Newark East, Barnett Shale Field, Wise and Denton Counties, Texas; Barnett Shale Frac Gradient Variances

By

David F. Martineau, Pitts Oil Company, Dallas, Texas

The Newark East, Barnett Shale Field is one of the largest producing gas fields in Texas. The initial development of the field was centered in the southeast quarter of Wise County, and, over the past 20 years the field has expanded to the north, west, to the east into Denton County and the the South in Tarrant County. With the development of the field came the increased knowledge of the nature of the reservoir, the frac gradients and the porosity zones, all of which was important in the economic development of the Barnett Shale play.

In the early development it was recognized that the Upper Barnett (+100') had a higher frac gradient (.70+) than the Lower Barnett (.50 to .60+) (+300'). As the field developed and expanded in aerial extent, it became apparent that in the north part of the field the Lower Barnett (+600') could be subdivided into five (5) ("A" thru "E") correlatable porosity units with limestones and non-bituminous calcareous shale separating the productive porosity units.

With further investigation and evaluation of the Lower Barnett it became apparent that the upper "A" and "B" porosity units could have a different frac gradient than the lower "C", "D" and "E" units in certain areas.

Even though the majority of the water frac treatments consist of two phases, one for Lower Barnett and another for Upper Barnett, certain areas of the field will require multi-stage fracs to adequately recover the true reserve potential of the Barnett Shale.

Production logs and radioactive tracer surveys have been used to evaluate the effectiveness of frac jobs covering 300' to 600' intervals, where each zone could have variances in frac gradient, fractures and/or porosities.

As the field continues to expand beyond the Viola/Ellenberger subcrop, additional new data will possibly dictate a change in frac procedure.

AAPG Search and Discovery Article #90010©2003 AAPG Southwest Section Meeting, Fort Worth, Texas, March 1-4, 2003