CONSTRUCTION OF A DEEP TUBE WELL- A CASE STUDY. A PRESENTATION BY T.S. BADRINARAYANAN, GEOSCIENTIST, B SQUARE GEO TECH SERVICES, KOLLIDAM, SIRKALI TALUK, NAGAI DISTRICT,TAMILNADU, PIN- 609 102. E-MAIL: tsbadri56@gmail.com, MOB- 94430 46102.
AREA & PURPOSE OF INVESTIGATION. Name of the village : Ko.Pavalangudi. Panchayat Union : Vridhachalam. Taluk : Vridhachalam. District : Cuddalore. State : Tamilnadu. Area of extent : 100 acres. Purpose of investigation : To construct a very deep tube well for agricultural purpose. BADRI. 2
CUDDALORE DISTICT MAP SHOWING THE AREA OF INVESTIGATION. KO.PAVALANGUDI BADRI. 3
VRIDHACHALAM UNION MAP KO.PAVALANGUDI BADRI. 4
PROBLEMS. The hydrogeological condition is such that, potential confined aquifers occurs @ a very deep depth of > 200 meters below ground level. A very huge thick layer of aquiclude. Exploring the very deep aquifer & construction of well are problematic. A huge investment has to be made for construction. BADRI. 5
STAGES OF GW EXPLORATION IN SEDIMENTARY TERRAIN. SURFACE METHODS. WELL SITE SELECTON BY INTEGRATED HYDROGEOLOGICAL & GEOPHYSICAL METHODS. SUB SURFACE METHODS. DRILLING PILOT BORE HOLE LITHOLOG ELECTRICAL WELL LOGGING WELL DEVELOPMENT BY AIR COMPRESSOR YIELD ASSESSMENT WELL COMPLETION PUMPING TEST- HYDROGEO CHEMICAL ANALYSIS OF WATER SAMPLE. BADRI. 6
METHODOLOGY. Three stages of ground water exploration surface, subsurface methods & well development. Surface method- hydrogeological investigation to select a bore hole point. Sub surface method-drilling drilling pilot bore well- litholog preparation- electrical well logging. Well designing & construction- Well development by compressor- yield assessment-well completion. BADRI. 7
GROUND WATER EXPLORATION METHODOLOGY ADAPTED. FIRST STAGE. SECOND STAGE. THIRD STAGE. SURFACE METHOD. HYDROGEOLOGICAL SELECTING FEASIBLE POINT. SUB SURFACE METHOD. PILOT BORE HOLE DRILLING. GEOLOGICAL- LITHOLOG. HYDROGEOLOGICAL WELL DESIGNING & CONSTRUCTION. WELL DEVELOPMENT WELL COMPLETION GEOPHYSICAL- ELECTRICAL LOGGING. BADRI. 8
1.1.FIRST STAGE- SURFACE METHOD. Geological and Hydrogeological investigations to select a feasible point to drill a pilot bore hole. BADRI. 9
GEOMORPHOLOGY MAP OF CUDDALORE DISTRICT. BADRI. 10
GEOLOGY OF THE AREA. Terrain- Sedimentary terrain. The area is covered by various geological formations ranging in age from Cretaceous to Recent represented by black clay, calcareous sandstones & marls [Upper Cretaceous] overlain by Gopurapuram formations of Eocene age, essentially argillaceous, comprising silts, claystones, calcareous sandstones, shales, black clay & soils. The area is about 60 to 65 kms away from sea shore. [SOURCE- CGWB]. BADRI. 11
HYDROGEOLOGY. Ground water occurs in all geological formations both under confined & unconfined conditions. The area receives maximum rain fall during northeast monsoon period which is the main source for ground water recharge. The shallow unconfined aquifers may not be potential to tap for irrigation purposes. The deep confined aquifer occurs below 200 meters below ground level. The principal & potential aquifers are sand stones, fine to medium grained sands, pebbles & gravels. The depth to water level ranges from 20 to 60 m bgl. BADRI. 12
2.1. SECOND STAGE- SUBSURFACE METHOD Drilling of pilot bore hole- Rig engaged- Rotary rig. Dia & depth of pilot bore hole- 300 mm- depth- 312 m. Soil samples collected for every 6 m-m litholog prepared- soil samples analyzed in depth. BADRI. 13
ROTARY RIG. MUD PIT. BADRI. 14
ROTARY RIG. ROTARY RIG. PEBBLES. PVC CASING PIPES. BADRI. 15
TYPICAL ROTARY WELL CONSTRUCTION SEQUENCE 1 2 3 OVERSIZED BOREHOLE DRILLED IDENTIFY AQUIFER INSTALL CASING (& SCREEN) 6 5 4 YIELD TEST & WATER SAMPLING WELL DEVELOPMENT GROUT ANNULAR SPACE BADRI. 16
2.2. LITHOLOG. JEYARAMAN, KO.PAVALANGUDI, LITHO LOG. 0 34 BLACK CLAY DEPTH IN M BGL 50 100 150 200 250 300 29 7 25 10 15 7 34 20 18 14 28 6 29 9 26 6 16 5 CONFINED AQUIFER GREY COLRED FS- YELLOWISH BALCK CLAY FMS BLACK CLAY GREY COLRED FS- SST BLACK CLAYEY SAND BLACK CLAY + SST BLACK FINE SILTY CLAY BLACK CLAYEY SST BLACK CLAY SST BLACK CLAY SST BLACK CLAY+ SST SST CLAYEY SST YELLOWISH WHITE SST BLACK CLAY TS +YELLOWISH BROWN COLORED CLAY 350 BADRI. 17
2.3. GEOPHYSICAL- ELECTRICAL WELL LOGGING One of the subsurface methods of ground water exploration namely the electrical well logging facilitates continuous recording of electrical response verses depth by a sensor when it moves inside the bore hole. Among the several methods of well logging the common method used for ground water exploration is electrical well logging which includes SP log and resistivity logs. BADRI. 18
WELL LOGGING. BADRI. 19
LOGGING CONFIGURATION. BADRI. 20
ELECTRICAL WELL LOGGING Logging equipment- Portable spot logger. Resistivity meter used- Microprocessor based signal stacking digital meter- model- SSR- MP- AT- S 0f IGIS, Hyderabad make. Logging modes- SP & Normal resistivity log- LN-64 64. BADRI. 21
SP LOG. JEYARAMAN, KO.PAVALANGUDI, SP LOG 0 SP IN MV 50 70 90 110 130 150 170 50 100 DEPTH IN M BGL 150 200 SP 250 300 350 BADRI. 22
NORMAL RESISTIVITY LOG- LN 64 JEYARAM AN, KO.PAVALANGUDI, RES LOG- SN-64'' RES IN OHM /M DEPTH IN M BGL 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 0 5 10 15 20 25 30 35 AQUICLUDE. AQUIFER ZONE. SN-64'' BADRI. 23
3.THIRD STAGE- WELL DESIGN & CONSTRUCTION. The success of well depends on the well design and construction. The tube well design shall ensure an efficient and economical well with a service life of more than a decade. Well design- The assembly of plain and slotted pipes. The aim of screened & gravel packed well is to draw clear water from the aquifer without excessive head loss and to keep the aquifer material cut. BADRI. 24
WHY CARE ABOUT WELL CONSTRUCTION? Poor construction can affect drinking water quality. Poor construction can contribute, promote, and facilitate pollution and contamination of the groundwater aquifer. Proper construction can prolong the life and yield of the well. BADRI. 25
CONSTRUCTION OF BORE WELL IN SEDIMENTARY TERRAIN Bore well Logging Rest. -curve Kankar Clay Sandyclay Sand shale BADRI. 26
TYPICAL DRILLED WELL CONSTRUCTION WITH SCREEN WELL BADRI. 27
3.1. KO.PAVALANGUDI TUBE WELL DESIGN. JEYARAMAN, KO.PAVALANGUDI, PD. DEPTH IN M BGL 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 213 18 36 18 9 18 SLOT PIPE + BD. PLAIN PIPE SLOT PIPE PLAIN PIPE SLOT PIPE PLAIN PIPE BADRI. 28
3.3. KO. PAVALANGUDI TUBE WELL CONSTRUCTION GROUND LEVEL. CLAY PACKING. DRY CLAY BALL PACKING PEBBLE PACKING. 175 M 200 312 M TUBE WELL DEPTH 312 M. 0 TO 213 M PLAIN PIPE. 213 TO 231 M SLOTTED PIPE. 231 TO 267 M PLAIN PIPE. 267 TO 285 M SLOTTED PIPE. 285 TO 294 M PLAIN PIPE. 294 TO 312 M SLOTTED PIPE + PVC PLAIN PIPE SLOTTED PIPE. BOTTAM DUMMY. 29
3.4. DEVELOPMENT AND COMPLETION OF WELL Development of well is essential to obtain an efficient and long lasting well. The fundamental purpose of development is to cause reversal of flow through the screen openings. A permeable zone is created around the well screen. The tube well constructed was developed after 10 days by an air compressor. 90 V- notch yield was ascertained while developing. The yield of the well is 760 liters per minute. The water is very clear and the quality is very good to drink. Finally the well was completed by grouting and sealing the casing. BADRI. 30
WELL DEVELOPEPMENT BY COMPRESSOR BADRI. 31
RESULT AND CONCLUSION. The depth of tube well [TW] constructed- 312 m & dia of TW- 150 mm. The principal & potential aquifers- sandstone, fine to medium grained sand [FMS] & fine sand. The thickness of FMS- 26 m. Number of slotted pipes provided- 18 pipes- 54 m. Yield of the TW, by 90 V-notch- 6-760 LPM. The quality of water is good. Thus by integrated geological, hydrogeological & geoelectrical investigations the deep potential confined aquifer could be explored & exploited successfully. 32
THANK YOU. LET US CONSERTVE WATER. BADRI. 33