New deepwater production continues to proliferate, mainly off West Africa, Brazil, and the US Gulf Coast. The Far East has potential, too, as explained in the first of three exclusive articles on deepwater operations in this issue's special report, starting in the Exploration & Development section.
Of these areas, the Gulf of Mexico deep water remains the most active in terms of number of wells and fields discovered and producing.
Currently in the gulf, the production coming from the deepest water is the gas flowing from Marathon Oil Co.-operated Camden Hills subsea wells completed in 7,209 ft of water on Mississippi Canyon Block 348. Marathon expects a 100 MMscfd peak production rate from the two wells in the field.
Other gulf water depth marks in- clude Unocal Corp.'s Alaminos Canyon Block 903 well, drilled in 9,743 ft of water, which holds the water depth record for an exploration well, and Shell Offshore Inc.'s Baha well, drilled in 7,620 ft of water on Alaminos Canyon Block 600, which the US Minerals Management Service lists on its website as the discovery well in the deepest water.
MMS statistics for the week of Oct. 21 show that the deepwater gulf has 3,227 active leases with 2,253 approved applications to drill and 27 active platforms in water depths greater than 1,000 ft.
MMS projections indicate that production in 2002 from the deepwater gulf will average 1.0-1.1 million b/d of oil and 3.4-4.0 bcfd of gas.
New insights
A recent IHS Energy Group and PetroSolutions Ltd. study benchmarked production and deepwater parameters for fields producing from gulf waters deeper than 1,000 ft. It provides new insights into what operators may expect from deepwater opportunities.
The study indicated that the average deepwater well in the gulf has in- creased—each by an eightfold increment—maximum flow rates in the past 20 years and monthly production volumes in the past 10 years.
It added that combined monthly production from 262 active deepwater gulf wells currently exceeds 40 million boe. One oil well's cumulative production now exceeds 30 million bbl, while four other oil wells each have produced in excess of 20 million bbl.
As for gas wells, the study indicated two gas wells each produced in excess of 100 bcf at nearly 200 MMscfd maximum rates.
It found that currently 20 gas wells each produce in excess of 100 MMcfd.
Oil still dominates deepwater production, with 190 oil wells outnumbering 73 gas wells and oil fields outnumbering gas fields by three to one.
Subsea tiebacks to both deepwater and shallow-water facilities account for one sixth of the completions covered by the study.
The study determined that, out of 45 fields, the time from discovery to first production is usually 3.5 years, with a median of 7 years.
Of the 45 fields covered by the study, 41 are active with 1-35 wells. The study found that the median field has 4 active wells.
The study examined about 400 completions, including 102 inactive wells, and found that many completions did not show a production decline, although some had very high decline rates. Annual decline rates were 15-100%, with a median value of 66% for 132 active wells with a production decline. The study attributed these high declines to such causes as liquid (water) loading, formation compressibility, and fines migration.
The study found that the median drainage areas of 108 oil completions were 140 acres in sheet sands, 60 acres in channels, and 40 acres in channel levees.
One of the study's conclusions was that deepwater oil reservoirs initially are undersaturated, with the three primary drive mechanisms being fluid expansion, aquifer influx, and formation compressibility. These mechanisms result in initially very steep pressure-cumulative production plots that flatten out later.
Answers
From such production and reservoir insights, the study's conclusions are expected to remove some barriers operators face when entering the high-cost deepwater environment by providing answers for such questions related to expected flow rate, peak rate, plateau rate, plateau length, time of water breakthrough, production decline rate, drained area, wells needed, original oil in place, reserves, and facility size.