Determination of the mechanical properties of the rocks from the well profiling in tight sands

Abstract

The knowledge of the rock mechanic properties is imperative when planning, executing and estimating costs of the exploration and production projects of petroleum. Those specifications will be determining for the viability of executing the project. Several times, core samples are not available for obtaining the mechanic properties of the rocks in lab. Intending to solve this problem, a sequence of empirical equations were applied in order to estimate the properties, using the well geophysical data and correlating the distinct properties with different equations. A case study was conducted, using the Microsoft Excel program, with data provided in an asci file of a well that crossed a tight sands gas reservoir (reservoir with low permeability and low porosity). It was made a quantitative and qualitative analysis of the geological profiles in order to determine the parameters such as: porosity, density, acoustic wave velocity and transit time (necessaries to obtain the uniaxial compressive strength –UCS), friction angle and cohesion. The analyses were made from empirical equations, evaluating the formation strength. After obtaining all the data, it was performed an interpretation of the Mohr-coulomb rupture criterion, watching for the reservoir tensions behavior. The behavior would justify the UCS values, cohesion and friction angle and indicates that the reservoir rock being studied is cohesively, hard, compacted, with low porosity, what results in a well with low-risk of producing sand, simulating a hydraulic fracturing.