A laboratory-based approach to determine Archie's cementation factor for shale reservoirs

Malekimostaghim, Ehsan; Gholami, Raoof; Rezaee, Reza; Asef, Mohammad Reza; Zhong, Zhiqi; Sarmadivaleh, Mohammad

doi:10.1016/j.petrol.2019.106399

Cited by 12 publications

(6 citation statements)

References 15 publications

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“…Likewise, some researchers stated "m" varied in a range of 1.0~3.0 according to lithology (1~1.5 in fractured hard rocks, 1.6~2.3 in sandstone, 2.28 in shaly sandstone, and 2.3~3.0 in carbonate) [3,49,52,53]. In terms of shale, the cementation factor m in gas shale reservoirs was around 1.6 to 1.7, below 2 in oil shale reservoirs, between 1.31 and 1.86 in Cauvery basin, and was around 1.6 in laboratory experiment [7,[54][55][56][57]. Recently, several relatively high m values of 2.9-3.6 under different salinity and 2.70 accounting for stress in Ordovician Goldwyer Formation from the Canning Basin are derived, together with 2.2 in Eagle Ford [58,59].…”

Section: Discussionmentioning

confidence: 99%

“…Since Archie proposed his representative equation in 1942, the barrier between fluid saturation calculation and resistivity logging data has been broken, sparking a scientific sensation throughout the entire energy industry [1][2][3][4]. Despite several alternative models, Archie formula is still popular for determining water saturation in shale [5][6][7]. These researchers were convinced that Archie's model was superior to other approaches if the accuracy of relative parameters could be improved.…”

Section: Introductionmentioning

confidence: 99%

“…Comparative analysis results of Archie's parameters in different rocks[1,3,7,26,37,[49][50][51][52][53][54][55][56][57][58][59].…”

mentioning

confidence: 99%

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A Laboratory Approach Considering Salinity to Investigate Archie’s Parameters in Deep Shale: A Case Study in Longmaxi Formation, Southern Sichuan

Liu

Cai

et al. 2022

Geofluids

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Archie’s parameters are substantial to be investigated in the evaluation of water saturation. Many researchers adhered to the opinion that Archie’s equation can still be applied to water saturation calculation in shale if the accuracy of relative parameters could be improved. External conditions, such as temperature, confining pressure, water salinity, wettability, and displacement, may influence the determination of Archie’s parameters. The aim of the study is to investigate the effect of salinity on Archie’s parameters and their correlation with mineral composition and pore structure. The mineral contents and petrophysical properties were firstly acquired through X-ray diffraction (XRD) and basic measurements. Rock-electric experiments under different salinity were conducted on deep shale samples taken from Longmaxi (LMX) Formation in Luzhou (LZ). The results indicate that Archie’s parameters of “ a ,” “ b ,” “ m ,” and “ n ” under actual brine salinity are assigned to 1.47, 1, 1.26, and 1.6, respectively. Our cementation factor is lower than that in other studies including (shaly) sandstones, carbonates, and shales, probably due to the extremely low porosity in study area. Salinity has a positive effect on cementation factor ( m ) and saturation exponent ( n ), suggesting the traditional assignment to Archie’s parameters is inappropriate. It was concluded that the complicated pore structure and high porosity mainly associated with clay mineral may trigger the increased cementation factor. Further mathematical derivations confirmed that the rock resistivity is inextricable from pore system and establish a physical model. The paper provides a solid evidence base for further understanding and evaluation of water saturation in unconventional shale reservoirs, more significantly, innovatively unveils the research into Archie formula in deep shale reservoirs of southern Sichuan basin.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A Laboratory Approach Considering Salinity to Investigate Archie’s Parameters in Deep Shale: A Case Study in Longmaxi Formation, Southern Sichuan

Liu

Cai

et al. 2022

Geofluids

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“…Values of 1, 2 and 2, are widely used in the conventional setting, however, these are appropriate only for clay-poor rocks with well-connected pores. Some authors have suggested that the cementation exponent is the fundamental parameter that should be adjusted in the case of shales, which led Malekimostaghim et al (2019) to conduct a laboratory study to determine a reasonable value for shale. We use their determined value of 1.6 in our calculations.…”

Section: Water Saturationmentioning

confidence: 99%

Determining reservoir intervals in the Bowland Shale using petrophysics and rock physics models

Anderson

et al. 2021

Geophysical Journal International

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SUMMARY An evaluation of prospective shale gas reservoir intervals in the Bowland Shale is presented using a wireline log data set from the UK's first shale gas exploration well. Accurate identification of such intervals is crucial in determining ideal landing zones for drilling horizontal production wells, but the task is challenging due to the heterogeneous nature of mudrocks. This heterogeneity leads to stratigraphic variations in reservoir quality and mechanical properties, and leads to complex geophysical behaviour, including seismic anisotropy. We generate petrophysical logs such as mineralogy, porosity, and organic content and calibrate these to the results of core studies. If ‘reservoir quality’ is defined by combined cut-offs relating to these parameters, we find that over 100 m of reservoir quality shale is present in the well, located primarily within the upper section. To examine the link between geophysical signature and rock properties, an isotropic rock physics model is developed, using effective medium theories, to recreate the elastic properties of the shale and produce forward-looking templates for subsequent seismic inversion studies. We find that the mineralogical heterogeneity in the shale has a profound impact on modelled elastic properties, obscuring more discrete changes due to porosity, organic content and water saturation and that the best reservoir quality intervals of the shale bear a distinctive response on rock physics cross-plots. Finally, we consider the density of natural fractures in the shale by developing an anisotropic rock physics model to reflect high-angle fractures observed on micro-imagery logs. We invert crack density using shear wave splitting well log data and find a crack density of up to 4 per cent which correlates well with micro-imagery observations. Our work further supports previous authors’ core-based studies in concluding that the Bowland Shale holds good reservoir characteristics, and we propose that there are multiple intervals within the shale that could be targeted with stacked horizontal wells, should those intervals’ mechanical properties also be suitable and there be adequate stress barriers between to restrict vertical hydraulic fracture growth. Finally, our rock physics templates may provide useful tools in interpreting pre-stack seismic data sets in prospective areas of the Bowland Shale and picking the best locations for drilling wells.

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“…The main method used for saturation evaluation is electrical logging, particularly the Archie evaluation method. , However, the Archie model has limited applicable conditions, i.e., medium-to-large-pore pure sandstone formations with formation water as the only conductive medium. For increasingly complex reservoirs, scholars have further developed and improved the Archie model.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Origin of Low Resistivity and Methods for the Calculation of Gas Saturation in Shale Gas Reservoirs in the Fuling Area

et al. 2021

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To address the challenge of inaccurate gas saturation values calculated by using Archie-type resistivity model as a result of the low resistivity of shale gas reservoirs in the Wufeng−Longmaxi Formation in the Fuling area, two nonresistivity gas saturation models were established, in this study, based on the relationships between the gas saturation and dipole array acoustic/conventional logging parameters as well as gas saturation and total organic carbon (TOC). The feasibility and accuracy of the proposed methods were verified with example wells. The results indicate that the main cause of the low resistivity in shale gas reservoirs in the Fuling area is shale graphitization; however, multiple factors such as the development of pyrite and the additional conductivity of clay also contribute. The S−P wave slowness ratio (RMSC) of shale gas reservoirs in the study area decreases significantly with increasing gas saturation and has a good correlation with the density (DEN). Thus, a saturation calculation model could be established based on the RMSC and DEN and the gas saturation from core analysis. The gas saturation in shale gas reservoirs increases logarithmically with increasing TOC with a good correlation. Therefore, a saturation calculation model could be established based on measured TOC values. The calculation accuracy of the two models is higher than that of the Archie-type resistivity model. This study shows that the saturation model established by fitting the RMSC and DEN is suitable for the case of core analysis with fair regional applicability. The TOC-based saturation model has good universality. Therefore, these two new models are suitable for gas saturation calculations in low-resistivity shale gas reservoirs and have the potential for wider applications.

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A laboratory-based approach to determine Archie's cementation factor for shale reservoirs

Cited by 12 publications

References 15 publications

A Laboratory Approach Considering Salinity to Investigate Archie’s Parameters in Deep Shale: A Case Study in Longmaxi Formation, Southern Sichuan

A Laboratory Approach Considering Salinity to Investigate Archie’s Parameters in Deep Shale: A Case Study in Longmaxi Formation, Southern Sichuan

Determining reservoir intervals in the Bowland Shale using petrophysics and rock physics models

Investigation of the Origin of Low Resistivity and Methods for the Calculation of Gas Saturation in Shale Gas Reservoirs in the Fuling Area

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