STUDY ON THE RESONABLE HORIZONTAL DRILLING TECHNOLOGY TO RECOVER METHANE GAS IN MAO KHE UNDERGROUND COAL MINE

Along with the application of traditional methods of ventilation to reduce the concentration of methane gas in the mine to a safe level; Mao Khe mine has also started to apply the method

MINISTRY OF EDUCATION AND TRAINING

HANOI UNIVERSITY OF MINING AND GEOLOGY

Nguyen Tran Tuan

STUDY ON THE RESONABLE HORIZONTAL DRILLING TECHNOLOGY TO RECOVER METHANE GAS IN MAO KHE UNDERGROUND COAL MINE

Major: Petroleum Engineering Code: 62.52.06.04

SUMMARY OF DOCTORAL THESIS IN ENGINEERING

HANOI - 2014

The research has been accomplished at Department of Drilling and Production, Faculty of Oil and Gas,

Hanoi University of Mining and Geology

Supervisors:

1 Assoc.Prof Dr Tran Dinh Kien

2 Dr Nguyen Xuan Thao

Examiner 1: Assoc.Prof.Dr Truong Bien

Vietnam Aschnology

Examiner 2: Dr Khuou Huu Bo

University of Transport and Communications

Examiner 3: Dr Nguyen Xuan Toan

Vietnam National Oil and Gas Group

This thesis is going to be defended at the committee of doctorate thesis examiners of Hanoi University of

Mining and Geology on date month year 2014

This thesis can be found at Hanoi National Library or Library of Hanoi University of Mining and Geology

Introduction

1 The necessity of thesis

In recent years, a number of mines in Quang Ninh has occurred the large gas explosion causing percussionage to people and property such as Mao Khe Coal Company in 1999 which killed 19 people, two consecutive gas explosion at Khe Cham II coal Enterprise and 909 coal exploitation Enterprise in 2002 that killed 13 people March 2006, the Thong Nhat coal Company had happened coal methane explosion that killed 8 people and the most recent gas explosion at Khe Cham Coal Company December 9, 2008 in which there were 11 deaths

Along with the application of traditional methods of ventilation to reduce the concentration of methane gas in the mine to

a safe level; Mao Khe mine has also started to apply the methods of drilling boreholes in different directions to remove methane in the coal seams in the mining production areas as well as in cover stone

In fact, drilling long horizontal boreholes are low effect and it is not reach to the design length, the reasons are mainly due to lack of choice of drilling method and drilling technology which is suitable with the purpose of removing mine methane Therefore, the study in the choice of drilling method, appropriate horizontal drilling technology to remove gas through the boreholes in Mao Khe mine in accordance with the geological and exploitation conditions in the mine to ensure the safety of Mao Khe, pollution reduction is needed with scientific and practical to meet the production demand of Mao Khe mine in particularly as well as in other mines in Vietnam

2 The purpose of this study

The study is the research in methods and choice of horizontal drilling technology to remove methane in Mao Khe mine

to ensure safety in production operating The results of this study will be scientific and practical basic application in remove gas in other coal mine in Vietnam

3 The objects and margin for research

- The object of study: selection in horizontal drilling technology of rotary – percussion drilling equipment RPD-130SL-F2W and the kits of sample threading drilling PS-89 to drill horizontal boreholes for removing gas in accordance with geological and exploitation conditions in Mao Khe coal mine

- The sphere of study: study in the characterization of horizontal drilling technology; rotary – percussion drilling technology in the geological conditions of the Mao Khe coal mine, the influence of these technologies to drilling rate

4 Detail of the study

- Study from the technical documents which relate to global and domestic drilling for remove gas

- Study on the characterizations of horizontal and rotary – percussion by sample threading drilling technology for horizontal boreholes for methane removing in coal pit mines

- Testing of rotary – percussion drilling of horizontal boreholes in actual conditions of the Mao Khe mine

Base on the theoretical and testing results to select the appropriate value of parameters in horizaontal rotary – percussion drilling for methane removing as well as define the efficiency of this method in the Mao Khe coal mine

- Application of statistical mathematic methods to analysis the actual monitoring data for selection of appropriate horizontal drilling technology

6 Scientific and practical meaning

- Scientific meaning: The study on application of rotary – percussion drilling technology using RPD -130SL – F2W drilling equipment and the kit of sample threading drilling tool PS -89 to drilling horizontal boreholes for gas off in Mao Khe coal mine is not only overcome the disadvantages of rotary drilling methods but also improve the drilling rate and the gas removable The results are the scientific basic as well as justification for the selection of gas removing technology in coal pit mine in Quang Ninh

- Practical meaning: the selection of appropriate drilling parameters in horizontal drilling using RPD – 130SL – F2W and PS – 89 for in Mao Khe mine that increase the efficiency of rotary drilling and gas removing are necessary and respond promptly to the current demand in methane remove

7 The new conclusion of thesis

The study proposed the application of horizontal drilling technology to remove methane in pit coal mines in Mao Khe by rotary – percussion drilling method and sample threading pipe drilling technology instead of conventional rotary drilling

Experiment in production conditions, selection of reasonable the rotary – percussion drilling parameters to drill horizontal boreholes for removing methane in Mao Khe mining conditions

8 The protective contentions

- Application of rotary - percussion drilling technology by RPD-130SL-F2W and kits of sample threading drilling pipe PS-89 to remove gas from horizontal boreholes in Mao Khe mine is reasonable and it is suitable with the geological conditions as well as the current demand of gas removed

- Horizontal drilling with rotary – percussion drilling equipment - RPD-130SL-F2W and kits of sample threading drilling pipe PS-89 has the average speed of a mechanical increasing from 1.45 times to 1.7 times and reducing the energy for rock destroyed from 70% to 51% in cooperation to rotary drilling method in the same conditions

9 The database of thesis

The thesis bases on the final report documents the geological exploration and the coal production documents of Mao Khe Coal Company, Vietnam Coal and Minerals Group as well as the member companies The study also uses the technical documents which relate

to the content of research as well as the articles and scientific studies

of the authors published in the domestic and international journals

10 The content and structure of thesis

The thesis consists of an introduction, four chapters study the content, conclusions, recommendations and a list of publish articles of author and the references The entire contents of the thesis

is presented in 138 pages of A4, font size of 14 in Time New Roman, Unicode, including 58 figures, 27 tables and appendices

CHAPTER 1

OVERVIEW OF GAS REMOVE IN PIT COAL MINE TECHNOLOGY IN OVER THE WORLD AND IN VIETNAM 1.1 The requirement of methane recovery from pit coal mine in over the world

Today, science has confirmed the released methane gas from coal mines entering the atmosphere is one of the main causes the environmental pollution and the greenhouse effect However, in positive perspective, the methane itself is energy resource for human, for the chemical industry, boilers, and industrial furnaces, used for production power Thus, in the coal mining industry, if the technology of methane recovery is suitable methane will be a precious energy resource, and the recovery of methane released during mining will contribute actively eliminate fire hazards and minimize mining causing environmental pollution

1.2 The technology of methane removable drilling in the pit coal mine in over the world

Today, there are two technology mainly used for removing and recovery methane from the coal mine: through the boreholes which

is drilled from the surface and through the boreholes drilled from the pit mine

1.3 The status of research and application of methane removing drilling technology

The research and application of methane removing drilling technology in Vietnam in general and in Khe Cham, Mao Khe in particular is just in beginning period, there is no scientific work published Thus, the study of selection appropriate drilling technology for gas removing in Mao Khe geological conditions as

well as other mines in Quang Ninh province is necessary in science and practical

CHAPTER 2

GEOLOGICAL CHARACTERIZATIONS, MINING STATUS

AND POTENTIAL FOR METHANE GAS

IN MAO KHE COAL MINE 2.1 Geology, physic and chemical characterizations

2.1.1 Geology structure

Geology structure of Mao Khe coal mine is in Quang Ninh sedimentary strata and divided into two clearly block North – South

by a fault [15]

2.1.2 Constructive characterization and faults system

The constructive characterization of the mine is rips and faults There are totally 18 faults along the direction of the mine and some of them

in South West direction

2.1.3 Physical characterization of rocks

The research of strata has showed that the geological structure of the Mao Khe is quite similar with Quang Ninh mine area The magma is distributed in right general layers Coal, claystone and siltstone near the coal reservoir form walls, coal pillars On the other side, sandstone and others are far from the reservoir

2.2 Characteristic and the nature of Mao Khe coal mine

The coal seams in Mao Khe coal mine were highly degenerated and the color of coal change between black and dark grey Coal is relatively hard, and the hardness in drilling levels from III-V; hardness f-level is usually greater than 2; density from 1.55 to 1.70 g/cm3 Common minerals in coal samples are arghilit, silica oxit

2.3 Current status of coal exploitation and the potential of methane in Mao Khe

2.3.1 Current status in exploitation of Mao Khe

Today, Mao Khe is in production from two wings which includes 9b West, level -80/25, V8 West, level -80/+30, V8 East, level -150/-80, V7 Đ.TR, level -80/-25; V6 W level -80/-25; V6 Đ.TR level -80/-25; V6 ĐMR level -80/-25 in the North side and 8CN-ĐN II, level -80/LV; V.8 CB-ĐN I, level -80/+25 in the South

2.3.2 Methane potential in Mao Khe coal mine

According to the results from the research of experts [1, 4,

12, 22, 35, 36], the classification of gas existing in coal seams and side walls depends on the forming conditions of the mine as below:

- Gas in free form exists in the fractures, pores of the reservoir

- Gas exists in the form of adhesion, sustainability chemical and physical link and usually coming out from the coal when under external force such as beating, crushing, etc

- Gas exists in connate water in the reservoir

2.3.3 Safety solutions to prevent methane appearance in pit

In the current period, along with the application of appropriate ventilation system, Mao Khe mine has been studying the application of drilling technology to remove methane from coal seams, or areas containing methane and other toxic gases

Chapter 3

Study in selection of appropriate technology

of horizontal drilling to remove methane in

Mao Khe coal mine

3.1 Characteristic of horizontal drilling

3.1.1 The lost of axial load on rock destroying

Figure 3.1 Shape of drilling pipe is compressed in

drilling horizontal boreholes The axial load on drill bit is actually defined as below:

P k = P o - P c - P t (3.4)

Where: P k : actual axial load on drill bit, N; P o: maximum allowance load of drilling head, depends on technical characteristic of drilling

machine, N; P c: weight of drilling pipe, N

3.2.1 Curving and oblique of horizontal boreholes

3.1.3 Difficulties in horizontal drilling

o

Figure 3.4 Curving borehole due to

eccentric drilling equipment

Figure 3.5 Direction of curving borehole

Figure 3.6 Ability of borehole deflected

when meet rock in different hardness

Figure 3.7 Deflection of borehole when

drilling in coal zone

In the static state, the upper part of the horizontal borehole in depth of Z, with in distance from borehole center (Figure 3.9) and subjected to the force:

The value of depends on type of rocks, clay from 0,35 - 0,4; sandstone 0,15 - 0,20; Carbonate from 0,25 - 0,30

In horizontal boreholes, side grooves and cavities often occurs in the lower borehole while drilling through the weak stratigraphy such as the clay-acgilit layer, the coal seams The main reason is due to the weight of drill pipe always prone to tend on the

Figure 3.8 Shape of upper boreholes

in horizontal drilling in fracture zone

Figure 3.9 Cover rock status in horizontal drilling boreholes

underside of borehole while tripping Grooving diagram in borehole

is described as in Figure 3.10

3.2 Study on the appropriate selection of horizontal drilling technology for removing methane in Mao Khe mine

3.2.1 Status of methane removing drilling in Mao Khe

Base on the development plan as well as the potential methane of 9Đ coal mine there are some long horizontal boreholes will be located along the side of longwall for removing gas before production time The borehole will be drilled at the drilling station which is about 350m away from the longwall (figure 3.12) All boreholes will be designed in the shape of paper fan with the direction to the longwall The first borehole is 30 degree with escape wind line; the second is 15 degree with the first one The next borehole is continuously designed in that way and gas recovery at coal seam and the side wall before producing The space of the longwall đã phá hỏa đánh sập after production time The position and the structure of gas off horizontal holes in 9Đ level -80 is showed in figure 3.12 and 3.13

Q

Q

n

Figure 3.12: Position of the holes in preparation

for mining at 9Đ seam

Figure 3.13: Boreholes structure for gas recovery in 9Đ seam The number of the boreholes in production area will be defined as below:

(3.19) Q: volume of gas in production area of longwall

QMT: volume of recovery methane flow at the long wall,

m3/month

Mining directional

Ventilation way Ventilation way