a plurality of horizontal wells are arranged in parallel and are positioned at the same or similar depth positions, and extend in a direction away from the corresponding vertical sections;
a plurality of fracturing sections are arranged along the length direction of the horizontal section and are used for perforation and fracturing operation;
in step (3), including a plurality of horizontal wells to same well head, every horizontal well has respective perforation equipment and fracturing equipment, is equipped with a plurality of fracturing section in every horizontal well, and a plurality of fracturing section evenly sets up along the length direction of horizontal well, adopts the volume fracturing method, specifically includes following step:
(i) Carrying out perforation operation of a target reservoir in a fracturing section I of a horizontal well I;
(ii) After the perforation of the first fracturing section of the horizontal well is completed, the first fracturing section of the horizontal well performs perforation operation, and meanwhile, the first fracturing section of the horizontal well performs fracturing operation of a target reservoir;
(iii) After the perforation of the first fracturing section of the second horizontal well is completed, perforating operation is carried out on the first fracturing section of the next horizontal well, liquid is not discharged temporarily after the first fracturing section of the first horizontal well is completely fractured, and fracturing operation is carried out on the first fracturing section of the second horizontal well;
(iv) After the perforation of the first fracturing stage of the next horizontal well in the step (iii) is completed, perforating operation is carried out on the first fracturing stage of the next horizontal well, after the first fracturing stage of the second horizontal well is completely fractured, liquid is not discharged temporarily, and fracturing operation is carried out on the first fracturing stage of the next horizontal well;
according to the construction method and the construction sequence, perforating and fracturing the first fracturing sections of a plurality of horizontal wells in sequence, and discharging no liquid;
(v) According to the construction method and the construction sequence, perforating and fracturing the second fracturing sections of the plurality of horizontal wells in sequence, and discharging no liquid;
(vii) According to the construction method and the construction sequence, a plurality of fracturing sections of a plurality of horizontal wells are perforated and fractured in sequence, and no liquid is discharged;
(viii) After the last fracturing section of the last horizontal well of the well platform is fractured, all the horizontal wells of the well platform are not discharged;
after the last fracturing section of the last horizontal well of other wellheads in the same fracturing area is fractured, uniformly discharging fracturing fluid from all fracturing sections of all horizontal wells in the fracturing area;
in the same horizontal well, the more far away from the fracturing section of the well platform, the earlier fracturing is performed.
2. The method of fracturing a reinforced slotted network for deep coalbed methane horizontal well reservoirs of claim 1, wherein in step (1), the coalbed methane geological properties include geological conditions and geological features, specifically including geological structure, hydrologic conditions, coalbed gas content, permeability, burial depth and thickness, and faults are avoided in the same fracturing zone; the geological conditions and the geological features of the same fracturing area are the same or similar.
3. The method of fracturing a reinforced slotted network for deep coalbed methane horizontal well reservoirs of claim 2, wherein the spacing of wells between different fractured zones is greater than 4 times the maximum fracture length of the region where the deep reservoir is located to avoid mutual interference of different wells.
4. A fracturing method for a reinforced slotted network of deep coalbed methane horizontal well reservoirs according to claim 1, characterized in that the perforation density of said horizontal well fracturing section is determined by the formula:
wherein W is pm Perforation density, number/m; p (P) Eyelet hole Pressure drop, MPa, of friction loss for perforations; ρ is the density of the fracturing fluid, kg/m 3 ；S t Is the surface coefficient of well completion, dimensionless; q is the discharge capacity of fracturing fluid, m 3 /min；C d The flow coefficient of the fracturing fluid is conveyed to a pump, and the pump is dimensionless; d is the aperture of the perforation, mm; h is a p The firing thickness, m, of the perforation.
5. A method of fracturing a reinforced slotted network for deep coalbed methane horizontal well reservoirs in accordance with claim 4, wherein said P Eyelet hole Is determined by the following formula:
P eyelet hole ＝P Rupture of -P Stratum layer
Wherein P is Rupture of The fracture pressure of the target reservoir, MPa; p (P) Stratum layer Rock burst pressure, MPa, for the target reservoir;
the S is t Is determined by the following formula：
S t ＝S bf +S P +S al +S z
Wherein S is bf Skin factor for a partially ejected formation; s is S p Is perforation skin coefficient; s is S al Is the skin coefficient of well deviation; s is S z The special skin coefficient of the fracturing method is obtained; the parameters are dimensionless;
the S is z Is determined by the following formula:
wherein K is the permeability of the target reservoir, mD; p (P) s The pressure of the stratum which is adjacent to the nearest well and is not discharged after fracturing is carried out is MPa; p (P) wf Is the pressure near the shaft, MPa; mu is the viscosity of the fracturing fluid and mPa.S.
6. The fracturing method for the reinforced slotted network of the deep coal bed methane horizontal well reservoir according to claim 1, wherein in the step (3), after the volume fracturing is finished, a blowout drainage method is adopted to drain fracturing fluid in the reservoir back out of the reservoir, then lifting equipment is installed, and the production test of coal bed methane is started.
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