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Production logging measures downhole flow properties under dynamic conditions with an objective to gain insight into the downhole flow dynamics and quantify zonal flow contributions. Production logs are acquired during "stabilized flowing and shut-in conditions" and the observed flow behavior is assumed to be representative of the reservoir flow behavior. In a homogenous reservoir this assumption may not be far from reality. Heterogeneous reservoirs, however, pose another challenge. Flow dynamics observed in heterogeneous reservoirs can be time dependent; therefore the time frame of data acquisition is critical to the conclusions that can be drawn from the interpretation.Presented herein is a case study of production logs acquired in a seemingly homogenous reservoir, the interesting dynamics observed from the data, and the methodology used to unravel the reservoir behavior. The production logs acquired during shut-in conditions revealed downhole cross flow between the reservoir layers. However a change in the direction of cross-flow between two shut-in acquisitions, acquired within 10hours of each other, revealed a much more complex reservoir than originally anticipated. Further analysis of the data and integration with other reservoir evaluation techniques revealed the heterogeneity of the reservoir with the existence of three radial compartments exhibiting different reservoir pressures, mobility and productivity index.The flow behavior observed from the production logs is unique and provides an insight to downhole flow dynamics in heterogeneous reservoirs. The methodology used in unraveling the reservoir behavior, and the integration of the production logs with other reservoir evaluation techniques, aided in improving reservoir characterization and ultimately reservoir management. IntroductionProduction logs provide measurements of downhole flow properties to promote an understanding of the downhole flow repartition of several zones, which then provides more information on the contribution the different reservoir layers make to the total production. In a homogenous reservoir, with constant properties, the reservoir response does not change with time and the flow behavior recorded at any time can be assumed to be representative of the reservoir behavior. However, in a heterogeneous reservoir, the nature of the reservoir may cause its flow behavior to change with time. A typical example will be a dual porosity reservoir system: in a dual porosity system, the reservoir is described to be composed of two systems -a block system and a matrix system. The matrix system has high permeability but low storativity, meaning that the fluid will flow faster through the matrix but it does not have enough volume to support the production (Fig 1). The block system on the other hand has high storativity but low permeability, meaning that fluid cannot flow directly from the block system into the wellbore. The fluid will flow from the block system into the matrix and then into the wellbore (Fig 2). When this type of reservoir is p...

A key uncertainty associated with Deepwater Turbidites is the reservoir continuity or connectivity, which has been observed in Bonga field. The Bonga field is one of the premier deepwater fields in Nigeria, discovered in 1996 and operated by Shell Nigeria Exploration and Production Company (SNEPCo) since 2005. With several wells under production, water flooding is employed for reservoir pressure management, aiding optimized recovery. Reservoir connectivity uncertainty is a typical issue with these deepwater turbidites, with adequate planning required to ensure risks associated with reservoir connectivity are accounted for and addressed. Although several producer and injector well-pairs have been drilled, data collected and analyzed, connectivity uncertainties still remain high in the field. One key source of information for understanding connectivity issues are formation pressure tests taken periodically (before and during the productive life of these reservoirs). In Deepwater Nigeria, these formation pressures are typically taken while drilling (Formation Pressure tests while drilling - FPWD), and augmented with data from down hole pressure gauges installed in many of the wells. This pressure data is acquired and analyzed to understand the reservoir pressure depletion trend, waterflood patterns and efficiency, as well as identify sand compartments within the reservoir. This paper discusses the use of formation pressure while drilling data in a new Bonga injector. The data was used to confirm connectivity with a paired updip oil producer, which was critical in making real-time decisions on completing the well, reducing drilling and completion risk, as wells as reducing the rig cost associated with the entire well operations.