Abstract
Recent work has shown strong correlations between magnetic measurements and key petrophysical parameters such as clay content and permeability in clastics (Potter, 2007; Potter and Ivakhnenko, 2008) and carbonates (Potter et al, 2011). The magnetic measurements in this previous work were mainly undertaken at ambient (room temperature) conditions. One of the main aims of the present paper is to show how these types of measurements depend upon temperature, and therefore depth downhole. Pure diamagnetic minerals such as quartz, calcite or the clay kaolinite should theoretically show no dependence of magnetic susceptibility with temperature, and therefore will show no variation in magnetic susceptibility with depth. In contrast, paramagnetic minerals (for
example, important permeability controlling clays such as illite or chlorite), should
theoretically show a decrease in magnetic susceptibility, according to the Curie Law for low applied fields. A series of theoretical model templates using the Curie Law were developed to model the temperature dependence of mixtures of diamagnetic and paramagnetic minerals. The model curves were compared with laboratory measurements on shoreface and turbidite reservoir samples. The experimental data showed a good match to the expected trend of the model curves. Moreover, the illite content derived from the model template curves agreed well with the illite content independently derived from magnetic hysteresis measurements at high field and X-ray diffraction (XRD)
measurements. These model templates, in conjunction with downhole magnetic
susceptibility and temperature data (or a known or assumed geothermal gradient), allow one to quantify the diamagnetic versus paramagnetic mineral content in situ downhole. This information is potentially useful for planning a coring and core analysis program, by allowing more quantitative mineral content data to be acquired for early in the development of a field at the appraisal well stage. Furthermore, knowing the temperature dependence of permeability controlling clay minerals may help one to make predictions of permeability in situ downhole.
example, important permeability controlling clays such as illite or chlorite), should
theoretically show a decrease in magnetic susceptibility, according to the Curie Law for low applied fields. A series of theoretical model templates using the Curie Law were developed to model the temperature dependence of mixtures of diamagnetic and paramagnetic minerals. The model curves were compared with laboratory measurements on shoreface and turbidite reservoir samples. The experimental data showed a good match to the expected trend of the model curves. Moreover, the illite content derived from the model template curves agreed well with the illite content independently derived from magnetic hysteresis measurements at high field and X-ray diffraction (XRD)
measurements. These model templates, in conjunction with downhole magnetic
susceptibility and temperature data (or a known or assumed geothermal gradient), allow one to quantify the diamagnetic versus paramagnetic mineral content in situ downhole. This information is potentially useful for planning a coring and core analysis program, by allowing more quantitative mineral content data to be acquired for early in the development of a field at the appraisal well stage. Furthermore, knowing the temperature dependence of permeability controlling clay minerals may help one to make predictions of permeability in situ downhole.
| Original language | English |
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| Pages | 1-6 |
| Number of pages | 6 |
| Publication status | Published - Sept 2011 |
| Event | 25th International Symposium of the Society of Core Analysts 2011 - Austin, United States Duration: 18 Sept 2011 → 21 Sept 2011 |
Conference
| Conference | 25th International Symposium of the Society of Core Analysts 2011 |
|---|---|
| Country/Territory | United States |
| City | Austin |
| Period | 18/09/11 → 21/09/11 |