This paper details the results of a three-year project to test horizontal waterflooding as a means of improving oil recovery from the Bartlesville sandstone in an abandoned 100-year-old oil field in Osage County, Oklahoma. Supported by a grant from the Department of Energy (DOE), this work was conducted by Grand Resources, Inc., an independent operator in Tulsa, Oklahoma. The project was initiated based on the concept of using three parallel horizontal wells (an injector straddled by two producers) in a heel-to-toe configuration. The pilot test evolved into an oil rim recovery project with pressure support coming from a vertical injection well, due to reservoir heterogeneities and lower-than-expected oil saturations.

Key technical aspects are discussed, including reservoir screening and the selection process; substantiating the primary and secondary production history; interpreting the depositional environment, including natural fracture orientation and a wellbore stability evaluation. Reservoir characterization is initially based on vertical logs and is modified when horizontal openhole logs become available. Characterization provides the details necessary for the reservoir simulation used to predict oil recovery and assess the economic viability. The simulation process is ongoing and updated as additional data is acquired.

Once waterflooding operations have begun, the technologies and methods employed to evaluate, manage and adjust both injection and production performance include:

  • Evaluating production results.

  • Conducting step rate and injection profile tests in the horizontal injection well.

  • Running a full suite of open hole logs through the short radius curve, including an acoustic borehole televiewer, to determine fracture frequency and orientation.

  • Adjusting injection water volume to assist in reducing operating expenses yet maintain adequate reservoir pressure support for high fluid withdrawal rates.

  • Re-drilling the horizontal producing wells closer to the top of the reservoir to significantly increase the oil cut.

The short radius drilling system is explained, in addition to the drilling of the lateral wellbores.

Oil recovery from the originally designed pilot was disappointing due to the unexpectedly high water saturations that were encountered. However, results from the modified pilot are much more encouraging, with 15 to 20 BOPD being produced from a thin oil column overlaying water.

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