08123-16

Primary Performer
Bureau of Economic Geology, The University of Texas at Austin

Additional Participants
Danmark Energy L.P.
John Linder Operating Co., LLC

Abstract
East Texas oil field (ETOF), the second most productive oil field in the United States, has produced 5.43 billion stock tank barrels (BSTB) from lower Woodbine sandstones since 1930. It has been the best giant field in the world, but it is now an aging giant field operated by a large number of small producers who encounter enormous technical, economic, and environmental challenges. Currently, 114 out of 117 operators in the field are small producers.

The objectives of this proposed 3-year study are to explore short- and midterm strategies for maximizing recovery from ETOF. After 88 years of production, >1.5 billion barrels (Bbbl) of oil remains in the reservoir that is exceedingly difficult to target. Development of strategies to recover this oil has become critical because most operators, mostly small producers, do not have sufficient expertise or support in geology or engineering, which are crucial to revitalizing production, as well as lowering production cost.

Currently ~1,580 million stock tank barrels (MMSTB) of oil remains in the reservoir—480 MMSTB of this total is remaining mobile oil and 1,100 MMSTB is residual oil. Of the 480 MMSTB of remaining mobile oil, ~70 MMSTB (Wang and others, 2008) will be produced by 2030, according to decline-curve analysis, and 410 MMSTB is untapped, unswept, or poorly swept. A fraction of the 410 MMSTB remaining mobile oil can be produced using strategically targeted recompletions and waterfloods guided by depositional trends, whereas residual oil can be produced only by enhanced oil recovery (EOR) methods.

In spite of the field’s excellent reservoir quality and stunning long-term performance history, details of its depositional environment and reservoir architecture have not been fully studied and are not well understood. The project comprises (1) a short-term field demonstration project on depositional-trend-guided deepenings and waterfloods and (2) a midterm research project on long-term recovery strategies, including feasibility studies of (a) CO₂ flooding, (b) surfactant/polymer flooding, and (c) their economic and environmental impacts.

The project area is the north part of ETOF in Gregg and Rusk Counties, Texas, covering >80 mi2 and containing ~10,000 wells. Goals of the short-term demonstration project are to demonstrate the technology of strategically targeted deepenings and optimized waterfloods guided by depositional trends and to identify 100 deepening targets and 10 waterflood sites in the 3-year study, which has the potential to increase ETOF short-term oil production by 15% and to add >10 MMSTB of untapped or unswept or poorly swept remaining mobile oil from the project area.

In addition, results of these field tests will allow us to estimate reliably the recoverable fraction of the 410 MMSTB remaining mobile oil, and results of laboratory EOR tests will provide us crucial information about the recovery factors of 1.1 BSTB residual oil. Technical, economic, and environmental impacts of EOR methods on ETOF will be evaluated. The resulting GIS database with well locations, raster logs, production data, and depositional-trend maps will be made available to all operators in the field.

As a field operated by a largest number of small producers, ETOF perfectly illustrates the situations and dilemmas faced by numerous other mature and marginal fields in the U.S. This large, semifieldwide study will develop techniques and methods of increasing short-term oil production, as well as maximizing long-term oil recovery for all small producers in ETOF. These techniques are low cost, low risk, and potentially highly profitable, even at lower oil price. They can also be applied to other similarly mature and marginal fields in the U.S. that are operated by small producers.

Principal Investigators: