Abstract
This paper discusses the use of continuous scratch testing for evaluation of rock heterogeneity and effective correction and calibration of mechanical properties predictions using wire line logging. Understanding the vertical variability of rock properties (strength and moduli) along the reservoir thickness is of primordial importance for sanding prediction analysis. Logging measurements (GR, Sonic, Density and Porosity) are traditionally used to identify troublesome intervals, to select sections for laboratory testing and for extrapolating laboratory data to untested reservoir sections. However, depending on the scale of the reservoir heterogeneity, the log measurements, by providing integrated values over their window of vertical resolution, can considerably underestimate the strong reservoir sections and overestimate the weak reservoir sections. This leads to misrepresentation of critical weak layers with high potential for sanding and potentially to large errors in the completion strategy with costly long-term consequences. Corrections are thus necessary and are traditionally based on simple unconfined compression (UCS) tests conducted sparsely or at high density, varying from operator to operator. This paper presents a method for log-correction based on continuous core scratching in the laboratory and shows that the methodology is effective in evaluating changes in properties with high accuracy and a resolution of at least 1 cm.
