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.

In order to evaluate the productivity of gas hydrate by the depressurization method, Japan Oil, Gas and Metals National Corporation and Natural Resources Canada carried out a full-scale production test in the Mallik field, Mackenzie Delta in April 2007 and March 2008. An extensive wireline-logging program was conducted in 2007 to evaluate physical reservoir properties of gas-hydrate-bearing sediments, to determine production-test and water-injection intervals, to evaluate cement bonding, and to interpret gas hydrate-dissociation behaviour throughout the production test. New open-hole wireline-logging tools, such as the Magnetic Resonance ScannerTM, True Resistivity ScannerTM, Sonic ScannerTM, and other advanced logging tools, such as Elemental Capture SpectroscopyTM, were deployed to obtain precise data on the occurrence of gas hydrate, lithology, gas hydrate pore saturation, porosity, and permeability. Perforation interval of the production-test and water-injection zones was determined through a multidisciplinary approach, using geological-petrophysical analysis and interpretation of open-hole logging data, construction of layered reservoir models, quick reservoir numerical simulations for several perforation scenarios, and operational constraints. A gas-hydrate-bearing formation from 1093 to 1105 m KB was selected for the 2007-2008 production test, and three zones (1224-1230, 1238-1256, and 1270-1274 m KB) were selected for the injection of produced water. Cased-hole logging measurements with the Reservoir Saturation ToolTM, Accelerator Porosity SondeTM, and Sonic ScannerTM were also conducted to evaluate physical-property changes of the gas-hydrate-bearing intervals before and after the production test (time-lapse analysis). Analysis of these cased-hole logging data provided important knowledge about gas hydrate-dissociation behaviour.

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The acquisition of high-quality logging-while-drilling (LWD) cased-hole borehole sonic data in real-time (RT) and in memory (RM) dramatically improves drilling efficiency. RT sonic waveform amplitudes and slowness-time-coherency (STC) measurements enable qualitative cement evaluation either while running in hole (RIH) or when pulling-out (POOH). Operators can make appropriate decisions on cement quality to either continue drilling or perform remedial work. Data acquisition is transparent to drilling operations, removing wireline logging that can contribute to additional time and cost. Furthermore, with RM data a quantitative cement evaluation can be performed, and when environment conditions are adequate, formation compressional slownesses through casing can be computed. The advent of the latest LWD sonic acquisition technology and related processing techniques has significantly reduced the challenge of cased hole LWD sonic acquisition. More powerful sonic transmitters, improved receivers, altered transmitter-receiver spacings, and fundamental changes in tool design have meaningfully improved the acoustic signal-to-noise ratio. An improved understanding of LWD cased-hole borehole acoustic modes, the ability to transmit acoustic energies at more optimal frequencies, and the capability to simultaneously acquire cement evaluation information have all contributed to improved LWD cased-hole sonic logs. Cementing is essential to well integrity, it supports casing and provides zonal isolation. Historically, quantitative cement evaluation has been acquired via wireline (WL) tools, the most common being the cement bond log (CBL), a principle based on the amplitude of casing arrivals. LWD sonics have historically been used for top of cement (TOC) logging, which shows cement presence or absence behind casing and is a quantitative cement evaluation. Contrary to WL CBL tools, LWD tools have a steel collar that permits acoustic propagation. As such with LWD tools it has been difficult to separate casing signals from those in the tool collar (Kinoshita, 2013). In poorly bonded conditions, the casing amplitude is much larger than the collar arrival. In well-bonded conditions, the casing signal is weak and can be less than the collar arrival. From multiple cased wells in Deep Water Offshore West Africa, this paper demonstrates the application and results for the latest LWD sonic tool and processing techniques for the following; RT TOC evaluation while RIH before drilling out the casing shoeQuantitative cement evaluation from tool memory waveform dataFormation compressional slowness through casingApproximately US$450,000 saving compared to wireline runs

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