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Technical Paper: Horizontal Cased Hole Evaluation Using a New Pulsed Neutron Spectroscopy Tool and Dipole Sonic

Society: Other
Paper Number: 2689778
Presentation Date: 2017
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Abstract

Over the past several years there has been increasing interest in running logs in horizontal wells for use in completion planning. Since it all started, there is evidence that placing stages and perforations using log data from lateral wells has made a positive impact on hydraulic stimulation results and the associated production in a number of areas. Much of the early success was based primarily on the use of dipole sonic derived stress calculations to improve the frac results, and secondarily on petrophysical rock properties which define the quality of the reservoir. Most operators are committed to completing the entire lateral regardless of reservoir quality with the philosophy that even if the well was not placed in the ideal reservoir quality, for whatever reason, hydraulic `stimulation would provide the conduit for production to the better rock in close proximity to the wellbore. Production logging has revealed that zones of better petrophysical rock quality near the wellbore have a greater relative contribution to production than those with poorer rock quality, even after a successful stimulation.

Given the current oilfield economic conditions, cased hole evaluation has become a more attractive option for logging because of the potential savings in rig costs associated with acquiring open hole logs in the lateral. This paper will recap some case studies where data was recorded through casing with a unique new spectral pulsed neutron tool and the latest generation dipole sonic tools. The spectral pulsed neutron tool is capable of recording elemental yields, a new gas measurement and refined versions of the basic pulsed neutron outputs in a single pass, which enables a more refined evaluation of reservoir quality. For completion quality, good quality cased hole sonic data is possible even when cement conditions are less than ideal. Examples of open and cased hole dipole sonics run in the same well will be shown with discussion of some of the considerations regarding tool selection and completion configuration as they relate to cased hole sonic data quality. Mechanical properties and stress obtained from cased hole sonic data can be combined with the petrophysical data from the new spectral pulsed neutron to obtain a comprehensive evaluation of reservoir and completion quality, similar to what was previously available from open hole logs. Case studies will illustrate how these interpretations can be used in completion design.

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