Navigating the Horizontal Section in a Heterogeneous Formation While Using Extra Deep Azimuthal Resistivity for Optimizing the Wellbore Placement within a Narrow TVD Window

Larsen, David (Baker Hughes Inc.) | Antonov, Yuriy (Baker Hughes Inc.) | Luxey, Pascal (Baker Hughes Inc.) | Skillings, Jon (Baker Hughes Inc.) | Skaug, Mats Bjørndal (Total E&P Norge) | Wagner, Vincent (Total E&P Norge)



The Martin Linge field (originally named HILD) is a new field development in the Norwegian North Sea. The field consists of two main reservoirs, the Eocene Frigg reservoir with oil accumulation, and the Jurassic Brent reservoir with gas/condensate accumulations. The paper describes the procedures applied during geosteering operations, observations and results of the oil production wells drilled on the Martin Linge field

The Frigg reservoir consists of unconsolidated multi-darcy sandstone. For optimal production, horizontal production wells have been selected. Drilling in unconsolidated reservoirs exposes risks related to wellbore instability. Reservoir navigation has been identified as an important measure to ensure optimal wellbore placement to reduce exposure to unstable formations. The production strategy however has several constraints that limit the geosteering options: 1) The horizontal production drains needs to be accurately placed within a narrow 4 meter True Vertical Depth (TVD) window at the top of the oil rim; 2) to achieve the desired productivity, the geometry and fluid contacts of the oil accumulation require horizontal sections longer than 1000 meter Measured Depth (MD) with net sand exposure; 3) The well trajectory needs to be designed so it minimizes shale exposure within the production window for two main reasons: optimizing the drainage and reducing the risk of wellbore instabilities; 4) limit to Dog Leg Severity (DLS) so the completion running of the well remains at low risk.

To achieve the optimal placement of the oil producers within the constraints stated above, Extra Deep Azimuthal Resistivity (EDAR) (Hartmann et. al., 2013) has proven to be of great value. EDAR measures low frequencies and is thereby able to obtain a radial detection capacity that is greater than 20m (Antonsen et. al., 2015 and Larsen et. al 2015).

This paper will first describe a mathematical analysis of the wellbore trajectory made prior to drilling in order to assess the best trajectory available. This analysis takes in consideration input such as formation dips and thickness along with all the constraints mentioned above. Once the drilling plan is established, the description of the real-time geosteering activities shows how the technologies in place down hole helped keep the drilling program close to plan.

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