Abstracts: The Gulf of Mexico Deep Water Play: 50 Years from Concept to Commercial Reality

BRAUNSDORF, NEIL R., GARY S. STEFFENS

The Gulf of Mexico deep-water play has 42 confirmed discoveries totaling 5 BBOE in proven reserves. It is estimated that the play's potential development may exceed 15 BBE. This turbidite reservoir play begins on the upper continental slope and extends onto the abyssal plain, encompassing present-day water depths of 1500--9000 ft. From an historical perspective, the deep-water play has taken more than 50 yr to evolve from a sand reservoir concept to a successful commercial reality. Three key factors led to this emerging success story: (1) a long-term, creative vision held by tenacious explorers, (2) an economic environment that had a high tolerance for risk and experimentation in the early exploration efforts, and (3) exploration and production technology advancement closely linked to the opportunity and its profitability.

The initial concept of the existence of deep-water reservoirs in the northern Gulf of Mexico had its origin in several pioneering studies conducted in the 1940s and 1950s. Frontier probe studies in the 1960s confirmed hydrocarbon charge, reservoir potential, and an abundance of salt structures (potential traps) on the continental slope. Early exploration efforts in the late 1970s and early 1980s tested the play limits beyond the present-day shelf margin and encountered numerous hydrocarbon-bearing turbidite sands. With the inception of area-wide federal lease sales, those early discoveries created a flurry of leasing activity and exploration drilling for the next few years. Many of the major discoveries that are currently producing or being developed were delineated during this period. By the late 1980s, development was underway for several of these discoveries. However, serious concerns remained about the profitability of the play with the prospect of $20/bbl oil or less. The tremendous technical challenges and uncertainties, coupled with the high cost of development, forced the industry to focus their efforts on how to make the current discoveries profitable. Technical advancements concentrated on creating cost-effective production systems and improving our understanding of the connectivity and continuity of these reservoirs. The recent revitalization of the play is largely due to these technical advancements and the timely realization of the potential high-rate production from several deep-water developments. The industry's collaborative efforts in building "infrastructure corridors" have also accelerated development activities and extended the exploration opportunities into the ultra-deep water (>5000 ft).

Several points are noteworthy from the exploration and development activities in the deep-water Gulf of Mexico.

1. Most of the deep-water fields were discovered using 2-D seismic data. However, 3-D seismic data are essential for efficient appraisal, development, and imaging difficult exploration targets.

2. Significant improvements in our understanding of deep-water basin-fill history came from regional tectono-stratigraphic studies, seismic facies analyses, and shallow analog studies.

3. Improved models of reservoir architecture were derived from the integration of field, outcrop, and shallow analog data.

4. The large capital expenditures necessary to develop discoveries in the deep-water Gulf of Mexico require that wells be capable of producing high per-well ultimates at high sustained rates.

5. Reservoirs with high per-well ultimates have several performance characteristics in common: large connected hydrocarbon pore volumes often in structurally simple traps and extensive architectural continuity, thick and highly permeable sands, high recovery efficiencies (strong aquifer support is common), and favorable hydrocarbon properties and pressures.

6. Most deep-water reservoirs, regardless of architecture, can produce high initial rates because of their high permeabilities and thicknesses.

AAPG Search and Discovery Article #90938©1997-1998 AAPG Distinguished Lecturers