- Good morning, today we will be talking about oceanographicconcepts for petroleum. It's critical to understand these to be able to run an exploration program and determine where source rocks may occur in different environments, and especially through time, as continents have movedand oceans have changed. We'll be focusing onthe source rock aspect with this lesson. And the critical aspects are nutrients, how they're distributed in the ocean, because the nutrientsare what the algae need to have major blooms and deposit a lot of source rocks. And algae is the primary source for oil, and thenultimately gas rematuration. And then also oxidation state of the bottom waters and the sediment is critical to preserve the biomass. So we will be talking about the biomass, the deposition, and the preservation. Key aspect of oceanography is the thermohaline circulationof the waters of the ocean. Start off with the major pump system starts in the Antarctic You super cool the surface water, and thenthat causes density to change. It becomes more dense, it goes to the bottom of the ocean and circulates up along the bottom, all the way to the north, and then comes circling back. And this provides oxygen from the surface, so that's why you don't find source rocks in abyssal ocean plains because there's oxygen in the bottom waters. And there will also be salinity changes. Surface waters can be highly saline, that can create denser water, but it's still usually not as dense as the waters created off Antarctica. The other aspect ofcirculation that's critical is the wind driven surface circulation. And this is criticalbecause depending whether if you're in the southern hemisphere, you develop a Coriolis effect. It's counter-clockwise. It takes surface waters away from western shores of continents. If you're in the northern hemisphere, the circulation is clockwise and it, again, causes upwelling. And major areas of upwelling are where you can expect to find algal blooms, as you know, probablyknow, major fisheries tend to be along these western areas, and they're utilized by allcountries around the world. So this is how that works. This is an example showing a view from the southern hemisphere. And as we said, in thesouthern hemisphere, the winds are blowing northward, and the Coriolis effect pullsthem out counter-clockwise. And as this water is pulled out, it creates space, anddeeper water gets pulled up. And this deeper water has oxygen, as we talked about earlier,and it has nutrients that have accumulatedfrom the algal materials that were at the surface,die and drop down. So you're creating abig feeding machine here that has oxygen and nutrients, and you can create major algal blooms. If then, those algalblooms are large enough, they'll settle to the bottom, they'll oxidize as theygo through the water, but if they can accumulate on the bottom, they can create anoxic sediments underneath these major upwelling areas. So that's why upwellingareas can be a location for proto-source rocks that you'd look for for petroleum deposits. And just to show youwhat it looks like today, the red shows the upwellingareas of the world. Most of them, as you can see, are along western shoresof the continents. Major fisheries along the western shores. You have major upwelling and algal blooms, even glauconite deposits in the sediments, so it's suboxic offshore,so that as this material sinks to the bottom, it will be preserved. And what you look for through time would be the position of the continents as they change through time and what the oceanographic systemmight have looked like, and whether or not youhad the proper conditions for marine algae formation. Now, there are other types of source rock, but right now we'retalking about marine algal, which is the major one.