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Delineation of apparent water resistivity and porosity exponent of the Miocene unconsolidated sandstone reservoir of coastal swamp depobelt, Niger Delta, Nigeria

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Apparent water resistivity (Rwa) and porosity exponent (m) were delineated using Pickett’s plot in Miocene, unconsolidated sandstone reservoirs of the Niger Delta Region. Quick log analysis was conducted using porosity (neutron-density-sonic) log lithology log and saturation (resistivity) log to delineate the reservoirs. The gamma values reported in this study varied from 40.00 to 45.91 gAPI indicating a spectrum of clean sand and with the resistivity range of 3.56–17.46 Ωm, the neutron density cross-over shows that the reservoirs are an Oil–Gas contact reservoir. The reservoir net pay range is between 18.5 ft and 96 ft, and it is clear that the reservoirs are suitable for economic production. Again, a linear association between porosity and porosity exponents has been developed as a decrease in porosity values will result in a decrease in porosity exponents. The measured values of apparent water resistivity in the study area were 0.208 Ωm, with the porosity exponent varying from 2.08 to 2.43 (representing variance from the theoretical value of 2 of 4 to 21.5%). These values (estimated from the Pickett plot may be a more accurate depiction of in situ condition) would aid in a better and more effective estimation of the formation factor in the area of study rather than incorporating theoretical constants from Archie’s equation.

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MI: proposed the title and carried out the conceptualization, OA: proposed the title, provided a detailed framework of the title, carried out statistical analysis, carried out interpretation and analysis designed the apparatus. GC and SE: sources for materials for literature review. All the authors were involved in the writing and proofreading of the manuscript. All the authors have read and approved the final manuscript.

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Correspondence to Okechukwu E. Agbasi.

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Communicated by Maria Virginia Alves Martins

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Igboekwe, M.U., Agbasi, O.E., Chukwu, G.U. et al. Delineation of apparent water resistivity and porosity exponent of the Miocene unconsolidated sandstone reservoir of coastal swamp depobelt, Niger Delta, Nigeria. J. Sediment. Environ. (2021).

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  • Archie’s equation
  • Formation factor
  • Lithology
  • Pickett’s plot