“Evaluation of Multiple Component Induction Logging in a Deltaic Environment:A case study”

摘要

The Lower Eocene C Misoa Formation was deposited on a tidally-influenced low deltaic plain in the Bloque 8 Field,Lake Maracaibo Basin.As a result of the environment deposition usually sand layer thickness is below of tool’s resolution,resulting in petrophysical properties being averaged across the shale and sand lamina.One of the measurements affected is resistivity hence is common to find low net pay reservoir.These low resistivity pays,characterized by electric anisotropy,are often overlooked or mistaken as water-bearing sands when conventional resistivity measurements are used for calculating their water saturation,especially when an oil based mud and traditional induction logs are acquired.More accurate and reliable petrophysical quantification is crucial for the economic decision to explore,develop, and produce these reservoirs.Klein et al.(1995)note that pronounced electrical anisotropy in porous sediments could be a good indicator of hydrocarbon pay. The Multi-Component Induction(MCI)tool is comprised of three pairs of mutually orthogonal transmitter-receivers measuring all nine magnetic field components at 10 different frequencies.The main objective in this paper is to show how information of seven wells with MCI logs was incorporated into the petrophysical model in order to reduce uncertainties about water saturation calculation.Using tensor resistivity equations,true sandstone resistivity and the volume of laminar shale were computed.Water saturation estimation using traditional resistivity measurements in the reservoir have predicted initial water production;meanwhile MCI predicts that some intervals should not have it.All Production data available was used to determine which log derived saturation match with the real reservoir production behavior.Finally,we summarized how the lack of core and image logs information may cancel the benefits of having vertical resistivity,because N/G and porosity has a great impact in calculations.