In high school we all learn about the single phase diagram for pure substances. Unfortunately, petroleum engineers don’t normally use it. In petroleum engineering we are dealing with multiple-component mixtures. In these cases, the phase diagram is different. Instead of a single line separating the vapor and liquid phases, there is a two phase region …
So far we have considered reservoir pressures maintained above the dew point. At reservoir pressures above the dew point, only single phase gas exists. At pressures below the dew point, condensate evolves out of the gas becoming oil condensate in the reservoir. When this occurs, gas and oil coexist in the reservoir. Under these circumstances, …
In past discussions we looked at how to keep track of reservoir produced volumes below and above the bubble point for oil reservoirs. For gas reservoirs, we do the exact same thing using a separate set of formation volume factors and ratios. In some gas reservoirs, condensate evolves out of the gas as it is …
Previously we discussed the two phase oil formation volume factor. It accounted for both free gas and oil in the reservoir and had units of . In order to relate the liberated gas volumes to reservoir barrels, a gas formation volume factor () was developed. An illustration of how gas formation volume factor is defined …
So far we have considered reservoir pressures maintained above the bubble point. At reservoir pressures above the bubble point, only single phase oil exists. Below the bubble point, solution gas evolves out of the oil becoming free gas in the reservoir. When this occurs, the oil and gas coexist in the reservoir. When multiple phases …
When oil is transported to the surface, we learned that it shrinks. It shrinks because gas evolves out of the oil as the pressure decreases. The gas that evolves from oil as it is transported from reservoir to surface conditions is called solution gas. The figure below illustrates the concept of solution gas for an …
The produced volumes measured at surface conditions are never equal to the volumes at reservoir conditions because of the differences in temperature and pressure. In order to carry out meaningful reservoir engineering analysis (such as material balance!!) and size pipelines upstream, it is important to understand how the volume of a fluid changes from the …
Previously we presented the macroscopic material balance equation. It includes many terms that can bog you down if you do not understand what they imply. Here we will make things a little bit clearer by associating the terms with reservoir drive indices. One of the most powerful applications of the material balance equation is it …
The material balance equation is one of the fundamental equations a reservoir engineer needs to understand. Some of it’s applications include the following: Determining the initial hydrocarbon in place Predicting an overall recovery factor Determining reservoir drive mechanisms The material balance equation can be intimidating for someone looking at it for the first time. It …
In petroleum engineering everything has compressibility including rocks, oil, and water. It’s not just gases anymore. The concept of compressibility shows up in several reservoir engineering applications including 1) material balance and 2) reservoir simulation, therfore you should try to master this concept. In fact compressibility is the main driving force behind the primary production …
Previously, we applied solid mechanics to determine the stress condition on a rock in the horizontal direction. So how does knowing the stress on a rock tell us how the formation will fracture?? Once again we have to go back to solid mechanics. Remember this statement: The fracture will orient itself perpendicular to the MINIMUM …
Previously, we learned that the rock in the formation is subject to a vertical compression load called the effective stress. In general if you apply a vertical compression load to any solid element, it will expand horizontally. Take cookie dough for instance. If you smush it vertically between both hands, the cookie dough will flatten …