CN116006076A - Method for drilling and completing multi-branch well with ultra-short radius by gas extraction in strip area - Google Patents
Method for drilling and completing multi-branch well with ultra-short radius by gas extraction in strip area Download PDFInfo
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- 238000005553 drilling Methods 0.000 title claims abstract description 77
- 238000000034 method Methods 0.000 title claims abstract description 30
- 238000000605 extraction Methods 0.000 title claims abstract description 17
- 239000003245 coal Substances 0.000 claims abstract description 104
- 238000003795 desorption Methods 0.000 claims abstract description 10
- 238000004458 analytical method Methods 0.000 claims abstract description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 230000035699 permeability Effects 0.000 claims description 8
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- 238000013461 design Methods 0.000 claims description 4
- 239000008398 formation water Substances 0.000 claims description 3
- 210000002445 nipple Anatomy 0.000 claims description 3
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 abstract description 24
- 230000000694 effects Effects 0.000 abstract description 6
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- 239000004568 cement Substances 0.000 description 2
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Abstract
The invention discloses a method for drilling and completing a multi-branch well with ultra-short radius by gas extraction in a strip area, which comprises the following steps: step 1, acquiring coal bed exploration data and adjacent well data of a target coal bed in a strip area, and calculating a branch well azimuth according to the acquired data; step 2, determining the analysis radius of the branch well according to the data obtained in the step 1, and taking the determined analysis radius as the optimal distance between the adjacent ultra-short radius multi-branch wells; step 3, constructing a main well according to the set drilling track of the main well, and finishing the drilling of the main well; and 4, completing the drilling and completion of the ultra-short radius branch well at two sides of the main well according to the azimuth angle of the branch well determined in the step 1 and the optimal distance between the adjacent ultra-short radius multi-branch wells determined in the step 2. The method realizes the drilling and completion of the ultra-short radius multi-branch horizontal well, and the branch well constructed by the method has controllable track, large effective control area and good coalbed methane desorption effect, and solves the problems of uncertain hydraulic fracturing cracks and unobvious yield increasing effect.
Description
Technical Field
The invention belongs to the field of coal bed methane exploitation, and particularly relates to a method for drilling and completing a multi-branch well with ultra-short radius by gas extraction in a strip area.
Background
The geological condition of the coalbed methane reservoir in China is poor, the yield increasing and transformation difficulty is high, the single well yield is low, the whole coalbed methane (gas) is in an inefficient development stage, meanwhile, the coalbed methane (gas) is also a major potential safety hazard in the underground roadway tunneling and coal resource exploitation processes, and the ground drilling is deployed along the coal roadway strip area to develop the coalbed methane, so that the gas pre-extraction is realized, waste materials are changed into valuable materials, the resources are fully utilized, and the requirement of gas outburst elimination of the coal roadway strip can be met.
The improvement of single well gas production is a key problem of current coalbed methane exploitation, the existing technical approaches mainly comprise two types, one type is to reform a reservoir by adopting technical measures, the permeability of the coalbed is improved, the technical measures mainly comprise hydraulic sand fracturing reformation, and the defects are that: because the coal seam cementing degree is weak, the mechanical strength and the elastic modulus are low, the poisson ratio is high, after sand fracturing, stable long cracks are difficult to form in a coal reservoir, the crack communication capacity is limited, the range of a pressure drop funnel formed around a shaft is small, and finally the effective transformation area is small. The other is to improve the coal bed gas well drilling and completion technology, at present, the coal bed gas exploration and development takes a vertical well or a single-branch horizontal well and a multi-branch horizontal well as main well types, and all the three well types have certain defects, so that the requirements of the coal bed gas development are difficult to be completely met, and the method specifically comprises the following steps: the control area of the conventional vertical well is small, frequent well repair is caused by coal dust output, and the gas yield is low; the pre-pumping effect of the single horizontal well applied to the strip area is not ideal; the multi-branch horizontal well is easy to collapse in the well wall of a coal layer section in the well drilling process, coal dust can enter a shaft in the drainage process, so that the coal dust particles are blocked in a pump accident, frequent well repair is caused, and the well drilling cost is high.
After the completion of the coal-bed gas well, drainage and depressurization are firstly carried out, and the existing drainage and gas production technology mainly adopts rod pumps such as pumping units and the like, and rodless pumps such as electric submersible pumps, screw pumps and the like to drain water from a shaft. The above processes all suffer from several drawbacks to varying degrees: the rod pump has small liquid yield and poor coal dust adaptability, is not suitable for horizontal well drainage, and has serious blocking, airlock and other phenomena of an electric submersible pump, a screw pump, a jet pump, a diaphragm pump and the like. Therefore, the technology capable of meeting the drainage and gas production process requirements is of great interest without being limited by the well type and the water yield of the coal seam.
In summary, there is a need to develop a coalbed methane development technology suitable for gas extraction in a strip area, so as to solve the technical dilemma of coalbed methane reservoir reconstruction, drainage and gas production in the prior art, and meet the requirement of eliminating gas outburst in the strip area of a coal roadway while efficiently developing coalbed methane, thereby ensuring safe and efficient tunneling of the roadway.
Disclosure of Invention
Aiming at the defects and shortcomings in the prior art, the invention provides a method for drilling and completing a multi-branch well with ultra-short radius for gas extraction in a strip area, which aims to solve the technical problems of low gas yield of a single well of coal bed gas in the strip area and unsatisfactory drainage and gas production effects in the prior art.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the method for drilling and completing the multi-branch well with the ultra-short radius by gas extraction in the strip area is characterized by comprising the following steps of:
step 1, acquiring coal seam exploration data and adjacent well data of a target coal seam in a strip area, wherein the adjacent well data comprise pre-drilling coal seam flowing pressure and branch well bottom flowing pressure, and the coal seam exploration data comprise coal seam elevation data, coal seam inclination, three-dimensional ground stress data of a coal seam, coal seam porosity and coal seam permeability; setting a drilling track of the main well according to the obtained data;
wherein the three-dimensional ground stress data of the coal seam comprises a minimum horizontal main stress sigma h Maximum horizontal principal stress sigma H And main stress sigma of vertical axis of branch well V ；
When sigma is H >σ h >σ V Or sigma H >σ V >σ h Calculating the azimuth angle of the branch well according to the obtained three-dimensional ground stress data;
step 2, determining the analysis radius of the branch well according to the data obtained in the step 1, and taking the determined analysis radius as the optimal distance between the adjacent ultra-short radius multi-branch wells;
step 3, constructing a main well according to a set drilling track of the main well, when the main well is drilled for the last time before completion, connecting a strong magnetic nipple at a near drill bit, installing a magnetic ranging probe at a preset communication point of a coal mine tunnel, realizing communication between a toe end of the horizontal well and the coal mine tunnel by means of a rotary magnetic ranging system, completing the main well in a sieve tube mode, and simultaneously temporarily plugging a water Ping Jingzhi end by a packer and a sleeve valve, thereby completing the drilling of the main well;
and 4, completing the drilling and completion of the ultra-short radius branch well at two sides of the main well according to the azimuth angle of the branch well determined in the step 1 and the optimal distance between the adjacent ultra-short radius multi-branch wells determined in the step 2.
The invention also has the following technical characteristics:
specifically, the azimuth of the branch well in step 1 is determined by the following formula:
wherein:
θ is the branch well azimuth in degrees;
σ H the unit is MPa, which is the maximum horizontal main stress;
σ h is the minimum horizontal main stress, and the unit is MPa;
σ V is the vertical main stress of the axis of the branch well, and the unit is MPa.
Further, the resolution radius described in step 2 is determined by the following formula:
wherein:
γ B the unit is m for the radius of the branch well shaft;
p is the coal seam flow pressure before drilling, and the unit is MPa;
p C the critical desorption pressure is expressed in MPa;
p VHP is the bottom hole flow pressure of the branch well, and the unit is MPa;
beta is stratum water leakage index, dimensionless.
Still further, the formation water drainage index is determined by the following formula:
wherein:
beta is stratum water leakage index, dimensionless;
t is the drainage time in d (days);
k is the permeability of the coal bed, and the unit is md;
Still further, the step 1 further includes: and according to the acquired coal seam elevation data and coal seam inclination angle data, taking a coal seam with the coal seam inclination angle smaller than 0 degree as a target coal seam, and then taking the highest point of the target coal seam as a window entering point of the deflecting section to finish the design of the main well deflecting section.
Furthermore, the main well drilling track set in the step 1 should satisfy the following conditions: the elevation of any point on the main well drilling path is lower than the elevation of the entry point.
Further, parameters of the construction of the ultra-short radius branch well in the step 4 include: the curvature radius of the ultra-short radius branch well bore is 2-3 m, and the horizontal extension distance of the ultra-short radius branch well in the target coal layer is 20-30 m.
Compared with the prior art, the invention has the beneficial technical effects that:
(1) The method realizes the drilling and completion of the ultra-short radius multi-branch horizontal well, and the branch well constructed by the method has controllable track, large effective control area and good coalbed methane desorption effect, and solves the problems of uncertain hydraulic fracturing cracks and unobvious yield increasing effect.
(2) After the well completion, the main well hole obtained by the method is communicated with the roadway, and the coal seam produced water of the well shaft can be discharged into a roadway manifold by regulating and controlling the opening and closing of the sleeve valve arranged on the sleeve pipe, so that the purpose of reducing pressure is achieved, and the desorption output of coal seam gas is accelerated.
(3) The diameter of the well bore drilled by the method can reach more than 200mm, the well bore has larger drainage area, the drilling torque can reach 30 kN.m, the drilling speed is high, the average drilling speed of a coal bed can reach 30m/h, the pressure of a liquid column of a well bore can balance the stratum flow pressure, and the collapse of the well wall of a soft coal bed is avoided, so that the technical problems of small bore diameter, slow drilling speed, poor bore wall stability, difficult pore forming and the like of the tunnel drilling in the prior art are effectively solved.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a horizontal cross-section of the main wellbore and branch wellbore of example 1;
fig. 3 is a vertical section of a wellbore of example 1.
The invention is described in detail below with reference to the drawings and the detailed description.
Detailed Description
The following specific embodiments of the present invention are given according to the above technical solutions, and it should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solutions of the present application fall within the protection scope of the present invention.
Technical terms related to the present invention are explained as follows:
ultrashort radius branch well: the effective curvature radius is 2-5 m, and the multi-branch well is in a horizontal state after being turned for 90 degrees.
Analytical radius: in the pressure drop funnel range of the coal-bed gas well, the coal-bed water pressure is lower than the area of the gas desorption pressure, and the distance from the edge of the area to the center of the shaft is called the desorption radius.
The well wall collapse prevention principle: the ground stress of the coal bed is a main external force for causing deformation and damage of the well wall, and the size and the direction of the ground stress have great influence on the stability of the coal bed around the well bore and are important factors for causing collapse of the well wall. The existing technology cannot reform the ground stress of the coal bed, so that the azimuth angle of the branch well bore is optimally designed through theoretical calculation, and damage of the ground stress to the well wall is avoided to the greatest extent.
The design idea of the method is as follows: drilling a ground horizontal well from a high point to a low point of a coal seam inclination angle along a strip area of a coal roadway, wherein the well body structure of the ground horizontal well is three-open, namely a first open straight well section, a second open deflecting section and a third open horizontal section; after drilling of the deflecting section and the horizontal section is completed, ultra-short radius branch wells are constructed on the target horizon by using flexible drilling tools along the two sides of the main well, two groups of oppositely arranged comb-shaped branch wells are finally formed in the coal bed, the whole gas pre-pumping area is uniformly covered by the branch wells, outburst elimination and coal bed gas exploitation and utilization are realized, and the technical problems of small hole diameter, slow drilling speed, poor hole wall stability, difficult hole forming and the like of tunnel drilling in the prior art are solved.
The present invention will be described in further detail with reference to examples.
Example 1
As shown in fig. 1, the embodiment provides a method for drilling and completing a multi-branch well with ultra-short radius by gas extraction in a strip area, which comprises the following steps:
step 1, acquiring coal seam exploration data and adjacent well data of a target coal seam in a strip area, wherein the adjacent well data comprise pre-drilling coal seam flowing pressure and branch well bottom flowing pressure, and the coal seam exploration data comprise coal seam elevation data, coal seam inclination, three-dimensional ground stress data of a coal seam, coal seam porosity and coal seam permeability; setting a drilling track of the main well according to the obtained data;
the set main well drilling track should satisfy the following conditions: the elevation of any point on the main well drilling path is lower than the elevation of the entry point.
The setting of the drilling track of the main well comprises the following steps: and according to the acquired coal seam elevation data and coal seam inclination angle data, taking a coal seam with the coal seam inclination angle smaller than 0 degree as a target coal seam, and then taking the highest point of the target coal seam as a window entering point of the deflecting section to finish the design of the main well deflecting section.
The coal seam is three-dimensionalThe ground stress data can be obtained through a hydraulic fracturing experiment, and comprises a minimum horizontal main stress sigma h Maximum horizontal principal stress sigma H And main stress sigma of vertical axis of branch well V ；
It should be noted that the method is only applicable to sigma H ＞σ h ＞σ V Or sigma H ＞σ v ＞σ h And when sigma H ＞σ h ＞σ V Or sigma H ＞σ V ＞σ h Calculating the azimuth angle of the branch well according to the obtained three-dimensional ground stress data; this is because when sigma V ＞σ H ＞σ h When the ground stress of the coal seam in the vertical direction of the axis of the branch well is the maximum value, the maximum value of the ground stress which can cause the collapse of the well wall is vertically acted on the well hole no matter how the well hole orientation is optimally deployed.
The lateral azimuth is determined by the following formula:
wherein:
θ is the branch well azimuth in degrees;
σ H the unit is MPa, which is the maximum horizontal main stress;
σ h is the minimum horizontal main stress, and the unit is MPa;
σ V is the vertical main stress of the axis of the branch well, and the unit is MPa.
In this example, σ was measured for coal rock by hydraulic fracturing H ＝14.43MPa，σ h ＝6.85MPa，σ V =8.52 MPa, and solving to obtain θ=51.22°, i.e. the branch wellbore azimuth should drill at an included angle of 51.22 ° with the maximum horizontal principal stress azimuth.
Step 2, determining the analysis radius of the branch well according to the data obtained in the step 1, and taking the determined analysis radius as the optimal distance between the adjacent ultra-short radius multi-branch wells;
the analytical radius is determined by the following formula:
wherein:
γ B is the radius of a branch well shaft, and the unit is m
p is the coal seam flow pressure before drilling, and the unit is MPa
p C Is critical desorption pressure in MPa
p VHP Is the bottom hole flow pressure of a branch well, and the unit is MPa
Beta is stratum water leakage index, dimensionless.
Wherein the formation water drainage index is determined by the following formula:
wherein:
beta is stratum water leakage index, dimensionless;
t is the drainage time in d (days);
k is the permeability of the coal bed, and the unit is md;
Branch wellbore radius gamma B Coal bed permeability k=0.03 mD, porosity=0.065 m
Coal seam initial flow pressure p=3.91 MPa, critical desorption pressure p C Bottom hole flow pressure p =2.35 MPa BHP After 120 days of drainage, the fluid is brought into a calculation formula to obtain a branch wellbore desorption radius gamma= 46.723m, namely, the optimal interval between adjacent ultra-short radius multi-branch wells is 46.723m.
Step 3, constructing a main well according to a set drilling track of the main well, when the main well is drilled for the last time before completion, connecting a strong magnetic nipple at a near drill bit, installing a magnetic ranging probe at a preset communication point of a coal mine tunnel, realizing communication between a toe end of the horizontal well and the coal mine tunnel by means of a rotary magnetic ranging system, completing the main well in a sieve tube mode, and simultaneously temporarily plugging a water Ping Jingzhi end by a packer and a sleeve valve, thereby completing the drilling of the main well;
the main well adopts a three-open-time well structure, and a straight well section adopts a drilling tool combination as follows: 12 1/4 'drill bit+5' drill rod, casing cement well cementation; and the drilling tool combination adopted by the two-opening deflecting section is as follows: 8 1/2 'drill bit+ 6 1/2' screw drilling tool+5 'weighted drill rod+5' drill rod, and a deflection section 'single-bending screw drilling tool+wireless measurement while drilling system' directional drilling tool assembly, and by means of sliding drilling, the torsion direction, the inclination increase and the inclination decrease are realized; the drilling speed and track control precision are effectively improved by stabilizing the inclination in a compound drilling mode, and the casing cement is well cemented; the drilling tool combination that three open main shaft horizontal sections adopted is: the method comprises the following steps of 6 'drill bit +4 6/8' screw drilling tool +3 1/2 'heavy drill rod +3 1/2' drill rod, wherein the main well horizontal section adopts a geosteering technology to monitor the well track in real time, and the main well horizontal section track is required to be completely in a target coal layer so as to meet the sidetrack requirement of a subsequent ultra-short radius branch well.
And 4, completing the drilling and completion of the ultra-short radius branch well at two sides of the main well according to the azimuth angle of the branch well determined in the step 1 and the optimal distance between the adjacent ultra-short radius multi-branch well determined in the step 2, wherein the parameters for constructing the ultra-short radius branch well comprise: the curvature radius of the ultra-short radius branch well bore is 2-3 m, and the horizontal extension distance of the ultra-short radius branch well in the target coal layer is 20-30 m.
High-curvature sidetracking is realized at the designed horizon by using the existing flexible drilling tools along the two sides of the horizontal section of the main well bore which is drilled completely, and sidetracking points are distributed at equal intervals so as to meet the requirements of coal bed gas extraction in the subsequent strip area, and tens of stable and long-term effective gas production pore channels shown in fig. 2 and 3 are finally formed in the coal bed. The well completion mode of combining the sieve tube and the sleeve is adopted, namely, the combination mode of an upper sleeve, a horizontal well section sieve tube, a sleeve valve and an external sleeve packer is adopted, the upper sleeve is subjected to half-way well cementation, an upper stratum is sealed and isolated, finally, the bottom of the well is completely communicated with a coal mine tunnel, a tail tube is connected with a drainage manifold in the tunnel, and water produced by the stratum and coal dust sand deposit are discharged into the coal mine tunnel manifold through adjusting the opening and closing of the sleeve valve, so that the effects of drainage depressurization and sand removal are achieved.
In this embodiment, after all the ultrashort radius branch wells arranged on two sides of the main well are completed, a branch well bore extending along each azimuth can be stably formed in the coalbed methane reservoir, the branch direction can be manually controlled, the length of the ultrashort radius branch well can reach more than 20 meters, and the fractures in each direction of the near well end and the far well end can be effectively communicated, so that the purpose of reservoir reconstruction is achieved.
Compared with the conventional borehole size of the conventional coal mine underground tunnel drilling, the theoretical torque is 6 kN.m, the average drilling speed is only 10m/h, and clear water can be used as drilling fluid, and a drilling fluid circulation system cannot be established, the diameter size of the completely drilled borehole obtained by the method can reach more than 200mm, the drilling torque can reach 30 kN.m, the drilling speed is high, the average drilling speed of a coal seam can reach 30m/h, the liquid column pressure of the shaft can balance the stratum flow pressure, and the collapse of a soft coal seam wall is avoided.
The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.
In addition, the specific features described in the foregoing embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, the present disclosure does not further describe various possible combinations.
Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.
Claims (7)
1. The method for drilling and completing the multi-branch well with the ultra-short radius by gas extraction in the strip area is characterized by comprising the following steps of:
step 1, acquiring coal seam exploration data and adjacent well data of a target coal seam in a strip area, wherein the adjacent well data comprise pre-drilling coal seam flowing pressure and branch well bottom flowing pressure, and the coal seam exploration data comprise coal seam elevation data, coal seam inclination, three-dimensional ground stress data of a coal seam, coal seam porosity and coal seam permeability; setting a drilling track of the main well according to the obtained data;
wherein the three-dimensional ground stress data of the coal seam comprises a minimum horizontal main stress sigma h Maximum horizontal principal stress sigma H And main stress sigma of vertical axis of branch well V ；
When sigma is H >σ h >σ V Or sigma H >σ V >σ h Calculating the azimuth angle of the branch well according to the obtained three-dimensional ground stress data;
step 2, determining the analysis radius of the branch well according to the data obtained in the step 1, and taking the determined analysis radius as the optimal distance between the adjacent ultra-short radius multi-branch wells;
step 3, constructing a main well according to a set drilling track of the main well, when the main well is drilled for the last time before completion, connecting a strong magnetic nipple at a near drill bit, installing a magnetic ranging probe at a preset communication point of a coal mine tunnel, realizing communication between a toe end of the horizontal well and the coal mine tunnel by means of a rotary magnetic ranging system, completing the main well in a sieve tube mode, and simultaneously temporarily plugging a water Ping Jingzhi end by a packer and a sleeve valve, thereby completing the drilling of the main well;
and 4, completing the drilling and completion of the ultra-short radius branch well at two sides of the main well according to the azimuth angle of the branch well determined in the step 1 and the optimal distance between the adjacent ultra-short radius multi-branch wells determined in the step 2.
2. The strip zone gas extraction ultrashort radius multilateral well drilling and completion method of claim 1, wherein the multilateral well azimuth of step 1 is determined by the following equation:
wherein:
θ is the branch well azimuth in degrees;
σ H the unit is MPa, which is the maximum horizontal main stress;
σ h is the minimum horizontal main stress, and the unit is MPa;
σ V is the vertical main stress of the axis of the branch well, and the unit is MPa.
3. The method for drilling and completing a multi-branch well with ultra-short radius for gas extraction in a banded region according to claim 1, wherein the analytical radius in the step 2 is determined by the following formula:
wherein:
γ B the unit is m for the radius of the branch well shaft;
p is the coal seam flow pressure before drilling, and the unit is MPa;
p C the critical desorption pressure is expressed in MPa;
p BHP is the bottom hole flow pressure of the branch well, and the unit is MPa;
beta is stratum water leakage index, dimensionless.
4. The strip zone gas extraction ultrashort radius multilateral well drilling and completion method of claim 3, wherein said formation water drainage index is determined by the following equation:
wherein:
beta is stratum water leakage index, dimensionless;
t is the drainage time in d (days);
k is the permeability of the coal bed, and the unit is md;
5. The method for drilling and completing a multi-branch well with ultra-short radius for gas extraction in a banded region according to claim 1, wherein the step 1 further comprises: and according to the acquired coal seam elevation data and coal seam inclination angle data, taking a coal seam with the coal seam inclination angle smaller than 0 degree as a target coal seam, and then taking the highest point of the target coal seam as a window entering point of the deflecting section to finish the design of the main well deflecting section.
6. The method for drilling and completing the multi-branch well with the ultra-short radius by gas extraction in the banded region according to claim 1, wherein the main well drilling track set in the step 1 is required to meet the following conditions: the elevation of any point on the main well drilling path is lower than the elevation of the entry point.
7. The method for drilling and completing a multi-branch well with ultra-short radius for gas extraction in a banded region according to claim 4, wherein the parameters for constructing the multi-branch well with ultra-short radius in the step 4 include: the curvature radius of the ultra-short radius branch well bore is 2-3 m, and the horizontal extension distance of the ultra-short radius branch well in the target coal layer is 20-30 m.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117823043A (en) * | 2023-12-29 | 2024-04-05 | 中国矿业大学(北京) | Directional drilling method and system for short-vertical-distance short-radius branch hole |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117823043A (en) * | 2023-12-29 | 2024-04-05 | 中国矿业大学(北京) | Directional drilling method and system for short-vertical-distance short-radius branch hole |
| CN117823043B (en) * | 2023-12-29 | 2024-06-21 | 中国矿业大学(北京) | Directional drilling method and system for short-vertical-distance short-radius branch hole |
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