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Understanding the Reservoir Rock

John D. Lawrance - DTK Group


Tue, 01/22/2013 - 14:20

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Q: What have been the highlights for DTK Group during 2012, and what has been your participation in the deepwater discoveries?

A: Business has been going very well; we have been particularly active on the core analysis side, where we have been working mostly on cores from offshore wells, including those that have come from the deepwater exploration wells drilled last year, which are becoming extremely important for the future of Mexico. It was interesting for us to be analyzing those cores and identify the interesting opportunities that are present there with what appears to be very light oil in productive reservoirs.

Q: Pemex has increased the number of core samples taken from each well, from two to an average of six, while extracting up to 20 in the more complex wells. How has this affected your work?

A: There has been a significant increase in the number of cores taken, especially in exploration wells. Our focus is on attending to the client’s needs and requirement for quick information, especially for wells where decisions regarding testing potential reservoir production have to be made. To better attend to those needs, we are constructing a new facility in Villahermosa that will duplicate the size of our operation. We hope that shortly we will be opening a lab in Poza Rica as well.

Q: How long does it take to run a sophisticated core analysis for each of those samples?

A: Depending on the rock type and the situation, the results of doing advanced flow studies can take up to two years. That tends to be a worldwide problem in the industry, because it can often be that two years later the information is of no use anymore. Because of timing alone, there is an enormous opportunity for technology based on microscopic imaging, and doing analysis on computer models built from the imaging, which recreates the internal structure of the rocks and enables all kinds of analysis, including flow studies, to be done on the models rather than on the rock. The turnaround time for this kind of studies – called e-core analysis – is much faster and this is one of the main reasons why e-core analysis is gaining importance in the oil and gas world today.

Q: What advantages does the e-core analysis hold against conventional core analysis?

A: You can actually apply e-core technology to all kinds of rock samples, whereas with conventional core analysis you must have a core. Therefore, the analysis you can do is limited to the depths where you obtain the cores. Perhaps this explains the more frequent cutting of cores for traditional analysis. Even so, six cores represent only six 9m intervals along the whole course of the well, which may or may not coincide with your key reservoir depths. E-core technology can be applied to core samples, but also to sidewall core samples, and to drill-cutting samples. Its microscopic technology only requires a very small piece of rock: any reasonably sized drill cutting can be used to obtain those images. Therefore, it lends itself to taking samples from a large number of depth points during the sequence of the well, including frequent points throughout the interval of most interest, which is the reservoir that will be producing. E-core technology gives you the opportunity to have much more complete sequence throughout the most relevant depth interval while conventional core analysis does not do so much.

With this being said, I have to point out that e-core analysis is not something that DTK Group proposes as a replacement of conventional core analysis: there is really nothing that can replace physical tests on rock samples. There is very little in the industry that provides the opportunity to do a real test on a real piece of rock, and the majority of technologies are based on remote sensing methods. E-core technology is not quite remote-sensing, but does not take measurements directly from the rock sample: it is recreating the internal structure of a rock sample in a computer model at a microscopic level and then blowing up the scale of that model, rather than analysing the physical rock. The technology is not cheap, but it is not as expensive as traditional core sample analysis.

Q: What does DTK Group identify as the main opportunities for core analysis in deepwater and shale gas plays?

A: The deepwater success in 2012 at both Trion and Supremus certainly indicates that there will be a lot more opportunities in deepwater, and I am sure there is going  to be plenty of work bringing those fields online and searching for new opportunities. We are also waiting for Maximino’s results to start core analysis there. Operations on deepwater drilling rigs are so expensive that the time required to cut a core in a deepwater well is consuming an awful lot of money. If you can provide the same information by doing analysis on samples that you can obtain without cutting a core then you are saving a lot of money. E-core technology certainly is a tremendous potential application for deepwater wells because of the economics.

For shale gas, it is more a question of the application of technology, rather than economics. Doing conventional core analysis on shale samples is extremely difficult, time- consuming, and costly, while the results obtained are questionable because of the characteristic of the rock. Shale rock has virtually zero permeability, so carrying out flow studies on a piece of shale and making a fluid flow through that piece of rock is pretty much impossible. To achieve that, it takes quite a sophisticated system and a long time. Whereas e-core technology microscopically recreates the internal structure of the sample and performs the analysis on that model, enabling to carry the whole process at a microscopic scale and extremely low permeability values, but in a much shorter time and with better precision. From a technical point of view, it is the better option.

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