NB/T 35066-2015Specification of overburden drilling techniques for hydropower projects (English PDF)

Foreword

This document was issued on 27 October 2015 by the National Energy Administration of the PRC and takes effect on 1 March 2016.

It is a NB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

It is classified under ICS 27.140, Chinese classification P 59.

This specification was compiled in accordance with the requirements of the Notice of the National Energy Administration on Issuing the First Batch of the 2013 Plan for Formulating and Revising Industry Standards in the Energy Field, Guo Neng Ke Ji [2013] No. 235.

The drafting group carried out extensive investigation and research, summarised practical experience, referred to the relevant domestic standards and prepared this specification on the basis of a wide solicitation of comments.

The main technical contents of this specification are: preparation work; drilling methods; drilling fluid and hole wall protection and loss shut-off; coring and sampling; experiment and test; drilling quality.

This specification is administered by the National Energy Administration.

It is proposed by, and placed under day-to-day administration by, the Hydropower and Water Resources Planning and Design General Institute; the Energy Industry Standardization Technical Committee for Hydropower Investigation and Design is responsible for the interpretation of the specific technical content.

Comments and suggestions arising during implementation should be sent to the Hydropower and Water Resources Planning and Design General Institute, No. 2 Liupukang Beixiaojie, Xicheng District, Beijing, postcode 100120.

The chief drafting organisations are PowerChina Chengdu Engineering Corporation Limited and Chengdu Water Conservancy and Hydropower Construction Co., Ltd.

The foreword lists twelve principal drafters and twenty-two principal reviewers by name.

Publication data

NB/T 35066-2015, Specification of overburden drilling techniques for hydropower projects, is an energy industry standard of the People's Republic of China issued by the National Energy Administration.

The cover carries the classification data ICS 27.140 and the Chinese standard classification code P 59, together with the filing (record) number 52245-2015.

The standard was issued on 27 October 2015 and came into force on 1 March 2016, as printed on the lower part of the cover.

No superseded document is named on the cover: this specification is a first edition and does not replace an earlier code.

The title page names the Hydropower and Water Resources Planning and Design General Institute as the department in charge of compilation and the National Energy Administration as the approving department, and repeats 1 March 2016 as the date of entry into force.

The volume was published by China Electric Power Press, Beijing, in 2016.

Announcement No. 6 of 2015 of the National Energy Administration, dated 27 October 2015, approved 96 energy industry standards (NB) under the rules of the Notice on Issuing the Administrative Measures for Standardization in the Energy Field (Trial) and its implementing rules, Guo Neng Ju Ke Ji [2009] No. 52.

In the attached catalogue of industry standards this specification is item 39; the catalogue entry confirms the approval date 2015-10-27 and the implementation date 2016-03-01 and leaves the columns for the replaced standard and for the adopted standard empty.

Structure of the document

The specification is organised in eight chapters followed by two appendices and three closing parts; the wording used below is that of the official English contents page bound with the Chinese text.

Chapter 1, General provisions, begins on page 1; Chapter 2, Terms, on page 2.

Chapter 3, Preparation work, begins on page 3 and is divided into 3.1 Technical preparation (page 3) and 3.2 Site preparation (page 4).

Chapter 4, Drilling methods, begins on page 6 and contains five sections: 4.1 Tungsten-carbide drilling (page 6), 4.2 Diamond drilling (page 8), 4.3 Pneumatic DTH hammer core drilling with casing (page 9), 4.4 Wire-line core drilling (page 10) and 4.5 Tubular drilling (page 11).

Chapter 5, Drilling fluid and hole wall protection and loss shut-off, begins on page 14 and contains 5.1 Drilling fluid (page 14) and 5.2 Hole wall protection and loss shut-off (page 17).

Chapter 6, Coring and sampling, begins on page 21 and contains 6.1 Coring (page 21), 6.2 Sampling (page 22) and 6.3 Core logging and storaging and transportating (page 25), the heading of 6.3 being reproduced here exactly as printed in the official contents.

Chapter 7, Experiment and test, begins on page 27 and contains 7.1 Hydrogeological test and 7.2 In situ test, both starting on page 27.

Chapter 8, Drilling quality, begins on page 28 and contains 8.1 Evaluation project of the drilling quality (page 28) and 8.2 Drilling quality assessment (page 29).

Appendix A, Overburden drilling method, is on page 32 and Appendix B, Cover borehole structure design, on page 33.

The closing parts are Explanation of wording in this specification (page 34), List of normative standards (page 35) and the appended Explanation of provisions, which starts on page 37.

The Chinese contents pages and the English contents pages agree item by item and give the same page numbers throughout.

1 Scope

NB/T 35066-2015 governs drilling through overburden on hydropower projects - the loose alluvium, glacial deposits, talus and fill that sit between the surface and the bedrock, which in the deep valleys of western China can be a hundred metres or more thick. Drilling through such ground without disturbing it is genuinely difficult: the hole collapses, the core washes away, and a sample recovered carelessly tells the designer nothing about the density and grading that actually govern the foundation. The specification sets the general provisions and defined terms, then the basic requirements on planning a borehole, the equipment and the drilling fluids, and the qualifications of the crew. It covers the drilling methods in turn - percussion and rotary drilling, casing advance and follow, single, double and triple tube core barrels, diamond drilling, and the wireline and sonic techniques used where recovery matters most - with the parameters and the precautions for each in sand, gravel, boulder and mixed ground. Core recovery, logging, photography, storage and transport are treated in detail, since the core is the product. Borehole deviation, water level observation, hole stabilisation and grouting, and the backfilling of the hole on completion are specified, as are the quality evaluation criteria for a completed borehole and the records and report that accompany it.

1.0.1 This specification is formulated in order to standardise the overburden investigation drilling work of hydropower projects, to define the work content, the methods and the technical requirements, to ensure the quality of the drilling exploration and to meet the needs of engineering geological evaluation.

1.0.2 This specification applies to overburden investigation drilling for hydropower projects; it may also be applied to overburden investigation drilling for renewable energy projects such as wind power and solar power.

1.0.3 The overburden drilling method shall be determined after comprehensive analysis and comparison, on the basis of factors such as the purpose of the borehole, the category of the overburden and the construction conditions.

1.0.4 In addition to complying with this specification, overburden investigation drilling for hydropower projects shall also comply with the provisions of the relevant current national standards.

Chapter 1 occupies page 1 of the printed text and consists of these four clauses only.

2 Terms

Chapter 2 defines two terms; each entry gives the Chinese headword, the official English equivalent and the definition.

2.0.1 Overburden drilling: the operation of drilling into the overburden with a drill bit or by other means so as to form a borehole and to obtain geological information, with the aim of ascertaining the underground resources and the condition of the overburden.

2.0.2 Hole wall protection: the operation of protecting and stabilising the wall of the borehole.

The English equivalents printed beside the Chinese headwords are 'overburden drilling' for 2.0.1 and 'hole wall protection' for 2.0.2; no further terms are defined and the chapter occupies page 2 only.

3 Preparation work

3.1.1 The drilling method may be selected in accordance with Appendix A of this specification and shall meet the following requirements.

3.1.1-1 It shall suit the natural geographical conditions of the working area.

3.1.1-2 It shall satisfy the requirements of the borehole task statement.

3.1.2 The hole structure may be designed in accordance with Appendix B of this specification and shall meet the following requirements.

3.1.2-1 The final hole diameter shall be determined according to the stratum conditions and the geological requirements.

3.1.2-2 The opening diameter, the number of diameter changes and the depths at which the diameter is changed shall be determined rationally according to factors such as the design depth of the borehole, the drilling method and the hole wall protection measures.

3.1.3 The selection of the drilling fluid and of the measures for hole wall protection and loss shut-off shall meet the following requirements.

3.1.3-1 The type of drilling fluid and its method of preparation shall be selected according to the different strata and to the requirements of the hydrogeological tests.

3.1.3-2 The drilling fluid system shall be suitable and rational.

3.1.3-3 The measures for hole wall protection and loss shut-off shall be feasible.

3.1.4 The selection of drilling equipment shall meet the following requirements.

3.1.4-1 The drilling rig shall suit the drilling method, the hole depth, the hole diameter, the natural environment and the site conditions.

3.1.4-2 The pump shall match the drilling method, the type of drilling fluid, the hole depth and the hole diameter.

3.1.4-3 The power equipment shall suit the natural environment and the site conditions and shall match the drilling rig, the pump and the ancillary equipment.

3.1.4-4 The derrick shall suit the depth of the borehole, the maximum hoisting load and the site conditions.

3.1.5 Safety and environmental protection measures shall meet the following requirements.

3.1.5-1 Safety management measures shall be drawn up so as to satisfy the requirements for prevention of collapse, prevention of caving, prevention of slipping, flood prevention and fire prevention.

3.1.5-2 Environmental protection measures shall be drawn up so as to satisfy the requirements for the discharge of drilling waste.

3.1.6 The technical briefing shall meet the following requirements.

3.1.6-1 The purpose and the requirements of the drilling exploration shall be made clear.

3.1.6-2 The hole structure, the difficult points, the key points, the time schedule and the quality requirements shall be made clear.

3.1.6-3 The key points of safety protection and of environmental protection shall be made clear.

3.1.6-4 The geological engineer, the person in charge of the drilling and the driller shall take part in the technical briefing, and corresponding records shall be formed.

3.2.1 In addition to complying with the relevant provisions of DL/T 5013, Code for drilling of hydropower and water resources engineering, the construction of the access road shall include safety warning signs at dangerous sections such as steep slopes and cliffs.

3.2.2 In addition to complying with the relevant provisions of DL/T 5013, Code for drilling of hydropower and water resources engineering, the layout of the drilling site shall comply with the following.

3.2.2-1 The area of the drilling site should not be less than 6 m by 12 m.

3.2.2-2 The foundation of the drilling site shall be firm and stable.

3.2.3 The construction of the drilling site shall comply with the following.

3.2.3-1 A drilling site on water shall have a reliable structure, a suitable area and a regular layout; it shall be fully decked with timber boards 40 mm to 50 mm thick, surrounded by safety railings not lower than 1.2 m, and provided with sufficient life-saving and fire-fighting facilities.

3.2.3-2 Where the drilling site is located on a river flood plain, a pipe or timber truss platform may be used and protective measures shall be taken.

3.2.3-3 Where the drilling site is located on a landslide body, interception ditches and drainage ditches shall be provided.

3.2.3-4 Where the drilling site is located on a slope, the filled part shall not be greater than one third of the area of the foundation, measures against collapse shall be taken and a pipe or timber truss platform may be used.

3.2.3-5 Where the drilling site is located below a cliff, the dangerous rocks on the cliff shall be removed or protective measures shall be taken.

3.2.3-6 Where the drilling site is located in a gully or channel, measures against floods, against debris flows and against collapse shall be taken.

3.2.4 Temporary building facilities shall meet the following requirements.

3.2.4-1 Production and living quarters should be built according to the volume of drilling work and in combination with the natural geographical conditions of the site.

3.2.4-2 The construction of temporary building facilities is forbidden in areas affected by natural hazards such as floods, landslides, debris flows, flying rock, collapse and lightning.

3.2.5 Blasting operations shall comply with the relevant provisions of GB 6722, Safety regulations for blasting.

3.2.6 Safe production and environmental protection shall comply with the relevant provisions of DL/T 5013, Code for drilling of hydropower and water resources engineering.

4 Drilling methods

4.1.1 Tungsten-carbide drilling may be used in soil, sand, sandy gravel and sandy cobble layers and in part of the layers of large boulders, cobbles and gravel; it may also be used in landslide bodies and in some collapse bodies, accumulation bodies and other open-framework layers.

4.1.2 The manufacture and use of tungsten-carbide bits shall comply with the following provisions.

4.1.2-1 The bit body may be made of steel of grade R780, P110 or DZ40, with a wall thickness greater than 7.0 mm.

4.1.2-2 The type of bit may be determined according to the category of overburden in accordance with Table 4.1.2-1.

Table 4.1.2-1, suitability of bit type to overburden category, gives: rib bits for soil, sand, loose sandy gravel and loose sandy cobbles; thin-blade bits for soft soil, expansive soil, loess and sand; single-grain and double-grain bits for hard soil, frozen soil, sandy gravel, sandy cobbles and landslide bodies; plough-type close-set bits and large octagonal bits for hard soil, frozen soil, sandy gravel, sandy cobbles, large boulder and cobble gravel, landslide bodies, collapse bodies and accumulation bodies; double-edge bits for hard soil, frozen soil, sandy gravel and sandy cobbles; needle-shaped bits for sandy gravel and sandy cobbles.

4.1.2-3 The grade of the carbide may be determined according to the type of bit in accordance with Table 4.1.2-2.

Table 4.1.2-2, matching of carbide grade to bit type, gives: rib bits, grades T105, T107 and T310; thin-blade bits, T010 and T412; single-grain and double-grain bits, T105 and T310; plough-type close-set bits, T105, T107 and T313; large octagonal bits, T110; double-edge bits, T107; needle-shaped bits, matrix blocks and T220.

4.1.2-4 The number of carbide inserts brazed into the bit may be determined according to the bit diameter in accordance with Table 4.1.2-3.

Table 4.1.2-3, number of brazed carbide inserts against bit diameter, gives 9 to 12 inserts for a bit diameter of 75 mm, 12 to 14 for 91 mm, 13 to 15 for 110 mm, 14 to 16 for 130 mm, 16 to 18 for 150 mm, 21 to 24 for 172 mm and 26 to 30 for 223 mm.

4.1.2-5 The inner and outer cutting edges formed by the brazed carbide shall be symmetrical and consistent, and the inner edge of a rib bit shall be enlarged by 3 mm.

4.1.2-6 The height of the water port at the lip shall be 10.0 mm to 25.0 mm.

4.1.2-7 A clearance of 0.1 mm to 0.2 mm shall be left between the slot in the bit body and the carbide insert, and the clearance shall be completely filled with brazing material.

4.1.2-8 A new bit shall be lowered to a point at least 0.5 m above the bottom of the hole and then rotated slowly to ream down to the bottom.

4.1.2-9 The wear of the bit shall be inspected at every trip out of the hole.

4.1.3 The selection and use of the drilling tools shall comply with the following provisions.

4.1.3-1 The type of drilling tool shall match the category of the overburden and the coring requirements.

4.1.3-2 The length of the drilling tool should not be greater than 3.0 m.

4.1.3-3 A suitable way of catching the core shall be selected.

4.1.3-4 A single-action double-tube core barrel should be selected for landslide bodies.

4.1.3-5 Chain tongs or free tongs shall be used to make up and break out the drilling tools; pipe wrenches shall not be used.

4.1.3-6 The drilling tools shall be dismantled and oiled at regular intervals.

4.1.3-7 Drilling tools shall be replaced in good time when they are badly worn or when the threads are damaged; deformed or cracked inner tubes and outer tubes shall not be used.

4.1.3-8 The single-action double-tube core barrel shall keep its single-action performance in good order, and the distance between the bottom end of the core-lifter seat and the inner shoulder of the bit should be 2 mm to 5 mm.

4.1.3-9 When the core is pushed out, the inner tube shall be tapped with a rubber hammer or a wooden mallet.

4.1.3-10 Drilling tools shall not be thrown down, and squeezing and knocking shall be prevented during transport.

4.1.4 The drilling process parameters may be determined according to the hole diameter in accordance with Table 4.1.4.

Table 4.1.4, drilling process parameters, gives for a hole diameter of 75 mm a bit load of 2.4 kN to 6.0 kN, a rotary speed of 65 r/min to 250 r/min and a pump rate of 20 L/min to 80 L/min.

For a hole diameter of 91 mm Table 4.1.4 gives a bit load of 2.7 kN to 7.2 kN, a rotary speed of 65 r/min to 220 r/min and a pump rate of 25 L/min to 80 L/min.

For a hole diameter of 110 mm Table 4.1.4 gives a bit load of 3.6 kN to 8.4 kN, a rotary speed of 65 r/min to 180 r/min and a pump rate of 30 L/min to 90 L/min.

For a hole diameter of 130 mm Table 4.1.4 gives a bit load of 4.2 kN to 9.6 kN, a rotary speed of 65 r/min to 180 r/min and a pump rate of 30 L/min to 100 L/min.

For a hole diameter of 150 mm Table 4.1.4 gives a bit load of 4.8 kN to 10.8 kN, a rotary speed of 65 r/min to 130 r/min and a pump rate of 30 L/min to 100 L/min.

4.1.5 Drilling shall comply with the following provisions.

4.1.5-1 The performance of the drilling tools shall be checked before running in, and for a single-action double-tube barrel the single action shall be checked.

4.1.5-2 The tools shall be run in smoothly and shall not be lowered directly to the bottom of the hole.

4.1.5-3 After running in, the hole shall be reamed to the bottom at low speed and light load, and the parameters shall then be adjusted gradually to the normal drilling values.

4.1.5-4 A uniform bit load and a suitable pump rate shall be maintained.

4.1.5-5 The rate of penetration and the footage per run shall be controlled rationally.

4.1.5-6 If the core drops off, fishing shall be carried out immediately.

4.1.5-7 The tools shall be pulled out of the hole smoothly.

4.1.5-8 Drilling fluid may be poured back into the hole when necessary.

4.2.1 Diamond drilling may be used for all types of overburden.

Section 4.2 continues beyond page 8 of the printed text, and sections 4.3 Pneumatic DTH hammer core drilling with casing, 4.4 Wire-line core drilling and 4.5 Tubular drilling follow on pages 9 to 13; their clauses are not reproduced here.