LWD Resistivity Tool Response Modeling in High Angle and Horizontal Maximum Reservoir Contact Wells and its Significant Impact on Water Saturation Calculation: Case Study in a Giant Carbonate Field in Middle East

Abstract

Resistivity is one of the most important log that is required in water saturation (Sw) calculation, reservoir characterization, field assessment and hydrocarbon production. However, borehole environmental and borehole-to-bedding geometric effects on LWD propagation resistivity logs are inevitable. For instance, severe "polarization horn" responses from LWD propagation resistivity logs are commonly encounted in High-Angle & Horizontal (HAHZ) wells near bed boundaries with high resistivity contrast. These "polarization horns" in LWD propagation resistivity responses in HAHZ wells are not accurate resistivity profile, and consequently, impacts Sw calculation. In this paper, an innovative LWD propagation resistivity Tool-Response-Modeling (TRM) workflow has been developed and applied to six typical Maximum Reservoir Contact (MRC) wells drilled in a giant carbonate field in Middle East. The inverted resistivity profiles along the well path result in more accurate resistivity and, hence, more accurate Sw calculations (as compared to capillary pressure- and core-based Sw calculations). Additionally, TRM results yield new insights on to both maintain the well in the target formation and reduce these "polarization horn" responses during geosteering operations. The case studies demonstrated that TRM and this workflow has an important and critical roles in accurate Sw calculation, formation evaluation and field assessment, and hydrocarbon production.