AAPG Southwest Section

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Application of Multiple pay Flags to determine landing targets in southern midland Basin Wolfcamp


The use of multiple specialty logs, in addition to density logs, help define higher TOC and larger pore intervals for landing target selection in the Wolfcamp A, B, and C zones. The study area included wells in Midland, Upton, and Reagan Counties. Litho-Density logs were used to define zones of higher porosity and/or kerogen. Magnetic resonance (CMR) logs were used to define total porosity and the distribution of pore sizes. Geochem (ECS and/or Litho Scanner) logs were used to define mineral distribution, including volume of clay.

Litho-Density pay flag cutoffs previously defined by others (Lewis, 2011 and Walls et al, 2012) are useful in defining zones with higher porosity and/or kerogen. Incorporating the CMR logs, Geochem logs, and ELAN OIP to these methods help provide additional support in optimizing landing targets compared to Litho-Density cutoff methods.

The understanding of magnetic resonance (CMR) pore size on productivity has changed significantly. Pore sizes that where once thought to be non-productive (T2<33ms), are now reservoir targets. Pore sizes between the 3ms and 33ms T2 time distribution contain most of the hydrocarbon being produced in unconventional reservoir targets. In addition, CMR data is a compliment to Litho-Density data by providing a matrix independent porosity and pore size distribution.

Geochem (ECS and/or Litho Scanner) logs either measure TOC directly (Carbon Subtraction Method) or provide the mineral composition percentages to use along with CMR and Density data for the TOC Porosity Deficit Method. TOC values calculated from these methods are much more accurate because they are direct measurements.