Circular No. 50/2025/TT-BNNMT on technical procedures for drilling works in basic geological surveys, mineral geological surveys, and mineral exploration

 

CIRCULAR

Technical regulations for construction work of drilling projects in basic geological surveys, mineral geological surveys, and mineral exploration

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On the basis of Law on Geology and Minerals November 29, 2024;

Decree No. Decision No. 193/2025/NĐ-CP dated July 2, 2025 of the Government detailing implementation of certain provisions of the Law on Geology and Minerals;

Decree No. Decision No. 35/2025/NĐ-CP February 25, 2025 of the Government stipulating functions, tasks, powers, and organizational structure of the Ministry of Agriculture and Rural Development;

At the proposal of the Director of the Vietnam Geological and Mineral Resources Administration;

The Minister of Agriculture and Rural Development issues this Circular to stipulate technical regulations for construction work of drilling projects in basic geological surveys, mineral geological surveys, and mineral exploration.

PART I

GENERAL PROVISIONS

Article 1. Scope of Regulation and Applicability

Article 1. This Circular stipulates technical regulations for construction work of drilling projects serving basic geological surveys, mineral geological surveys, and mineral exploration. Related geophysical and hydrogeological works during drilling construction are not within the scope of this Circular.

Article 2. This Circular applies to state management agencies for geology and minerals; organizations and individuals participating in or related to basic geological surveys, mineral geological surveys, and mineral exploration.

Article 2. Interpretation of Terms

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

1. Rotary drillingis a mechanical drilling method where soil and rock at the bottom of the drill hole are destroyed by the force of pressure and the rotary motion of the drill bit.

2. Mechanical rotary drillingis a rotary drilling method using a motor as the source of power to drive the drill bit.

3. Hand rotary drillingis a rotary drilling method without using a motor, where the drill bit is operated manually by human power.

4. Core drillingis a rotary drilling method combined with the collection of soil, rock, or mineral samples at specific locations and depths during drilling.

5. Single-tube core drillingis a mechanical rotary core drilling method using a single-tube sample barrel, where the drill pipe simultaneously houses the drill bit to destroy soil and rock and contains the core sample.

6. Double-tube core drillingis a mechanical rotary core drilling method using a double-tube sample barrel consisting of an outer tube housing the drill bit to destroy soil and rock and an inner tube standing still or rotating to destroy soil and rock, receiving and containing the core sample.

7. Cable-tool core drillingis a mechanical rotary core drilling method where, after each drilling pass, the inner tube containing the core sample is retrieved to the surface by pulling through the drill mast using a specialized steel cable.

8. Percussion drillingis a rotary drilling method without core sampling, serving the purpose of creating and expanding drill holes or constructing structures.

9. Hydraulic percussion drillingis a core drilling method using a hammer or hydraulic equipment to act upon the core sampling tool to retrieve the core sample.

10. Offshore drillingis a core drilling or percussion drilling method where drilling equipment is installed on self-elevating platforms, ships, boats, or floating platforms. The construction range extends from the river mouth towards the sea.

11. Tidal flat drillingis a core drilling or percussion drilling method where drilling equipment is arranged on a drilling platform capable of raising and lowering to adapt to tidal movements.

12. Air drillingis a core drilling method for non-intact sediment by using a high-pressure air-water mixture to break up sediment and transport it to the surface.

13. Vertical drillingis a drilling method where the drill hole axis is designed perpendicular to the horizontal plane, forming a 90° angle.

14. Inclined drillingis a drilling method where the drill hole axis is designed inclined relative to the horizontal plane, with an inclination angle ranging from 10° to less than 90°.

15. Horizontal drillingis a drilling method where the drill hole axis is designed parallel to the horizontal plane, forming a 0° angle.

16. Casingis a section of pipe installed inside the drill hole to stabilize the hole wall and isolate the space within the drill hole from the surrounding environment.

17. Drill core sampleis a segment of soil or rock extracted from the drill hole by the sample barrel during drilling, serving for observation, analysis, and geological evaluation.

18. Drilling under complex conditionsrefers to drilling activities carried out in geological layers characterized by features such as fractures, loss of washing water; weathered zones; zones of structural destruction; karst caves; filled-in landfills; artificial tunnels; old mines; expansive clay layers, flowing clay; quicksand; pressurized water layers. Under these conditions, drilling construction must use appropriate materials, equipment, tools, and drilling technology to meet the technical requirements of the project/approach/task (hereinafter referred to as the project) approved.

Chapter II

DESIGN AND PREPARATION FOR DRILLING CONSTRUCTION

Article 3. Principles for Designing Drill Holes

The design of drill holes shall comply with the following principles:

1. Meeting the objectives and tasks of the project approved by the competent authority.

2. Being suitable for the geological structure characteristics, rock grade, construction surface, and the planned location of the drill holes in the drilling area.

3. Ensuring labor safety and environmental hygiene requirements during the construction process.

4. Selecting drilling methods and equipment appropriate to the drilling objectives, geological conditions, and construction conditions.

Article 4. Contents of Drill Hole Design

The design of drill holes shall include the following main contents:

1. Location of drill holes, foundation plane.

2. Cross-section design, anticipated stratigraphic column of the drill hole.

3. Orientation, inclination angle of the drill hole.

4. Structure of the drill hole.

5. Drilling method, drilling regime for different types of rocks.

6. Drilling equipment.

7. Other technical requirements (if any).

Article 5. Determination of Drill Hole Locations and Foundation Plane

1. Determination of drill hole locations

a) The location of drill holes is determined based on the project approved by the competent authority and the results of geological and mineral surveys at the site;

b) The coordinates of the drill hole locations are determined according to the geodetic technique specified in the project, ensuring accuracy appropriate to the requirements of each type of drilling project.

2. Foundation plane

a) The foundation plane must ensure sufficient space for equipment layout, material stockpiling, fuel, materials; construction activities; safety for surrounding structures, buildings, and environmental landscapes. The ground surface of the foundation plane must be flat and stable during construction, meeting the conditions for water supply and drainage. The size of the foundation plane is designed based on the depth of the drill hole according to the table below:

In cases where actual conditions cannot meet the size of the foundation plane as stipulated in the above table, the construction unit is responsible for developing a construction plan suitable for the current site conditions, which has been approved before implementation;

b) If the initial foundation plane does not meet the construction requirements, it is necessary to install and reinforce it with materials such as wooden floors, steel floors, or other suitable materials to ensure safety during the construction process;

c) For machine drilling work on rivers, seas, drilling platforms, or drilling vessels, stability under fixed construction conditions must be ensured, while also providing a sufficiently wide area for equipment installation, operation, material storage, sample placement, and working space for the drilling team. The area must not be less than 50 m²;

d) For machine drilling work on tidal areas, the drilling foundation plane is designed and arranged so that when the tide rises, the water level does not exceed 50 cm from the drilling floor.

Article 6. Drilling Cross-Section Design, Anticipated Drill Hole Diagram

1. Drilling cross-section design

a) The drilling cross-section design is established based on the approved project, taking into account factors such as topography, geology, geophysical data (if available), and related actual geological data. The scale of the cross-section design must be equal to or greater than the corresponding scale of the ongoing geological research;

b) The cross-section design includes all information: topography of the area, ore body morphology, geophysical results (if available), geological environmental information (if available), scale ratio, basic technical data such as coordinates, anticipated drilling depth, and relevant annotations.

2. Anticipated drill hole diagram

a) The content of the anticipated drill hole diagram includes the following information: drill hole number, coordinates, diameter, orientation of the drill hole, geological and ore characteristics, and final depth of the drill hole. The scale of the anticipated diagram is selected within the range of 1:50 to 1:200. The format of the anticipated drill hole diagram is specified in Model No. 01, Appendix III issued together with this Circular;

b) The anticipated drill hole diagram serves as the basis for designing the drill hole structure, ensuring compliance with technical requirements according to the objectives of the approved project.

Article 7. Drilling Hole Structure

1. The drilling hole structure is designed based on geological investigation materials, mineral resources, and other related documents. Depending on the depth and geological conditions of the drilling hole, one or more different diameter levels may be applied. The final diameter of the drilling hole must match the selected drilling method in the technical design and should not be less than 76 mm.

2. When designing the drilling hole structure, it is necessary to determine the final diameter of the drilling hole, ensuring that it meets the requirements for geological research, including sample collection requirements for minerals and mechanical properties; and the requirement to deploy equipment for geophysical and hydrogeological work.

Article 8. Casing Pipe

1. The casing pipe is chosen to ensure suitability with construction conditions, requirements for rigidity, mechanical strength, pressure resistance, and chemical and electrochemical corrosion resistance.

2. Sections of the casing pipe are connected firmly to each other using appropriate methods such as clips, threads, or welding, ensuring tightness, concentricity, and stability during use.

Article 9. Drilling Methods

1. Principles for Selecting Drilling Methods

The selection of drilling methods shall comply with the following principles:

a) Fully meeting the geological requirements and construction objectives determined in the project;

b) Being suitable for the characteristics of the strata, types of mineral deposits, geographical and natural topographical conditions of the construction area;

c) Ensuring high construction efficiency, low consumption of materials, labor safety, and environmental protection; ensuring the quality of drilling work, reducing labor intensity, and aiming for optimal economic and social benefits;

d) For core sampling drilling: the core recovery rate must reach at least 80% for rock and 90% for ore. In basic geological surveys, mineral resource surveys, and mineral exploration in areas with very complex geological structures (such as karst caves, quicksand, fault zones...), the minimum core recovery rate for rock and soil is 70%, and for ore, it is 80%, and appropriate geophysical logging methods must be supplemented to ensure comprehensive collection of geological and mineral information.

2. Drilling Methods

a) Rotary Core Drilling (or Sample Drilling):

- For stable rock formations: apply rotary drilling using diamond drill bits or hard alloy drill bits; drilling equipment includes core barrel assemblies, double-tube or single-tube core barrels. Drilling fluid has the following characteristics: specific gravity γ < 1.15 g/cm³; apparent viscosity T = 19 to 21 seconds; water discharge B < 8 cm/30 minutes;³- For soft, loose, weakly bonded rock formations: apply rotary drilling using double-tube core barrels, short core drilling (core length ≤ 1.0 m). Drilling fluid has the following characteristics: specific gravity γ ≥ 1.15 g/cm³; apparent viscosity T = 22 to 25 seconds; water discharge B < 8 cm/30 minutes;³- When drilling through moderately fractured, strongly fractured, faulted, and fractured zones requiring higher core recovery rates: apply rotary drilling using core barrel assemblies or double-tube core barrels with basket stems, combined with short core drilling (core length ≤ 1.0 m). Drilling fluid has the following characteristics: specific gravity γ ≥ 1.15 g/cm³; apparent viscosity T = 25 to 27 seconds; water discharge B < 8 cm/30 minutes;

- b) Percussion Core Drilling:³Applied to clayey, silty clay, sandy clay, and plastic cohesive soils with hardness grades I to III. Use percussion/core drilling with single-tube core barrels equipped with valves. Drilling fluid has the following characteristics: specific gravity γ > 1.15 g/cm³; apparent viscosity T = 22 to 23 seconds; water discharge B < 8 cm/30 minutes;³- When drilling through moderately fractured, strongly fractured, faulted, and fractured zones requiring higher core recovery rates: apply rotary drilling using core barrel assemblies or double-tube core barrels with basket stems, combined with short core drilling (core length ≤ 1.0 m). Drilling fluid has the following characteristics: specific gravity γ ≥ 1.15 g/cm³; apparent viscosity T = 25 to 27 seconds; water discharge B < 8 cm/30 minutes;

c) Hand Auger Drilling:³Applied to weathered rock and soil with hardness grades I to IV. Maximum drilling depth up to 20 m;³- When drilling through moderately fractured, strongly fractured, faulted, and fractured zones requiring higher core recovery rates: apply rotary drilling using core barrel assemblies or double-tube core barrels with basket stems, combined with short core drilling (core length ≤ 1.0 m). Drilling fluid has the following characteristics: specific gravity γ ≥ 1.15 g/cm³; apparent viscosity T = 25 to 27 seconds; water discharge B < 8 cm/30 minutes;

d) Air Percussion Drilling:

Applied to soft, loose rock formations. Use air compressors with stable airflow and high air pressure to break and blow drilling material to the surface.³; apparent viscosity T = 22 ÷ 23 seconds; water discharge B < 8 cm³- When drilling through moderately fractured, strongly fractured, faulted, and fractured zones requiring higher core recovery rates: apply rotary drilling using core barrel assemblies or double-tube core barrels with basket stems, combined with short core drilling (core length ≤ 1.0 m). Drilling fluid has the following characteristics: specific gravity γ ≥ 1.15 g/cm³; apparent viscosity T = 25 to 27 seconds; water discharge B < 8 cm/30 minutes;

c) Hand auger drilling:

Applies to weathered rock with hardness from class I to class IV. The maximum depth of the borehole is up to 20 meters;

d) Air percussion drilling:

Applies to soft, loose strata of soil and rock. Uses air compressors with stable airflow and high air pressure to break and blow drill cuttings to the surface.

Article 10. Drilling Equipment

1. The selection and use of drilling equipment must meet the technical requirements of the project and be suitable for the actual topography, geology, and construction environment.

2. Priority should be given to using advanced technology drilling equipment capable of measuring, recording, and monitoring technical parameters (such as load force, rotational speed, drilling fluid flow rate, pressure, wellbore inclination...) in real-time to enhance construction quality, ensure safe operation, and increase labor productivity.

Article 11. Drilling Construction Preparation Work

1. For each drilling project, a technical construction plan for drilling must be established in accordance with the approved technical design. The model of the technical construction plan for drilling is specified in Appendix I attached to this Circular.

2. Adequate equipment, tools, and technical materials for drilling must be prepared, including drilling machines, drilling tools, construction materials (sample drums, wood, plywood, galvanized iron), drilling house erection equipment, camp facilities, and other construction materials; water sources for drilling construction must also be prepared. For drilling on rivers, seas, and tidal flats, floating platforms or specialized drilling vessels must be used to install the drilling equipment system.

3. New or repair access roads to the drilling site (if necessary) to ensure safety during the transportation of materials and drilling equipment. In difficult construction areas such as swamps or tidal flats, appropriate technical solutions must be applied to stabilize the drilling foundation.

4. Organize the assembly, transportation of machinery, equipment, materials, and personnel to the construction site. Install the drilling tower, drilling equipment, pumps, lighting systems, and camp facilities; install safety equipment; prepare drilling fluid and sample core trays; dig foundation pits for equipment installation, build water storage tanks, drilling fluid pits, circulation channels, and tower foundation pits.

5. Install the water supply system for drilling construction and implement other necessary technical auxiliary measures.

6. Conduct comprehensive checks and evaluations of technical safety conditions before construction starts, including the condition of drilling equipment, electrical systems, anchoring systems, foundation conditions, landslide risks, and other abnormal geological factors. Implement appropriate preventive measures according to regulations.

Article 12. Installation of Equipment

1. Drilling equipment should be reasonably arranged on the drilling site surface to facilitate equipment usage and high-efficiency labor organization while ensuring safety and environmental hygiene.

2. For drilling operations conducted on rivers, seas, or tidal areas, drilling equipment should be designed, manufactured, and installed on drilling platforms or vessels capable of lifting and lowering during construction, ensuring mobility and movement along the drilling route.

3. After completing the equipment installation, conduct a thorough inspection and calibration of the entire system, followed by a trial run to assess operational capability.

Article 13. Installation of Drilling Tower

1. The height of the drilling tower should be selected appropriately based on the depth of the borehole, the type of equipment used, and the required length.

2. If the ground foundation is not stable enough to support the drilling tower, reinforcement measures such as additional beam laying at the base of the tower, concrete foundation pouring, and pile driving for ground reinforcement must be implemented.

3. The assembly and erection of the drilling tower must follow the manufacturer's instructions. After completion of assembly, a comprehensive inspection and calibration of all connections and the tower erection system must be carried out to ensure safety and stability during operation.

4. The drilling tower must be securely braced and equipped with lightning protection systems. Electric motors, drilling machine bases, control panels must be grounded. Lightning protection system installation standards and grounding procedures comply with TCVN 9385:2012 on Lightning Protection for Construction Projects: Design Guidelines, Inspection, and Maintenance Systems.

Article 14. Drilling Machine Placement

1. The drilling machine shall be placed on steel beams, concrete, or wood structures, securely fastened with bolts or clamps. The placement of the drilling machine must ensure balance, correct orientation, and inclination angle according to the design of the drill hole.

2. The orientation and inclination angle of the drill hole shall be inspected and confirmed by geological technical staff before commencing drilling.

Article 15. Drilling Rig Placement

1. The drilling rig shall be placed on a flat, stable, and well-drained drilling surface. Wooden beams at least 7 cm thick shall be laid under the rig's jacks. The wheels shall be securely wedged and fixed.

2. The installation and use of the drilling tower of the drilling rig shall comply with the provisions of Article 13 of this Circular.

Article 16. Drilling Fluids

1. Drilling fluids used in construction projects include mixtures prepared from clay, bentonite powder, or similar materials, processed with chemical additives to ensure technical parameters suitable for the geological conditions of the drill hole.

2. In cases where drilling is conducted in complex geological conditions, if the mixture of clay, bentonite powder, and chemical additives does not meet technical requirements, cement grouting or casing methods shall be applied to isolate and stabilize the drill hole.

3. In cases where drill hole accidents are caused by geological factors such as high-pressure water, collapse, swelling, or narrowing of the drill hole diameter, it is permissible to use drilling fluids with a density greater than 1.3 g/cm³.³.

4. The use of various types of drilling fluids for specific cases shall be designed in the project proposal.

Chapter III

DRILLING CONSTRUCTION AND TECHNICAL TREATMENT

Article 17. Steps for Implementing Drilling Construction Work

1. Drilling to Open Hole

Use a core barrel with a length of 0.3 m to 1.0 m to drill, applying the minimum drilling regime and technical parameters to ensure the centering of the drill hole according to the design. The depth of drilling to open the hole can reach up to 7.0 m, depending on the thickness and characteristics of the overburden layer of the drill hole.

2. Casing Installation

a) Casing installation shall be carried out immediately after completing the drilling to open the hole. The casing shall be reinforced firmly, with the casing foot placed in relatively stable ground layers and securely grouted with cement.

b) In cases where the ground layers below the casing foot are not yet stable enough for casing installation, temporary casing installation shall be performed, followed by continued drilling until reaching a stable ground layer to install new casing and perform formal casing installation.

c) For drilling operations on rivers, seas, or tidal flats, casing installation shall be carried out from the drilling platform or drilling vessel to the stable and solid ground layers.

3. Drilling

a) In cases where the geological strata consist of soft rock or weakly bonded material with hardness levels I to IV according to the rock classification table for drilling work, rotary drilling using a double-tube core barrel with non-rotating inner tube, using alloy drill bits, and short rotary drilling method shall be applied. The drilling regime shall be as follows:

b) In cases where the geological strata consist of soft, pliable material difficult to sample, rotary drilling using a core barrel with a valve or using a bucket-type or spoon-type drilling tool shall be applied. The length of each drilling stage shall not exceed 1.0 m.

c) In cases where the geological strata have medium to hard hardness (levels V to VII according to the rock classification table for drilling work), with few to severe fractures, weathering, or tectonic destruction zones making sampling difficult, one of the following methods shall be applied: rotary drilling using a single-tube core barrel; rotary drilling using a double-tube core barrel with non-rotating inner tube, or rotary drilling using a jetting core barrel. The drilling regime shall be as follows:

d) In cases where the geological strata are stable and hard with hardness levels VIII to XII according to the rock classification table for drilling work, rotary drilling using a double-tube core barrel with non-rotating inner tube or single-tube core barrel shall be applied. The drill bit used shall be diamond drill bits. The drilling regime shall be as follows:

e) Enlarging the diameter of the drill hole, using a reaming core barrel equipped with a centering device. The drilling regime shall be as follows:

4. Depending on the objectives, geological conditions, and available technology, the construction unit may apply advanced drilling technologies such as automatic control drilling, directional drilling, real-time measurement systems, and digital support technologies to enhance construction efficiency, ensure safety, and quality of the drill hole.

5. Core Sampling After Each Drilling Stage:

a) For rotary drilling using a single-tube core barrel: when drilling through uniform geological strata, after completing the drilling stage, clean the drill hole by pumping; use quartz sand or gravel particles with sizes from 1.0 mm to 2.0 mm to retain the core sample; lift the entire drill string and core barrel to the surface; remove the core from the core barrel, place it on a tray, clean, and arrange the samples in the sample container in order; describe the samples and label them.

b) For rotary drilling using a double-tube core barrel: after completing the drilling stage, clean the drill hole by pumping, lift the entire drill string and core barrel to the surface; remove the core from the core barrel, place it on a tray, clean, and arrange the samples in the sample container in order; describe the samples and label them.

c) For rotary drilling using a single-tube core barrel with a liner: after completing the drilling stage, clean the drill hole by pumping, use a specialized cable grabber to retrieve the inner core barrel; lift the inner core barrel and core sample to the surface; remove the core from the core barrel, place it on a tray, clean, and arrange the samples in the sample container in order; describe the samples and label them.

d) When drilling within the section from 10 m to 20 m above the anticipated mineral body, limit long drilling stages while frequently monitoring technical parameters such as drilling speed, pump pressure, weight indicator readings, characteristics of the drilling fluid, etc., to promptly detect mineral seams.

d) When encountering mineral bodies, the following preparatory works shall be carried out: stop drilling construction; carry out cleaning pumping of the drill hole and collect all drill cuttings; conduct inspection and measurement of the depth of the drill hole and organize drilling to take mineral body samples; at the same time, prepare all necessary tools for sample collection work.

e) The selection of sampling tools must be suitable for the characteristics of soil and rock and minerals as follows: for solid rocks and minerals with few cracks, little damage from water flow and vibration, double-tube samplers should be used; for rocks and minerals with strong cracking, brittle, easily fragmented, loose, reverse circulation drilling methods or core barrel samplers should be used; for easily soluble minerals (such as salt deposits), non-pumping drilling methods or single-tube samplers with corresponding saturated brine solutions should be used; for soft soils and rocks that are easily fragmented and eroded (such as sand, loose sandstone, coal dust, clay, etc.), non-pumping drilling methods, double-tube samplers with stationary inner tubes or reverse circulation samplers should be used.

g) To improve the sampling rate, the following measures shall be applied: reduce the drilling time in each interval (shorten the drilling interval to 0.5 m to 1.0 m); decrease the speed of the flushing fluid passing through the sample using reverse flushing pumps; use drilling equipment with centering devices, alloy or diamond drill bits suitable for the mechanical properties of the rock (or mineral); securely pack the sample, gently pull the sample, avoid hitting or sudden changes in speed; use valves to isolate the sample from the drill column water when pulling the tool up.

h) During sampling, it is necessary to ensure the preservation of the original form of the sample, arrange the samples in natural order, clean and store them according to the prescribed regulations.

6. Monitoring, describing, recording, and compiling materials during drilling

a) Data and information collected during drilling shall be fully and promptly recorded in the drilling logbook according to the format specified in Appendix II issued together with this Circular. Core samples shall be photographed comprehensively and clearly during construction. Throughout the drilling process, geological technical staff must be present on-site regularly to monitor and describe, compile geological and mineral materials according to technical regulations.

b) Based on the data and information collected during drilling, it is necessary to conduct synthesis and analysis to timely propose adjustments to technical methods and drilling regimes appropriate to the actual conditions of the drill hole.

Article 18. Technical Requirements for Drill Hole Pipe Support

1. Determination of the position, length of the support pipe column, diameter of the support pipe, method of pipe support, and diameter of the backup support pipe must be based on the design and actual geological conditions of the drill hole. The final diameter of the support pipe must be at least one size larger than the drill hole diameter. The bottom of the support pipe must be placed in a stable, solid rock layer.

2. In cases where the bottom of the support pipe is placed in a fractured, loose, weakly bonded, or alternating hard and soft rock layer, diamond support pipe bases and cement grouting must be used to ensure the stability of the support pipe column and prevent it from sinking during drilling.

3. Before implementing pipe support, the drill hole must be thoroughly cleaned by pumping to ensure the designed length of the support pipe column.

4. Prior to pipe support, the diameter and concentricity of the drill hole must be checked; the quantity and quality of the support pipes must be inspected; at the same time, the operational status of the drilling equipment, derrick, and hoisting system must be checked.

5. The sections of the support pipe must be numbered and arranged in the correct structural sequence from bottom to top.

6. The sections of the support pipe must be connected at the mouth of the drill hole during pipe support and ensure concentricity. The connections must be tight and secure.

7. During the lowering of the support pipe column, if obstructions occur, external force must not be used to push the pipe column down. The support pipe column must be pulled up and appropriate measures taken to resolve issues within the drill hole. Lowering of the pipe can only continue once the drill hole is completely unobstructed.

8. The technique for supporting pipes for drill holes serving exploration, evaluation, and geothermal water survey is implemented according to the provisions of Clause 5, Article 9 of Circular No. 59/2015/TT-BTNMT dated December 14, 2015, issued by the Minister of Natural Resources and Environment on drilling techniques for underground water exploration, evaluation, and survey.

Article 19. Prevention and Handling of Incidents

1. Prevention of Incidents

a) When formulating technical construction drilling plans, it is necessary to assess the types of incidents that may occur under specific geological-technical conditions and to anticipate corresponding preventive and remedial measures;

b) Preparatory work before construction must adequately stockpile technical materials and necessary conditions to be able to promptly and effectively implement rescue measures when incidents occur;

c) During the construction process, comply with procedures and regulations stipulated in this Circular; use appropriate drilling equipment and technology; allocate personnel to meet all current technical standards, specifications, and regulations.

2. Rescue and Treatment of Incidents

a) Upon occurrence of an incident, the drilling monitoring technical staff must promptly cooperate with the drilling team to record the incident, determine its cause, and implement rescue measures according to the technical procedures specified in the approved design;

b) During the incident rescue process, all information related to the incident and the measures taken to address it must be accurately and timely recorded in the drilling logbook;

c) After completing the incident rescue work, the construction unit shall conduct inspections, handle, and rectify the entire system of machinery and equipment, as well as the condition of the drill hole, ensuring technical conditions before continuing construction;

d) For offshore and tidal flat drilling machines, if the drilling rig's support foot sinks or tilts during drilling, drilling must be stopped for inspection. In cases of slight sinking without further complications, the rig can be adjusted and raised to balance and continue drilling. In cases of significant sinking (exceeding 0.5 m), lower the rig and move the drilling location to a nearby area with more stable ground.

Article 20. Requirements for Measuring Drill Hole Deviation and Allowable Azimuth Errors

1. For vertical drill holes deeper than 100 meters and inclined or horizontal drill holes, azimuth and deviation measurements must be conducted every 10 to 20 meters.

2. For inclined and horizontal drill holes, upon completion of construction, the allowable azimuth error of the drill hole is from 1° to 2°.

Article 21. Backfilling Drill Holes

1. Backfilling of drill holes is carried out after the completion of geological research within the drill hole. The backfilling plan and materials must comply with resource protection regulations, ensure safety, and economic efficiency, as reflected in the construction project proposal. If the drill hole is not backfilled for other purposes as proposed, measures to protect underground water sources must be implemented according to legal provisions.

2. After backfilling the drill hole, set up markers indicating the drill hole number, depth, start date, and end date of drilling.

3. Upon completion of the final drill hole work, prepare the final drilling project completion report according to Model No. 09, Appendix III issued along with this Circular.

Article 22. Completion of Drilling Construction

1. Completion of drilling construction can only be carried out after fully meeting all technical requirements as specified in the design.

2. Contents of the completion of drilling construction work

a) Collect geological and mineral information; take various samples; photograph core samples; determine and mark the drill hole;

b) The actual coordinates of the drill hole are determined using the geodetic method specified in the approved project proposal;

c) Prepare the final drilling project completion report according to Model No. 09, Appendix III, and prepare the drilling machine project acceptance report according to Model No. 06, Appendix III, issued along with this Circular;

d) Implement drill hole backfilling or non-backfilling as required by the project proposal; properly mark the drill hole according to regulations;

đ) Transport core samples to the project storage facility; establish and complete the official documentation of the drill hole;

e) Dismantle and transport machinery, equipment, and materials out of the construction site; simultaneously implement comprehensive safety measures for the area after construction completion, including: clearing materials, placing warning signs at hazardous locations, and restoring the site to its original state according to environmental and labor safety regulations.

Article 23. Occupational Safety

Occupational safety work during drilling construction shall comply with the provisions of the law on occupational safety and the following requirements:

1. Workers directly working at the construction site must meet the job title standards appropriate to their tasks, be fully equipped with knowledge on safety and labor protection as prescribed.

2. Machinery systems, equipment, and drilling towers must be installed, operated, maintained, and repaired according to technical requirements and regular schedules as prescribed. Drive components must be installed with protective barriers. Drill pipes and drilling tools must be regularly inspected to ensure safety during construction.

3. At the construction site, sufficient warning signs, safety rules, entry and exit regulations, work rules, and warning signs at dangerous locations must be arranged; security guards must be assigned as prescribed.

4. For drilling operations on the sea and tidal flats:

a) Drilling platforms must not be moved, erected, or lifted when wave height exceeds level 3 or at night (except in special cases to avoid typhoons and storms, accompanied by detailed plans). Drilling must not be conducted under conditions of thunderstorms or strong winds exceeding level 5;

b) Life-saving, firefighting, and communication equipment (such as personal life jackets, life buoys, rubber boats or inflatable rafts, dry powder fire extinguishers, gas fire extinguishers, etc.) must always be checked, maintained, and kept in a ready-to-use state;

c) Ships must not be moored directly to the drilling platform. Supply ships and tugboats must limit approaching the drilling platform when wave height exceeds 0.4 meters; in necessary cases, small boats must be used to approach the drilling platform to ensure safety;

d) A complete system of signaling lights and warning lights for the drilling construction area must be arranged; patrol boats must be deployed to monitor and protect the drilling platform throughout the construction process. Patrol boats must conduct slow rounds around the drilling platform every two hours, from one to two rounds at distances ranging from 50 meters to 100 meters, to assist safety officers in observing the condition of the drilling platform and promptly warn watercraft and fishing vessels not to approach the drilling area;

e) Throughout the marine drilling construction process, communication between shore support bases and the drilling platform, and between the drilling platform and service vessels must be ensured. At the shore support base, a continuous radio maritime transmitter-receiver must be arranged to maintain communication with walkie-talkies on service vessels. On the drilling platform, at least one loudspeaker and one to two walkie-talkies must be provided to ensure effective communication with the support base, service vessels, and vessels operating in the construction area.

Article 24. Environmental Sanitation

Environmental sanitation work during drilling construction shall comply with the provisions of the law on environmental protection and the following requirements:

1. Materials, fuel oil, lubricants, and other chemicals must be stored and preserved safely to prevent leakage that could cause environmental pollution.

2. After completion of construction, the construction unit must organize the collection of all materials and equipment, leveling, and restoration of the construction site.

3. Protection of underground water sources during drilling construction shall be carried out in accordance with Clause 3 of Chapter IV of Circular No. 03/2024/TT-BTNMT dated May 16, 2024, issued by the Minister of Natural Resources and Environment detailing the implementation of certain provisions of the Water Resources Law.

Chapter IV

DOCUMENTS AND PRODUCTS OF DRILLING WORK COMPLETION AND FINALIZATION

Article 25. Editing documents and completing records

1. Data and information collected during each drilling shift, including drilling progress, core sample recovery rate, and unusual phenomena occurring during construction, must be promptly updated at the site.

2. Upon completion of the drilling project, all documents collected during the drilling process shall be edited to complete the drilling project record according to the Model prescribed in Appendix III issued together with this Circular.

3. The consolidation and editing of geological and mineral resource documents shall be carried out in accordance with the provisions of Article 12 of Circular No. 43/2016/TT-BTNMT dated December 26, 2016, issued by the Minister of Natural Resources and Environment on technical regulations for collecting and establishing original documents in basic geological surveys and mineral exploration.

Article 26. Drilling work products

1. Completed drill holes that meet the technical requirements specified in the design and current regulations.

2. Core samples or drill cuttings (if necessary).

3. Technical documents as stipulated in Appendices I, II, and III issued together with this Circular.

4. Drilling project diagrams as prescribed in Circular No. 43/2016/TT-BTNMT dated December 26, 2016.

Article 27. Digitization of Original Documents

1. Original documents of the drilling construction work shall be established in digital form, ensuring full and accurate representation of information as prescribed in Circular No. 43/2016/TT-BTNMT dated December 26, 2016.

2. Tools, software, and applications used for digitizing and storing digital documents must ensure information security and confidentiality.

3. Digital information and data shall be stored and updated on storage devices of organizations and individuals assigned to perform tasks in accordance with the regulations.

4. In cases where necessary, printed copies of updated and stored digital records may be made from the database system.

Chapter V

IMPLEMENTING PROVISIONS

Article 28. Effective Date

1. This Circular takes effect from October 3, 2025.

2. In case the legal normative documents cited for application in this Circular are amended, supplemented, or replaced, they shall be implemented in accordance with the provisions of the amended, supplemented, or replacing documents.

Article 29. Implementation Organization

1. The Director of the Ministry's Office, heads of agencies, organizations, and individuals specified in Article 1 are responsible for implementing this Circular.

2. During implementation, if there are difficulties or obstacles, they should be reported to the Ministry of Agriculture and Rural Development for timely consideration and resolution./.