The U.S. Energy Information Administration (EIA) has added four countries to its global shale resource assessment, bumping up the world’s total estimated shale oil and gas resources assessed by 13% and 4%, respectively.

Chad, Kazakhstan, Oman and the United Arab Emirates (UAE) are believed to have vast shale resources capable of boosting production and adding revenue. However, economics, including commodity prices, could stand in the way.

“Although these formations contain significant volumes of technically recoverable resources, there is currently no shale exploration underway in any of the four countries, meaning the new assessed resources are not yet economically recoverable,” the EIA said in its report. “The portions of these resources that become economically recoverable in the future will depend on crude oil and natural gas market prices, as well as the capital and operating costs and productivity within the countries.”

The central African country of Chad could stand to gain the most, considering EIA stats show its oil production has plummeted 55% in the last 10 years as fields have matured. In 2014, about 78,000 barrels per day (bbl/d) of oil was produced in Chad, which depends on the hydrocarbon to provide more than 60% of government revenues.

Chad has shale gas and oil potential in six basins: the Termit in the west; Bongor, Doba, Doeseo and Salamat in the south; and the Erdis in the north. The EIA estimates that four of these basins alone—Bongor, Doba, Doseo and Termit, the four basins for which there is sufficient resource data—could hold about 16.2 billion barrels (Bbbl) of risked, technically recoverable tight oil and 44 trillion cubic feet of risked, technically recoverable wet shale gas resources.

“A significant shale oil (and shale gas) resource exists in Chad that could help reverse the decline in oil production,” the EIA said in its report on Chad’s shale resources. “In addition, the new model productive-sharing contract provides reasonable terms for international companies to pursue this shale resource. Shale exploration would be enhanced if a market for natural gas would be developed in Chad, mostly for gas-fired electric power, or if the produced gas could be transported for conversion to LNG for export.”

The country has already attracted majors including ExxonMobil, which has oil fields in southern Chad; but others have divested in recent years—most notably Chevron, which sold its 25% interest in an oil concession in the Doba Basin and its 21% interest in a pipeline for a combined $1.3 billion to the country’s government in 2014.

Despite the ExxonMobil-led concession’s fields having an average net daily oil production of about 18,000 barrels, Chevron opted to exit due to “the combination of current market conditions and the size of the assets” relative to its portfolio. At the time, Reuters reported the departure was seen as a way for Chevron to refocus on its Permian shale assets in Texas.

In addition to Chad, Kazakhstan, Oman and the UAE were added to the assessment. Unlike Chad, oil and gas production have been increasing in these countries since 2005.

Kazakhstan: The Caspian country could hold about 10.6 Bbbl of unproved technically recoverable shale oil along with an estimated 27.5 Tcf of wet shale gas. The resources are located in the North Caspian, Middle Caspian/South Mangyshlak and South Turgay basins among others.

In the last nine years, Kazakhstan has grown its oil production by nearly 25% to 1.7 MMbbl/d and increased its gas production by 37% to 1.9 Bcf/d, the EIA said.

Oman: Already a producer of tight gas in the Khazzan Field, the EIA reported that Oman could have about 6.2 Bbbl and about 48.3 Tcf of unproved technically recoverable shale oil and gas. Basins with potential include: the South Oman Salt, North Oman Foreland and the Rub’ Al-Khali basins.

“Oman is a significant producer of hydrocarbons, providing an estimated 920,000 barrels of oil and 2.6 Bcf of natural gas per day in 2012, from 5.5 billion barrels of proved conventional oil reserves and 30 Tcf of proved conventional natural gas reserves,” according to the EIA. “After five decades of exploration, many of the conventional oil and gas plays of Oman have been discovered, leading to renewed interest in exploring and producing shale gas and shale oil.”

UAE: Of the four additions, the UAE has the greatest potential with an estimated 22.6 Bbbl of unproved technically recoverable shale oil and more than 205 Tcf of risked, technically recoverable shale gas. Sources are the Lower Silurian Qusaiba Shale, the Upper Jurassic Diyab and the Middle Cretaceous Shilaif Formation, the EIA said.

Since 2005, oil production has risen by 21% to 3.7 MMbbl/d in 2014, while gas production has jumped to 5.6 Bcd/d, an 18% increase. Despite ample gas supplies, the EIA said the UAE imports some gas from Qatar. But efforts are underway to diversify the country’s energy mix and lessen its dependence on others for gas. Such efforts include the Shah sour gas project.

In all, the EIA said the 46 countries covered in its global shale resources assessment indicate proved and unproved technically recoverable resources of an estimated 419 Bbbl of shale oil resources and 7,576 Tcf of shale gas resources.

At this time, however, only Argentina, Canada, China and the United States are producing from shale formations at commercial scale. But none are on the same level as the United States, which the EIA said is “providing 4.4 million b/d, or more than 90%, of global tight oil production and 42 Bcf/d, or more than 89%, of global shale natural gas production.”

Velda Addison can be reached at vaddison@hartenergy.com.