Adrian Zett

Multidisciplinary approach in determining the best zone to land a Haynesville horizontal well

AbstractThe Upper Jurassic Haynesville Shale Formation in the East Texas Basin, North America, is a black, organic-rich, calcareous mudstone that lies below the Bossier Shale and above the Cotton Valley Limestone. The reservoir quality was controlled by primary depositional process and secondary diagenesis. The best lithology type in terms of drilling, completion, and production is the organic-rich, silty calcareous mudstone with low clay content. The studied well traversed the entire Haynesville Formation with the objective to assess the production potential of this formation. We acquired open-hole, triple-combo logging while drilling (LWD) logs, two types of production logs, and regional microseismic data. Postdrill log modeling confirmed that the horizontal well stayed on the planned trajectory, based on the log correlation between the horizontal and offset wells. Log modeling demonstrated that the LWD resistivity logs in horizontal wells are subject to resistivity anisotropy and polarization horn effe...

Reservoir Surveillance and Successful Infill Well Delivery in a Mature Asset

Production Petrophysics plays a key role in reservoir surveillance and field management. This is particularly true for mature assets which present several challenges related to fluid contact movement, connectivity of reservoir layers and well productivity. Identification of infill targets therefore requires an integration of all sub-surface data. This paper presents examples from a mature North Sea field where cased-hole surveillance helped minimize risks in a high cost infill project. The Machar field, located in the UK Central North Sea is a fractured Cretaceous chalk and Palaeocene sandstone oil reservoir. The field development has been carried out in a phased manner due to a high degree of reservoir uncertainty, especially in the eastern flank. Enhancing the seismic sufficiently to fully assess prospects on the east became a priority, and ultimately led to drilling the east flank of the field in 2008. Machar is a subsea field development and therefore petrophysical surveillance has been restricted due to limited well access and logistical challenges. During the infill drilling, it was therefore decided to use the opportunity and capture cased-hole saturation and production logs in existing wells. This data enabled the asset teams to understand fluid displacement mechanisms and upon integration with LWD and other logs provided the basis for the side track strategy. In particular, location of the imbibition flood front, fracture conduits and differentiation between formation and injection water were critical in the delivery of a successful producer. Two wells have been drilled on the eastern flank, one in 2008 and another in 2010. Baseline petrophysical surveillance was part of the data acquisition program in both wells. The initial objective was to use such data in Time Lapse mode with later surveillance. However, in-depth work identified immediate use when integrating with LWD and Wireline data.