No end in sight for giant conventional discoveries
Despite the developments in unconventionals over recent years, giant conventional oil and gas fields continue to be discovered around the world. Over the past 10 years, eight of the top 10 discoveries have been offshore and have been transformational in opening completely new plays. This brief overview outlines these key project developments.
The top 10 discoveries of the last 10 years ranked in terms of their in-place resource volumes, are summarized in Table 1 (see overleaf) and located in Figure 1. Values are expressed in barrels of oil equivalent (boe) to be able to directly compare oil and gas resources; in-place volumes have been used as these figures tend to be more widely quoted and for the as yet un-appraised and undeveloped fields, recovery factors are unknown.
Top 10 discoveries of the last 10 years. Table 1: Top 10 discoveries (2004-2013), both on- and offshore, based on publicly quoted resource volumes, standardized to in-place boe. Quoted volumes are in-place unless otherwise stated. Source: Gaffney, Cline & Associates.
What is interesting to note is their wide geographic distribution and that they comprise new plays in both already proven basins and in new petroleum provinces. Seven are located in deepwater, one on the shelf and two on land.
By far the most significant discovery since 2004 is the Galkynysh gas field (previously named Yolotan) onshore Turkmenistan. Over 100km long and with gas initially in place (GIIP) estimates ranging between 462 and 745 Tcf this discovery dwarfs all other finds, being the world’s second largest gas field. Despite the gas being sour (combined 8-14% of H2S + CO2 impurities), the first phase of development was completed in 2013, with a capacity of 30 Bcm (over 1Tcf) per annum for export by pipeline to China.
Figure 1. Source: Gaffney, Cline & Associates.
The pre-salt in the Santos Basin, offshore Brazil, provides the fields in second, third and fifth places. Since the first discovery in this play by Petrobras in 2006, (Lula, original name Tupi) there have been high levels of activity and a number of giant accumulations, including Libra and Iara, have subsequently been discovered. Development of these fields have utilized enhanced oil recovery (EOR) techniques from the start, including water alternating gas CO2 flood (WAG-CO2) injection. Whilst more than doubling Brazil’s hydrocarbon resource base, the success of this play has led to pre-salt plays being actively pursued across the other side of the Southern Atlantic in Angola, Congo and Gabon.
Huge gas discoveries in the Rovuma Basin offshore Mozambique take fourth and seventh places in the rankings and are a new play and basin opener. Operated by Anadarko (Area 1) and Eni (Area 4) drilling activities have achieved phenomenal success with up to 150 Tcf already discovered. Commercialization is principally dependent on liquefaction and export, although many additional gas utilization options are also being considered. However, equally significant is that the results in Mozambique have opened up the whole of the East African offshore although individual discoveries are smaller, Tanzania has already confirmed up some 35 Tcf of gas in place.
Very significant discoveries in the Ultra-high pressure and high temperature (HPHT) of Gulf of Mexico (Tiber, Kaskida, Gila) and a normally pressured giant find in Norway (Johan Sverdrup) have confirmed new plays in established basins and perhaps encourage a fresh look at some of the world’s more mature basins. However, the other discovery in the above list, which was part of a true game-changing basin opener, was the Leviathan gas field offshore Israel. Operator Noble, with the Leviathan and Tamar in Israel and a subsequent Cyprus gas discovery has put the eastern Mediterranean firmly on the map for the industry.
Jeremy Berry serves as global business development director at Gaffney, Cline & Associates. His primary technical strength is in the geosciences. Berry has an in-depth understanding of sub-Saharan Africa.