A Blind Study of Four Digital Rock Physics Vendor Laboratories on Porosity, Absolute Permeability, and Primary Drainage Capillary Pressure Data on Tight Outcrops
- Shreerang S. Chhatre (ExxonMobil Upstream Research Company) | Hemant Sahoo (ExxonMobil Upstream Research Company) | Sergio Leonardi (ExxonMobil Upstream Research Company) | Keili Vidal (ExxonMobil Upstream Research Company) | Jennifer Rainey (ExxonMobil Upstream Research Company) | Edward M. Braun (ExxonMobil Upstream Research Company) | Prateek Patel (Consultant)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- Publication Date
- February 2018
- Document Type
- Journal Paper
- 15 - 24
- 2018. Society of Petrophysicists & Well Log Analysts
- 1 in the last 30 days
- 281 since 2007
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Estimation of reservoir rock properties using multiscale imaging of the pore structure, followed by mathematical modeling of the segmented images, i.e., digital rock physics (DRP), is a promising technique. However, DRP workflows are highly variable in terms of imaging tools, resolution of those tools, segmentation algorithms, handling of unresolved porosity, gridding of the resolved pore structure, and mathematical modeling of flow properties. As a result, users familiar with physical measurements of reservoir properties struggle to judge the quality of DRP data, and to incorporate DRP data in commercial workflows in a suitable manner.
In this work, we present a DRP study on tight rocks (kabs < 10 mD) conducted at the laboratories of four vendors of digital rock services, anchored to high-quality physical measurements conducted in our laboratory. We selected core plugs from a set of six outcrop rocks. We cleaned the plugs, measured porosity (φ) and absolute permeability (kabs), and then split the plugs into four quarter plugs that are each 1.5-in. long. Four commercial DRP labs conducted blind porosity and permeability predictions on those quarter plugs using (a) only micro-CT based tools, and (b) all the tools accessible to DRP service providers. We also compare primary drainage capillary pressure (Pc) calculated by four DRP vendors on quarter plugs with centrifuge-based gas-water measurements conducted in-house on companion plugs.
As a result of this blind study, we gained insights into workflows, strengths/weaknesses of DRP predictions carried out by four vendors. Various levels of physical measurements (e.g., laboratory-based kabs, and φ data, MICP, or none) are used by different vendors to anchor DRP data. DRP predictions for porosity ranged from 33 to 96% of the measured values, whereas permeability ranged within a factor of 0.3 to 4 from the experimental measurements. At low Pc values, predictions by the four DRP vendors generally agreed with each other, and with experimental measurements. However, the values diverged significantly at high Pc. Based on this study, we conclude that the dominant source of error in DRP data is highly specific to a given sample, technique, or operator. A lot more uncertainty quantification is necessary to allow DRP data to be used instead of physical measurements for business decisions on tight rocks. We outline learnings for hydrocarbon resource owners and DRP data providers so that commercial workflows could benefit from DRP-based data.
|File Size||2 MB||Number of Pages||10|