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I suppose the oval are almost in the same area (first column or last column of the page). I will restrict the search to these columns only, perform a contour detection with [findContours](http://docs.opencv.org/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html?highlight=findcontours#void findContours(InputOutputArray image, OutputArrayOfArrays contours, OutputArray hierarchy, int mode, int method, Point offset), and try to fit ellipse, with [fitEllipse](http://docs.opencv.org/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html#RotatedRect fitEllipse(InputArray points). If the results are poor, you could try the face detection to see if it working on the drawing, and try to fit the ellipse only in the neighborhood of faces.
If none of these solutions are working, you probably have to train a classifier, try a binary SVM, with samples of your ellipses and samples of text words. Or look at the HAAR and LBP cascade classifiers here and here.
