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 …
When dealing with rocks, we are always interested in the fracture pressure. One application of fracture pressure is in drilling and completions. If we fracture the formation while we are drillng due to excessive mud weight, lost circulation could occur in the well bore which could eventually lead to a blow out if we are …
Overburden pressure is the vertical stress imposed by the overlying formation at a reference point below the surface. In other words it is the hydrostatic pressure exerted by all the material above a reference point. The overlying layers can include rock columns and bodies of water. Why is it important? Because we can use it …
Overburden Pressure: What is it and Why is it important? Read More »
In its simplest form, the subsurface consists of two things: 1) Rock grains and 2) fluid. Because we as petroleum engineers are so interested in pressure, we need a way to calculate the density of fluid-grain mixtures which can eventually get us pressure. This is where bulk density comes into play. In petroleum engineering, bulk …
The initial reservoir pressure and temperatures is one of the most important parameters we need in petroleum engineering. From initial reservoir pressure and temperatures we can determine fluid properties with correlations, estimate the amount of hydrocarbons in place, and predict an overall recovery factor from a well. How do we estimate reservoir pressure and temperature?? …
Everything we just applied to linear flow, extends to radial flow. Nothing too different! The same analogy works! The only difference is we apply Darcy’s law for radial flow. We will know work through the derivations of average permeability for series radial flow and parallel radial flow. Series Radial Flow-Harmonic Average Consider radial flow for flow units in …
Average Permeability of Flow Units in Parallel and in Series (Radial Flow) Read More »