A NOVEL HIGH-DEFINITION INVERSION OF DEEP DIRECTIONAL ELECTROMAGNETIC MEASUREMENTS WHILE-DRILLING ENHANCES LAYERED RESERVOIR MAPPING

摘要

The most recently developed deep directional electromagnetic technology is capable of investigating reservoir resistivity profiles more than 150 ft away from the wellbore. The experience acquired worldwide highlighted the opportunity to improve the quantitative delineation of limited thickness layers farther away, compared with currently used inversion techniques. In this paper, we present a high-definition inversion method for mapping layered reservoirs, taking into account prior reservoir knowledge.The novel model-driven inversion methodology provides a high-definition reservoir map suited for narrow strata delineation and early reservoir detection that are useful in well placement operations. By integrating the prior field geology knowledge, the algorithm is able to consistently and accurately map more detailed features of the layered formations farther away from the wellbore, resulting in an enhanced and expedited real-time steering decision-making process.Information from offset wells and/or the seismic interpretation are defined as a reference pattern used in the inversion cost function minimization process, in addition to traditional data misfit and regularization. Moreover, this method has a unique fault-tolerant ability in the event the reference model is not representative, or when there is a depth shift in the entire reference model.The inversion method has been tested on several datasets including geo-steering in an ENI field within an oil reservoir consisting of fluvial and deltaic deposits of Triassic age. The enhanced interpretation of reservoir structure through the new inversion helped to better understand the well production behavior. The reservoir resistivity map obtained using the new method depicted geological features earlier than previously available with superior lateral continuity and less artifacts. The interpretation is enhanced by defining a reference model based on prior reservoir knowledge, naturally preserving these details if they are supported by deep directional measurements, resulting in finer structural interpretation, consistent with all of the data. The novel workflow eliminates the trade-off between high-definition and increased depth of investigation in reservoir mapping applications, providing high-definition geologically consistent structural information.