Advanced Geosteering with Azimuthal Deep Resistivity Helps in Optimal Well Placement, NOVEMBER 2009, By Roland Chemali

Halliburton, Sperry Drilling Services

Early production, as well as ultimate oil and gas recovery, from a reservoir often depends on the timeliness and the accuracy geosteering decisions. Exiting the reservoir during drilling results in costly non-productive intervals.Even staying within the reservoir but in a non-optimal location eventually leads to early water break-through while leaving behind valuable attic oil. In recent years, azim

Fig 1- Geosteering with deep resistivity images from azimuthal deep resistivity LWD.

uthal deep resistivity measurements have been recognized as beneficial to real-time steering decisions. Because of their deep investigation, they give adequate warning to prevent from exiting the reservoir. Their azimuthal sensitivity clearly points to the direction of preferred evasive actions. Best results are achieved by jointly interpreting several measurements from the azimuthal deep resistivity, corresponding to multiple depths of investigation. In the simplest cases, the up-down resistivity curves exhibit a characteristic behavior that has proven valuable both to petrophysicists and to geosteering engineers. When approaching overlaying shale, for example, the up-curve consistently reads the resistivity of the reservoir while the down-curve exhibits amplified horns beneficial to reservoir navigation. Resistivity images feature bright spots whose progression with increasing depth of investiga

tion facilitates avoidance of unwanted boundaries. 4 new measurement designated as Geosignal features strong lateral sensitivity. The Geosignal from the deepest spacing is best suited to provide an early indication of the approaching boundary, with a near- exponential dependence on the distance to

Fig 2- Geosteering with up-down and with bright spot resistivity images from an azimuthal deep resistivity LWD.

boundary. Examples from around the world are shown in detail to help illustrate the applications.


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