- [Instructor] So, I'm gonna talk today about oil movability quicklook using dielectric measurements at four depths of investigation. At first, I'm going to review dielectric concepts, talk about the new tool, the movability quicklook, and invasion concepts that it's based on. And then give a heavy oil sandstone example. And then heavy and light oil diatomite examples. And then show the application with sidewall cores. So, just kind of a review, the dielectric measurement is similar to an induction resistivity, except the frequency is much higher. The highest frequency in use is up to a gigahertz, and then there's frequencies lower than that. But at one gigahertz, the measurement is very sensitive to the water molecule. The water molecule aligns when the one gigahertz energy is applied, and, as a result, the tool is very sensitive to water and we actually output a water filled porosity in the field. And so, the use of that, for the quicklook technique, that's been around for a number of years, is that when you compare water filled porosity with total porosity, you can identify oil saturation regardless of the salinity. So, it's an interpretation technique that's relatively salinity independent. And here's an example of the historic methodology using a single depth of investigation dielectric water filled porosity here in blue. And the total porosity, either density or In a water zone, which you see down in this lower portion, the curves overlay. And in an oil-bearing zone, heavy oil zone, they separate out. The measurement is fairly shallow, so that's why it explores what we normally call the flush zone. And so, that's why heavy oil is the environment which this has been used for more than anything else. And so, when we see this separation, this is a clear indication that we have hydrocarbon there and a hydrocarbon saturation is proportional to the separation. So, where this technique works, it's very clear, it's very easy to use, and it helps identify, especially in freshwater environments where you have higher resistivities all over the place, some due to oil, some due to freshwater, this pops the oil zones right out. So, we have a new tool here that gives us additional capabilities to make these dielectric measurements. And this tool is a multi-frequency dielectric dispersion tool that operates at four different frequencies, two different polarizations, and multiple transmitter receiver spacings. So, still having the vertical resolution of about one inch. And now we've got a depth investigation that varies from one to four inches due to this transmitter receiver spacing. It also has a fully articulated path, similar to a density tool, so when we have rough borehole, the tool can conform to the borehole and actually it's 3D articulation, not only does it move this way, but it rotates left and right. The other thing we take advantage of is this transmitter receiver spacing. See, you can see the pad which is horizontal, which is vertical in the actual tool, has the transmitters in the middle, four receivers above, four receivers below. And so, we have multiple pairs of transmitter receivers, and since we have a symmetrical design, we have a borehole compensation system integrated into the tool. So, what we're really doing is examining this region we see from transmitter to receiver and transmitter to receiver, we're really exploring this interval right here. Giving us a very high vertical resolution measurement, and because we have identical, symmetrical transmitter receiver configuration, and we have a very robust comparison between the response function, between transmitter receiver pairs, where the only the different is the increasing distance between them. Giving us a nice depth investigation increase. It makes a robust comparison from one measurement to the next. So, we use this for an oil saturation quicklook that's available at the well site, using four curves where we used just the one before. So, the movability quicklook presentation takes advantage of these four depth investigation measurements and gives us an invasion profile in the region between one and four inches depth of investigation. So, the quicklook presentation has comparison to total porosity of the four curves, the four water filled porosity curves available from the dielectric, and we explore the separation between the total porosity and dielectric porosities, which gives us a hydrocarbon indication. And then the separation between dielectric curves themselves indicate movability. And so, the interpretation of this data says that when you have zone with low movability, the dielectric curves will read the same. They'll lay on top of each other. And when they separate out, that means we've got oil movement in that region between one and four inches. So, this is a quicklook presentation that focuses on the porosity track. So, we've got a porosity scale here from 10 to 40 porosity units. And we have a density curve in red and the neutron curve in blue and the four dielectric curves. We have the one inch step investigation, two, three. So, when you examine the separation between the one inch curve and the density curve, then you're observing the oil that's present at a one inch depth of investigation from the borehole wall. When you explore the separation between the density and the two inch curve, now you're able to see how much oil is out of two inches. And so by observing the subsequent depths of investigation, you're able to see what the oil saturation is and how it's changing in the region. So, when you have separation between all four of the curves, that indicates that the invasion process has moved the oil passed one, passed two, passed three, and affected between three and four inches into the formation and swept some of the oil back. In a situation where you have the three and the four inch curves laid on top of each other, that indicates that the invasion process is affected out to between two and threes inches. So, it's a very nice visual exploration of the oil saturation profile in the near wellbore region. When we have this observation capability, then we want to take a look or think about what are the causes for variations that we see in invasion. Tried to list few of them, the main one, the one that I started out with on this project, is oil viscosity. When you have heavy oil versus lighter oil, you're going to see variations in this invasion profile. Also, wettability, mud properties, how much over balance you have, and then what's the permeability. So, permeability variations are gonna cause changes in the invasion profile. And, as well, I've got an example later on of stimulation of a nearby well. At the end of the day, when you see in these environments of heavy oil and low permeability, when you see movability, it's predictor of producibility. It's either identifying zones with lighter oil, or zones with better permeability. So, here's a couple of examples where I've built a cartoon of a reservoir to try to better visualize what this log response is showing. So, here we have a log with the density neutron and the four dielectric curves on a 10 to 50 scale, and this is in a sandstone with about eight gravity oil, and the interpretation of that is illustrated by this cartoon. We've got channel layers in brown, this is an oil sand here, and this is a borehole, and the four depths of investigation of the dielectric tool. And this is obviously not drawn to scale. But in this case, the mud filtrate tries to invade, tries to move oil back but it can't, because the oil is heavy, and so this is the log response we get. An then, in this kind of situation, where we have movement of oil, we get a log response similar to this, at one, two, three, and four inches we have different oil saturations, because mud filtrate has swept back and, obviously, it's gonna do more sweeping on one inch and a little bit less on the two inch, until it gets to a point where the invasion has stopped and you're into aversion formation. So, I'm calling this a high movability zone, but this is in the realm of the low-perm, heavy oil environment where this has the best application.