Category: Monthly Articles

Molar Distribution Models Applied to Petroleum Reservoir Fluids

By Bilal Younus, July 2021 This article discusses two common molar distribution models – discrete exponential and continuous gamma – used to describe heavier components such as heptanes-plus (C7+) in petroleum reservoir fluids. A molar distribution model relates component molar amount (mole fraction) to molecular weight (MW). The discrete exponential distribution is used exclusively to […]

Should We Use Binary Interaction Parameters

By Markus Hays Nielsen, June 2021 The question we want to try and answer in this article is if there are any reasons for using binary interaction parameters (BIPs) as a part of our EOS model development. There are a few things that need to be addressed right away, namely what is meant by “using […]

Flowing Bottomhole Pressures Calculations Using the Black-Oil PVT Model

By Stian Mydland, May 2021 The flowing wellbore pressure at the perforated interval, commonly referred to as bottomhole pressure (BHP | pwf) or sandface pressure, is a required input for all classical well-performance forecasting techniques. The BHP is available in real-time for wells having pressure gauges installed sufficiently close to the perforated interval. For wells […]

Lost volumes in MPSR fluid sampling bottles, and the impact on fluid properties

This article was written in collaboration with Gerardo Seri from Wintershall DEA. What is the difference between an MPSR and SPMC bottle? SPMC stands for single phase multisample chamber, which are nitrogen compensated bottles. The nitrogen is used to maintain the pressure of the bottle at or above the sampling pressure. MPSR stands multisample production […]

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How to quality check a developed EOS?

Author: Sissel Martinsen Whether you receive an EOS or you yourself have developed an EOS, it is always a good idea to quality check the EOS. You want to make sure that the EOS calculates physically consistent properties and thermodynamic valid solutions, and that it does not give any non-physical three-phase solutions that will slow […]

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Decreasing CGRs above Saturation Pressure in “Shales”

Author: Mathias Lia Carlsen * This is a snippet from SPE-199982-MS that was presented on the SPE Canada Unconventional Resources Conference held virtually in 2020. The full manuscript can be found attached to this blog post. Decreasing CGRs are observed while flowing bottomhole pressures are above the (apparent) saturation pressure in several unconventional basins throughout […]

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Frac-to-Frac Gas EOR—The Future of Unconventional Gas EOR?

Author: Ilina Yusra, Stian Mydland & Mathias Lia Carlsen After EOG Resources reported uplift results from their Eagle Ford Huff-n-Puff (HnP) activities, gas injection has gained significant traction in tight unconventionals. The success in the Eagle Ford has led companies to pursue gas HnP in other basins including Permian, SCOOP/STACK, Bakken and Montney. The HnP […]

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Using Contaminated PVT samples

Authors: Ahmad Alavian & Curtis Hays Whitson A contaminated sample is collected in an openhole formation testing tool (OFT) like MDT or RCI. The well has been drilled with oil based mud (OBM), where some percentage of the collected sample being OBM and the remainder being in-situ reservoir fluid. Finding a good estimate of the […]

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EOS Component Lumping Optimization

Author: Arnaud Hoffmann To reduce CPU time in compositional petroleum simulation models (e.g. compositional reservoir simulations), a minimum number of components should be used in the equation of state (EOS) to describe the fluid phase and volumetric behavior. A ″detailed” EOS model often contains from 20 to 40 components, with the first 10 components representing […]

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Black-Oil and Compositional Reservoir Simulation of Gas-Based EOR in Tight Unconventionals

Author: Stian Mydland *This is a short-version of URTEC-2020-2765-MS presented at Unconventional Resources Technology Conference (URTeC) 2020. Paper can be downloaded in the end of this article. Reservoir simulation requires a fluid model to describe the volumetric behavior of gas and oil. When initiating a reservoir simulation study, we have to choose whether to use […]

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