Harold Vance Department of Petroleum Engineering
Spraberry Trend Area

The naturally fractured Spraberry Trend Area in west Texas covers approximately 2,500 square miles over a six county area. There are approximately 9,000 wells cuurently producing in the Spraberry Trend. Some 6-10 Bbbls of original oil is contained yet after 50 years of production, only 700 million bbls have been produced. Low recoveries associated with low matrix permeability and stress-sensitive natural fractures have thwarted attempts to improve recovery. This tremendous resource has been difficult to utilize due to the complicated nature of the reservoir. Many wells are near the economic limit.

The naturally fractured/integrated reservoir program at the Harold Vance Department of Petroleum Engineering is collaborating with Pioneer Natural Resources in a Class III Field Demonstration sponsored by the National Petroleum Technology Office and the U.S. Department of Energy. The overall goal of this project is to assess the economic feasibility of CO2 flooding the naturally fractured Spraberry Trend Area in west Texas. This objective is being accomplished by conducting research in four areas: 1) extensive characterization of the reservoirs, 2) experimental studies of crude oil/brine/rock (COBR) interaction in the reservoirs, 3) analytical and numerical simulation of Spraberry reservoirs, and, 4) experimental investigations on CO2 gravity drainage in Spraberry whole core. Additionally, we are in the process of completing all wells and surface facilities prior to CO2 injection in an 80 acre field demonstration pilot project in the E.T. O'Daniel Spraberry Unit shown in the map below.

During the field demonstration phase of the project sixteen new wells are scheduled:

  • 3 central production wells equipped with permanent BHP gauges
  • 6 water injection wells
  • 4 CO2 injection wells
  • 2 logging observation wells
  • 1 horizontal well

Four vertical wells and the horizontal well were cored for identification of net pay, oil and water saturation and core-log integration. 300 feet of horizontal core was acquired to characterize the fracture system. Currently, 12 wells have been completed with two CO2 injection wells and two logging observation wells slated for completion in the next quarter. Water injection was initiated after completion of a multi-well interference test. Stable water injection was initiated in October of 1999 in order to increase the reservoir pressure above the miscibility pressure for Spraberry crude and CO2. Positive results have been observed as a result of water injection. We anticipate injection of CO2 to commence by the 3rd quarter of this year. Please visit Naturally Fractured Reservoirs for more details or contact david.schechter@pe.tamu.edu

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