셰일 특성에 따른 탄화수소 저류층 전기비저항 모델 구성법 분석

In evaluating hydrocarbon saturation of reservoir, taking consideration of not only the amount of shale but also its distribution is very important. Since Archie’s equation, which is the most widely used equation for the evaluation of hydrocarbon reservoirs, is originally developed for electrically isotropic clean sandstones. Thus, employing Archie’s equation produces errors when evaluating shale-contained sandstone reservoirs: distributed shale or laminated sand-shale. For sand-shale lamination, generating macroscopic electrical anisotropy, consideration on the anisotropy is important to reduce possible errors in hydrocarbon-saturation evaluation. When the resistivity of shale layer has a microscopic anisotropy, more errors are produced if Archie’s equation is employed. In this paper, we review and analyze methods of constructing electrical resistivity models for hydrocarbon reservoirs to classify them according to characteristics of shale distribution. Further, this paper reviews case histories to analysis the importance of considering electrical anisotropy in evaluating hydrocarbon saturation.