A Proposed Data Acquisition Program for Successful Geomechanics Projects

Abstract

There has been a growing interest in geomechanics in the oil industry. From simple rock mechanical properties to fully coupled reservoir geomechanics simulation, real-time wellbore stability monitoring, stimulation job design, or sand management, the value of geomechanics has now been demonstrated and is applicable throughout the entire life of a field. Because it has become a key component for a number of departments, geomechanics is now considered a discipline by itself, and most of the major oil companies have established their own teams of rock mechanics experts. The mechanical earth model is the core of any geomechanical work. It is an integration process characterizing the field in terms of rock mechanics properties. Like any other type of project, it requires a minimum amount of specific information to be successful. Practically speaking, because data acquisition programs rarely focused on rock mechanics aspects in the past, it often appears that part of the key data required to perform a proper evaluation is not available. In such a case, one may have to use correlations to estimate the missing information or apply default parameters with their associated uncertainties. Ultimately, there is no equivalent to real data to ensure the accuracy of any study. The paper summarizes the data requirements for a reliable mechanical earth model and proposes a standard data acquisition program that would guarantee the availability of critical information. It will demonstrate that most of the data required are needed for other disciplines as well. The key is to make sure it is systematically acquired. Introduction Better understanding of the concepts and theory, technical advances, value added demonstration and recognition of the discipline have significantly changed the way geomechanics is perceived in the oil industry, resulting in an increased number of research and studies being initiated. A number of major oil companies have now established their own teams of experts to focus on rock mechanics related topics. From exploration to abandonment of the field, geomechanics relates to most of the technical aspects of the life of a reservoir. Pore pressure prediction, wellbore instability planning and management, casing design and well engineering, open hole completion stability, solids control, perforation design, reservoir stimulation, fault activation, subsidence and compaction, fully coupled reservoir geomechanics (etc…), it has been demonstrated and acknowledged that the range of application for the discipline is rather large. Rock mechanics is not new to the oil industry, but the concept of mechanical earth model (MEM) was only introduced in the late 1990s. The MEM consists in integrating data from various sources into a model that provides the rock mechanics parameters for a field, a well or a reservoir. Standard outputs from the model include elastic properties, rock strength and in-situ stress magnitude and direction. Those represent the main input to any subsequent failure analysis. With time, the MEM has become the core of any geomechanics work and potentially the most important step of the workflow.

A Comparison of Hydraulic and Propellant Fracture Propagation in a Shale Gas Reservoir

“…UCS tests are conducted by dragging a carbide cutter along the surface of the material while both the normal and shear stresses at the cutter are recorded. Because UCS tests measure an index rock property, the results are a function of sample geometry and are only the relative strengths of the layers measured (6) . Figure 3 shows the outline of the propellant fracture as preserved by the wellbore fluid which was a dyed KCl solution.…”

Stress state in the Cuu Long and Nam Con Son basins, offshore Vietnam

“…Data from unconfined compression tests in the laboratory were available for estimation of E s , n and C o . Tensile strength, T o , is usually estimated to be one-eighth to one-twelfth of C o (Chardac et al, 2005). In this study we used…”

Stress Estimation at the Otway CO2 Storage Site, Australia

“…The construction of such a model and the associated data requirements have been described in detail elsewhere 30,31,32,33 and are briefly summarized below. For that purpose, a mechanical earth model is built that incorporates the ambient stresses together with the pore pressure and the strength properties of the rock formations along the well trajectory.…”