What Is Enhanced Oil . . . How the Enhanced Oil . . . Limitations of Passive . . . Need to Take Into . . . How to Monitor Possible Our Main Idea Side Effects of Enhanced Oil What Seismic Signals . . . How Pumped Liquid . . . Recovery Process What We Know . . . How We Can . . . Home Page Jose Manuel Dominguez Esquivel 1 Solymar Ayala Cortez 2 , Aaron Velasco 2 , and Title Page Vladik Kreinovich 3 ◭◭ ◮◮ 1 Mexican Petroleum Institute jmdoming@msn.com, jmdoming@imp.mx ◭ ◮ 2 Department of Geological Sciences 3 Department of Computer Science Page 1 of 25 University of Texas at El Paso, El Paso, Texas 79968, USA sayalacortez@miners.utep.edu Go Back aavelasco@utep.edu, vladik@utep.edu Full Screen Close Quit
What Is Enhanced Oil . . . How the Enhanced Oil . . . 1. What Is Enhanced Oil Recovery Process Limitations of Passive . . . • Traditional oil and gas industry mostly rely on loca- Need to Take Into . . . tions where oil and gas are stored under high pressure. Our Main Idea What Seismic Signals . . . • Because of this pressure, oil and gas flow out of the How Pumped Liquid . . . well on their own. What We Know . . . • As the pressure decreases, production decreases ac- How We Can . . . cordingly. Home Page • Hence, higher pressure pumping is needed to enhance Title Page mobility of oil and gas to the surface. ◭◭ ◮◮ • This is performed by water, nitrogen, or CO 2 injection. ◭ ◮ • Alternatively, instead of pumping high-pressure fluids, Page 2 of 25 we can pump chemicals that Go Back – convert difficult-to-extract heavy carbohydrates – into easier-to-extract lighter ones. Full Screen • This is known as enhanced oil recovery process . Close Quit
What Is Enhanced Oil . . . How the Enhanced Oil . . . 2. Enhanced Oil Recovery Process (cont-d) Limitations of Passive . . . • The resulting chemical reaction must be as efficient as Need to Take Into . . . possible. Our Main Idea What Seismic Signals . . . • It is known that the speed of chemical processes expo- How Pumped Liquid . . . nentially grows with temperature; hence: What We Know . . . – to speed up the corresponding processes, How We Can . . . – chemicals at high temperatures – between 200 ◦ C Home Page and 350 ◦ C – are injected into the well. Title Page • This leads to a better extraction of oil from the pro- ◭◭ ◮◮ duction wells which are near the injection well. ◭ ◮ Page 3 of 25 Go Back Full Screen Close Quit
What Is Enhanced Oil . . . How the Enhanced Oil . . . 3. Enhanced Oil Recovery Process: Successes Limitations of Passive . . . And Problems Need to Take Into . . . • The enhanced oil recovery process has enabled us to Our Main Idea extract up to 75% of the remaining oil. What Seismic Signals . . . How Pumped Liquid . . . • However, the problem is that the chemically aggressive What We Know . . . hot liquids seep out. How We Can . . . • The corresponding chemicals can eventually pollute Home Page the sources of drinking water. Title Page • It is thus important to monitor how the pumped liquids ◭◭ ◮◮ propagate at the corresponding depths. ◭ ◮ • Also, we need to monitor the location of the injected Page 4 of 25 liquids after the injection process is over. Go Back Full Screen Close Quit
What Is Enhanced Oil . . . How the Enhanced Oil . . . 4. How the Enhanced Oil Recovery Process Is Limitations of Passive . . . Monitored Now Need to Take Into . . . • When the liquid propagates, it fractures the minerals Our Main Idea and thus, causes minor earthquakes. What Seismic Signals . . . How Pumped Liquid . . . • Just like for major earthquakes: What We Know . . . – the location of these minor earthquakes How We Can . . . – can be detected by the seismic waves that they gen- Home Page erate. Title Page • This passive seismic approach is indeed used for the ◭◭ ◮◮ desired monitoring. ◭ ◮ Page 5 of 25 Go Back Full Screen Close Quit
What Is Enhanced Oil . . . How the Enhanced Oil . . . 5. Limitations of Passive Seismic Monitoring Limitations of Passive . . . • In contrast to major earthquakes, disturbances caused Need to Take Into . . . the pumped liquid are small. As a result: Our Main Idea What Seismic Signals . . . – the generated seismic waves are very weak (they How Pumped Liquid . . . are imperceptible to human senses), What We Know . . . – the signal-to-noise ratio is very low. How We Can . . . • Hence, the accuracy with which we can trace the Home Page spreading of the pumped liquid is very low. Title Page • We only get a very crude approximate understanding ◭◭ ◮◮ of how and where the hot liquids propagate. ◭ ◮ • In this talk, we propose active seismic technique, that Page 6 of 25 enables us to provide a more accurate picture: Go Back – of liquid propagation and Full Screen – of the resulting location of the liquids. Close Quit
What Is Enhanced Oil . . . How the Enhanced Oil . . . 6. Need to Take Into Account Uncertainty, In Limitations of Passive . . . Particular, Fuzzy Uncertainty Need to Take Into . . . • How is all this related to fuzzy and soft computing? Our Main Idea What Seismic Signals . . . • We do not know the exact characteristics describing How Pumped Liquid . . . the propagation of the corresponding seismic waves. What We Know . . . • Instead, we need to rely on expert understanding of How We Can . . . this process. Home Page • This understanding is often described in terms of im- Title Page precise (“fuzzy”) words from natural language. ◭◭ ◮◮ • To describe this knowledge in precise terms: ◭ ◮ – it is reasonable to use techniques specifically devel- Page 7 of 25 oped for processing such expert statements, Go Back – namely, the technique of fuzzy logic. Full Screen Close Quit
What Is Enhanced Oil . . . How the Enhanced Oil . . . 7. Our Main Idea Limitations of Passive . . . • Micro-quakes generated by enhanced oil recovery pro- Need to Take Into . . . cess are weak. Our Main Idea What Seismic Signals . . . • As a result, the location accuracy is low. How Pumped Liquid . . . • Thus, to improve this accuracy, a natural idea is to What We Know . . . generate stronger seismic waves and measure their re- How We Can . . . sults. Home Page • Such techniques, when we actively generate seismic Title Page waves, is known as active seismic analysis . ◭◭ ◮◮ • To describe this idea in detail, we need to describe: ◭ ◮ – what kind of seismic signals we can generate, Page 8 of 25 – how the generated signals propagate, and Go Back – how we can determine the location of the liquid based on the measurement results. Full Screen • Let us consider these topics one by one. Close Quit
What Is Enhanced Oil . . . How the Enhanced Oil . . . 8. What Seismic Signals Can Be Generated Limitations of Passive . . . • To generate an active seismic signal, we have basically Need to Take Into . . . two main options: Our Main Idea What Seismic Signals . . . – we can use all the available energy at once, thus How Pumped Liquid . . . producing an explosion, or What We Know . . . – we can spread this energy over time, thus generat- How We Can . . . ing a periodic seismic signal; Home Page – this is done by using especially equipped truck Title Page called a vibroseis . ◭◭ ◮◮ • In this paper, we consider both options. ◭ ◮ Page 9 of 25 Go Back Full Screen Close Quit
What Is Enhanced Oil . . . How the Enhanced Oil . . . 9. How Seismic Waves Propagate: Reminder Limitations of Passive . . . • Sometimes, the medium is: Need to Take Into . . . Our Main Idea – either reasonably homogeneous, What Seismic Signals . . . – or has inhomogeneities whose size is much larger How Pumped Liquid . . . than the wavelength of the seismic wave. What We Know . . . • Then the waves propagate geometrically, by following How We Can . . . paths. Specifically: Home Page – the path between points A and B followed by a Title Page wave ◭◭ ◮◮ – is the path for which the propagation time is the ◭ ◮ smallest possible. Page 10 of 25 Go Back Full Screen Close Quit
What Is Enhanced Oil . . . How the Enhanced Oil . . . 10. How Seismic Waves Propagate (cont-d) Limitations of Passive . . . • This shortest-time idea leads to the known Snell’s Law Need to Take Into . . . of propagation, according to which: Our Main Idea What Seismic Signals . . . – when a wave crosses the border between the two How Pumped Liquid . . . layers with wave propagation speeds v 1 and v 2 , What We Know . . . – then the angles α 1 , α 2 between the paths and the How We Can . . . direction ⊥ the border satisfies: Home Page sin( α 1 ) = sin( α 2 ) . Title Page v 1 v 2 ◭◭ ◮◮ • In such homogeneous situations, waves behave as if ◭ ◮ they were particles. Page 11 of 25 • The situation changes drastically if we have inhomo- geneities whose size is smaller than the wavelength. Go Back • In this case, in the analysis of the wave propagation, Full Screen we can no longer view the wave as a single whole. Close Quit
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