Hydrocarbon production from low permeability heterogeneous clastic reservoirs consisting of a sequence of thin, interbedded sand and shale laminations is challenging. Hydraulic fracturing is essential to achieve good production rates. An understanding of fracture geometry is very important for optimal reservoir management and development. This paper describes the application of an advanced logging system to evaluate near-wellbore vertical fracture properties.

Conventional production logging focusing primarily on wellbore flow geometry such as perforation and behind casing flow through poor cement may not adequately evaluate fracture properties due to a limited radius of investigation. To overcome this, a campaign using an advanced logging system containing spectral acoustic and high precision temperature measurements to evaluate near-wellbore fracture flow distribution was implemented. The main feature of this logging technique is the ability to scan the active flow behind the casing a few meters from the wellbore. The reservoir flow profile is assessed by temperature modelling enabling differentiation of the different flow regimes and inflow contributions.

Two vertical water injection wells hydraulically fractured into the low permeability clastic reservoir were logged. Vertical fracture geometry was precisely determined for each case and reservoir injection profile determined based on temperature modelling. Detailed pre-job modelling was necessary to define the logging program including optimal flowing and shut-in regimes. This enabled improved efficiency and accuracy when interpreting the results. The results enabled the determination of any out of zone injected volumes. This study revealed new insights in evaluating fracture geometry that can then be applied to reconcile post-job fracture modelling and improve reservoir management and water flood optimization.

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