1 Scope
This document provides guidance on the general principles of CBM abandoned well disposal, plugging operations, construction and acceptance, safety and environmental requirements, quality evaluation and record archiving.
This document applies to the abandonment disposal operations of CBM vertical and directional wells.
2 Normative references
The contents of the following documents constitute essential provisions of this document through normative references in the text. In which, the date of the reference documents, only the date of the corresponding version applicable to this document; do not note the date of the reference documents, the latest version (including all the revision of the list) applicable to this document.
GB/T 31537 Terminology of coal bed methane (coal mine gas)
SY/T 5587.5 Code of practice for the repair of wells, Part 5: Preparation of wells for underground workings
SY/T 5587.14 Code of practice for conventional well workover Part 14: Plug injection and drilling plug
SY/T 6646 Guidelines for the disposal of abandoned wells and long stoppages
3 Terms and definitions
The terms defined in GB/T 31537 and the following terms and definitions apply to this document.
3.1
Abandoned coalbed methane well
A coalbed methane well that cannot be reused due to geological, engineering, economic, coal mining and environmental factors in the course of coalbed methane surface exploration and development.
Note: This includes wells that have had accidents and cannot be rehabilitated. Wells that are no longer in production at the end of exploration. Wells that do not achieve the expected benefits, wells that have reached the end of their gas production life, etc.
4 General principles
4.1 Dispose of abandoned CBM wells in a reasonable manner to prevent safety hazards and environmental pollution caused by unreasonable disposal.
4.2 To isolate the hydraulic connection between the target layer of the CBM well and the aquifer and surface water, and to prevent water pollution caused by the interflow of fluids from different layers.
4.3 The disposal of abandoned CBM wells within the mining rights of a coal mine should be carried out in such a way as to ensure the safe exploitation of the coal mine and to prevent coal mine safety accidents caused by the entry of stratigraphic fluids into the coal seam through the well profile.
4.4 The landforms of abandoned CBM wells that are no longer planned for construction after disposal should be restored to meet the requirements for reclamation and greening.
5 Coalbed methane abandoned well plugging operations
5.1 Design
An engineering design report should be prepared prior to the plugging and disposal of abandoned CBM wells, with the required data and design format shown in Appendix A.
5.2 Site
The site should meet the requirements for plugging and disposal operations.
5.3 Well profile.
5.3.1 The pressure at the wellhead prior to CBM disposal operations is 0MPa.
5.3.2 Well penetration prior to lowering the bridge plug . Scraping operations.
5.3.3 Procedures and quality control of well preparation operations shall be in accordance with SY/T5587.5.
5.4 Plugging materials
5.4.1 Selection of cement
Cement of grade G or above shall be used. The preparation of cement for well sealing shall be in accordance with the provisions of SY/T 5587.14.
5.4.2 Cement dosage
The amount of cement can be calculated according to formula (1).
Additional coefficient (1.2~1.4);
- Theoretical volume of the filling section in cubic metres (m');
I - the amount of cement used to prepare a unit volume of cement slurry, in kilograms per cubic metre (kg/m').
5.5 Blocking method
The pumping method is usually used, i.e. the cement is pumped into the well through the tubing and the column is lifted at the right time so that the cement remains in the injected formation. During the injection process, the well is kept in a static state (neither spillage nor leakage).
5.6 Plugging operations
5.6.1 Casing Intact CBM abandoned wells
5.6.1.1 The production tubulars and extraction equipment are removed and records are kept.
5.6.1.2 Lower the tubing to the sand face and record the depth. Record the number, size and length of the manhole tubulars.
5.6.1.3 Using the pumping method, pump the cement slurry from the tubing to the sand surface and inject the cement into the wellhead for a minimum of 48 hours, as shown in Figure 1.
5.6.1.4 When the depth of the well exceeds 1 200 m, it is advisable to use the segmental replacement cement injection method. After the first segment is plugged, repeat 5.6.1.1 to 5.6.1.3 until the whole segment is plugged.
5.6.2 Abandoned CBM wells with casing deformation
5.6.2.1 Lift out the production tubulars and extraction equipment and record detailed information on any unrecoverable downhole remains.
5.6.2.2 Lower the tubulars to investigate the depth of obstruction. Record the number, size and length of the manhole tubulars. Specification and length.
5.6.2.3 Using the pumping method, pump the cement slurry from the tubing to the point of casing deformation and inject the cement into the wellhead for a minimum of 48 hours, as shown in Figure 2.
5.6.2.4 When the well depth exceeds 1200 m, refer to 5.6.1.4.
5.6.3 Abandoned coal bed methane wells in extraction areas
5.6.3.1 Remove production tubulars and extraction equipment and keep records.
5.6.3.2 Access the tubing to explore the sand surface and record the depth. Record the number of manhole columns. Record the number, size and length of the tubulars.
5.6.3.3 If the coal reservoir has been hollowed out or otherwise does not meet the requirements for cement replacement, it is advisable to fill with gravel to not less than 20 m above the coal seam before filling with cement, then fill with sand to not less than 20 m above the gravel, and finally inject water slurry from the sand surface to the wellhead, as shown in Figure 3.
5.6.3.4 When the depth of the well exceeds 1 200 m, refer to 5.6.1.4.
6 Construction and acceptance
6.1 The construction unit has the appropriate construction qualifications.
6.2 The construction unit prepares a construction design based on the geological and engineering design issued. If changes to the construction design are required, the CBM well owner will issue an approved supplementary design or design change.
6.3 The construction process will be supervised on site by the CBM well owner or by a third party appointed supervisor, who will submit a confirmation of key processes.
6.4 At the end of construction, the construction unit will submit a construction summary and the CBM well owner will organise acceptance and issue an acceptance letter.
7 Safety and environmental protection requirements
Safety and environmental protection requirements shall be in accordance with SY/T 6646.
8 Quality evaluation.
8.1 Exploration of cement plug surface
When using segmental injection of water mud method, it is advisable to probe the cement surface after each segment is blocked and waiting for condensation, and to probe the cement surface with 5kN~10kN pressure twice to confirm the depth of the cement plug.
Determine the depth of the cement plug.
8.2 Differential pressure check
When using segmental replacement injection of water slurry method, it is appropriate to block each section after waiting for condensation, positive pumping pressure of 15 MPa, steady pressure for 30 minutes pressure drop is not
The pressure drop is not greater than 0.5 MPa, the pressure test is qualified.
9 Record filing
Records of CBM abandoned well plugging operations are required to be kept in Appendix B and archived by the construction unit as a permanent document for easy access.
The owner of the abandoned CBM well will keep the drilling data of the abandoned well for subsequent reference by the coal miner, and if there is a clear coal mine owner, the relevant data of the abandoned well and the abandonment summary report will be forwarded to the coal mine owner for their reference.
Foreword
1 Scope
2 Normative references
3Terms and definitions
4 General principles
5 Coalbed methane abandoned well plugging operations
6Construction and acceptance
7Safety and environmental requirements
8 Quality evaluation
9 Records archiving
Annex A (Informative) Design Report on Coal Bed Methane Abandoned Well Plugging and Disposal Works
Annex B (Informative) Form of Basic Data Sheet for Coal Bed Methane Abandoned Well Plugging Operations
1 Scope
This document provides guidance on the general principles of CBM abandoned well disposal, plugging operations, construction and acceptance, safety and environmental requirements, quality evaluation and record archiving.
This document applies to the abandonment disposal operations of CBM vertical and directional wells.
2 Normative references
The contents of the following documents constitute essential provisions of this document through normative references in the text. In which, the date of the reference documents, only the date of the corresponding version applicable to this document; do not note the date of the reference documents, the latest version (including all the revision of the list) applicable to this document.
GB/T 31537 Terminology of coal bed methane (coal mine gas)
SY/T 5587.5 Code of practice for the repair of wells, Part 5: Preparation of wells for underground workings
SY/T 5587.14 Code of practice for conventional well workover Part 14: Plug injection and drilling plug
SY/T 6646 Guidelines for the disposal of abandoned wells and long stoppages
3 Terms and definitions
The terms defined in GB/T 31537 and the following terms and definitions apply to this document.
3.1
Abandoned coalbed methane well
A coalbed methane well that cannot be reused due to geological, engineering, economic, coal mining and environmental factors in the course of coalbed methane surface exploration and development.
Note: This includes wells that have had accidents and cannot be rehabilitated. Wells that are no longer in production at the end of exploration. Wells that do not achieve the expected benefits, wells that have reached the end of their gas production life, etc.
4 General principles
4.1 Dispose of abandoned CBM wells in a reasonable manner to prevent safety hazards and environmental pollution caused by unreasonable disposal.
4.2 To isolate the hydraulic connection between the target layer of the CBM well and the aquifer and surface water, and to prevent water pollution caused by the interflow of fluids from different layers.
4.3 The disposal of abandoned CBM wells within the mining rights of a coal mine should be carried out in such a way as to ensure the safe exploitation of the coal mine and to prevent coal mine safety accidents caused by the entry of stratigraphic fluids into the coal seam through the well profile.
4.4 The landforms of abandoned CBM wells that are no longer planned for construction after disposal should be restored to meet the requirements for reclamation and greening.
5 Coalbed methane abandoned well plugging operations
5.1 Design
An engineering design report should be prepared prior to the plugging and disposal of abandoned CBM wells, with the required data and design format shown in Appendix A.
5.2 Site
The site should meet the requirements for plugging and disposal operations.
5.3 Well profile.
5.3.1 The pressure at the wellhead prior to CBM disposal operations is 0MPa.
5.3.2 Well penetration prior to lowering the bridge plug . Scraping operations.
5.3.3 Procedures and quality control of well preparation operations shall be in accordance with SY/T5587.5.
5.4 Plugging materials
5.4.1 Selection of cement
Cement of grade G or above shall be used. The preparation of cement for well sealing shall be in accordance with the provisions of SY/T 5587.14.
5.4.2 Cement dosage
The amount of cement can be calculated according to formula (1).
Additional coefficient (1.2~1.4);
- Theoretical volume of the filling section in cubic metres (m');
I - the amount of cement used to prepare a unit volume of cement slurry, in kilograms per cubic metre (kg/m').
5.5 Blocking method
The pumping method is usually used, i.e. the cement is pumped into the well through the tubing and the column is lifted at the right time so that the cement remains in the injected formation. During the injection process, the well is kept in a static state (neither spillage nor leakage).
5.6 Plugging operations
5.6.1 Casing Intact CBM abandoned wells
5.6.1.1 The production tubulars and extraction equipment are removed and records are kept.
5.6.1.2 Lower the tubing to the sand face and record the depth. Record the number, size and length of the manhole tubulars.
5.6.1.3 Using the pumping method, pump the cement slurry from the tubing to the sand surface and inject the cement into the wellhead for a minimum of 48 hours, as shown in Figure 1.
5.6.1.4 When the depth of the well exceeds 1 200 m, it is advisable to use the segmental replacement cement injection method. After the first segment is plugged, repeat 5.6.1.1 to 5.6.1.3 until the whole segment is plugged.
5.6.2 Abandoned CBM wells with casing deformation
5.6.2.1 Lift out the production tubulars and extraction equipment and record detailed information on any unrecoverable downhole remains.
5.6.2.2 Lower the tubulars to investigate the depth of obstruction. Record the number, size and length of the manhole tubulars. Specification and length.
5.6.2.3 Using the pumping method, pump the cement slurry from the tubing to the point of casing deformation and inject the cement into the wellhead for a minimum of 48 hours, as shown in Figure 2.
5.6.2.4 When the well depth exceeds 1200 m, refer to 5.6.1.4.
5.6.3 Abandoned coal bed methane wells in extraction areas
5.6.3.1 Remove production tubulars and extraction equipment and keep records.
5.6.3.2 Access the tubing to explore the sand surface and record the depth. Record the number of manhole columns. Record the number, size and length of the tubulars.
5.6.3.3 If the coal reservoir has been hollowed out or otherwise does not meet the requirements for cement replacement, it is advisable to fill with gravel to not less than 20 m above the coal seam before filling with cement, then fill with sand to not less than 20 m above the gravel, and finally inject water slurry from the sand surface to the wellhead, as shown in Figure 3.
5.6.3.4 When the depth of the well exceeds 1 200 m, refer to 5.6.1.4.
6 Construction and acceptance
6.1 The construction unit has the appropriate construction qualifications.
6.2 The construction unit prepares a construction design based on the geological and engineering design issued. If changes to the construction design are required, the CBM well owner will issue an approved supplementary design or design change.
6.3 The construction process will be supervised on site by the CBM well owner or by a third party appointed supervisor, who will submit a confirmation of key processes.
6.4 At the end of construction, the construction unit will submit a construction summary and the CBM well owner will organise acceptance and issue an acceptance letter.
7 Safety and environmental protection requirements
Safety and environmental protection requirements shall be in accordance with SY/T 6646.
8 Quality evaluation.
8.1 Exploration of cement plug surface
When using segmental injection of water mud method, it is advisable to probe the cement surface after each segment is blocked and waiting for condensation, and to probe the cement surface with 5kN~10kN pressure twice to confirm the depth of the cement plug.
Determine the depth of the cement plug.
8.2 Differential pressure check
When using segmental replacement injection of water slurry method, it is appropriate to block each section after waiting for condensation, positive pumping pressure of 15 MPa, steady pressure for 30 minutes pressure drop is not
The pressure drop is not greater than 0.5 MPa, the pressure test is qualified.
9 Record filing
Records of CBM abandoned well plugging operations are required to be kept in Appendix B and archived by the construction unit as a permanent document for easy access.
The owner of the abandoned CBM well will keep the drilling data of the abandoned well for subsequent reference by the coal miner, and if there is a clear coal mine owner, the relevant data of the abandoned well and the abandonment summary report will be forwarded to the coal mine owner for their reference.
Contents of GB/T 41025-2021
Foreword
1 Scope
2 Normative references
3Terms and definitions
4 General principles
5 Coalbed methane abandoned well plugging operations
6Construction and acceptance
7Safety and environmental requirements
8 Quality evaluation
9 Records archiving
Annex A (Informative) Design Report on Coal Bed Methane Abandoned Well Plugging and Disposal Works
Annex B (Informative) Form of Basic Data Sheet for Coal Bed Methane Abandoned Well Plugging Operations
