Application of AFR Sensor for the Purpose of Integrated Interpretation of High-Resolution Electrical Images and Geosteering of Horizontal Wells in Carbonate Reservoirs

摘要

Horizontal wells were drilled for the first time in the survey area. The target formation is mainly composed of dolomites and irregularly dolomitized limestones. Voids in reservoirs include pores, vugs, and fractures. Effective capacity of the reservoir is determined by intergranular and vuggy porosity, while fracturing provides for reservoir properties. In view of insufficient knowledge of the operation area, a decision was made regarding penetration of the target formation throughout the entire thickness and identification of a zone with the best reservoir properties for further positioning of a horizontal borehole in this zone. An azimuthal focused resistivity (AFR) sensor of 4 3/4 in. was used during drilling. This sensor generates high-resolution electrical images of borehole walls, measures at-bit resistivity, and provides laterolog data. This paper describes the process and procedures for interpretation of geological and geophysical logging while drilling (LWD) data for building a petrophysical model of the reservoir, determination of porosity and permeability, calculation of fluid, fracture and mineralogical models, and identification of structural geometry of rock bedding. Electrical microimages were used to update geological and petrophysical reservoir models.