Opishnyanske Field is a mature Ukrainian gas field that began producing in 1972 from three formations: Visean, Serpukhovian, and Bashkirian. A reservoir simulation study was implemented to understand the movement of the water in the reservoir and to maximize the field recovery. Some wells showed high water production at their late life and this was the key question that we wanted to understand. If this was a water breakthrough, which means that the aquifer water swept the gas in the reservoir and reached these wells, then there is little potential left in this field. If this was not a water breakthrough, there could still exist some unswept areas to be produced. The second key question was to understand the aquifer strength and direction to be integrated into the simulation model.

The field has different sources of data that could be used to understand the water movement in the reservoir, which are:

  • Observed production data

  • Water analysis reports (surface water salinity and density measurements)

  • Production logging data

  • Pressure data and geological maps to understand the communication between the wells

Although different sources of data are available, each one has a level of inaccuracy, which was the key challenge. The field also has some other challenges, such as:

  • Commingled production

  • Contradiction between the observed water/gas ratio (WGR) and water analysis data

  • Limited water analysis data points in some wells

  • Issues with backallocation of the observed data.

Integrating all the available data had a significant effect on understating the water behavior. Data analysis and integration resulted in excluding all the data anomalies and reaching a good understating regarding:

  • The wells that are showing a water breakthrough

  • Aquifer strength and direction

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