Nearly half of the total area of the Republic of Ghana is covered by sedimentary rocks. These rocks are found mainly in four different parts of the country: Tano basin, Keta basin, Voltaian basin, and the continental shelf. The possibilities of finding oil and gas onshore and offshore Ghana have thus been concentrated in these four areas.
Because oil seeps in saturated superficial sands were found in the Tano basin, efforts to find oil in Ghana started as far back as 1896 in this basin, which is located at the extreme southwestern part of Ghana and has an area of 1,165 km2 (450 mi2). Seventeen onshore wells have been drilled so far in this basin, which is underlain by Upper Cretaceous Apollonian sediments consisting mainly of thin alternations of sand and clay with a few thin beds of gravel and fossiliferous limestone.
The Keta basin, located at the extreme southeastern part of Ghana, has an area of 2,200 km2 (850 mi2). It is covered in the north by Pliocene and in the south by Holocene deposits. Since 1966, three onshore wells have been drilled in this basin.
The continental shelf of Ghana is at the southern part of the country and has an area of 27,562 km2 (10,640 mi2). Prospecting for oil in the shelf started in 1968. In all, 34 offshore oil wells have been drilled by foreign companies in this area, which has been divided into 24 concession blocks. At present, oil is being produced from wells in Block 10. The possibility of finding oil and/or gas at the extreme western part of the continental shelf cannot be overemphasized.
The expansive Voltaian sedimentary basin, located in the central part of Ghana, covers an area of about 103,600 km2 (40,000 mi2). The basin is underlain by Precambrian to lower Paleozoic epicontinental Voltaian series comprised of a thick sequence of marine and continental sediments. Although no trace of hydrocarbon was found in the only well that has been drilled so far in this basin, the presence of traces of bitumen in some parts of the basin indicates that, despite of its age, the basin might prove to be an oil province.
The recent discovery of oil in the Ivory Coast means that it is possible to find oil or gas in Ghana, inasmuch as Ghana’s petroleum potential is closely associated with that of the Ivory Coast basin, which extends for 560 km (300 mi) along the entire Ivory Coast and persists eastward into Ghana for an additional 320 km (200 mi), terminating in the area directly west of Accra. The Ghanian part of the Ivory Coast basin, therefore, holds the greatest possibility of finding oil or gas in Ghana.