According to an Energy Information Administration (EIA) report, estimated U.S. and international shale resources represent 10% of the world's crude oil and 32% of its technically recoverable gas resources.

The report, “Technically Recoverable Shale Oil and Shale Gas Resources,” estimates that shale resources taken in conjunction with EIA's own assessment within the U.S. indicate technically recoverable resources of 345 billion barrels of world shale oil and 7,299 trillion cubic feet of global shale-gas resources.

More than half of the identified shale-oil resources outside the U.S. are concentrated in Argentina, China, Libya and Russia, and more than half of the non-U.S. shale-gas resources are concentrated in five countries—Algeria, Argentina, Canada and Mexico. The US ranks second after Russia for shale-oil resources and fourth after Algeria for shale gas if compared with the 41 countries included in the report.

While the latest EIA report considers more shale formations than were assessed in a previous version, it still does not assess many prospective shale formations, such as those underlying the large oil fields in the Middle East and the Caspian region. Currently, only the US and Canada are producing shale oil and shale gas in commercial quantities.

–Larry Prado

1 Colombia

Bogota-based Cepsa has made an oil discovery at exploration well #1-Curiara on the El Porton Block in Colombia's Llanos Basin. The well flowed more than 800 bbl. per day of light 40-degree-gravity API oil from Mirador from a 5-ft. perforated interval. Tested on a 20/64-in. restricted choke over a 22-hour period, the well flowed 818 bbl. of oil and 3.4 million cu. ft. of gas. The wellhead flowing pressure was approximately 3,300 psi. Logs indicate 8 ft. of net pay and a possible gross hydrocarbon column of 50 ft. in Mirador. The well is currently shut in for a pressure build-up and further evaluation. The venture was terminated in Los Cuervos and did not evaluate the deeper reservoir objectives of Gacheta and Une. Cepsa is the operator, with 50% interest, in partnership with Petroamerica, holding 25%, and Talisman Colombia Oil & Gas with the remaining 25%.

2 Peru

Gran Tierra Energy completed testing a 1,595-ft. sidetrack to an exploration well, #95-2-1XD Bretana Norte, in Peru's onshore Block 95. Initial testing of the Vivian sandstone reservoir and log interpretation indicates an oil-bearing sandstone reservoir in the formation between 10,735-12,262 ft. with a total net pay in the lateral section of 1,283 ft. The average porosity was 22.8%. Tested on a 32/64-in. choke, the approximate flowrate was 1,699 bbl. oil per day. Long-term testing is expected to begin in early 2014. Block 95 and Bretana Field are operated by Calgary-based Gran Tierra, which holds 100% interest.

3 France

An independent resources report for Elixir Petroleum Ltd. has indicated three conventional prospects in France's Moselle Permit have recoverable resources. The report estimates 626 billion cu. ft. of gas in unrisked total resources in all four sequences. The Bullseye Prospect contains an estimated 208 billion cu. ft. and the West Chaumont Prospect could hold 157 to 861 billion cu. ft. The study was performed on a Lower Triassic sequence in both the Bullseye and West Chaumont prospects, which hold oil and some gas. RPS has determined a prospective resource of approximately 116 million bbl. of oil initially in place in Bullseye and 104 million bbl. in West Chaumont. Elixer Petroleum's headquarters are in Perth.

4 Romania

On Romania's Suceava Block, Raffles Energy Ltd. announced results from a production test at the discovery well, #1-Sude Dornesti. The Climauti Field well produced 918,200 cu. ft. per day. A previous well, #1-SE, had an initial production rate of 900,000 cu. ft. of gas per day. The new discovery is part of an ongoing feasibility study to bring the two wells into production, and the partners plan to create a pipeline to carry production to a processing facility. According to the operator, output from the concession may average 2.33 million cu. ft. per day. Singapore-based Raffles is the operator of the Suceava Block and wells with 50% interest. Zeta Petroleum holds the remaining 50%.

5 Equatorial Guinea

At a sidetrack to the exploration well #7-I, in offshore Equatorial Guinea Block I, Houston-based Noble Energy Inc. encountered oil in good-quality sandstones in approximately 9 to 11 meters of net pay. The sidetrack, #1-ST Carla South I-7, reached 3,460 meters. Drill cuttings, wire-line log data and downhole measurements indicate that the sidetrack encountered the pay at several levels, and the well is now being plugged and abandoned. According to partner PA Resources, the initial Carla South discovery extends the proven Carla trend from Block O into Block I with proven additional oil pay at several levels on the Carla trend. Further analysis will be required to assess the results. The 2013 drilling program in Block I will continue with an appraisal well and long-term test on Diega Field later in the year. Noble Energy is operator of Equatorial Guinea's Block I and the Carla South discovery and sidetrack wells with 38% interest, in partnership with Atlas Petroleum, holding 27.55%, Glencore, 23.75%, PA , 5.7%, and GE Petrol, 5%.

6 Cameroon

Bowleven announced a condensate and gas discovery at the appraisal/development well #5-IM in the Etinde Permit, offshore Cameroon. The 3,430-meter venture is in 56 meters of water in Block MLHP-7 of the Rio Del Rey Basin. Two reservoir intervals had condensate- and gas-bearing sands that totaled 95 meters of net pay. The first reservoir interval in Middle Isongo logged 25 meters of hydrocarbons. In Intra Isongo, 70 meters of hydrocarbons were discovered and 43 meters were perforated for the production tests. The production tests for Middle Isongo had a maximum flowrate of 23 million cu. ft. of gas and 3,155 bbl. of condensate per day, and Intra Isongo had an average daily flowrate of 37 million cu. ft. of gas and 4,664 bbl. of condensate. The total volumes of hydrocarbons (P50 in place) of Isongo Marine Field are now estimated at 155 million bbl. of condensate and 1.05 trillion cu. ft. of gas.

7 Gabon

An initial evaluation of the potential resources in offshore Gabon's Nkembe Block estimates that the mean recoverable prospective resource is 815 million bbl. of oil. According to Perth, Australia-based Pura Vida Energy NL, the resource estimate is based on the first four prospects outside of the Loba M 1 resource reviewed to date, and additional testing is planned. Pura Vida is the operator of the Nkembe Block with 80% interest. Société Nationale Petrolière Gabonaise, the national oil company, holds the remaining 20%.

8 Namibia

A resource potential estimate of offshore Namibia license area EL0037 indicates a mean prospective resource of 8.7 billion bbl. of oil. According to Pan-continental Oil & Gas, the estimate was not adjusted for geologic or economic risk. Light oil was encountered at the exploration well, #1-Wingat, in PEL23, by HRT Participacoes em Petroleo. In EL0037, the Perth, Australia-based company indicated that very large leads appear to be an extensive channel with basin-floor turbidite sand accumulations. In an initial interpretation these appear to be at about the same stratigraphic level as oil at #1-Wingat. Pancontinental is the operator of Block EL0037 with 95% interest. Paragon holds the remaining 5%.

9 India

Reliance Industries Ltd. announced an offshore India gas and condensate discovery at #55-D in the KG-D6 Block, Bay of Bengal. A formation evaluation indicates a gross gas and condensate column of about 155 meters in Mesozoic reservoirs. The well was drilled to 4,509 meters in 1,024 meters of water. During a drillstem test, the well flowed 30.6 million cu. ft. of gas per day with a liquid rate of 2,121 bbl. per day. Flowrates were constrained by rig and well test equipment configurations. An appraisal well is planned to define the field's scale and hydrocarbon quality. Reliance is operator of the KG-D6 Block and the discovery well with 60% interest. BP holds 30%, and Niko has the remaining 10%.

10 Indonesia

RH Petrogas announced a West Papua, Indonesia, oil discovery at #2-North Kalin in the Kepala Burung Block. The well hit 103 ft. of total net pay and produced at a combined rate of 105 bbl. per day of 36.3-degreegravity API oil and 1.14 million cu. ft. per day of gas. The venture was drilled to appraise the northeast extension of the original gas and condensate discoveries made at #1-North Klalin in 2011 and the further successful appraisal made by #3-North Klalin in 2012. RH Petrogas and its subsidiaries have an aggregate 60% operating interest in the Kepala Burung Block. PetroChina International holds 30%, and PT Pertamina Hulu Energi has the remaining 10%. RH Petrogas is based in Singapore.