Pressure, Volume, Temperature (PVT) Tests Offer Valuable Insights
PVT tests are an essential part of the exploration and production process. The behaviors of reservoir fluids are nothing short of complex, but for oil and gas exploration projects to reach an optimal outcome, companies need to understand these unique behaviors so that they can make data-driven engineering decisions. A PVT (pressure, volume, temperature) analysis takes a deeper dive into the behaviors of a reservoir’s fluids to collect this essential data that will advance your project to the next phase.
True to the nature of the oil and gas industry, the amount of time required to extract the hydrocarbons from the subsurface will directly impact the cost of the well (more time = higher costs). Because oil and gas companies have no control over the commodity pricing of the market, experiencing increased costs will reduce the overall profit margin for each project.
In response, companies can determine the properties of the oil and gas contents in the reservoir to discover how hydrocarbons flow from the well, which will allow operators to determine the most cost-effective methods for extraction.
In essence, the PVT analysis looks at the way a specific reservoir’s fluids behave under certain conditions. The results of the study serve to answer critical business questions, including
- What is the volume of crude oil and gas in the reservoir?
- How can we optimize the liquid recovery process?
- What are the unique flow properties of this reservoir?
- What do we need to know to maintain the pressure?
PVT Tests and Analysis are conducted by a professional petroleum service provider that can not only collect the essential data but also provide insight and guidance on next steps.
Pressure Volume Temperature Analysis (PVT): A Brief Overview
Companies can perform a PVT analysis for any stage of the hydrocarbon extraction process. This method collects samples from specific well sites to study so you can make decisions based on your unique data, not just industry standards. As a result, PVT Analysis has made it easy to understand how reservoir fluids behave so engineers can maximize the hydrocarbon recovery process at a minimal cost.
Here’s a closer look at what a PVT Test and subsequent Analysis entails:
Finding the Bubble Point
To fully understand the mechanics of fluids in an oil well, we perform a test to find the bubble point of the sample fluid. This is a major component of a PVT Analysis that allows us to understand the characteristics of the reservoir.
Geologists will use the results of the bubble point test to determine information related to the expected recovery of oil in the well. If the oil to be recovered is undersaturated (i.e. contains very little dissolved gas), then only a small percentage of the oil can be recovered without the intervention of advanced tools or other methods. This can have a significant influence on the overall operating costs of the well.
PVT Analysis examines the differential liberation process, where the gas is separated from the liquid sample in a continuous cycle. Because the pressure is reduced gradually, the gas doesn’t reach equilibrium with the liquid.
A PVT analysis will also look at the flash liberation process. This occurs when a sudden drop in pressure causes the crude oil to separate into an oil and gas mixture quickly.
Understanding the Reservoir to Surface Volume Relations
Though the bubble point test is a critical component of a PVT analysis, there are additional steps and measurements to take that will help to determine the best way to move forward.
The results of the flash liberation test and differential liberation test will yield three essential factors that will determine the relationship between the reservoir to surface volume: the oil formation volume factor, gas formation volume factor, and solution gas to oil ratio.
Let’s look at each one:
Oil Formation Volume Factor
This factor represents the ratio of the volume of oil at the reservoir conditions to that of the surface conditions. The results are used to convert the flow rate of the oil at the surface to that of reservoir conditions.
Gas Formation Volume Factor
Similar to the Oil Formation Volume Factor, the Gas Formation Volume Factor is the ratio of the volume of gas at the temperature and pressure of the reservoir compared to the gas at the temperature and pressure of the surface.
Solution of Gas to Oil Ratio
This ratio indicates the amount of gas dissolved in the oil or water at any pressure. This ratio increases linearly with pressure and reflects the oil or water and gas composition. For perspective, a light oil contains more dissolved gas than a heavy oil.
Compositional Analysis: The Ultimate Goal of Performing PVT Analysis
The main reason that oil and gas companies choose to drill a well is to turn the project into a revenue-producing asset eventually. However, the main complication in doing so is the fact that the value of the oil extracted from one well is not the same as the value of oil extracted from another well.
This can complicate the process of determining the valuation of a project, calculating an ROI, and deciding whether to move forward or seek another drill site.
The composition of the oil, which can be discovered with compositional analysis, is an essential piece of the process. The results from this analysis can help companies determine with greater confidence how profitable a play will be. Once completed, the analysis can help companies learn just how much of each type of petroleum product (e.g. gasoline, kerosene, diesel fuel, etc.) can be produced from a single barrel of oil from that particular well.
Also, every refinery is set up to produce specific types of crude oil. A heavy crude oil and a light crude oil have very different production processes, which means they each require different refining methods. On the surface, this may seem like a small concern, but the differences in oil composition and the wells from which they came can have a major impact on your profit margins.
Depending on your projects, you may need to investigate refining along the Gulf Coast, where refiners are geared toward heavy crude oils, or in places like Europe or the East Coast of the U.S., where refineries are set up to handle lighter crudes.
Sierra Pine Resources International works with clients throughout the upstream oil and gas industry to solve problems and provide solutions that increase the value of their assets in every stage of the production curve.