How electromagnetics could have changed the drilling sequence creaming curve in the Barents Fibre optics in wells to record seismic - now competitive with ocean bottom nodes? Improving workflows for non- seismic data - one data set can help you better understand another Non-seismic Geophysical Technologies and Non-Conventional Seismic, London, Oct 11 2017 Special report Non-seismic Geophysical Technologies and Non-Conventional Seismic October 11 2017, London Event sponsored by: Non-seismic Geophysical Technologies and Non-Conventional Seismic Electromagnetics, well fibre optics and combining data Finding Petroleum’s London forum looked at non-seismic geophysical tech- nologies and non-conventional seismic, with a special focus on using elec- tromagnetics to reduce risk, working with well fibre optics, and combining seismic and non-seismic data This is a report from the Finding Petroleum conference “Finding Petroleum: Non-seismic Finding Petroleum’s London forum on Oc- Garth Naldrett, Chief Product Officer of Geophysical Technologies and Non-Conventional Seismic”, held in London tober 11 2017, “Non-seismic Geophysical Silixa presented the company’s technology in October 2017 Technologies and Non-Conventional Seis- to record acoustics in wells using fibre optic Event website mic,” looked at how companies can work cables, which can be used for (active) seis- Many of the videos and slides from the with electromagnetics, in-well fibre optic mic and passive seismic. In particular, it is event can be downloaded from the event seismic, and combining seismic data with useful for repeat surveys, if the fibre optic agenda page. other types of data. cable is permanently installed, and it may www.findingpetroleum.com/event/ef071. prove to be better than ocean bottom nodes aspx Daniel Baltar, Global Exploration Advisor (OBN). with electromagnetic company EMGS, ex- Report written by Karl Jeffery, editor of Digital Energy Journal plained how electromagnetics might have Markus Krieger, Managing director of [email protected] been used to get a better understanding of Terrasys Geophysics presented some Tel 44 208 150 5292 the different risk of well prospects in the techniques to use different kinds of data Barents Sea – and then showed how the together, for example gravity and seismic. Conference chairman Karl Jeffery drilling sequence creaming curve might It may be helpful as an intermediate step Report author Karl Jeffery have been changed if EM had been used. to use crude or low granularity models, as Conference Producer David Bamford This can then be compared to the actual you try to understand what the subsurface Layout by Laura Jones, Very Vermilion Ltd success of the wells, which is now known. actually looks like. Finding Petroleum www.findingpetroleum.com It illustrates that EM data only reduces ex- Perhaps it is better if you don’t try to invert Future Energy Publishing, ploration risk by a quantifiable degree. It all of your seismic (from time to depth) at 39-41 North Road, also highlights the significant value of the the same time, but just convert the seismic London, N7 9DP, UK www.fuenp.com EM negative case Considering the large where you have a good idea of the density Sales manager amounts of money involved in drilling, / velocity model at that point, for example Richard McIntyre particularly in the Barents Sea, derisking using well data, he suggested. [email protected] improvements over the portfolio scale are Tel 0208 150 5296 well worth having. 2 Non-seismic Geophysical Technologies and Non-Conventional Seismic, London, Oct 11 2017 Non-seismic Geophysical Technologies and Non-Conventional Seismic Using electromagnetics together with seismic Electromagnetic data is perhaps best used in practise to de-risk, or get a better understanding, of targets selected from the seismic. Daniel Baltar explained how to do it, with an example from the Barents Sea Electromagnetic (EM) surveys of the subsur- Working with just seismic ally underestimated in size. So you can’t just face can directly reveal one thing – material dial down all of your estimates, in case you with less resistivity than the norm – and that Seismic itself can tell you about the geometry leave large reservoirs behind thinking they are means salty water. Both hydrocarbons and dry of the subsurface, and if you have 3D seismic too small, he said. rock show up as high resistive bodies. you can interpret amplitude patterns to get an understanding of depositional patterns of the CSEM in more detail Explorers are not looking for salty water, of rock. But it cannot tell you anything about the course. But understanding the salty water fluid in the rock. The ability of CSEM to image a reservoir is can help you understand where hydrocarbons a function of the area of low resistivity (= the might be, as Daniel Baltar, Global Exploration When oil and gas explorers want to understand area of the briny water volume), the thickness, Advisor for EMGS ASA, explained. the hydrocarbon potential of part of the world, and the level of resistivity (= the concentration they generally start by interpreting seismic to of the brine). In this way, build a structural and geological model. EM could If a reservoir is entirely filled with hydrocar- have been They use this to try to understand whether bons, or there is just a small volume of briny used to better there might be a reservoir (an accumulation water, then it will not show up in the EM data. understand of hydrocarbons), a seal (which stops hydro- the risk for carbons leaking), and a trap (an arrangement But if the EM data shows low resistivity in the a number of of the reservoir and seal which does not allow same place as your reservoir, it might be tell- Barents Sea leaks). All of these factors need to be present ing you that the reservoir is entirely filled with wells. Mr to produce oil. brine (no hydrocarbons). Baltar ex- plained in Then they estimate the amount of oil by calcu- If the reservoir is nearly all full of brine but his talk what lating the gross rock volume, saturation and ex- with a small amount of oil on the top, then the Daniel Baltar, Global Exploration the drilling pected recovery. A combination of the estimate oil will be hard to see, so it will look like a field Advisor with EMGS sequence of the amount of oil (the prize) and estimate of full of brine on the EM data. was based on the risk leads to a decision about whether to seismic alone, how understanding from EM develop the field. But if you have a reservoir part filled with oil could have led to changes in the drilling se- and part filled with brine, the reservoir will quence, and how much could have improved It is very hard to do successfully. In the Barents show up as having a higher resistivity than if it the final result, based on the actual success of Sea, 106 wells have been drilled, but an an- was filled with brine, but not the same resistiv- the well. alysis by the Norwegian Petroleum Directorate ity as the surrounding rock. showed that about 95 per cent of them did not Controlled Source Electromagnetics (CSEM) turn out to be economically viable, and only This is how EM can provide more insight into is a technology to generate an electromagnetic 10 per cent had more than 100m barrels of oil your target reservoirs. signal, send it through the earth, and see what equivalent (with 200 to 300m boe minimum you receive back, some distance away. Elec- field size in the Barents Sea). Five Barents prospects tromagnetics are also used for communications between a mobile phone and an antenna. An One oil company did an analysis of the reason Mr Baltar presented an example where CSEM EM signal will travel through the subsurface behind 120 of its dry “wild card” wells, and was used to help evaluate five prospects in the more easily if there is salty water (brine), be- found that 45 per cent of them turned out to Barents Sea, named Korpjell, Blåmann, Gem- cause it conducts electricity. have no seal on the reservoir, and 30 per cent ini North, Koigen and Kayak. had no charge, a pressure force pushing oil The value of EM is based on the fact that it into the reservoir. So there were no fluids in Korpfjell was in the most bid on block in the can see something which seismic cannot – i.e. the reservoir. previous license round in Norway, with “real whether there is brine in a reservoir – and then fights” between companies to gain access, he using EM together with seismic to get a better In another example, Mr Baltar showed a graph said. picture. of volume predictions of fluids in reservoirs made in Norway, comparing the predicted vol- Blåmann and Gemini North were close to Reservoirs usually have salty water beneath umes with the actual volumes. There is so little already known discoveries, which put them the oil, pushing the oil upwards against the correlation, essentially it shows that companies higher in the ranking (lower risk). seal (oil is less dense than water). So if the res- cannot make predictions at all, he said. Nearly ervoir space appears to be partly full of some- all the predictions are over-estimates. thing with lower resistivity, that makes it more Koigen and Kayak were considered more out- likely that the rest of the reservoir has a seal liers. At the same time, records show that most of the and a trap, Mr Baltar said. really big discoveries ever made were origin- Kayak is cretaceous, the other four, Koigen, Non-seismic Geophysical Technologies and Non-Conventional Seismic, London, Oct 11 2017 3 Non-seismic Geophysical Technologies and Non-Conventional Seismic Gemini North, Korpjell and Blåmann are lower website.