At the time of the "contesté franco-brésilien" boundary dispute between colonial France and Brazil, Coudreau worked in the service of Governors of the states of Brazil, mapping the Amazon's tributaries and identifying possible resources for farmers and foresters.

Their first expedition in 1899 ended tragically, as detailed in the book Voyage au Trombetas begun by Henri Coudreau, describing their voyage up the Trombetas tributary of the north bank of the Amazon.

Aided by his traveling companions, she made a coffin from the planks of the boat and prepared a burial on a promontory overlooking lake Tapagem.

After Henri Coudreau's death, Octavie continued the exploration work begun by her husband for seven years.

She later wrote the final chapters of the book, following the repatriation of his remains to Angoulême in France.