Normalizing Gamma-Ray Logs Acquired from a Mixture of Vertical and Horizontal Wells in the Haynesville Shale
- Chicheng Xu (BHP Billiton Petroleum) | W. Sebastian Bayer (BHP Billiton Petroleum) | Marcus Wunderle (BHP Billiton Petroleum) | Abhishek Bansal (BHP Billiton Petroleum)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- Publication Date
- December 2016
- Document Type
- Journal Paper
- 638 - 643
- 2016. Society of Petrophysicists & Well Log Analysts
- 2 in the last 30 days
- 236 since 2007
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This article introduces a practical workflow of normalizing gamma-ray (GR) logs acquired from both vertical and horizontal wells penetrating different geological subzones in the Haynesville shale. Gamma-ray logs are first normalized in all vertical wells over the same stratigraphic zone. The normalized GR log in the nearest vertical well is then used to reconstruct synthetic GR logs along horizontal well paths using true stratigraphic projection method. The measured GR logs from the horizontal wells are then compared and normalized with the synthetic GR logs to enforce statistical consistency with the normalized GR logs in the associated vertical well. The workflow delivers a set of normalized GR logs in a group of vertical and horizontal wells that provide a reliable basis for reservoir description and modeling.
A gamma-ray (GR) log is available in almost every well drilled in the Haynesville shale. In many horizontal wells, LWD GR is the only acquired log that provides critical information for business decisions on drilling, fracturing, and completions. Due to the underlying tool physics, GR logs acquired under different drilling conditions and borehole environments need to be normalized to be quantitatively comparable across different zones and wells (Neinast and Knox, 1974; Aly et al., 1997). The GR log normalization procedure has been well established for multiple vertical wells penetrating the same stratigraphic zones; however, the workflow for normalizing GR logs from multiple horizontal wells drilling through different geological subzones has not yet been reported. The standard log-normalization procedure cannot be directly applied to horizontal wells because different horizontal wells drill through different target subzones (Fig. 1). Consequently, the GR-log histogram in horizontal wells is not supposed to be comparable with nearby vertical wells because it measures rock populations in different subzones.
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