When oil prices were up to $100 per barrel (WTI), development and exploration investments were booming — even in high-risk areas. From Arctic oil to deepwater drilling, oil and gas majors were not afraid to invest, despite production costs of $95 per barrel and above.

This has changed significantly with the price slump since mid-2014, which saw prices fall to an average of $48 per barrel (WTI) in 2015.

Among these high-risk destinations, West African countries had attracted significant investment, but the rig count has since dropped from 69 in July 2014 to 53 in July 2015. Overall, West and Central Africa attracted about one-third of foreign direct investment, including oil and gas in Sub-Saharan Africa.

West Africa's lead investor was Tullow Oil, which spent a record sum of $788 million in exploration in 2014, compared to $256 million in 2015. This was despite the fact that much of West Africa's oil and gas is offshore where drilling is expensive and subocean wells can cost about $100 million each.

But the number of offshore oil and gas rigs has fallen to its lowest point in Africa since 2009, demonstrating the effects of the price fall on the sector.

Oil firms have put major projects in West Africa on hold. In April 2016, Shell made the announcement to delay its final investment decision for the Bonga South West Project offshore Nigeria. Tullow Oil in the meantime announced it would stop the drilling of new offshore wells in Ghana and halve its annual investment in West and Central Africa to $100 million in the coming years.

The impacts on natural-resource-dependent economies in the region have been significant with Gabon cutting its 2016 budget, while Ghana is considering to do the same.

On the other hand, the continent as a whole has tried to rein in new investment by offering generous investment incentives. For instance, Mozambique recently passed an LNG Decree Law favorable to foreign investment. And West-African Mauritania has been listed as the country with one of the continent's most generous tax legislations, requiring no royalty payments and a reduced corporate income tax rate of 25 percent.

While the oil price matters, PwC's latest review of the oil and gas industry in Africa (which collates interviews of major investors across the continent) demonstrates that the main challenges to investment in the sector remain. Among the top three are uncertainty in the regulatory frameworks of African countries, poor infrastructure and corruption.