Traditionally, migration and refugee flows information is obtained from surveys and border control operatives. Here we propose a method to detect migration flows worldwide using geolocated Twitter data. In particular and as a practical example, we focus on the current migratory crisis in Venezuela. We study if the flows calculated are quantitatively reliable when compared with official numbers at the country level. Our method is versatile and can be used to study different features of migration such as the routes, settlement areas, mobility to more than one country, spatial integration in cities, etc.