Computed tomography in petroleum engineering research

Akın, Serhat; Kovscek, Anthony R.

doi:10.1144/gsl.sp.2003.215.01.03

Cited by 237 publications

(169 citation statements)

References 47 publications

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“…CT mat is determined by averaging the single modes of all CT numbers at every pressure stage, assuming that the most frequent CT number dominates the matrix of the rock sample. Our results reveal a matrix number of CT mat = 1862 HU, which is in line with other CT-based sandstone studies (Akin and Kovscek, 2003;Huo et al, 2016;Vinegar et al, 1991). Careful calibration with different spacers (0.19, 0.29, 0.41, 0.52 mm) within the fracture indicates a slope of the linear calibration line of 5890 ± 38.3 HU mm −1 (Fig.…”

Section: Image Processingsupporting

confidence: 91%

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

et al. 2016

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Abstract. Various geoscientific applications require a fast prediction of fracture permeability for an optimal workflow. Hence, the objective of the current study is to introduce and validate a practical method to characterize and approximate single flow in fractures under different stress conditions by using a core-flooding apparatus, in situ X-ray computed tomography (CT) scans and a finite-volume method solving the Navier-Stokes-Brinkman equations. The permeability of the fractured sandstone sample was measured stepwise during a loading-unloading cycle (0.7 to 22.1 MPa and back) to validate the numerical results. Simultaneously, the pressurized core sample was imaged with a medical X-ray CT scanner with a voxel dimension of 0.5 × 0.5 × 1.0 mm 3 . Fracture geometries were obtained by CT images based on a modification of the simplified missing attenuation (MSMA) approach. Simulation results revealed both qualitative plausibility and a quantitative approximation of the experimentally derived permeabilities. The qualitative results indicate flow channeling along several preferential flow paths with less pronounced tortuosity. Significant changes in permeability can be assigned to temporal and permanent changes within the fracture due to applied stresses. The deviations of the quantitative results appear to be mainly caused by both local underestimation of hydraulic properties due to compositional matrix heterogeneities and the low CT resolution affecting the accurate capturing of sub-grid-scale features. Both affect the proper reproduction of the actual connectivity and therefore also the depiction of the expected permeability hysteresis. Furthermore, the threshold value CT mat (1862.6 HU) depicting the matrix material represents the most sensitive input parameter of the simulations. Small variations of CT mat can cause enormous changes in simulated permeability by up to a factor of 2.6 ± 0.1 and, thus, have to be defined with caution. Nevertheless, comparison with further CT-based flow simulations indicates that the proposed method represents a valuable method to approximate actual permeabilities, particularly for smooth fractures (< 35 µm). However, further systematic investigations concerning the applicability of the method are essential for future studies. Thus, some recommendations are compiled by also including suggestions of comparable studies.

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Section: Image Processingsupporting

confidence: 91%

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

et al. 2016

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“…Para avaliar a possibilidade de recuperar a permeabilidade absoluta a partir de modelos descritos pelas equações (8) e (14) e via processamento de imagens utilizamos amostras sintéticas de microesferas de maneira análogaà [49][50][51][52]. As amostras foram microtomografadas no laboratório do CENPES.…”

Section: Imagens Micro-ct Da Amostra De Esferasunclassified

Estimativa de Permeabilidade Absoluta com Processamento de Imagens Utilizando Distribuição de Tamanho de Grãos

Dias¹,

Alves²,

Albuquerque³

et al. 2017

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Resumo: A determinação da permeabilidadeé fundamental na caracterização de meios porosos em especial para estimar a capacidade de armazenamento e escoamento em formações particuladas. Diversos modelos baseados em tamanhos de grãos foram propostos para quantificar a permeabilidade. Todavia tais modelos apresentam limitações significativas que tornam seu uso restrito em diversas aplicações práticas. Neste trabalho apresentamos dois modelos, o primeiro, baseado no trabalho de Panda e Lake e o segundo, no trabalho de Kozeny e Carman, discutindo suas potenciais aplicações em imagens digitais de rochas geológicas e limitações com relaçãoà forma de medição de alguns parâmetros. Para analisar o desempenho destes modelos realizamos testes com imagens de microtomografia de amostras confeccionada com microesferas, buscando simular imagens de solo. As amostras sintéticas permitem construir um ambiente controlado para comparação com medidas obtidas apósà análise digital. Propomos uma cadeia de processamento de imagens para estimar medidas de permeabilidade e comparamos com quantidades obtidas através de simulações de fluxo. Verificamos que o modelo analítico Kozeny-Carman Generalizado obtivemos uma estimativa de permeabilidade absoluta em uma distribuição de partículas sintéticas com uma precisão de ±0.4µm 2 e ±61.1µm 2 (em duas amostras distintas).Com taxa de exatidão de 98% e 99% respectivamente, quando comparados com os valores obtidos através das

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“…Therefore, in the CT images, brine and solid salt were treated as a single phase. The files were imported into and processed in MATLAB to calculate brine saturations at different time steps (Akin and Kovscek 2003;Simjoo et al 2012). When imported into MATLAB for processing, the values are stored as HU+1024 in order to do calculations.…”

Section: Ct Scanningmentioning

confidence: 99%

Capillary-Driven Transport of Dissolved Salt to the Drying Zone During $$\hbox {CO}_{2}$$ CO 2 Injection in Homogeneous and Layered Porous Media

et al. 2016

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A major challenge of CO 2 injection into saline aquifers is the risk of formation clogging due to salt precipitation. Capillary-driven flow of brine can provide a continuous transport of dissolved salt toward the dry zone around the injection well where it ultimately precipitates due to evaporation. In this study, core flooding experiments were performed in homogeneous coarse-textured cores and in layered cores consisting of a coarse-textured layer overlying a fine-textured layer. CO 2 was injected through a well in the upper part of the cores, and the bottom parts functioned as brine sources. Impairment in injectivity was found due to accumulation of precipitated salt caused by capillary-driven flow from the brine sources to the upper dryer region. Compared to flow domains without a brine source, we found that capillary-driven upward flow at first prevents complete clogging because the porous medium remains wet, but eventually leads to a more severe clogging of the entire domain. The results show that after sufficient dry-out, a coarse-textured injection layer can draw brine from an underlying fine-textured layer by capillary forces. A connected fine-textured layer can therefore contribute to salt precipitation and clogging of the injection layer.

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Computed tomography in petroleum engineering research

Cited by 237 publications

References 47 publications

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

Estimativa de Permeabilidade Absoluta com Processamento de Imagens Utilizando Distribuição de Tamanho de Grãos

Capillary-Driven Transport of Dissolved Salt to the Drying Zone During $$\hbox {CO}_{2}$$ CO 2 Injection in Homogeneous and Layered Porous Media

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