Wednesday, 26 August 2015

Open extensional fracture mapping - 22nd and 23rd August

Last year, some large features were observed, but appeared to have little to no off set along them, suggesting they were not faults.

Before leaving for this field season, I developed a map using satellite imagery, identifying where with in the caldera these features appeared to be. So one of the surveys is to find as many of these features as possible and collect data. The data to be collected include: dip, strike, depth, width, off set (if any) and direction of down throw (if any).

The location of most of these features, believed to be open extensional fractures, appear to be in the centre of the caldera. Due to the lavas in the centre, we would be limited as to how many we could access. For safety, only those that could be accessed from roads and well pads would be obsevered and recorded.

Inside the termination point of an open extensional fracture

Many of the open extensional fractures observed appear to pinch out at each end and accessing the deepest point of the fractures was not always possible. We used a hand held DISTO laser measurement equipment for the width and depth. 

Inside an open extensional fracture

Standing along the strike of an open extensional fracture

We found some of the features identified, not to be open extensional fractures, and also found that access to even those near roads and well pads, very difficult. Altogether, we only managed to collect data on 34 of these features. It is hoped that the data can be used to establish whether, as seen in parts of north-east Ethiopia and northern Tanzania, the extension is this region is now accommodated by dyke intrusions, or if it is still being accommodated by faulting.  

This was a short survey, therefore a short post, so,

Lala Salama from Kenya!

Steaming ground survey - days 15th, 16th and 17th August

Over the next couple of days we completed a detailed survey of the steaming grounds situated almost at the centre of the caldera, very close to the location where I believe part of the structural ring fault sits below the young lavas.

The steaming grounds and fumarole were very active last year and although the temperatures are still very high, there does not seem to be as much steam. Published isotope data has already demonstrated that the main source of the steam and therefore the main Menengai recharge source is Lake Nakuru approximately 8km to the south.

Lake Nakuru along with most of the rift lakes of Kenya and possibly parts of Ethiopia have flooded in very recent (2-3 years) and are yet to recede by a notable amount. The amount of flooding far exceeds that of the annual average rainfall for the region. The reasons for the flooding though unknown, already has hypotheses associated to the phenomena and will hopefully be investigated in the near future.

So two main hypotheses to explain why the steaming grounds and fumaroles at this locality are less vigorous in comparison to last year are (1) despite coming to the end of rainy season, it has been a much dryer few months. So the addition of  meteoric water to the system, through rainfall has dropped. This would need testing from the aspect of infiltration speeds, heating and circulation. It might be that the system circulates and heats the fluid at a rate that would not support this hypothesis. (2) MW-10 is just a few 10's of meters to the north of these steaming grounds and fumarole. It has just completed the drilling of a directional well that cuts directly beneath the steaming grounds, targeting the feature responsible for the fumarole. This will have created a conduit for the steam to escape along at a much quicker rate with less resistance.

So on to the survey. We completed a detailed grid map of a section of the steaming ground. The location for this was identified based on early morning observations of where there was a higher amount of steam escaping to the atmosphere.

Mairi recording some data

We created a 10m x 10m grid, split in to 2m x 2m squares. The GPS co-ordinates of the corners of the 10m x 10m square were recorded. Then a grid sketch was made of the key features and the positions where temperatures were recorded from, the temperatures were noted and the strike of any fractures. The highest temperature recorded during this survey at 11cm depth was just over 78 degrees Celsius. We had predicted very early on that the temperatures would be higher the closer to the fumarole we surveyed. Though this became apparent very early on, the second part of the survey actually demonstrated the ground temperatures immediately over and around the fumarole were generally lower. 

In addition to the data collected as described above, we also collected three soil gas samples and data on the CO2 efflux in the centre of each 10m x 10m square. 

Me completing soil gas sampling and efflux recording

This part of the survey covered 2400m square, which due to early starts, we managed to complete in two days, including the end of the last day when we got caught in a very heavy down pour and thunderstorm. The rain drops are huge in Kenya and so cold! 

The second part of the survey, originally had been planned the same as the first. However on looking at the slope and knowing the challenges we had moving the grid from one section to the next, I changed it. So instead of detailed grid mapping of the area, we did 4 transects starting at the top of the slope.

Working down slope on one of the transects, with MW-10 in the background

Each transect was 30 meters long and spaced 10m from the next. The grid co-ordinates for the start and the end of each transect was recorded. At every 5m, starting at 0m, the temperature at 11cm depth was recorded and additionally at every 10m, starting at 0m, on transect 1 and 4, soil gas samples and CO2 efflux data were collected.

I hope this survey will present data that will show the changes in the shallow sub-surface behaviour of fluids and gases depending on where the samples were collected in relation to any major features, eg. a fault. From this, it should then be possible to make some inferences that due to the environment being similar, this behaviour also occurs at other fumarole localities across the caldera. 

The total area covered was just under 2500 meters square. Here's hoping it worked! :-)

Lala Salama from Kenya! 

Tuesday, 25 August 2015

Soil gas sampling, the student becomes the teacher, days 12th, 13th, 14th, 18th, 20th & 21st August

Today the real work begins and I woke up feeling a little nervous.

After spending a month on the Canary Islands, myself being taught how to do soil gas sampling and the concepts behind the accumulation chamber method for efflux data collection, it was time to pass on what I had learnt to my two field assists Beth and Mairi - just a little scary for a moment!

I'm lucky that both Mairi and Beth are quick at picking up new things, so it wasn't long before they were getting on with the survey at hand.

The area to be surveyed is 77 km square and we have about 6 days to complete 300 sample sites. Each sample site is approximately 200 meters apart and follow the road network that has been constructed in the caldera, for ease of access.

Soil gas sampling involves knocking a stainless steal rod in to the ground with a hole through its length. at the top there is a rubber septum that a needle is inserted through. This needle is connected to some tubing, valves and a syringe. The syringe is used to draw the gas from the ground. The first time the syringe is filled, the collected gas is used to 'flush the system', which in turn reduces the possible effects of contamination from the atmosphere. More gas is sampled also, to flush the vials for the same reason.

Mairi soil gas sampling

Showing Beth the 'PP' efflux equipment - kindly on loan from Oxford University

Beth on soil gas duty

Both girls getting stuck in by well MW-01 venting at 35MW

During this survey, the extra site we got to see include being in the right place at the right time and catching well MW-07 discharge for the first time.

This was something I never thought I would get to see, so a first for me too!

Sampling in the south of the caldera was very hot and very peaceful, but very pretty - we did have our driver on leopard watch. Though they are nocturnal and would move away if they heard us approach, most of the caldera's resident leopards are mothers with young, so we have to be extra vigilant. 

A short time out to take in the serenity of the southern part of the caldera

Trucks as wide as the lanes - only in Kenya! The installation of the steam pipes, X-ray checks of the welding of the pipes and the start of the installation and construction of the Menengai sub-station.

We also met this inspirational young woman Gathoni, a female Drilling Engineer and rig supervisor at just 28 years old and a perfect role model for young girls here in Kenya. As her rig is currently awaiting the go ahead to start drilling, she took some time out to talk to us about the rig and how things work. Though we were kitted out in our personal protection equipment, we were not allowed on the rig, but were able to have a bit of a walk around the well pad so Gathoni could point things out to us as she talked about them and the equipment role in the bigger process. 

Myself, Gathoni, Mairi and Beth
Steam pipe installation near the site of the Menengai sub-station

The rods we use for the soil gas surveys become very blocked every day. And although most of the time we manage to unblock them enough to finish a days work, it is likely that they would get blocked to a point where they can no longer be used. So we found a garage on our way back to our accommodation where they had a power washer. Every day Ailisha would clean the probes for us, so the inside of each was completely clar for the next day.

Equipment cleaning!

The survey team grows by two!

Mairi soil gas sampling with an audience!

One day's worth of soil gas samples!

So that is our soil gas survey almost complete. We just have 28 sites left to do along the south rim of the caldera, which is planned for the end of August. We had hoped to have already completed this survey, but we got lost. So we are waiting for the availability of someone who knows where they are going a lot more than I do!

Lala Salama from Kenya!

What and Why?

So after last year's fieldwork, I developed a geological map of the caldera in it's entirity. All the maps of the caldera that I have managed to find so far are from the late 50's and 60's. And though these maps are really quite beautiful in that they have been done by hand (I could look at geological maps for hours! Bit geeky? Maybe! But who cares!) Never be afraid to be yourself, and if that means you're a bit of a science nut, then so be it! You will be successful in all your endeavours and the world needs more of us!

Trying to get rock samples out of Kenya can be a challenge, as several permits are needed, the rocks need to be checked for any economic value (and if found to be so, they may be taken from you), there is of course the cost of shipping them also. So the map does not contain specific dates of individual flows, but is based on observations made in the field with regards to age relations of one flow to the next. There is some literature available with dates of some of the youngest lavas, so it is possible I could add some dates at a later stage.

The idea behind developing this map was to look at the flows and the relations with the localities of the drilled and proposed wells. The map also provided striking evidence for the possible location of a ring fault, something that has largely been inferred. In addition to this inference, inferences have also been made as to the location of faults and fracture networks. Having a good understanding of the locality of such features, especially those that are active conduits for gas and fluid movement, is of vital importance in understanding geothermal systems.

Here at Menengai, the locations of these features are largely based on inferences because any surface traces have been buried by the very young lava flows associated with the post-collapase resurgent volcanics of the Upper Menengai Sequence (McCall, 1958-1959).

So based on last years observations, map development, LiDar and satellite imagery and further research, the plans for this year are as follows:

Soil gas sampling and in situ CO2 efflux data collection - the soil gas sampling involves drawing gas form a depth of 40 cm down in to syringes, the samples are then transferred to vials. Over 300 sites have been sampled across the caldera with 2 samples collected at every site and a further third sample collected at approximately 15% of the sites. The samples will be analysed at the InVolcan labs on Tenerife, looking for quantitative values of CO2 and Helium using micro-gas chromatography and quadrupole mass spectrometry, with the third samples analysed for 13C/12C ratios using isotope mass spectrometry. These gases are the first to rise to the surface from a magmatic body and are therefore perfect gases to target. The efflux data is used to determine the amount of diffuse degassing occurring in Menengai - the degassing no one sees! Collectively this data can be used to generate sequential Gaussian simulation (sGs) maps that will identify the locality of active faults and fractures buried below the young lavas, a key requirement for geothermal development and system modelling. Further to this, the data can also be used to monitor how much CO2 Menengai is degassing naturally to the atmosphere in relation to climate change, and for volcanic risk monitoring of volcanoes that are still classed as active.

Soil gas sampling (and educational filming commitments! in the Canaries)

CO2 efflux data collection in the Canaries, using the accumulation method with a Leica sensor - slightly different to the sensor to be used in Menengai - but does the same job.

An active volcano does not need to be erupting to be classed as active. Any volcano that has erupted in the last 10,000 years, has shown to have ground movement (inf;ation and/or deflation) recorded by geophysics and InSar satellites and has active fumaroles, geysers and springs is classed as active.

Further surveys connected to above include detailed mapping of a steam field where soil gases will be collected, CO2 efflux data, surface temperatures and thermal imaging.

Additional surveys include Ground Penetrating Radar and Transient Electromagnetics. As neither of these surveys have been completed in Menengai before, it is very difficult to predict how the electrical signals used with behave; what the attenuation depth will actually be and how much signal scatter there might be.

I checked with GDC on arrival and found that all the surveys I have  planned to complete during this field season, have not yet been completed. This is quite exciting, as it allows for the development of further data that will complement the data already available, testing the capability and relevance of the methods and equipment to be used.

So keep watching to see how we get on.

Lala Salama from Kenya!

Sunday, 23 August 2015

It's good to be back! - 11th August

Following on from last year's fieldwork,, this blog is all about the follow up work this year.

So after 6 months of preparation, funding applications and training in field techniques such as soil gas sampling and geophysics, along with finding 2 field assists. The time is here and I am finally back in "my caldera", Menengai, for 5 weeks of intense fieldwork and catching up with some great friends.
Pic of me training with geophysics

My two field assist, Mairi and Beth are first year undergraduates from the University of Glasgow and were successful in their applications to the Royal Geographical Society for an award as part of the Fieldwork Apprenticeship Scheme.

Mairi, Beth and myself setting a new fashion trend!

After 20 hours of travelling we arrived at our accommodation, Maili Saba Camp just north of Nakuru. I was quite happy that we had arrived in the dark, as Beth and Mairi would get a fab surprise in the morning, their first glimpse of the caldera, a view I will never get tired of!

On arriving at Maili Saba, we were greeted by old friends and some new, singing "Jambo Kenya" with drums, dancing and changing some of the words to include our names.

So the first thing we needed to do before entering the caldera was to visit the GDC offices in Nakuru to collect our security passes. This was arranged very quickly by Geoffrey Mbia and off we went, heading for the gate 2 on the west side of the caldera.

Today was a day that allowed me to get re-acquainted with "my caldera", the beautiful and mysterious Menengai caldera. And it gave the girls their first taster of what to expect with regards to the complex road networks, the heat, the dust and the very friendly GDC team, as well as the contractors from the likes of Cluff Geothermal and Target Directional Drillers. So much has changed! There are new well pads, new roads, huge steam pipes to connect the production wells to the sub-station and piles are in place ready for the electricity pylons.

The girls really enjoyed the first day. They said after everything I had told them it was great to see it all. Some things started to make sense. They were a little in awe of the size of the caldera and were amazed that I had said we would cover the entire area in five weeks. They were excited to start seeing geology they had not yet seen, and excited to start learning. The reality of everything occurred at our very first stop,MW-01, when it was time to put on the hard hats and high visibility jackets ready to go on to the well pad. MW-01 is currently under venting conditions of two out of five directional wells. It is holding at a vent energy of approximately 35MW and has been doing so since December 2014.

MW-01 venting at 35MW from two directional wells

This well is adjacent to MW-21 that is also under venting conditions of both directional wells and is currently holding at a vent energy for 15-20MW.

I was really excited that some of the wells were venting, as the girls would get to see it and despite the huge mufflers, hear the jet engine like noise they produce that we can hear 7km away at our accommodation.

The next stop was the steam fields, where last year my small team cooked boiled eggs for breakfast. I wanted show Beth and Mairi this location, because last year I found the place fascinating and we would be completing a detailed survey later in the trip. I wanted to get some ideas from them also.

I took the girls over to see the Predator rig, owned by Cluff Geothermal, I hope I can arrange for them to go on the rig at some point during our 5 weeks.

Cluff Geothermal's Rig

There were many smaller sites I took them too. I had spent so long talking about the features, I had to show them. So we first went to the south of the caldera where last year evidence of syn-collapse and post- collapse eruptions occurring at the same time could be seen, supporting a piecemeal collapse mechanism discussed in literature. This was followed to a visit to the highest point in the caldera, where post-collapse resurgence has occurred and is the source of the young lavas. From this point it is possible to view the caldera in 360°, so with some maps in hand, I was able to explain some key features and areas of the caldera.

Heading out of the caldera, I was able to show them the 'cross-bedding' structures in the tuffs and the clay quarry, where it is now possible to see the relationship between the clay and the lavas.
Though this was not a particularly long or busy day, after 20 hours of travelling, this was plenty for Beth and Mairi to think about. And despite how much has changed, I remember so much, so well.
Tomorrow the real work begins.

It has taken two weeks of waiting to get internet speed fast enough to load this, so I hope to load more, at a much more regular interval from here on in.

Lala Salama from Kenya.