What is the fine-grained topic of the following text: Since 2012 TransGlobe has steadily built up its acreage position in the Western Desert and now has approximately 4,625 km2 covering three concessions: South Alamein, North West Sitra and South Ghazalat, operator in all three. Only return the topic.
TransGlobe's acreage position in the Western Desert since 2012