Imaging Gravel-Pack Quality: Application to Deviated and Horizontal Wells

AbstractHorizontal well gravel-packing operations are known to exhibit a higher rate of premature screenout. The suggested causes of such failure range from extreme reservoir conditions (e.g., low in-situ stresses), to suboptimal drilling practices (e.g., extensive washouts), or even to limitations of the gravel placement process (i.e., accelerated carrier fluid leakoff). Premature screenouts are postulated with theoretical studies or with laboratory experiments. These approaches rely on idealized assumptions and therefore fail to explain gravel placement behavior observed in field practice. Further, currently available gravel-pack logging tools can provide only borehole-averaged measurements. These are inadequate in horizontal wells where the gravel-pack quality may not be radially uniform. In horizontal wells, an azimuthal, or localized, gravel-pack measurement is necessary for a proper understanding of the gravel deposition over the reservoir section.This paper describes the development and application of a new gravel-pack logging procedure. The associated logging tool is based on a radically different concept of fullbore gravel-pack imaging. It focuses on discrete sectors around the wellbore, providing the ability to azimuthally measure the gravel-pack quality. Further, its combinability with other production-logging sensors ensures that all parameters pertinent to gravel-pack evaluation can be obtained using a short, compact toolstring with minimal logging time.The gravel-pack tool can also be operated in memory mode and deployed with certain downhole completion components (i.e., the washpipe) before gravel injection. These components are normally retrieved upon completion of the pumping operation, bringing the logging tool through the gravel pack and back to surface. One can therefore obtain a gravel-pack log concurrently with the gravel placement procedure. This "logging while completing" approach will provide an enhanced gravel-pack quality measurement at a fraction of the cost of conventional electric line logging operations.Multiple field examples that illustrate the field application of this logging tool are provided. The paper also provides field evidence of the gravel placement failure mechanisms that have been previously postulated by theoretical studies.