HIGH-RESOLUTION FACIES PREDICTION BY MEANS OF INTEGRATING DIP QUALITY INDEX AND TEXTURE ANALYSIS FROM RESISTIVITY BOREHOLE IMAGE LOGS IN A PRE-SALT COMPLEX CARBONATE RESERVOIR LOCATED IN A BRAZILIAN FIELD

摘要

The texture of the rock is an important parameter that must be considered when performing a petrophysical characterization of complex carbonate reservoirs due to the relationship it has with the depositional and diagenetic mechanisms and the effect it has on fluid flow capacity of the rocks. The presented workflow describes a methodology to extract texture information from resistivity borehole image logs in order to generate a high resolution ordered textural facies log which once integrated with conventional logs greatly contribute to the improvement of facies models. Two approaches are combined to extract texture from resistivity borehole image logs. The first one relies on the quality index from dips of the stratigraphic laminations detected such as contrast, lamination and planarity to delineate laminated intervals, and characterize them in terms of dip facies by means thickness, density of laminations, mean contrast and mean planarity. Considering the fact that dips are irregularly spaced and computed at point level, the dip facies are computed at point level as well. To overcome this challenge of describing continuous rocks interval, either laminated or not, by means of facies observed at irregular depth, a histogram upscaling technique was applied, as a result, a continuous and regularly sampled log was obtained and it was possible to conciliate high-resolution data with conventional logs to qualify intervals in terms of diagenetic or depositional facies. The second approach comprises the texture detection based on covariance information of resistivity image logs and a posterior facies definition using statistical and unsupervised algorithm that will guide the texture identification as a function of contrast. The integration of the high-resolution facies with production data reveals a good correlation between flow potential and the zones obtained by these approaches.