Bakarledaar Water Well Drilling and Construction Completion Report

Transcription

1 1. Project Name: ETH 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) = , , 464m Figure1. Location map of Bakarledaar borehole Page 1 of 14

2 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/ 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. Page 2 of 14

3 Table 1 Geological Logging (Lithologic Description) of Bakarledaar borehole Depth Range No. Inferred Lithologic description From (m) To (m) Brownish silty clay with few gravel Thickness (m) Clay, silt and fine sand deposit Fine to medium sand deposit Coarse sand with fine gravel deposit Light brown clay with fine gravel Light brown clay with weathered gravel Light brown clay Dark gray clay accordingly rented Weathered basalt Moderately fractured basalt Highly fractured basalt Moderately fractured basalt Highly fractured basalt Moderately fractured basalt Highly fractured basalt Moderately fractured basalt Highly fractured basalt Moderately to highly fractured basalt Highly weathered formation 2 Page 3 of 14

4 Figure2. Lithological well log and well design of Bakarledaar borehole Page 4 of 14

5 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) From To Casing type/steel Blind Screen Blind Screen Blind Screen Blind Page 5 of 14

6 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. Page 6 of 14

7 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 15m 3 of volume. It was packed manually using shovels. Before the borehole was subjected to air lifting about 7m 3 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/breakingapart 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. Page 7 of 14

8 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 M 8 Well screen, steel 6 diameter 30 M 9 Selected river gravel, 4-6mm dia. 14 m 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 Page 8 of 14

9 15. Drilling events and Challenges Drilling of Bakarledaar borehole was conducted by 12 ¼ diameter TCI tricone bit using directrotary 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 crossover 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. 3 a. b. 1 Figure 6. Pictures of the old TCI bit : a. 2 a. Page 9 of 14

10 Tricone bit 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 Page 10 of 14

11 Bakarledaar Water Well Drilling and Construction Completion Report 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. Page 11 of 14

12 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 Page 12 of 14

13 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. Page 13 of 14

14 18. Drilling cost Bakarledaar Water Well Drilling and Construction Completion Report Bakarledaar borehole drilling cost Unit cost, ETB Total cost, ETB No Description Qty Unit 1 Mobilization and demobilization cost 1.1 Fuel for Rig 180 Lit , Fuel for crane truck 450 Lit , Fuel for light vehicle 200 Lit , Perdiem for stakeholder 1 LS 7, Cost for Trailer mobilization 1 LS 15, Cost for river gravel & well casing mobilization 1 LS 20, Sub total 56, Drilling cost 2.1 Fuel and lubricant Fuel for Rig 9600 Lit , Fuel for site car 580 Lit , Fuel for Generator 150 Lit , Fuel for water trucking 525 Lit , Sub total 186, Cost for drilling water (water truck rent) 1 Month , Material cost Cement 200 Kg Surface casing, 13 1/2 diameter 5 M , Bentonite 500 Kg 17 8, Foam: drilling fluid 50 Lit 21 1, Well casing, Steel 6 diameter M , Well screen, Steel 6 diameter 30 M , Selected river gravel, 4 6mm dia. 14 m , Sub total 272, Total 593, Page 14 of 14