--> Abstract: A New Tool for High-Resolution Sedimentological Imaging of Deepwater Clastic Reservoirs, by Laronga, Robert J.; Kear, Rick; Kumar, Anish; Vessereau, Patrick; Bloemenkamp, Richard; and Zhang, Tianhua; #90166 (2013)

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A New Tool for High-Resolution Sedimentological Imaging of Deepwater Clastic Reservoirs

Laronga, Robert J.1; Kear, Rick; Kumar, Anish; Vessereau, Patrick; Bloemenkamp, Richard; and Zhang, Tianhua
1[email protected]

We introduce for the first time in this paper a new high-definition full-coverage wireline formation imaging tool and illustrate its direct relevance to the identification of depositional environment in deepwater wells drilled with nonconductive synthetic-base drilling fluids (NCM).

Literature documents the use of borehole images to interpret depositional environment in deepwater clastics, with the best examples coming from wells drilled with conductive water-base fluid (WBM), where high-definition, full-coverage images are easily acquired. Channel, proximal or distal levee, crevasse splay, proximal or distal lobe, slope, and basin floor are distinct environments that have been readily identified from such images based on an association of detailed sedimentological observations.

Today NCM fluids dominate deepwater, and even the most successful NCM-adapted formation imager has had interpretive limitations.

We field-tested a new high-definition full-coverage formation imaging tool for NCM fluids, based on a new measurement principle. A recent version provides over 90% coverage via 192 microelectrodes (3mm by 5mm), resulting in images like those acquired in WBM. Further, the chosen physics result in a more natural response to formation texture.

Based on a review of images from the field test, it is clear that nearly every area of borehole image interpretation is improved in NCM compared to previous technology. Even simple determination of structural dip benefits greatly because the new tool is significantly more sensitive to bedding. Tabular nature of sandstones and lamination in shale that were previously invisible are revealed. Resolution allows to evaluate each contact for planarity, and lapping or crosscutting relationships are more likely to be spotted. Ripples are observed in individual cm-scale sands within levee deposits. Slumps from a few cm to several meters are clear where previously this was an expert's judgment call. Conglomeritic formations such as traction deposits or debris flows that were previously unrecognizable are now ‘photographically’ imaged.

Deepwater geologists interpreting these images now have a full range of core-like observations upon which to base their conclusions. The depositional environment and depositional axes so-derived from these images give operators a valuable input to realistically constrain the distribution of reservoir facies in 3D models, aiding pragmatic field development or enhanced oil recovery plans.

 

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013