Investigation of depletion process influence on relative permeability and residual oil saturation of thick transition zone carbonate reservoir

  • Abdessamia Jebbouri

    Student thesis: Master's Thesis

    Abstract

    A rock type is a very essential tool in characterizing carbonate reservoirs. It is defined as a set of petrophysical characteristics that several reservoir rocks have in common and this is due to the fact that they went through similar diagenetic processes. These characteristics are mainly related to fluids flow and fluid storage capacity, in other words, it will be related to porosity and permeability of the rock sample. Knowledge of different rock types of a carbonate reservoir and their impact on the petrophysical properties and the special core analysis data are a key factor for determining fluids saturations distribution, fluids mobility and recovery factor. The fluids saturation distribution and flow behavior as a function of height in the transition zones (TZ) is often very complex in carbonate reservoirs where these reservoirs are typically characterized with low permeability values. It is believed that variation in oil recovery and residual oil saturations from oil reservoirs are mainly controlled by factors related to the relative permeability of existing and flowing fluids in the reservoir. Relative permeability (Kr) is a critical parameter to evaluate the reservoir performance and when combined with capillary pressure is considered a key factor in defining saturation distributions above Free Water Level (FWL). The impact of different reservoir rock properties such as pore geometry, wettability, fluids saturations, and reservoir temperatures on relative permeability has been investigated thoroughly. As a result of the depletion process occurs in the reservoir, the effective stresses increases and consequently, several petrophysical parameters such as porosity, permeability, pore geometry, and pore throats may alter significantly. Limited studies were performed on the effect of reservoir depletion on relative permeability and residual saturations for carbonate reservoir in the Gulf Region. The purpose of this research is to: 1. Identify the major rock types of the carbonate transition zone studied through series of routine (RCAL) and special (SCAL) core analysis measurements on core samples. 2. Experimentally investigate the effect of different rock types on RCAL and SCAL data for the transition zone studied. 3. Investigate the depletion process effect on relative permeability and residual oil saturation for carbonate core samples. The experimental procedure consists of routine porosity and permeability measurements using gas at ambient conditions. The special core analysis measurements were conducted on couple of samples at high pressure to mimic the reservoir conditions. Capillary pressure (Pc) measurements for different rock types at ambient conditions were conducted using an air-brine porous plate system and accordingly Pc curves were generated. Unsteady State (USS) relative permeability (Kr) was measured under different effective stresses to study the depletion process and its impact on the relative permeability curves and residual saturations. Drainage and imbibition USS relative permeability was measured on different samples representing the different rock types existing in the reservoir. The drainage imbibition hysteresis may be used for modeling to calculate fluid saturation in the reservoir due to the movement of water-oil contact. Resistivity measurements at ambient conditions were measured to determine the electrical parameters including cementation factor (m) and Archie's saturation exponent (n), which they are unique to a specific reservoir and need to be measured on reservoir core samples to allow accurate evaluation of down-hole electrical logs for water saturation determination. The experimental results are supposed to highlight the understanding of multiphase flow in the depletion process where the dynamic SCAL occur and expected to in light of the understanding of the thick capillary transition zones formation.
    Date of AwardDec 2016
    Original languageAmerican English
    SupervisorHadi Belhaj (Supervisor)

    Keywords

    • Applied sciences
    • Carbonate reservoirs
    • Fluids saturation
    • Relative permeability
    • Transition zone
    • Petroleum engineering
    • 0765:Petroleum engineering

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