Study Independently Validates SLB Digital SCAL | SLB

Digital SCAL opens a new era in reservoir characterization

Italy, Europe, Onshore

Digital SCAL services proved reliable for Eni S.p.A. by providing accurate analysis that matched, within the range of uncertainty, the laboratory test results on the same cores. Using this technology produces results up to 100 times faster than traditional laboratory analysis, reduces the time required for petrophysical characterization, and provides a better understanding of transport mechanisms at the smallest scales.

Digital rock analysis (DRA) gives petroleum engineers a unique look into the pore spaces of rocks by combining experimental and numerical studies that help evaluate fluid transport and petrophysical properties at pore scale. Technical evolution and the integration of processes have enabled DRA to effectively replace long-duration laboratory core testing with digital tests that are up to 100 times faster.

To confirm the effectiveness of DRA techniques, both SLB and its research partners at Eni performed a series of rigorous tests and validation studies using digital SCAL digital rock and fluid analytics services from SLB.

The studies used the DHD™ direct hydrodynamics pore flow simulation component of digital SCAL services to obtain relative permeability vs. water saturation curves for a wide range of rock types—including coarse-grained and fine-grained sandstones as well as carbonates—and to verify the results through a comparison with relative permeability data produced from laboratory experiments. The study used both a basic rock model (with porosity resolved in meso- and micropores by microcomputed tomography [microCT]) and an advanced model combining resolved porosity, micrometer porous matrix, and solid rock components.

DHD simulation computes multiphase flow by solving density functional hydrodynamic (DFH) equations. The pore-scale flow simulator uses digital rock imaging and fluid data that enables detailed digital routine core analysis (RCA) and SCAL, as well as enhanced oil recovery (EOR) agent optimization. Digital rock imaging uses high-resolution X-ray scanning along with images from scanning electron microscopy (SEM) to construct digital rock models that reveal the complex pore geometry of real rocks. Constructed rock models are then used with digital models of reservoir and injection fluids to model multiphase hydrodynamic processes at the pore scale.

The study was executed in three phases for each reservoir rock sample. First, RCA properties were established using DRA and compared with the experimental lab data. During the second phase, a set of steady-state relative permeability digital experiments was performed using fluid data, flow rates, pressures, and temperature conditions that replicated experimental lab tests.

The DRA models were fully saturated with brine and then desaturated to irreducible water saturation (Swi). After this, a steady-state flooding cycle was performed using varying oil and water injection ratios for different core wettability scenarios. Next, SCAL data was compared with Eni-provided experimental laboratory data. In the final phase, a further sensitivity study was performed to evaluate the effects of micrometer porosity on multiphase transport properties.

Relative permeability normalized with effective oil permeability (Ko) at Swi saturation.
Relative permeability modeling results for two of the samples studied. Resulting curves were normalized with effective oil permeability (Ko) at Swi and obtained using both basic and advanced digital rock models. Experimental lab data is shown on each chart for comparison. (In the chart, Krw = relative water permeability, Kro = relative oil permeability, MW = mixed wettability, and WW = water wet.)
3D phase saturations at the end of steady-state oil-brine flooding modeling.
These diagrams show 3D phase saturations (red, oil; blue, water) after steady-state brine flooding of the same two samples shown for the relative permeability comparison. Results of the basic DRA model are shown on the left and the advanced DRA model on the right. The digital imaging data included microCT, which helped to image meso- and micropores, as well as high-resolution SEM imaging to distinguish and map micrometer porosity.

A comparison of laboratory and digital data showed an excellent match for all the studied rock samples. Digital SCAL services provided accurate and reliable SCAL within the range of uncertainty of repeated laboratory test results on the same core. Applied in combination with traditional laboratory analyses, Digital SCAL reduces the time required for petrophysical characterization and provides a better understanding of transport mechanisms at the smallest scales.

More technical details

For more details, read the full technical paper SPE-212617-MS.

"SLB digital rock technology was proven to be a reliable technology for all studied rocks providing accuracy levels that are within the range of uncertainty of repeated laboratory test results on same core."

Francesco Radaelli, Technical Leader Experimental Research, Eni S.p.A.
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