Category: Monthly Articles

What is Fractional RTA?

An inherent assumption in most industry RTA is equally spaced fractures. However, as shown in several field studies (Raterman 2017, Gale 2018), the distance between individual fractures tends to be unevenly spaced along the wellbore (e.g., “fracture swarms”). Fractional RTA extends industry standard RTA workflows to account for uneven fracture spacing. Flow Regimes 1.01 To […]

Crossing K-values from a tuned EOS model

Author: Sissel Martinsen In our monthly article “How to Quality Check a Developed EOS” we addressed methods to check that an EOS model calculates physically consistent properties and thermodynamic valid solutions. A thermodynamic consistent EOS model is a model that gives consistent phase behavior of mixtures, and individual components. Part of our standard EOS QC […]

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Analytical vs. Numerical RTA

Author: Ilina Yusra Analyzing infinite-acting linear flow using the square root of time plot has been important in tight unconventional reservoirs since it was first introduced in 1988 by Wattenbarger et al. The goal of the analysis is to determine the fundamental reservoir parameters by solving the analytically derived equations for the two flow regimes […]

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To tune or not to tune BIP’s when lumping: That’s the question

EOS Component Lumping Optimization 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 […]

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whitson+ in the cloud … with diamonds

Author: Markus Blytt With the creation of Fortran during the 1950s and 1960s, computer science took a giant leap in the direction of popularizing the art of coding. Today, Fortran is considered an ancient language, mainly because of two things: (1) a wide range of much more high-level programming languages exist, making it easier for […]

The Gas Huff-n-Puff PVT Experiment

By Mathias Lia Carlsen, July 2021 *This is a short-version of URTeC 5016 by Mydland, Carlsen and Whitson found attached to this article. Gas EOR in Tight Unconventionals The gas-based Huff-n-Puff (HnP) process is currently the dominating EOR process in tight unconventionals.  This has happened as a result of operators looking to find new ways […]

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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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