BAKARLEDAAR WELL DRILLING REPORT - … Zwischenbericht... · Bakarledaar Water Well Drilling and Construction Completion ... Mille town water supply borehole • Drilling Diameter

Bakarledaar Water Well Drilling and Construction Completion Report

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1. Project Name: ETH 1110

2. Donor : Welthungerhilfe/GAA,BMZ

3. Project Implementer : Afar Pastoralist Development Association (APDA)

4. Well Name: Bakarledaar

5. Location:

• Region: Afar National Regional State

• Zone: One/1

• Wereda: Mille

• Site Name: Bakarledaar

• GPS Location: Zone 37, Datum- Adindan ,UTM (X,Y,Z) = 697608, 1270730, 464m

Figure1. Location map of Bakarledaar borehole


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6. Drilling Information

Drilling machine (Rig) name: AGBO600

Drilling Method Used: Direct Rotary

Drilling Fluid: Bentonite and water

Source of drilling water: Mille town water supply borehole

• Drilling Diameter :

o From 0.0 to 170m = 12 1/4”

• Well Depth: 170m

• Well Status: Abandoned due to technical problem

7. Mobilization Date: 02/12/2013 to 11/12/2013

- Long mobilization period was due to absence of crane truck on time

8. Demobilization Date:

9. Field Observation

- Water strike depth : near 125m estimated (corresponds to 339 m.a.s.l)

- Static water level : 78m (below ref. point) corresponding to 386 m.a.s.l

- Reference/Measuring point : 1.0 m above ground level

- Type of aquifer material : the main aquifer was highly and/or highly to moderately

fractured basalt

- Aquifer type : Confined

- Estimated aquifer thickness (inferred) : 27 meters

The drilled cutting samples were collected every one meter interval and whenever there is

change in lithologic type. The inferred field description of the drilled samples was

summarized in Table1.


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Table 1 Geological Logging (Lithologic Description) of Bakarledaar borehole

No. Depth Range Inferred Lithologic description Thickness (m) From (m) To (m)

1 0.0 2.0 Brownish silty clay with few gravel 2

2 2.0 10.0 Clay, silt and fine sand deposit 8

3 10.0 12.0 Fine to medium sand deposit 2

4 12.0 18.0 Coarse sand with fine gravel deposit 6

5 18.0 26.0 Light brown clay with fine gravel 8

6 26.0 36.0 Light brown clay with weathered gravel 10

7 36.0 92.0 Light brown clay 56

8 92.0 125.0 Dark gray clay accordingly rented 33

9 125.0 126.0 Weathered basalt 1

10 126.0 130.0 Moderately fractured basalt 4

11 130.0 137.0 Highly fractured basalt 7







17 165.0 169.0 Moderately to highly fractured basalt 4

18 169.0 171.0 Highly weathered formation 2


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Figure2. Lithological well log and well design of Bakarledaar borehole


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10. Surface Casing / Conductor pipe:

5m length with 13 ½” diameter steel casing was installed so as to protect caving-in

and collapsing of the upper soft formation. It was grouted and left permanently in the

well to serve as sanitary protection around the well.

11. Installation of Production Casings :

- Type: Steel (6’’)

- Size: 150mm internal diameter

- Wall thickness: 5mm

- Total Blind Length: 140m + 0.5m (a.g.l*)

- Total Screen Length: 30m

- Total depth that was cased : 170m + 0.5m stick up

*- above ground level

The well casings were installed through welding.

Table 2 Casing arrangement of Bakarledaar borehole

No Depth (m) Casing type/Steel From To

1 0.00 125.0 Blind 2 125.0 137.00 Screen 3 137.00 143.00 Blind 4 143.00 152.00 Screen 5 152.00 158.00 Blind 6 158.00 167.00 Screen 7 167.00 170.00 Blind


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a.

Figure3. Installation of 6’’ Steel production casing for

Bakarledaar borehole: a. while connecting two pieces

using rigid wrench; b. while reinforcing the connected

pieces through welding

b.


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12. Gravel packing and well development :

The annular space between well wall and well casing was packed with selected river gravel of

diameter 4 – 6mm and 15m3 of volume. It was packed manually using shovels. Before the

borehole was subjected to air lifting about 7m3 of the gravel was packed, and the remaining

amount was packed while well development.

Even though, such amount of gravel was packed, the borehole water has not been free of silt and

clay. Clay material was ejected out in-between while well development and even sometimes clog

the flow of water towards the borehole. At this stage two assumptions were made for the reason

why such clay materials was came out of the borehole. The first assumption for the source of clay

might be the clay that initially filled the borehole during mud-rotary drilling. While, the second

assumption was the clay that might came out from bottom of the borehole. The later assumption

was given a greater weight because of the following reasons:

- The volume of the clay material that came out was relatively large

- There were small boulder size clay and weathered basaltic fragments that

came out from the borehole

- The bottom part of the production casing was put over the lost jammed drill

tools. The interface has certain open space /gap that allows clay formation to

pass through.

By considering the second assumption, different techniques were utilized in order to make the well

water free of clay and silt. Among the techniques used include diluting the drilling fluid with clean

water, injecting compressed air in both sides of the casing (outward and inside of the steel casing)

for extended number of days, and continuous pouring of gravel in to the annular space.

The collapsed clay formation resulted in development of cave along the borehole’s section. This in

turn caused the groundwater not to easily flow out by compressed air. To minimize the effect using

of submersible pump was set as one option. But, pump installation was failed due to clogged clay

material as well as some defect on the casing itself.

Despite of the above effort, the problem has persisted and this lead to another assumption that will

be responsible for the source of clay material which in turn resulted in turbid water and clogging of

the borehole with clay. Therefore, the possible cause of the problem will be rupturing/breaking-

apart of the casing at its adjoining part. The ruptured section of the casing was estimated near 66m

depth. This event was perceived on the later trial of well cleaning activity using 5’’ drill pipes.


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Because of the aforementioned problems and its consequences the well cleaning and development

activity was completed without tangible outcome.

13. Materials :

Table 3 Materials utilized for drilling & construction of Bakarledaar borehole

No Material type Quantity Unit

1 Fuel for Rig 5,000 Lit

2 Fuel for Generator 120 Lit

3 Surface casing, 13 ½” diameter 5 M

4 Bentonite 5 Quintal

5 Foam: drilling fluid 50 Lit

6 Cement 2 Quintal

7 Well casing, steel 6’’ diameter 140.50 M

8 Well screen, steel 6’’ diameter 30 M

9 Selected river gravel, 4 - 6mm dia. 14 m3

14. Personnel:

List of personnel involved in the drilling of Bakarledaar borehole

1. Getaneh Kinfu ………….. Hydrogeologist

2. Kasahun Sileshi………….. Chief driller

3. Aschalew Demise……… Electrcian/ from out-side

4. Hailu Gebre ………… Rig driver & assistance driller

5. Abdela Ahmed…………… Helper

6. Solomon Ayenachew...…… Helper

7. Ahamed Mahammed …… Helper

8. Ranem Taha……………… Helper

9. Hussen Ali …………… Helper

10. Ismael Musa ………………Helper

11. Kedir ………… Water truck driver

12. Abdela ...................... Water truck helper


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15. Drilling events and Challenges

Drilling of Bakarledaar borehole was conducted by 12 ¼’’ diameter TCI tricone bit using direct-

rotary method. Bentonite mixed with water was used as a drilling fluid. 13 ½’’ diameter steel

surface casing having 5m length was installed to protect the top loose soil from collapsing. The

borehole was drilled to 171m depth. The drilling phase of the work was relatively successful and

took very few days.

After completion of the drilling to the intended target depth of 171m, it was followed by pulling out

of the drill tools. While removing of the drill tools, there were tools jamming and later it was freed.

It was here that a strange phenomenon had occurred, i.e the drill bit together with connecting cross-

over sub were detached from drill pipes and lost to the well bottom (Fig.4).

A lot of efforts were performed to fish-out the lost tools, but it was too tough to remove-out. As a

result, it was left to the borehole’s bottom and the remaining section of the borehole was cased.

a.

b.

Figure 6. Pictures of the old TCI bit : a.

a.

1

2

3


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b.

Figure4. The Drill tools (1, 2 & 3) that was broken and lost in to the borehole’s bottom : a. the

complete tools that lost; b. a tricone bit alone

1. Tricone bit : Ø 12 1/4'' full hole, Tungsten carbide inserted, connection 6 5/8'' reg pin

2. Cross-over sub that connects drill bit to drill collar: 6 5/8” reg. box to 7 5/8’’ reg box

3. Cross – over sub that connects drill collar to drill pipe: 7 5/8’’ reg. pin to 4 ½’’ IF box

Water strike depth was inferred from drilled cutting samples, change in viscosity and volume of flow

of the drilling fluid. Thus, it was estimated that the first water strike depth was near 125m. The main

aquifer material is highly fractured and/or highly to moderately fractured basalt.

Problems/Challenges

⇒ The breaking of the drill tools (connecting cross-over sub + drill bit) after drilling completion;

⇒ Gravel packing and well development problem, which was induced by rupturing of the well

casing at its adjoining section; and

⇒ The nature of bottom formation where the tools lost has made the fishing activity more

complex.

Since the bottom most part of the borehole is relatively soft formation, it was made the fishing

of the lost tools very tough. The broken tools were moved further downward while it was tried

Tricone bit


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to tie with tapper tap /fishing tool (Fig.5). Although, the tapper tap was seized the tool, it was

failed to pull-out.

Figure5. The fishing tool used to recover the

broken tools: a. tapper tap connected to the drill

pipe; b. tapper tap/fishing tool alone

a.

b

.

b.


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16. Action taken

- In order to take out the lost drill tools fishing was done using tapper tap.

- To remove collapsed formation, the borehole was flashed with drilling fluid and air using

direct rotary and reverse circulation method respectively (Fig.6).

- To pack the annular space, 4 - 6mm diameter well rounded river gravel was poured

manually using shovel.

- To clean and develop the borehole, compressed air was injected in to the borehole.

- To minimize collapsing of clay formation while well development, the gravel level was

monitored continuously and additional gravel was packed.

- To check the plumpness of the well and to detect the problem on the well casings, 5’’

drill pipes were lowered down through the casing.

Lowering of the 5’’ drill pipes through the casing helped to perceive some defect on the

well casing.

Figure6. Flashing the borehole with drilling fluid in order to remove collapsed formation that

blocked the broken tools


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17. Conclusion and recommendation

Because of the breaking apart of the well casing, the borehole was filled with clay material and the

aquifer zone was almost entirely clogged by clay. Stratigraphically, thick clay formation was overlaid

fractured basaltic formation (the possible aquifer formation).

Recommendation:

- As the possibility of maintaining the ruptured well casing and cleaning of the

clogged clay material were almost impossible, it was recommended to pull out the

installed well casing as much as possible.

- Since we already have promised to drill a borehole for the community, it is better to

drill another borehole in the vicinity of the existing system.


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18. Drilling cost

Bakarledaar borehole drilling cost

No Description Qty Unit Unit cost, ETB

Total cost, ETB

1 Mobilization and demobilization cost 1.1 Fuel for Rig 180 Lit 17.20 3,096.00 1.2 Fuel for crane truck 450 Lit 17.20 7,740.00 1.3 Fuel for light vehicle 200 Lit 17.20 3,440.00 1.4 Perdiem for stakeholder 1 LS ‐ 7,500.00 1.5 Cost for Trailer mobilization 1 LS ‐ 15,000.00

1.6 Cost for river gravel & well casing mobilization 1 LS 20,000.00

Sub‐total

56,776.00 2 Drilling cost

2.1 Fuel and lubricant

2.1.1 Fuel for Rig 9600 Lit 17.20 165,120.00 2.1.2 Fuel for site car 580 Lit 17.20 9,976.00 2.1.3 Fuel for Generator 150 Lit 17.20 2,580.00 2.1.4 Fuel for water trucking 525 Lit 17.20 9,030.00 Sub‐total

186,706.00

2.2 Cost for drilling water (water truck rent) 1 Month 78000 78,000.00 2.3 Material cost

2.3.1 Cement 200 Kg 3 600.00 2.3.2 Surface casing, 13 1/2” diameter 5 M 2448 12,240.00 2.3.3 Bentonite 500 Kg 17 8,500.00 2.3.4 Foam: drilling fluid 50 Lit 21 1,050.00 2.3.5 Well casing, Steel 6’’ diameter 140.5 M 1270 178,435.00 2.3.6 Well screen, Steel 6’’ diameter 30 M 1360 40,800.00 2.3.7 Selected river gravel, 4‐6mm dia. 14 m3 2200 30,800.00 Sub‐total 272,425.00 Total

593,907.00

Documents

BAKARLEDAAR WELL DRILLING REPORT - … Zwischenbericht... · Bakarledaar Water Well Drilling and Construction Completion ... Mille town water supply borehole • Drilling Diameter