Horizontal Directional Drilling (HDD) Method Statement

This document has been prepared to describe the methodology by which MCD/HDDT propose undertaking the site preparation, mobilization, drilling operations, pipe installation, pre-commissioning and reinstatement operations for the installation of the 6 HDD crossings on the Block B Omon Project - Onshore Pipeline.


Horizontal Directional Drilling (HDD) Method Statement

Table of Contents

  1. CONTRACTORS SUMMARY
  2. INTRODUCTION
  3. CONSTRUCTION RISK ASSESSMENT
    1. Risk Ranking of Likelihood
    2. Risk Ranking of Consequence Risk
    3. Risk Legend
    4. Assessment
  4. PROJECT GEOLOGY
  5. DOWN HOLE SURVEY SYSTEMS
    1. Downhole Survey Techniques
    2. Survey Overview
    3. Survey Systems – Magnetic Steering Tool – Description
    4. Survey Systems – Paratrack 2 Wire Tracking – DescriptioSurvey Systems – A.C. Solenoid System – Description
  6. EXECUTION
    1. Pilot Drilling
    2. Pilot Tooling
    3. Reaming
    4. REAMED HOLE SIZE
    5. REAMING STEPS
    6. REAMING RATE OF PENETRATION
  7. PULL BACK
  8. MUD PROGRAM
    1. Cuttings Treatment & Displacement Removal
  9. FRAC-OUT MANAGEMENT
    1. Prevention
    2. Frac out management
    3. Frac-out Contingencies
  10. DEMOBILISATION
  11. PRELIMINARY CONSTRUCTION EQUIPMENT LIST
    1. Rig - American Augers DD440T
  12. PRELIMINARY KEY PERSONNEL CHART
  13. DESIGN AND CONSTRUCT SCHEDULE........................................................................................................................... 18
  1. CONTRACTORS SUMMARY

HDD (Thailand) Co. Ltd. is an HDD specialist with expertise in delivering technically challenging multi rig HDD projects worldwide. We strive to exceed industry standards and bring exceptional quality and value to our clients. HDDT has over 150 professionals working on projects worldwide including Asia, Australasia, and Africa. HDDT have ensured success on crossings of 42” over 1,465 metres and smaller diameters over 3,014 metres Our carefully selected specialist staff provide the highest standards of quality, safety, and environmentally considerate production possible.

HDDT’s objective is to exceed industry standards and bring exceptional quality and value to our clients. HDDT has continued involvement in every major pipeline project in Thailand since 2012 and continues to deliver the best Horizontal Directional Drilling experience.

HDD

Contractors summary

  1. INTRODUCTION

This document has been prepared to describe the methodology by which MCD/HDDT propose undertaking the site preparation, mobilization, drilling operations, pipe installation, pre-commissioning and reinstatement operations for the installation of the 6 HDD crossings on the Block B Omon Project - Onshore Pipeline. The 30” pipelines are to be installed with an additional 6” FOC duct as per the supplied alignment sheets.

Prior to construction a detailed engineering design will need to be prepared to further evaluate and determine the final design and methodology. The following method statement presents our proposal based on our understanding of the crossing requirements and may alter following the detailed design works.

  1. CONTRUSTION RISK  ASSESSMENT

To provide suitable mitigation measures risks need to be properly identified, a Construction Risk Assessment has been developed to help identify constructability risk and consequences without control. The risk is measured by likelihood, consequence, and severity. Risk is then reassessed with control measures in place to determine if the risk is acceptable. Ideally our risk score after control measures should be 6 or below to be considered tolerable.

    1. Risk Ranking of Likelihood

Rank

Probability

Description

Likelihood

1

1% chance

Occur only in exceptional circumstances

Rare

2

5% chance

Could occur at some time

Unlikely

3

10% chance

Should occur at some time

Possible

4

50% chance

Probably occur in most circumstances

Likely

5

100% chance

Expected to occur in most circumstances

Almost certain

    1. Risk ranking of Consequence

Rank

Financial Impact

Environmental Impact

Consequence

1

< $10,000

Minor localized environmental harm rectified within hours

Insignificant

2

$10,000 - $100,000

Minor transient environmental harm that requires days for recovery

Minor

3

$100,000 - $250,000

Significant environmental harm that requires weeks for recovery

Moderate

4

$250,000 - $1M

Very serious long-term environmental harm or contamination

Major

5

> $1M

Severe environmental harm or contamination

Catastrophic

    1. Level of Risk

LIKELIHOOD

SEVERITY

1 - Insignificant

2 - Minor

3 - Moderate

4 - Major

5 - Catastrophic

5 - Almost certain

5

10

15

20

25

4 - Likely

4

8

12

16

20

3 - Possible

3

6

9

12

15

2 - Unlikely

2

4

6

8

10

1 - Rare

1

2

3

4

5

    1. Risk Legend

H

VERY HIGH RISK (15-25) - Intolerable - Do not start activity

H

HIGH RISK (8-12) - Undesirable - Additional controls required to reduce risk

M

MODERATE RISK (4-6) - Tolerable – With controls implemented

L

LOW RISK (1-3) - Broadly acceptable - Manage by routine procedures

    1. Assessment

#

Risk

Effect

Primary Risk Assessment

Control Measures

Residual Risk Assessment

Likelihood

Consequence

Risk Score

Likelihood

Consequence

Risk Score

1

Unsuitable site access

  • Damaged equipment

- Loss of production

3

3

9

  • Access and site preparation to suit heavy vehicle traffic up to 45 ton
  • Stay within the access roads and site boundaries

1

3

3

2

Adverse weather

  • Loss of production through access issues
  • Damage to sensitive electrical equipment

3

3

9

  • All weather access tracks to be maintained
  • Shelter for crews on rig side and pipe side
  • Ensure all equipment and processes are suitable for all weather operation
  • Shut down completely in electrical storms

1

3

3

3

Community impact

- Stop production or complete shut down

3

4

12

  • Ensure local community understands the process and all approvals are in place
  • Courteous, professional demeanor when interacting with local residents

1

3

3

4

Inadequate engineering, planning

- Twist off drill pipe

- Bogged tooling

- Loss of production

- Stuck pipe

- Increased pull loads

4

4

16

  • Ensure rate of penetration “ROP” is relative to pump power to ensure cuttings are removed from the bore
  • Calculate theoretical solids against actual solids removed

- Evaluate ground conditions

  • Accurate records kept for reference
  • New or Premium drill pipe only to be utilized specifications relevant to the expected torque and pull-force

2

3

6

5

Encounter unforeseen ground conditions

  • Down hole tooling not suitable

- Drill spread not suited

- Deflected pilot hole

- Hole collapse

4

3

12

  • Ensure sufficient geotechnical information available
  • Ensure tooling and drill pipe is premium quality and capable for all conditions
  • Ensure drill pipe is inspected to API 5DP

2

3

6

  • Ensure rig is suited to the proposed tooling
  • Design around faults or unstable strata

6

Encounter obstruction

  • Tooling and equipment onsite not suitable

- Drill string failure

  • Inability to steer to designed profile
  • Reamers follow formation features

4

3

12

  • Carry out site and geotechnical investigation
  • Use only quality tooling matched to the formation
  • Make up connections as per API specifications
  • Use well stabilized bottom hole assemblies
  • Avoid drilling through highly fractured or cobbles and boulder formations

2

3

6

7

Loss of fluid returns

  • Compromised hole cleaning

- Stuck product pipe

- Reduce drilling rates

  • Loss of down hole assembly due to cuttings build up

4

3

12

  • Implement engineered mud program to suit geological information
  • Regular drill fluid checks to optimize drill fluid cutting suspension and filter cake
  • Well planned profile designed to pass through the most ideal geology
  • Regular flushing of hole
  • Regular reporting to qualified mud doctor

2

3

6

8

Tooling failure

  • Fishing operations

- Possible re-drill

3

3

9

  • Drill pilot diameters relative to drill string
  • Use NEW or premium grade tooling only matched to the expected ground conditions
  • Track tooling hours with detailed drill records
  • Trip for tooling checks when required

1

3

3

9

Drill string failure

  • Fishing operation

- Possible re-drill

3

3

9

  • Use only NEW or premium inspected drill pipe to API 5D
  • Use drill pipe with a torsional strength greater than the rig capacity
  • Drill within the limitations of drill pipe
  • Regular drill pipe inspections to API 5D

1

3

3

10

Increased pull load

- Stuck pipe

  • Equipment damage

4

3

12

  • Properly engineered and planned over-bend and stringing alignment

- Well prepared launching pit

1

3

3

- Damage to pipe or coating.

  • Properly rated rollers and cradles
  • Ensure suitable pipe handling equipment for the weight of the pipe and the height of the over- bend
  • Calculate estimated buoyant force per meter of product pipe
  • Calculate estimated pull force required based on profile, formation and buoyant forces
  • Engineer required buoyancy control measures to control buoyancy

- Quality pilot profile

11

Coating damaged

  • Abandon pipe
  • Excavate pipe for repair of damaged section
  • Additional corrosion control

3

5

15

  • Additional sacrificial coating required for HDD strings to protect pipe coating in detrimental conditions
  • Use of coating designed for HDD and geological conditions expected

- Final ream size to be minimum

1.3 times the product diameter

- Buoyancy control when required

1

5

5

12

Pipe stuck

- Possible re-drill

- Abandon pipe

3

5

15

  • Carry out hole conditioning after completion of each reaming stage
  • Increased viscosity to flush cuttings from the bore
  • Check pass on completion of conditioning pass to check for additional torque
  • Pilot profile drilled to ensure minimum radius is met and without doglegs or other deviations

1

5

5

13

Loss of connection to the product pipe

  • Pipe unscrews from swivel

- Pin retainers fail

2

4

8

  • All connections to be torqued up to make up torque
  • Double check all connections and pin retainers
  • Retaining compound used on bolted retainers.

1

4

4

  1. ROJECT GEOLOGY

An overview of the geotechnical information is shown above, the green shaded cells indicating jetting pilot hole methodology and barrels for reaming. All suitable tooling options will be available with a suitable number of spares on- site. The final tooling plan will be prepared before mobilizing and is site specific to design, services, and final geotechnical information.

Local borehole information is indicated by a Standard Penetration Test (SPT), this is a field test that involves driving a 2” split spoon sampler into the soil by dropping a hammer of a specific weight to determine the number of blows necessary to drive the sample 12 inches. The number obtained is the standard penetration resistance value (N) and is used to estimate the relative density of cohesion less soils. The geotechnical borehole information supplied suggest predominantly soft silty sands with clay and should present a relatively straightforward approach for HDD methodology with a good mud program, jetting pilot tooling, and LTBR neutral buoyancy barrel reamers.

5. DOWN HOLE SURVEY SYSTEMS

  1. 1. Downhole Survey Techniques
  2. It is proposed to use three separate downhole surveying techniques to achieve the accuracy required for these crossings. The three methods/techniques have been selected after considering all the available surveying methods, and are as follows:
  3. Magnetic steering tool utilizing the Vector Magnetics P2 Magnetic Steering ToolSurface Coil Tracking utilizing the Vector Magnetics P2 system.
  4. Solenoid Tracking utilizing the Vector Magnetics AC Solenoid system.
  5. 2. Survey Overview
  6. The methods proposed will allow for optimum tracking of the drill bit during the drilling process, so that the position of the drill will be known always in relation to the proposed profile.
  7. The primary steering tool will be the Vector Magnetics Steering Tool, the secondary system will be surface tracking utilizing the Vector Magnetics Paratrack 2 wire tracking system, and the third system will be surface tracking utilizing the Vector Magnetics AC Solenoid system.
  8. A wire will be laid along or offset to the center line at the entry point and a closed loop will be formed by running a return line back to the start of the wire. The main problems associated with directional control through this section are expected to be magnetic interference from the drilling equipment near the entry point. This is typically only experienced over the initial 20 or 30 meters, and the use of the tracking from the wire will eliminate any error from this source. An accurate determination of the line azimuth (entry to exit reference line) is expected from this entry wire. It is proposed to have available a AC Beacon to be used once over the water or areas where the surface wire is not possible. By utilizing these tracking systems, the position of the drill will be known confidently by a minimum of 2 independent systems at any one time to a position of +/- 200 mm.
  9. 3. Survey Systems Magnetic Steering Tool Description
  10. The Magnetic Steering Tool is manufactured by Vector Magnetics LLC. The tool consists of a sensor package located in the bottom half of the tool, and a data processing section located in the upper half. The sensor package consists of three triaxial fluxgate AC and DC magnetometers, and three triaxial accelerometers. The triaxial configuration allows the tool to be all angle capable.
  11. The fluxgate magnetometers measure the parameters Bx, By, and Bz where B is the magnetic vector component along the axis of each magnetometer. The x axis is defined as the high side of the tool. The accelerometers measure Gx, Gy, and Gz where G is the measured acceleration component of the earth’s gravitational field.
  12. From these raw sensor readings, the direction of the tool is computed in degrees of Azimuth relative to magnetic north, as well as the inclination in degrees from vertical and tool face in degrees from high side (x axis of the tool).
  13. The tool is linked to the surface via a single core cable of size 4-6mm square, which enables real time data to be viewed whilst drilling, and for surveys to be taken directly on to a surface computer. The tool is placed in the drill string inside one or two non-magnetic drill collars. This will allow the tool to be placed in a relatively magnetically clean environment away from interference from the drill string and the jetting assembly. As well as recording the inclination and azimuth, the instrument also measures the total magnetic field, B total, and the angle of magnetic flux, the Dip. These two parameters are used for Q.A purposes as they indicate the presence of any external magnetic interference.
  14. The B total and Dip are known for any area and can be derived either from published magnetic charts, commercially available modelling software, or simply by measuring the earth’s background field in the local area. Additionally, the measured parameter, G total, is used as a Q.A indicator as it indicates that the tool was stationary while the survey was being taken.
  15. ​​​​​​​4. Survey Systems Paratrack 2 Wire Tracking Description
  16. Paratrack 2 is a wire based locating system. An AC current is passed through a single core wire that either forms a closed coil of known geometry, or a single wire grounded at both ends. As the current passes along the wire, an alternating magnetic field of known strength and geometry is produced. The magnetic vector component of this field is measured by the steering tool downhole, and the software is then able to model the position of the steering tool in relation to the coil. As the generated field is of a known frequency, it is possible to filter out most the background noise, enabling a much higher signal to noise ratio, and hence more accurate tracking at greater depths.
  17. The Paratrack 2 system requires a local based co-ordinate system based on a reference azimuth. This is usually the line azimuth and is the line between entry point and exit point. Positions measured by the Paratrack 2 system are defined by the distance along this line, (Away), the distance to the right of the line, (Right), and the elevation. Each corner of each coil needs to be pegged. These pegs will be placed to provide the maximum accuracy achievable. Corners will be set so that the wire can be placed between the corners in a straight line both in the horizontal and vertical planes. If this is not possible then an extra corner will be added.
  18. Generally, the wire will be placed so that it will be positioned above the steering tool downhole, i.e. on center line. As the accuracy of the system relies on the accurate positioning of the coil itself then it is important that the coil corners are defined as accurately as possible. The corners will be pegged out, and then picked up by a land surveyor. The grid co- ordinates as supplied by the land surveyor can then be translated into the Away, Right, and Elevation co-ordinate system for entry into the Vector software.

​​​​​​​​​​​​​​5. Survey Systems A.C. Solenoid System Description

 

The AC Beacon consists of two wire wound coil solenoids mounted bi-axially on a non-magnetic table. Power to the AC Beacon is supplied via a 12 V DC deep discharge battery. Typically, the Beacon is oriented with a Total Station to a known azimuth, either the line or actual drill azimuth, and is placed either on or offset to the drill path. The Beacon can then be remotely actuated via the Paratrack software. Once the Beacon has been energized, it generates a known AC magnetic field. As the Beacon is in effect a point source, the generated field can be modeled accurately, allowing for an accurate determination of the steering tool position. Depending on the signal to noise ratio, it is possible to track up to 125m away from the Beacon, allowing in effect for a 250m tracking window.

The AC solenoid will work on the same local based co-ordinate system (away, right, elevation) that is used both for the Steering Tool and the Paratrack 2 system. The solenoid can be placed anywhere that is convenient along the drill path.

 

  1. EXECUTION
    1. Pilot Drilling

Successful drilling projects require the use of quality down hole tooling, drill pipe, connections, and tooling management. The following overview of tooling proposed for this project is as follows, however can change with ground conditions. A 9 7/8” tri-cone bit and jetting assembly is planned for soft crossings and a down-hole mud motor will be used if conditions require for firmer ground conditions.

The pilot drill string will be advanced along the engineered and approved path from the entry surface location to the exit location, as the string is advanced the action of the bentonite being pumped down the string and through the bit erodes the soil formation in the soft formations. For harder formations, as the drill fluid is pumped through the drill string it flows through the mud motor and rock bit and uses mechanical action to cut or chip away the hard and rock formations before it exits through nozzles in the bit and flows back to surface through the annulus between the drill pipes and the borehole walls. The drill fluid then carries these cuttings out of the hole.

The bit is steered by means of an offset behind the bit, the string is rotated to drill straight and the offset positioned to achieve build or steer depending on the design profile and the ongoing survey data. Pilot-hole data will be recorded for as-built drawings and at the completion of the pilot-hole drilling as-built information will be prepared including, tabulation sheets of co-ordinates, length, depth, inclination, azimuth and drawing, which accurately describe the location of the pilot hole, will be submitted.

The anticipated rate of penetration (ROP) suggests that the pilot drilling bit will not need to be changed during the drilling of each pilot hole.

    1. Pilot Tooling

Premium drill pipe will be used for this project built to API RP7G and API 5D specifications. Based on the information available the BHA will entail a 6 ½” non-magnetic drill collar, orienting sub, offset or bent sub, 9 7/8” tri-cone bit, and 6 5/8” drill pipe employed on the longer crossings and more flexible 5” drillpipe for the shorter crossings.

Based on the the geotechnical information supplied, we expect soft ground jet tool pilot however, if hard ground is encountered the jetting assembly will not be suitable therefore a 6 ¾” BICO mud motor will be available. This will be coupled with a 9 7/8” tri-cone bit and 6 ½” NMDC.

Motor Specifications 6-3/4" P100 XL Flex Drill

Operating Data

Flow Range

1,135 - 2,270 lpm

300 - 600 gpm

Motor Pressure

47 bar

675 psi

Bit Speed

60 - 145 rpm

Torque

9,080 Nm

6,700 ft-lbs

Power

HP (Kw)

185 (138)

Physical Data

Power Section Configuration

Stages

5

Lobes

7/8

Bit to Stabilizer

648 mm

25.5 in

Bit to Bend

2,160 mm

85.1 in

Overall Motor Length

7.9 m

26.0 ft

Weight

1,035 kg

2,285 lbs

Connections

Box

4-1/2" REG, Top and Bottom

Bit Size

200.0 - 250.8 mm

7-7/8 to 9-7/8 in

Based on the information on the regional geology, the jetting assembly will be available for soft sections and if required, a standby motor will be on-hand.

    1. Reaming

On successful completion of the pilot hole, reaming tools of various sizes will be progressively added at pipe side and drawn back through the hole to enlarge the hole over its full length. Typically, reamers will be sized to manage the amount of additional material cut with each reaming pass such that it is reasonably consistent. The drilled hole will be progressively enlarged until its diameter is approximately 30 to 50 % larger than the product pipe, depending on soil conditions. Combinations of tools such as fly cutters, barrel reamers and hole openers may be used during reaming operations as conditions require.

There are many different reamers of varying design and quality available to the HDD market today however generally speaking there are 4 main styles of reamers used in most HDD applications.

Fly-cutters

Fly-cutters are used in softer ground conditions and have their place in stiff clay with compacted sand applications, these tools need to be stabilised front and rear to ensure the tool is centralised and to help with the conditioning of the borehole. They are quite aggressive and designed to tear away at the formation and should always be followed with a barrel reamer to stabilise the borehole.

Barrel reamers

Fly cutter

Fly cutter


Barrel reamers are a great option in soft to medium clayey silts and sands, they are specially designed to be self- centralising and self-conditioning. The LTBR style barrels are built with chambers to lessen the down hole weight of the tool and therefore cut straight and evenly. They are mostly used in soft ground as a hydraulic cut but are armed with enough teeth that if harder sections are encountered the mechanical cut can take over.

Mixed ground hole openers

Barel reamers

LTBR barrel

Mixed ground backstay style hole openers are specially designed to cut through softer material with rock sections, the body is designed to allow enough flow through for clays and sand without packing off the cutters. The cutters are interchangeable so that soft rock or hard rock cutters can be changed to suit the expected conditions.

Transco mixed ground backstay type hole opener

Transco mixed ground backstay type hole opener

Conclusion

For the ground conditions on this project both fly cutter style and LTBR barrel reamers will be employed to cover the range of soft ground expected.

    1. REAMED HOLE SIZE

There are a great many factors to consider on appropriate ream sizes that should be considered for the hole opening of any HDD project. A general industry standard is 1.5 times the diameter of the product pipe being installed however this is generally aimed at the smaller rigs and pipe diameters. Examples of variations to this rule can include;

Hard rock

Hard competent rock is challenging to drill however the borehole once drilled is very stable and unlikely to change, there is no swelling, danger of collapse, and if properly cleaned and conditioned requires very little pull force. As such the reamed diameter can be much closer to the diameter of the product pipe therefore 1.2 times the diameter in shorter crossings to 1.3 time the diameter in longer installations is acceptable.

Clay

Reactive clays swell with the introduction of liquid (including standard drill fluids) and as such the 1.4 times the pipe diameter rule is often strongly recommended. Any delays (such as breakdowns or tie-ins) during pullback in reactive clays can be detrimental to the installation as the clay swells around the partially installed pipeline.

Unstable strata

Unstable materials such as loose sand, gravel, cobble or boulders are generally not suitable for HDD methodology however given suitable control measures are implemented or the section is short the hole size could be very important. The type of ground should be carefully considered during pilot hole and primary reaming passes to determine the safest final ream size.

Length of crossings

Shorter crossings can be installed into holes closer to the size of the pipe to mitigate the risk of subsidence and ground heave however longer crossings may require a larger reamed diameter especially in distances over 2,000 metres. These designs should be considered site specific and no hard and fast rule is applicable.

As-built pilot profile

The geometry is also a determining factor in the final ream size, this is due to the geometry and any deviations encountered during the pilot bore phase and should be considered after the completion of the pilot bore.

    1. REAMING STEPS

Reaming steps are also geotechnical and site specific, for this project we have chosen a preliminary staged program of between 0.2m3 per metre cut and 0.4m3 per metre cut, this is a conservative figure and may be modified to suit the actual encountered conditions.

Step

Type

Diameter

Cut Volume (m3/m)

Pilot hole

Jet or motor

9 7/8”

0.02 m3/m

Ream 1

Barrel

12”

0.22 m3/m

Ream 2

Barrel

24”

0.29 m3/m

Ream 3

Barrel

34”

0.37 m3/m

Ream 4

Barrel

42”

0.30 m3/m

Conditioning pass

Barrel

34”

-

Pullback

Swivel / barrel

34”

-

    1. REAMING RATE OF PENETRATION

The Rate of Penetration (ROP) must be balanced against the quality, flow rate, carrying capacity and bottom up time of the drill fluid. Several factors can determine the optimum ROP for reaming and it is very important that proper hole cleaning is maintained during this operation. To maintain borehole stability the return fluid should contain no more than 25% cuttings with 15% ideal and 20% absolute planned maximum.

Reaming Step

Pump rate (ltr/min)

Annular velocity (m/min)

Desired Cuttings %

Maximum ream speed (min/joint)

12” Ream

800

13.27

15%

1.86

24” Ream

1,500

5.38

15%

9.23

34” Ream

1,800

3.14

15%

10.32

42” Ream

2,000

2.27

15%

9.74

The maximum rate of penetration in minutes per joint is determined by the pump rate multiplied by the desired maximum cuttings percentage in the return drill fluid divided by the cut volume. Minimum optimal reaming annular velocity is around 2 metres per minute. The chart shows the maximum ream speeds using 5” drill pipe.

  1. PULL BACK

Barrel Reaming Schematic

The pipe string will be prepared in one string along the ROW. Pipe rollers will be laid between the end of the string and the HDD exit point. A barrel reamer and swivel assembly will be attached to the pulling head and the rig will take up the tension. The pipe string will be lifted into the over bend position the pipe string is pulled into the drilled hole and continue to completion.

  1. MUD PROGRAM

A good quality freshwater mud program is expected to be suitable for these crossings. Fresh water will be delivered to site from a local approved water source. All drilling fluid used for the project will consist of water (more than 95%) plus natural clay, also referred to as bentonite. Small quantities of additives may be used to improve the properties of the mud to suit the ground conditions encountered.

The mud serves several purposes, including the stabilization of the bore-hole walls, lubrication and cooling of down hole tools and the suspension and transport of the cuttings produced during drilling operations. When the mud is at the correct parameters for the prevailing drilling conditions it will be pumped from the tank and then via the mud pump to the drill string. The mud will return to surface via the annulus carrying the cuttings with it and in order to reduce the total volume used, the mud will be cleaned and recycled with the separation system on site and spoil removed from site to an approved disposal area.

All materials used in the mud, including the bentonite are environmentally harmless. Suppliers will be requested to provide MSDS to confirm this and copies of these MSDS sheets will also be present on each site.

    1. Cuttings Treatment & Displacement Removal

During the drilling process cuttings are produced by the reaming process, these will be stored in the disposal pit on-site and taken by dump truck to an approved dumpsite on completion of the drilling activities. During pull back the drill fluid will be displaced and stored in the disposal pit to be removed with the cuttings.

  1. FRAC-OUT MANAGEMENT

During drilling in very soft or fractured formations inadvertent fluid returns can be encountered at the surface, this is termed a ‘frac-out”. Frac-outs occur when the annular pressure exceeds the hydrostatic head required to reach the surface either through very soft formation or via natural or manmade faults in the ground.

    1. Prevention

To reduce the chances of a frac-out occurring, the quality of mud will be monitored by frequent inspection of the mud returns. The solids generated by the reaming process are estimated by using the fluid weight (drill fines contained in the fluid), this in turn, can be used to calculate the minimum minutes needed to drill each joint to ensure the fluid is not over loaded with cuttings causing undue down hole pressure.

Mud tests will be regularly carried out and recorded to ensure and monitor the quality of the drilling fluid, mud weight, viscosity, sand content and a log of water, bentonite, and additives.

The drill profiles will be designed considering the geotechnical and topographical information available to best suit the conditions and reduce the risk of frac-outs.

    1. Frac out management

Early detection of imminent frac-outs can be identified in three ways, returns, mud pressure or gradual loss of fluid levels in the storage tanks. The driller will monitor and record the mud pressure for each joint, drill fluid returns or lack thereof is also monitored at both entry and exit pits and are coordinated by the driller and drill supervisor.

Throughout the drilling operations, the drillers, foreman and HDD crew will be in constant communication via radios to act on and minimize the event of frac-outs without delay.

For bentonite spills on land, sandbags, pumping equipment, materials and plant will be stored where they can be easily and quickly brought to the breakout point. The crew monitoring the site will be equipped with radios for instant communication with drill operator.

    1. Frac-out Contingencies

The use of advanced formula drilling fluids will help to minimize the risk of frac-out. These blended products form an impermeable filter cake around the drill annulus due to the alignment of the clay platelets. However, if drilling mud continues to break out at the surface in addition to the contingency action above a loss circulation material (LCM) will be prepared and pumped into the system to stem the flow. In extreme cases and where the ground conditions are favorable it may be necessary to ‘trip out’ and recommence drilling at a different elevation.

  1. DEMOBILISATION

On satisfactory completion of the installation the drilling rig and ancillary equipment will be dismantled and loaded out for demobilization to base. All temporary excavations will then be either backfilled or securely fenced for shorter periods if they are to be left open for tie-in activities, any open pit or excavations must comply with the Safety, Health & Environment (SHE) Plan. All surplus materials and waste will be removed from the work areas.

  1. PRELIMINARY CONSTRUCTION EQUIPMENT LIST

Crossing

Length

Rig

Calculated Pull force

Xeo ro Canal Crossing

360 m

DD440

43 tons

Cai Lon River

980 m

DD440

107 tons

Cai Be River

486 m

DD440

55 tons

National Road No 61

270 m

DD440

33 tons

Thot Not Canal

372 m

DD440

43 tons

National Road No 91

230 m

DD440

31 tons

Proposed rig for this project is an American Augers DD440T (200 ton). This rig is well within the capacity to complete any of the crossings currently planned.

    1. Rig - American Augers DD440T

POWER TRAIN

Engine

Cummins

Rating

600 HP (447 kW)

Fuel Capacity

160 U.S. Gallons (605 L)

Hydraulic Capacity

200 U.S. Gallons (757 L)

CARRIAGE CAPACITIES

Maximum Thrust/Pullback

440,000 lbs. (200 Tonnes)

Carriage System

2 motor rack and pinion drive

Maximum Carriage Speed

(29 m)/minute

Carriage Motors

2 Hydraulic 160cc, Radial Piston

Carriage Gearbox

2 Planetary Drives

ROTARY CAPACITIES

Rotary System

3 Pinion & Gear Drive

Maximum Rotary Torque

43,90 ft-lbs. (59,590 Nm) @ 37 RPM

Maximum Rotary Speed

150 RPM

Rotary Motors

(2) Hydraulic, 486cc, Axial Piston

BREAKOUT UNIT

Wrench Style

Triple Jaw 10 3/4 in (273 mm) Separation

Maximum Breakout Torque

60,000 ft-lbs. (81,350 Nm)

Clamp/Grip Range

2 3/4 in. – 10 3/4 in. (70 – 273 mm) OD

DRILL RIG

Drill Angle

10° - 18°

Drill Pipe

Range II 4-1/2 in and 6 5/8 in API pipe

Travel System

Self Propelled Steel Track Crawler Assembly Maximum Travel Speed: 1.4 mph (2.25 kph)

DIMENSIONS

Length

50 ft. 9in. (15.47 m)

Width

8 ft. 2 in. (2.51 m)

Height

11 ft. 10 in. (3.61 m)

Weight

90,260 lbs. (40,941 kg)

#

Crossing

Pipe

Length

Rig

Days

1

Xeo ro Canal Crossing

FOC, 30”

360 m

DD440

30

2

Cai Lon River

FOC, 30”

980 m

DD440

49

3

Cai Be River

FOC, 30”

486 m

DD440

37

4

National Road No 61

FOC, 30”

270 m

DD440

30

5

Thot Not Canal

FOC, 30”

372 m

DD440

32

6

National Road No 91

FOC, 30”

230 m

DD440

29

Total drilling days

207

At rig side, the rig anchor will consist of a steel piled wall with an I‐beam spreader to the rig dead man, the position of which will be surveyed and pegged to ensure correct position in relation to any services and entry position. The piles will be driven with a vibrating piling hammer, ensuring all services have been identified, located, and exposed prior to commencing work. This will be done at the time of the civil works and before the mobilization of the drilling spread.

 

 

 

CÔNG TY CP TƯ VẤN ĐẦU TƯ & THIẾT KẾ XÂY DỰNG MINH PHƯƠNG

Địa chỉ: Số 28B Mai Thị Lựu, Phường Đa Kao, Q.1, TPHCM

Hotline:  0903649782 - (028) 3514 6426

Email: nguyenthanhmp156@gmail.com

 


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