in the last 10 years, more than half of new global oil and gas reserves were discovered offshore. Deepwater and ultra deepwater discoveries are becoming the dominant source of new reserve additions, accounting for 41% of total new reserves based on a statistical evaluation of discoveries between 2005 and 2009.
In this paper, we used the following definitions: shallow water (SW) <= 400 m (1,312 ft), 400 m < deepwater (DW) <= 1,500 m (4,921 ft), and ultra deepwater (UDW) > 1,500 m; all related to bathymetric depth.
Although the first offshore well may have occurred as early as the late 1890s, by and large, significant offshore activity was not forthcoming until after World War II.
Despite limited technology and infrastructure, the first phase of offshore exploration continued from the 1940s to 1982. The year 1982, was a peak year for new field discoveries. In the 10 years prior to 1982, the number of offshore fields discovered per year more than doubled to 198.
The second phase of offshore development may be viewed as the time period from 1983 to 2005. During this time, the number of new fields fluctuated dramatically from a low of 116 new offshore fields in the years 1993 and 1994, to the largest number of offshore fields discovered in the year 1990 (192 discoveries), never reaching the previous high noted in 1982.
his span of time is notable for a large increase in inventory of offshore contract area as the number of countries offering acreage spiked from 95 in 1985 to 133 in the year 2005. There was an increase of valid contract area inventory from about 5.5 million sq km (2.1 million sq mi) in 1995 to 9.2 million sq km (3.6 million sq mi) in 2005. In 1985, the number of contracts for offshore acreage was about 2,300. In 2005, at the end of Phase Two, just over 12 years later, the number of contracts exceeded 8,500.
Phase Three of offshore development represents an increase in offered acreage mainly due to the increase in new deepwater and ultra deepwater areas. At the start of 2010, valid contracted areas approached nearly 12 million sq km (4.6 million sq mi). In addition, more than 10,300 valid contracts for offshore acreage were in place at the start of 2010. While new deepwater production is masked by the greater volumes of new and ongoing shelf production, the balance is tilting towards the critical point where deepwater and ultra deepwater will dominate. This third phase of offshore exploration was ushered in during 2006, with the Tupi discovery in Brazil, which was a forerunner of a number of significant discoveries dominated by oil and liquids.
deepwater (DW) and ultra deepwater (UDW) combined are becoming the predominant source of new oil and gas discoveries. From 2005 through 2009, giant and significant deepwater discoveries of oil and gas (41 Bboe, 2P reserves) were made in Brazil, the US, Angola, Australia, India, Nigeria, Ghana, and Malaysia.
In fact, 2009 became a record year for UDW drilling, totaling 150 wells.
On average, through 2005 and 2009, the drilled depth offshore increased from 3,100 m to 3,600 m (10,171 ft to 11,811 ft) and the average water depth from 450 m to 600 m (1,476 ft to 1,969 ft).
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