A Brief Review of Carbonate Discovery Trends of the Decade (2000-2009)

Benton, Jeremy ¹
(1)Energy, IHS, Tetbury, United Kingdom.

A dataset comprising more than 5,000 conventional new field discoveries made around the world over the first decade of the millennium has been investigated, to characterise broad trends in carbonate finds and their resources.

The dataset comprises most known conventional discoveries made around the world, with the exception of onshore North America. The resource estimates are compiled individually for each field by reservoir, and the estimates are then rolled up into field-level volumes, which are used as the basis of this study. The aggregate discovery total over the decade 2000-2009 is approximately 308 Bboe, with yearly totals ranging from a high of 58 Bboe in 2000 to a low of 20 Bboe in 2007, of which the annual total of carbonate resources shows considerable volatility and ranges from a maximum of 27 Bboe in 2004 to a low of only 6 Bboe in 2008. In terms of reservoir lithology of the main reservoir, carbonates account for some 40% of all resources discovered in the period, though clastics dominate with approaching 60%. It is clear that carbonates are most important in the former CIS and Middle East, but the recent sub-salt discoveries in carbonates in the Santos and Campos basins of Brazil have also swung the overall mix in favour or carbonates in Latin America, whereas plays in Africa, Europe and Australasia remain dominated by clastics. The decade is marked by something of a renaissance in carbonate finds, with the largest finds of the decade all having carbonate plays. The most significant oil discovery was made in the shallow waters of the Caspian Sea at the turn of the century, namely Kashagan, which has 13 Bbbl trapped in Carbonferous algal and coral limestones. In the second half of the decade, the discovery of the deepwater sub-salt plays of the Campos and Santos basins, have been the most notable development. The supergiant Lula (Tupi) oil field, is the largest sub-salt find revealed to date, with recoverable resources of 6.5 Bboe in stromatlitic limestones. In terms of gas, Yoloton-Osman is the most significant find - and is one of the largest gas fields in the world, with the gas in Upper Jurassic limestones and dolomites. Gas in place is estimated at around 140 Tcf in the low case, with a best estimate of around 210 Tcf, and around 490 Tcf in the high case. The importance of carbonate reservoirs is reflected in their average discovery size of around 155 MMboe, compared to an average of around 40 MMboe for clastic discoveries.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.