08123-16

Goal
The goal of this project is to develop and demonstrate short- and mid-term strategies for maximizing recovery from the East Texas Field. The research team will identify strategically targeted deepening locations and optimized water flood sites with the potential to increase short-term oil production and add reserves. Further, the researchers will evaluate the enhanced recovery alternatives and their technical, economic, and environmental impacts. Finally, the team will build and deploy a publically available Geographic Information System (GIS) data set including well locations, raster logs, production data, and depositional-trend maps.

Performers
UT Austin Bureau of Economic Geology (BEG), Austin, TX 78713-8924

Background
The East Texas Field, discovered on September 3, 1930, has produced 5.43 billion stock tank barrels (BSTB), of 39° API oil from lower Woodbine sandstones from >31,000 wells. The estimated original oil in place (OOIP) for the East Texas Field varies from 6.8 to 7.5 BSTB. Given a midrange OOIP value of 7.0 BSTB, the current recovery efficiency of 77 percent is the highest of any giant oil field in the world. Currently it is an aging giant field operated by a large number of small producers (~114 companies), that face significant technical, economic, and environmental challenges to maintaining production.

After 88 years of production, it has been estimated that >1.5 BSTB of oil remain in the reservoir, but this volume is exceedingly difficult to target. Since the late 1990s, major oil companies have sold most of their producing properties within the field to small independent producers. Development of strategies to recover this oil has become a critical issue because many current operators lack expertise in the higher technology geology and engineering methods that are crucial to revitalizing production and lowering production cost.

In spite of the field’s excellent reservoir quality and remarkable long-term performance history, technologists have not fully studied the details of its depositional environment and reservoir architecture. Currently, of the ~1.5 BSTB of oil that remain in the reservoir, an estimated 0.48 BSTB is mobile oil and 1.1 BSTB is residual oil. Of the 0.48 BSTB of remaining mobile oil, ~70 MMSTB will be produced by 2030, according to decline-curve analysis, and 410 MMSTB remains in areas that are untapped, unswept, or poorly swept. A fraction of the 410 MMSTB of remaining mobile oil is producible using strategically targeted recompletions and waterfloods guided by depositional trends, whereas residual oil is producible only by enhanced oil recovery (EOR) methods.

Potential Impacts
The research team will identify 100 strategically targeted deepening locations and 10 optimized waterflood sites (small and large), which have the potential to increase short-term oil production by 15 percent and add >10 MMSTB of untapped or unswept remaining mobile oil reserve. Further, the researchers will estimate the recoverable fraction of the 410 MMSTB of remaining East Texas Field mobile oil and evaluate the enhanced recovery alternatives and their technical, economic, and environmental impacts. Finally, the team will build and deploy a publicly available GIS data set including well locations, raster logs, production data, and depositional-trend maps.

The study will develop techniques and methods for increasing short-term oil production, as well as maximizing long-term oil recovery for all small producers operating in the East Texas Field. These techniques are low cost, low risk, and potentially highly profitable. They will be applicable to other similarly mature and marginal fields in the U.S. operated by small producers.

Accomplishments
Work on this project began in October 2009, with the initial work going toward development of a Project Management Plan and Technology Status Assessment. The Project Management Plan consists of a work breakdown structure that concisely addresses the objectives and approach for each task with all major milestones and decision points, and the Technology Status Assessment describes the state-of-the-art of the proposed technology.

The tertiary oil Recovery Project (TORP) at the University Kansas was selected as the subcontractor for the EOR tests. The tests are scheduled to begin in year two of the project.

Progress has been made on the BEG publication on the East Texas Oil field, including geologic correlations, raster logs, five volumes of production and completion data, expansion of the area on well and lease line correction, and map digitization for the GIS database.

Well workovers (part of the project cost share contribution) have been carried out on two wells. The operator mistakenly recompleted at the Main Woodbine which is about 30 ft above the intended target. Because of this error, the workover was unsuccessful. Nevertheless, the lower zone remains as a potential target for a subseqent test, and the operator has selected a well to do this.

Current Status (January 2011)
The key tasks are outlined below.

Data Compilation and Database Implementation – The research team will collect well and wireline log data from the East Texas Engineering Association and individual operators and create a well database.

Well Tops Determination and Net-sandstone Calculation – Stratigraphic units will be identified and tops of reservoir units will be picked at each well. Lithofacies will also be identified, and the net-sandstone thickness of each unit will be calculated at each well.

Well Correlation and Depositional-Trend Mapping – The research team will correlate stratigraphic units using cross sections to determine reservoir architectures and will prepare structure and net-sandstone thickness maps to determine depositional trends.

Petrophysical Properties and Engineering Analysis – The researchers will characterize petrophysical properties using core and wireline log data, and analyze well completion and production history.

GIS System Implementation – The research team will implement a GIS well and map database.

Workover Target Identification and Ranking – The team will identify potential targets for deepening and waterflooding using depositional-trend maps, develop a plan for eliminating shut-in, depleted, and problematic commingled locations, estimate the oil reserve for each location, and rank potential targets by their potential for adding reserves.

Mini-waterflood Design and Field Test – The researchers will select final waterflood sites and design waterflood patterns based on depositional-trend maps and active well locations.

Laboratory Tests of CO₂ Flooding – The research team will measure CO₂ minimum miscibility pressure with East Texas crude and perform laboratory tests on miscible and immiscible CO₂ flooding options.

Laboratory Tests of Surfactant/Polymer Flooding – The research team will study the phase behavior of crude/surfactant-co-solvent/brine systems, including the effects of varying surfactant type and concentration and water salinity. The team will also perform laboratory studies of surfactant/polymer flooding.

Economic and Environmental Impacts of EOR – The researchers will evaluate the economic and environmental impacts of CO₂ flooding and surfactant/polymer flooding.

A final report will be the primary deliverable for this project. Data and results will also be disseminated through workshops, presentations, and interim reports.

Project Start: October 26, 2009
Project End: October 25, 2012

DOE Contribution: $700,000
Performer Contribution: $700,000

Contact Information:
RPSEA – Martha Cather (martha@prrc.nmt.edu or 575-835-5685)
NETL – Chandra Nautiyal (chandra.nautiyal@netl.doe.gov or 918-699-2021)
UT Austin Bureau of Economic Geology – Dr. Fred P. Wang (fred.wang@beg.utexas.edu or 512-471-7358)