3D RESERVOIR CHARACTERIZATION OF THE MARCELLUS SHALE, LYCOMING COUNTY, PA

This presentation introduces a 3D reservoir model of the Marcellus Shale in Lycoming County, PA. We constructed this model to enhance our understanding of a complex shale gas reservoir and to provide a set of reservoir property grids for reservoir simulation.

The static modeling process began with data review and loading. Five vertical wells supplied us with well logs and some core analysis data for reservoir characterization. Two horizontal boreholes with IP test data were incorporated into the model for history matching and simulation. Several other wells offered additional well top controls for mapping.

We delineated the target rock column into the Tully, Mahantango, Marcellus, and Onondaga intervals. The Marcellus was further divided into Upper and Lower Marcellus, separated by the Cherry Valley.

Extensive petrophysical analysis was performed on the five key vertical wells, including log normalization and Neural Networks estimation, calibrated with core data. Key log-derived reservoir properties were summarized for the Marcellus intervals.

Due to the limited well controls, we contoured various structural maps using the Onondaga seismic horizon as a trend surface, adjusted by well top picks from well logs. In addition, we also constructed basin-wide pore pressure and isotherm maps for volumetric gas-in-place estimation.

We then constructed a 3D structural framework containing five faults and eight zones, with a total of 40 million cells. Well log data were scaled up into this 3D grid along the wellbores and populated into the 3D space using stochastic approach. A set of 3D property models were generated, including gamma-ray, bulk density, TOC content, gas-filled porosity, permeability, gas content, and pore pressure.

Two 3D seismic volumes and the FMI data from one well were analyzed to define the distribution, orientation, and density of natural fractures in the areas near the two horizontal wells. Both the 3D seismic curvature attributes and FMI data revealed a complex naturally fractured reservoir with dominated fractures trending NW-SE.