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A Success Case of Revival of an 80 Year Old Oilfield through New 3D Seismic Interpretation and Reservoir Modeling, Lak Ranch, Weston County, Wyoming, USA

Abstract

Newcastle Formation is the eastern equivalent of well-known Albian Muddy Formation. The Muddy and its equivalents are responsible for nearly 1.5 billion barrels of oil equivalent hydrocarbons. Production is mainly from unconformity related incised valleys, estuaries, transgressive sands in larger paleo-topographic lows, etc. The Muddy/Newcastle Formation exists in Wyoming, Montana, and North and South Dakota. Many of these fields are very mature. Mature fields meet one or more of the following criteria: fields that have produced for more than 25 years, fields that have produced water cuts around 95%, fields that have been neglected during low demand since the1980s, and fields that are currently in operation with obsolete technology, poor facilities and market access. According to the U.S. Energy Information Administration, these mature oil fields are contributing up to 80% of world production, which could translate to 89 million barrels of oil per day. Often poor infrastructure and poor state of record keeping pose steep hurdles in monetizing these assets. A surprising fact is that in many of these fields, for example in Wyoming, Colorado, Montana, and Illinois, the oil is in very low risk Stratigraphic plays, often very shallow reservoirs, with low cost of recovery. Conservative estimates of reserves are about 15–30 billion barrels in some of these basins.

Despite the large well data in these basins, comprehensive paleogeography has not been established for this highly productive Newcastle Formation. High price environment sustained until early 2014 rejuvenated many of these prospects with newly acquired 3D seismic data. Some of these fields are being revisited armed with 3D seismic data and new horizontal drilling technology. Sound regional and prospect level geology, chronostratigraphic mapping, fit-for-purpose reservoir modeling to guide the flooding program, and a new breed of entrepreneurial spirit are key ingredients for substantial rewards in these fields. Understanding complex geology, with deltaic to transgressive marine sands and stratigraphic traps, has been a challenge. Recent 3D acquisition and interpretation are showing new promise in the region, and helping revival.