Effect of Fluid Invasion to Formation Resistivity

Abstract:

Clay is the primary cause for resistivity reduction in most of the low resistivity pay cases. While dry clay acts as insulator, reaction with water made wet clay a good conductor. Clay conductivity is contributed by the exchangeable cation properties of the mineral. This reduces the actual resistivity of the formation, especially in the invaded zone. The effect is more severe if clay existed as dispersed type in the formation; which will also reduce other important petrophysical properties such as porosity and permeability. The study was conducted to observe the mechanism and reduction of formation resistivity due to mud invasion and find the relationship between resistivity reduction and petrophysical properties of the formation. The resistivity was measured on four types of samples with different grain size and sorting; well sorted fine grain size, well sorted medium grain size, well sorted coarse grain size and not well sorted sand. Three types of fluids were flushed into sand pack those are brine, crude oil and water based mud to simulate the invasion process. Sand pack with not well sorted sand and fine grain size had the most resistivity reduction, which possibly due to the high clay content that interacted with water.

• Periodical: Advanced Materials Research (Volume 1113)
• Pages: 285-295
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.1113.285
• Online since: July 2015
• Authors: Wan Zairani Wan Bakar, Arina Sauki, Mohd Haziafiz Abd Halim, Norrulhuda Mohd Taib
• Keywords: Clay, Grain Size and Porosity, Low Resistivity Pay

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