Circular No. 59/2015/TT-BTNMT stipulates technical drilling methods for investigating, assessing, and exploring underground water using rotary drilling techniques.

CIRCULAR

TECHNICAL REGULATIONS ON DRILLING INVESTIGATION, ASSESSMENT AND PROSPECTING OF UNDERGROUND WATER

AND PROSPECTING OF UNDERGROUND WATERorganize credit institutions, foreign bank branches are responsible for organizing the implementation of this Circular.

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On the basis of the Law on Water Resources dated June 21, 2012;

Pursuant to Decree No. 21/2013/NĐ-CP dated March 4, 2013, promulgated by the Government, stipulating the functions, tasks, powers, and organizational structure of the Ministry of Natural Resources and Environment;

At the request of the Director of the National Water Resources Management Department, the General Director of the National Center for Water Resources Planning and Investigation, the Head of the Science and Technology Department, and the Head of the Legal Affairs Department;

The Minister of Natural Resources and Environment issues this Circular on technical regulations for drilling investigation, assessment and prospecting of underground water using rotary drilling methods (sampling or coring).

PART I

GENERAL PROVISIONS

Article 1. Scope of Regulation and Applicability

1. This Circular stipulates the contents, techniques, and products of drilling investigation, assessment, and prospecting of underground water using rotary drilling methods (sampling or coring).

2. This Circular applies to state agencies, organizations, and individuals related to drilling investigation, assessment, and prospecting of underground water.

Article 2. Interpretation of Terms

In this Circular, the following terms are understood as follows:

1. Casing is a section of pipe constructed within the borehole to stabilize the borehole wall and isolate the borehole from the surrounding rock and soil environment.

2. Filter Pipe is a section of pipe constructed within the borehole to ensure water circulation between the borehole wall and the aquifer, prevent the movement of mechanical components from the aquifer into the borehole, and stabilize the borehole wall.

3. Packing Material refers to various materials packed or filled into the space between the casing, filter pipe, and the borehole wall to form a cushion layer that enhances the water flow through the filter pipe or isolates different layers of rock and soil containing water according to technical requirements.

4. Core Sample Drilling is a section of rock and soil extracted during the drilling process.

5. First Encountered Water Level is the underground water level encountered in the borehole when drilling reaches the first depth containing water from the ground surface or the first depth containing water after installing the isolation pipe above and continuing to deepen the borehole.

6. Pre-Release Water Level is the water level in the borehole measured at the mouth of the borehole immediately before releasing the drilling tool.

7. Post-Release Water Level is the water level in the borehole measured at the mouth of the borehole immediately after lifting the drilling tool to the surface.

8. Stable Water Level is the water level measured before and after releasing the tool in a drilling round without exceeding a difference of 5 cm.

9. Auxiliary Works include works supporting drilling construction such as road and drilling site preparation; installation of drilling machines and pumps; excavation of fluid pits; construction of camp sites; water supply for drilling; production of drilling fluids on-site; cleaning of debris on the guide chute; recovery of drilling fluids; hoisting and lowering of drilling tools; inspection, maintenance, and replacement of drilling equipment and tools; dismantling of equipment; site clearance after completion of construction.

Article 3. Purpose and Tasks of the Borehole

1. Study the characteristics and lithological composition of rocks and soils; determine the existence and properties of underground water sources with depth.

2. Structure of casing and filter pipes for specialized purposes.

3. Geophysical study of the borehole.

4. Pumping, injecting, and testing water pressure in the borehole.

5. Monitor changes in water levels and water quality during cluster tests; long-term monitoring of underground water resources in the area.

Chapter II

DRILLING DESIGN

Article 4. Principles for Drilling Hole Design

1. Meeting the general objectives and tasks of drilling work and the specific tasks of the drilling hole as determined in projects for groundwater investigation, evaluation, and exploration.

2. Being suitable to the construction site and layout.

3. Being compatible with geological structure, rock composition, and soil grade.

4. The drilling hole structure must be simple and feasible under actual conditions.

5. Ensuring labor safety regulations and environmental hygiene standards.

Article 5. Contents of Drilling Hole Design

The design contents must specify the following information:

1. Location and layout of the drilling hole.

2. Expected stratigraphic column of the drilling hole.

3. Structure of the drilling hole.

4. Construction and materials of casing and filter pipes.

5. Packing material.

6. Drilling method.

7. Drilling equipment.

8. Special studies during the drilling process.

Article 6. Requirements for Drilling Hole Design

1. Determining the location and layout of the drilling hole:

a) The determination of the drilling hole location must be based on the approved layout plan of the project. In cases where the determined location does not ensure construction feasibility or there is another location that better meets the investigation and exploration objectives, the location may be re-determined but must not change the drilling hole's mission.

b) The drilling layout must provide sufficient space for equipment arrangement, material storage, worker production activities, ensuring safety for surrounding structures, buildings, and environmental landscapes; the ground surface must be designed to ensure stability during construction and meet drainage conditions.

c) Within the drilling layout area, the upper space must ensure safe operation of the drilling tower in all circumstances.

2. Expected stratigraphic column of the drilling hole:

a) It must be determined based on geological, hydrogeological investigation materials and related materials available at the time of design.

b) The level of detail must distinguish different rock layers by geological age, rock composition, grain size, homogeneity, bonding strength, weathering, fracturing, hardness, and stability.

3. Structure of the drilling hole:

a) Drilling holes in stable rock formations up to 30 meters deep can only be designed with one diameter grade.

b) Drilling holes in unstable rock formations over 30 meters deep can be designed with more than one diameter grade.

c) The minimum diameter of investigation, evaluation, and groundwater exploration drilling holes is 76mm.

d) Drilling holes designed for permeability tests in loose or poorly stable fractured rock formations must have a minimum size to accommodate a filter pipe with a diameter of 91mm.

đ) Drilling holes designed for permeability tests in stable fractured rock formations must have a minimum intake section diameter of 91mm.

e) The diameter of observation holes in permeability test clusters and monitoring holes must be able to accommodate a filter pipe with a minimum diameter of 40mm.

4. Construction of casing and filter pipes:

a) Casing and filter pipes for drilling holes must be selected to ensure rigidity, durability, and resistance to chemical and electrochemical corrosion.

b) The filter pipe structure must ensure a minimum open area of 20% of the surface area; it must have mechanical and chemical cleaning capabilities if required.

c) The depth placement of casings and filter pipes, their diameters, and lengths must be based on the expected stratigraphic column of the drilling hole and meet the purpose and mission of the drilling hole according to the project design.

d) In simple strata, the casing and filter pipe structure must be designed with all sections fixed by threading, welding, or adhesive bonding.

đ) In complex strata, the casing and filter pipe structure may include some transition sections without fixed connections using pillow or nested forms combined with fixed connection sections.

5. Isolation of water-bearing layers:

a) For drilling holes researching one or several water-bearing layers that need to be isolated from other water sources, the drilling design must specify isolation methods, isolation locations, and materials to ensure separation between water-bearing layers.

b) Packing materials for isolating water-bearing layers and stabilizing casings are clay, cement, bentonite-cement mixtures, or other non-harmful materials that do not reduce water quality.

6. Creating reverse filtration layers:

a) For drilling holes investigating, evaluating, and exploring groundwater in sand, gravel, and small pebble-bearing aquifers, packing layers with appropriate sizes and gradations can be designed to create reverse filtration layers around the filter pipe.

d) Materials for creating reverse filtration layers between water-bearing layers and filter pipes and stabilizing the filter pipe are sand, gravel, and pebbles with appropriate sizes and gradations.

7. Drilling methods:

a) When the drilling hole requires rock sample collection, the drilling design must select rotary core drilling methods. The core drilling method must be based on the physical and mechanical properties of the rock, clearly specifying the type of core barrel and drill bit to ensure that the collected core samples have a recovery rate of no less than 65% for loose rocks, 30-50% for gravel, and 75% for hard rocks, while meeting the following requirements:

- In stable and simple rock strata, use rotary circulation drilling with single-tube core barrels and drilling fluid with a density less than 1.3g/cm³.³;

- For soft, loose, weakly bonded rock strata, use rotary circulation drilling with short core barrels and double-tube core barrels, and drilling fluid with a density greater than 1.3g/cm³.³;

- When drilling through strongly fractured rock strata, use rotary circulation drilling with single-tube core barrels and drilling fluid with a density less than 1.3g/cm³.³.

b) When the drilling hole does not require rock sample collection, use rotary percussion drilling methods with coring bits or core-breaking tools combined with centralizers; drilling fluid density should range from greater than 1.0g/cm³ to less than 1.3g/cm³.³.

8. Drilling equipment:

a) The selection and use of fixed or self-propelled drilling machines must meet the technical requirements of the project and be suitable for construction conditions.

b) When replacing or modifying equipment components, ensure equivalent technical specifications and do not alter the technical performance designed by the manufacturer.

9. Other special requirements.

a) Monitor, record, observe, measure phenomena related to geological and hydrogeological characteristics;

b) Conduct geophysical studies of boreholes before installing casing and other special requirements of the project must be determined and clarified.

Chapter III

DRILLING CONSTRUCTION TECHNOLOGY

Article 7. Drilling preparation and completion work

1. Preparation work:

a) Receive tasks, request files, and conduct site surveys;

b) For boreholes with depths >300m, a drilling construction technical plan must be established according to the approved design; the layout of the drilling construction technical plan is specified in Appendix 01 of this Circular;

c) Construct foundations, roads, reinforce drilling foundation, dig fluid pits, and foundation pits;

d) Assemble machinery, equipment, materials, and manpower at the construction site; install the drilling tower, pump equipment, lighting system, safety systems; prepare drilling fluids and packing materials;

đ) Develop water supply plans for drilling and other auxiliary measures;

e) Coordinate with competent authorities to resolve issues related to the implementation of the project as stipulated by law;

2. Completion work shall only be carried out after all technical requirements have been met and approved by the project leader. The contents of completion work include:

a) Pumping and cleaning the borehole;

b) Preparing the completion report of the borehole;

c) Backfilling the borehole if groundwater monitoring is not conducted;

d) Processing and reinforcing the mouth of the casing when long-term monitoring equipment is installed;

đ) Handling core samples according to the approved design; preparing and completing the official documentation of the borehole;

e) Restoring the construction site in accordance with the law;

g) Disassembling and transporting machinery, equipment, and materials from the site.

Article 8. Drilling Fluids

1. Drilling fluids used for investigation, evaluation, and exploration of underground water are natural water sources such as rivers, streams, ponds, lakes with total mineralization less than 1g/liter.

2. In cases where the strata of the borehole consist of loose or highly fractured rock, bentonite slurry or polymer solutions with specific gravity less than 1.3g/cm³ should be used, or other fluids capable of cleaning through technical methods to restore the natural permeability of the surrounding rock.³ or other solutions capable of cleaning through technical measures to restore the natural permeability of the surrounding rock and soil around the borehole.

3. In cases of emergency repair of boreholes, it is permissible to use fluids with specific gravity greater than 1.3g/cm³.³.

Article 9. Drilling Work

1. Drilling to Open Hole

Use core barrels with lengths not exceeding 0.7m; apply the minimum drilling parameters to ensure that the borehole axis aligns with the design; the initial drilling depth should be from 3m to 3.5m.

2. Casing installation:

a) Casing installation must be immediately performed after open-hole drilling is completed; the casing must be reinforced and secured; the bottom of the casing should be placed in stable and solid rock layers.

b) If the rock layer below the casing is unstable, temporary casing installation should be carried out first, followed by continued drilling until reaching a stable and solid rock layer before proceeding with permanent casing installation.

3. Deepening drilling:

a) In soft, weakly bonded rocks with hardness grades I to VII on the drilling classification chart, single-tube core barrels and alloy drill bits should be used, with the following drilling parameters applied:

- Rotational speed from 90 rpm to 290 rpm;

- Bottom hole pressure from 640 kg to 1200 kg;

- Flow rate of washing water from 130 liters/min to 200 liters/min.

In cases where rock samples are difficult to obtain, double-tube core barrels with short core bits should be used.

b) In stable, hard rocks with hardness grades VII to XII on the drilling classification chart, single-tube core barrels and diamond drill bits should be used, with the following drilling parameters applied:

- Rotational speed from 150 rpm to 380 rpm;

- Bottom hole pressure from 640 kg to 960 kg;

- Flow rate of washing water from 90 liters/min to 130 liters/min.

c) When the project does not require rock sampling, use a drilling rig equipped with a centering device to drill through the entire bottom.

4. When enlarging the diameter of the borehole, use a drilling rig equipped with a centering device or specialized core barrels with the following drilling parameters applied: Set the machine's rotational speed to number 1, reduce the bottom hole pressure to half of normal drilling, and use the minimum flow rate of the pump.

5. Casing installation and technical requirements for casing boreholes:

a) Based on the design and actual strata of the borehole, determine the position, length of the casing column, filter pipe, and method of connecting pipes by threading, welding, or adhesive bonding;

b) The borehole must be cleaned at the bottom before casing installation, ensuring the depth allows the full length of the casing column and filter pipe as designed;

c) Before casing installation, inspect the borehole diameter and concentricity, quantity and quality of the casings to be installed, and the operational status of the drilling equipment, tower, and hoisting system;

d) Number and arrange the sections of the casing in structural sequence;

đ) Sections of the casing can only be connected at the mouth of the borehole during installation and must ensure concentricity; joints must be tight and secure;

e) During the lowering of the casing column, if obstructions occur, lift the column to address them; under no circumstances should external force be used to press the column down.

6. Pumping and cleaning the borehole:

a) Before and after placing the casing column and filter pipe, use mud pumps and drilling rigs combined with slush pipes to wash and clean cuttings from the borehole;

b) The washing process ends when the washing water coming out of the borehole mouth is clear, and the drilling tools can be lowered to the bottom of the borehole when pumping stops.

Article 10. Drilling physical measurement borehole service work

1. Pumping and cleaning drill cuttings at the bottom of the borehole; maintaining the stability of the borehole wall to ensure safety for physical measurement tools and equipment when they are inserted into the borehole.

2. Arranging drilling shifts on standby to serve physical measurement of the borehole and participate in handling and addressing incidents during the physical measurement of the borehole.

Article 11. Prevention and remediation of incidents

1. Incident prevention:

a) When formulating technical construction plans for drilling, all types of incidents that may occur under specific conditions must be considered, and preventive measures must be anticipated and planned;

b) Preparatory work before construction must adequately provide technical materials and necessary conditions to promptly and effectively implement remediation measures;

c) During construction, strict adherence to technical procedures, regulations, and standards must be maintained; materials, equipment, and personnel must meet technical standards and requirements.

2. Incident remediation:

a) Upon occurrence of an incident, the drilling monitoring technician and the drilling shift must promptly record the incident, determine its cause, and implement remediation measures according to the approved design's technical procedures;

b) During the incident remediation process, information about the incident and implemented remediation measures must be accurately and timely recorded in the drilling logbook;

c) After completing incident remediation, the construction unit must inspect, address, and rectify the machinery, equipment, materials, and condition of the borehole before continuing construction.

Article 12. Labor safety and environmental hygiene

1. Labor safety:

a) Direct workers on the drilling site must meet occupational standards corresponding to their job responsibilities, be equipped with knowledge of safety and labor protection as prescribed;

b) Machinery and equipment systems, drilling towers must be installed, operated, maintained, and repaired according to technical requirements; drive components must be protected with barriers; drill pipes and drilling tools must be regularly inspected as required;

c) The construction process must strictly follow the design, technical regulations, and professional safety rules;

d) In areas marked with leftover unexploded ordnance from war, clearance operations must be conducted before construction begins.

2. Environmental hygiene:

a) Discharging wastewater and waste from daily activities and construction processes into the surrounding environment must comply with environmental protection regulations;

b) Upon completion of construction, cleanup, leveling, and restoration of the site must be carried out.

Chapter IV

MONITORING, MEASUREMENT, RECORDING, COMBINING, EDITING DOCUMENTS,

COMPLETING FILES AND DRILLING WORK PRODUCTS

Article 13. Monitoring, Measurement, Recording, Combining, Editing Documents, and Completing Files

1. Monitoring, Measurement, Recording, and Combining Documents During Drilling:

a) After each drilling session ends, the drilling shift leader is responsible for recording all collected data and information accurately in the drilling logbook; the format of the drilling logbook is specified in Appendix 02 of this Circular;

b) Based on the collected data and information during drilling, the drilling team leader is responsible for summarizing and analyzing to adjust technical methods and drilling regimes to suit actual borehole conditions.

2. Editing Documents and Completing Files:

a) For data and information collected during the drilling shift such as: drilling speed, core recovery rate, fluid consumption by depth and drilling session time, water level and fluctuation amplitude by drilling depth, abnormal phenomena during drilling, editing of these documents must be done immediately on-site;

b) Upon completion of the borehole, all collected drilling data must be edited for the final time to complete the actual geological strata column of the borehole as stipulated in Appendix 03 and the drilling project file as stipulated in Appendix 04 of this Circular.

3. Monitoring, Measurement, Recording, Summarizing, and Editing Geological and Hydrogeological Data shall be performed by the drilling monitoring technician.

Article 14. Drilling products

1. Completed drilling holes that meet technical requirements.

2. Core samples from drilling holes (for sampling holes).

3. The books and documents specified in Appendices 1, 2, 3, and 4 of this Circular.

Chapter V

IMPLEMENTING PROVISIONS

Article 15. Implementation Organization

1. Ministries, ministerial-level agencies, agencies under the Government, Chairpersons of People's Committees of provinces and centrally-run cities, Directors of the Water Resources Management Agency, General Directors of the National Water Resources Planning and Investigation Center, Heads of units under the Ministry, and related organizations shall be responsible for implementing this Circular.

2. The Water Resources Management Agency and the National Water Resources Planning and Investigation Center shall be responsible for guiding and inspecting the implementation of this Circular.

Article 16. Effective Date

1. This Circular takes effect from February 5, 2016.

2. During the implementation process, if there are difficulties, agencies, organizations, and individuals are requested to promptly reflect them to the Ministry of Natural Resources and Environment for research, amendment, and supplementation.