AAPG Annual Convention and Exhibition

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Overcoming Complex Geosteering Challenges in the Cardium Reservoir of the Foothills of Canada to Increase Production Using an Instrumented Motor with Near Bit Azimuthal Gamma Ray and Inclination


The Cardium Formation is a conventional sandstone reservoir in the Western Canadian Sedimentary Basin. In the undeformed basin, the Cardium Formation is currently at a phase of exploitation requiring long horizontal penetrations and large scale, multi-stage, fracture stimulation to ensure productivity. In the Canadian Foothill, the Cardium is complexly deformed and naturally fractured. Correctly placed wells take advantage of these natural fracture permeability pathways to support extremely prolific wells. To maximize production and effective reservoir drainage, horizontal wellbores need to be drilled to intersect multiple fracture networks within the deformed Cardium reservoir. Sub-seismic scale folds and faults result in rapid changes in reservoir bedding orientation and/or position and require very sensitive geosteering responsiveness in order to create an optimal reservoir penetration. The reservoir exhibits very good gamma character; and therefore gamma has been shown to be an effective tool for geosteering. An innovative instrumented motor that provides azimuthal gamma and continuous inclination 9ft from the bit was used for geosteering several wells, and has proven to be a vital component in the drilling process. For example, in the case of a 5deg change in apparent bedding orientation compared to the wellbore resulting in the wellbore exiting the reservoir, re-entry can occur as quickly as 100ft when using the instrumented motor compared to 185ft when using a conventional gamma positioned 50ft from the bit. The 41ft of “advance” notice allows you to get back in reservoir sooner resulting in an increase in reservoir penetration interval of 84ft. In one case study, a horizontal leg was drilled using a conventional gamma, the well exited the reservoir due to an abrupt change in bedding orientation and 1138ft of non-reservoir was drilled prior to re-entering the reservoir. With the near-bit information, this non-productive interval would have been avoided or significantly reduced. The paper will start out by introducing the complex reservoir of the Foothills. It will then present the unique challenges faced when attempting to geosteer and place the wellbore within the reservoir. We will review the near bit instrumented motor and discuss the workflow of how data was used from the instrumented motor to help with geosteering the well. Finally; the results will be presented and a discussion of future work will be presented.