 My name is Greg King and I'm an alumnus here from Penn State Petroleum National Gas Engineering Department. I graduated in 79 and worked for Chevron for 32 years. I came back and they asked me to put this class together for you. We're having a review session here for the first midterm and I thought it would be better if we asked one of your colleagues to give the review. He's a senior so he's further along his academic career than most of you are. I thought a senior would be a good choice because he'll be able to tell you how this material fits into your academic career and give you insights on what's important for which future classes you may be taking and what's not important for those classes but may be important for other classes. Let me turn it over to Alex now. As Dr. King said, my name is Alex and I am a senior in P&G at the moment. I decided to take this course to reinforce my knowledge on the material and also it being an online class gives me more flexibility with my schedule with being as busy as I am and I feel like having the personal experience of being a senior would be valuable to the sophomores in this class. P&G or not P&G to show how this stuff is important, when you're going to use it and why knowing this information will be helpful for your future classes. So let's get started with question one on the midterm review. So as you can see we have light oil we're going to be working with. So for your problem you're going to have light oil and intermediate oil. The difference between the two really is the components that make up the oil and so in general terms lighter oil has more, has a greater capability for gas to dissolve where like intermediate oil and heavier oil have heavier components so it's more likely to stay in the liquid phase. And so for this case our temperature is going to be 120 degrees Fahrenheit and so in ranking that's 580 degrees ranking so you just add 460 to whatever your temperature is in Fahrenheit to get ranking. Our API of our oil is going to be 42. The specific gravity of our gas is going to be 0.7 and our gas oil ratio is going to be 700 SCF per STB which stands for standard cubic feet over standard stock tank barrel. For this problem we're going to be finding the compressibility of the oil, solution gas oil ratio, oil formation volume factor, density of the oil, pseudo reduced pressure, compressibility factor Z, gas formation volume factor, density of the gas, the viscosity of the oil and the viscosity of the gas. So really this is going to be a PVT problem where we're given 4 bits of information and really we're going to expand it into a lot more using the correlations we've learned in class. So the first thing we're going to do is we're going to actually find what the specific gravity of the oil will be and that's going to be using equation 3.38 which is going to be the specific gravity of the oil at 60 degrees Fahrenheit equals 141.5 divided by your API of your oil plus 131.5. And so when you do this you get your specific gravity of your oil to be 0.8155 sticks. So we'll just say 0.816 to make it simple. And so from here we can find what our bubble point of our oil is and this is really important because your fluid and your reservoir will act different based off of your pressure and the reservoir is above bubble point, below bubble point or maybe even at bubble point and you'll see with some of these correlations some are used below bubble point some are used above bubble point and that's why it's really important to know which equation to use, which pressure you're at. So to find your pressure for your bubble point of your fluid you're going to be using equations 3.41 and 3.42. And so first let's use equation 3.42 to find what CPB is which is just a constant and so equation 3.42 is going to be CPB equals your solution gas oil ratio which is given divided by your specific gravity of your gas which is also given to 0.83 power and that's going to be multiplied by 10 to the power of 0.00091 times your temperature in Fahrenheit so in this case it's going to be 120 degrees and an important note for this notice we're using 120 degrees Fahrenheit here and not 580 degrees ranking some of your equations will be using Fahrenheit some will be using ranking so take note of that and in this case it is isothermal meaning your temperature is going to be the same throughout this process and so that's just really important to note so that's going to be minus and times your API of your oil which is given which is 42 and then doing that calculation we get that CPB is going to equal 74.555 and using this in equation 3.41 which actually find your bubble point of your fluid in PSIA which is going to be 18.2 equals 18.2 times your CPB you just found minus 1.4 which when you do this it'll give you so important to note I just realized is I made a mistake here this should not be 700 this should be 900 for the light oil so because of that the CPB will not be 74.55 let me recalculate that and see what I get so CPB after doing the calculation will be 146.147 and plugging that right here into this equation to find out what the bubble point pressure is in PSI we get that the bubble point is going to be 2634.4 PSIA once we know what the bubble point pressure is this helps us use like what relationships for above bubble point and below bubble point so this is I'm going to write that down what that is then so CPB is going to equal 2634.4 PSIA okay and so for the next part what we're going to do is find the compressibility of the oil above bubble point so for that we're going to be using equation 3.46a and this yeah yeah so this will be CO equals 5 times what our RS value is which we will need to find to do this so we'll just put the equation down and then we'll use this after we find what our RS is at different pressures so it will be that plus 17.2 times our temperature which I said it's isothermal and it's going to be in Fahrenheit for this equation so you can just put 120 in right away and minus 1180 times the specific gravity of gas which is going to be constant which is 0.7 and then plus 12.61 times the API of our oil which is 42 and then it's going to be minus 1433 and we're going to divide all that by 1 times 10 to the 5th times our pressure of interest so in this case let's do we're going to do one pressure above bubble point one pressure below bubble point we're also going to calculate the properties at bubble point so we'll use the pressure of 4000 PSIA and we'll also use the pressure of say 2000 PSIA and then so to find RS what we need to do is for below bubble point for our equation for RS we need to use equation 3.44 and equation 3.45 and one important thing to note is your solution gas oil ratio which is RS is going to be constant above bubble point because above bubble point gas is no longer going to be able to dissolve into the oil because there is no more free gas present so what we assume is that gas is infinitely soluble in oil so meaning once you're at bubble point and above bubble point there will be no free gas in the reservoir everything will be dissolved in the oil which is why your gas oil ratio will be the same above bubble point so in this equation here for the compressibility of oil you notice it's a function of your RSL your solution gas oil ratio which in cases above bubble point will always be constant because we assume that above bubble point there is no longer free gas in the reservoir all free gas is actually dissolved in the oil because we assume that gas is infinitely soluble in oil and so for this reason when you're at pressure above bubble point the only liquid you'll find in reservoir is going to be like water or like oil or maybe some other type of liquid but there will no longer be any free gas because all that gas will be dissolved in the oil and so to find this out and so the equation for solving for RS is actually going to be a rearrangement of equations 3.42 and 3.41 so you're going to be solving for this RSO and so this PB that you see in equation 3.41 it's good for any pressures at bubble point and also below bubble point like as I said earlier this equation won't work for pressures above bubble point just because RS will be a constant above bubble point and so when you rearrange that equation it turns into this pressure which is going to be your pressure of interest so in this case we're going to be doing 2000 psi so P plus and this is going to be times 10 to the power of which is going to be your API of your oil which is 42 and then this is all going to be divided by 10 to the power of 0.000 9 1 times temperature which is going to be in Fahrenheit so it's going to be 120 degrees Fahrenheit and so this whole equation will be to the power of 1 over 0.83 and you're going to multiply this by your specific gravity of your oil and so when you do this equation for RS at 2000 psi you should get 648.145 there's going to be SCF for STB and once you have this RS value you can then plug in this equation to find what your compressibility of your oil is pressure, well this equation is actually for pressures above bubble point so you wouldn't actually be plugging this into here so as we know the difference, we can use this equation because we already know RSO is going to be 900 at bubble point and above and so the difference here is going to be P so we can just use this equation actually right now so compressibility of the oil at 4000 psi is just going to be let's see it'll be 1.208 times 10 to the power of negative 5 this will be 1 over PSI for the units for the compressibility of the oil now to find the compressibility of the oil for below bubble point so in this case for the 2000 psi we're going to be using equation 3.46B which is going to be so we're going to find the compressibility of the oil at 2000 psi so with this equation it's going to be the natural log of the compressibility of the oil equals a term but we're going to exponentiate both sides to get CO by itself so that turns into a pretty long equation so it's negative 7.633 minus 1.497 times the natural log of your pressure which in this case like I said we're going to be doing it for below 2000 we're going to be below bubble point I mean so we're going to be using 2000 psi in this case and then plus 1.115 times the natural log of temperature which is going to be 120 Fahrenheit and then plus 0.533 which is going to be the natural log of your API which is going to be 42 plus 0.184 times the natural log of your RSOB which is going to be your solution gas oil ratio at bubble point so when you see that B subscript that means at bubble point so like you might say BOB which means your oil formation volume factor at bubble point using this equation for 2000 psi we will get that the compressibility of oil will be equal to 0.00 0029 5 43 and then unit error 1 over psi so now we have the compressibility of the oil below bubble point at 2000 psi and then compressibility of the oil above bubble point on at 4000 psi and if you wanted to calculate the compressibility of the oil is at bubble point you can just use this equation right here and you'll get that your bubble point compressibility of your oil will be 1.955 times 10 to the negative 5 and so for our next thing we can solve for formation volume factor at pressures above the bubble point