The hard road - Drilling update

I guess I was more than naive to expect that our first borehole drilling operation would run smoothly.
We are drilling where there is no available hydro-geological information, with new technology, new equipment and with a relatively inexperienced team. To complicate things we are drilling at the village Chairman's house which is on top of a small hill (perhaps not the easiest place to find water compared to the majority of areas in the Kilombero Valley which are located within a flat alluvial river delta). On top of all this, we are in Africa! Nothing happens smoothly and things take about 10 times longer than they want you think. haha.

Anyway, the drilling program started well with MSABI and the SHIPO team finding a suitable drill site within the Chairman's land. We used two copper wires to "devine" where the underlying water was likely running. It was a fun group exercise and the wire showed a definite flow path across the Chairman's land.

We progressed through the first 15m without too many dramas. There was a seasonal aquifer at only 1.5m depth! Below that was a very nice clay layer at 3m (a good sanitary seal for underlying aquifers). I did spend one Sunday fixing a number of drill pipes that had poor quality threads originating from the Njombe workshop. We had to truck them to Ifakara to be re-threaded.

At 15.5m we hit soft rock. We had been warned that in this area there was the possibility of rocks. The rock is consolidated sandstone - not very hard. However, it slowed our progress considerably from around 5m/day to less than 2m/day. At 21.5m we hit a harder layer and decided to check our equipment and do a pump test. The pump test took a whole day. It was a great team exercise. We found there was an aquifer at around 15m, overlying the soft rock layer. The flow rate was around 275 L/hr, or 4.5L/min which is below the recommended minimum of 300-350L/hr for a productive water point. So we decided to battle the rock. We had one painfully slow day where we made 1m before we broke through the hard layer into a soft sand layer followed by more soft rock. At 24.5m we hit something very hard. At the same time we broke the cutting handle on our drill rig. We decided to stop drilling and do another pump test - in expectation/hope that the softer sand layer is a yielding aquifer. Unfortuantley, when we pulled out our equipment we found that the hard object we hit was not rock but our own drill bit. It had come off our equipment. We then spent the whole day trying to "fish" out our drill bit, but it seems firmly wedged down the hole.

On inspection, the drill bit had unscrewed itself off the drill pipe thread. It was a design/manufacture fault from the Njombe Workshop. They were supposed to install a socket joint on the drill bit, not a thread. The rotating cutting action had been loosening the drill bit until it fell off. I should have picked up on this design fault earlier, but I thought things were ok as we were under the direction from the SHIPO staff. Also, the handle that broke used Class A GS pipe instead of a stronger Class B GS pipe. It is a bit dissapointing and annoying, but we will fix the equipment and soldier on. The worst thing is that we are unable to continue drilling this borehole. We will do a pump test tomorrow to determine the flow rate from the well.

In a funny twist SHIPO sent through a new special drill bit for rock which arrived today. This one has a socket joint instead of thread. Unfortunatly it is one day too late.

I am confident that this rock issue will not be a big issue for the majority of our jobs. This particular area is nestled closely to the Udzungwa mountains whilst most of our work will be within the river delta area. Even so, it is encouraging to know that the rock is relatively soft and can be drilled. It is a credit to the MSABI team who on their first job managed to drill 10m through rock!

I will let you know ASAP how the pump test goes.