Black Shale Lithofacies Identification and Distribution Model of Middle Devonian Intervals in the Appalachian Basin
The Marcellus Shale, marine organic-rich shale deposited during Middle Devonian in the Appalachian basin, is considered the largest unconventional shale-gas resource in US. Two critical factors for shale-gas reservoirs are units amenable to hydrologic fracture stimulation and high free and adsorbed gas content. The effectiveness of hydrologic fracture stimulation is influenced by rock geomechanical properties, which are related to rock mineralogy. The natural gas content in shale reservoirs has a strong relationship with organic matter, which is measured by total organic carbon (TOC). For a study are in the Appalachian basin, a 3D shale lithofacies model is constructed using mineral composition, rock geomechanical properties and TOC content. This model could be applied to optimize the design of horizontal well trajectories and stimulation strategies. Core analysis data, log data and seismic data were used to build a 3D shale lithofacies model from core scale to well scale and finally to regional scale. Artificial neural network (ANN) was used for lithofacies prediction. Core XRD and chemical analysis data and wireline logs were utilized as inputs and target outputs to petrophysical analysis and various pattern recognition methods. A limited set of eight derived parameters from common logs were determined as critical inputs. Advanced logs such as elemental capture spectroscopy (ECS) with mineral composition and TOC data were used to improve and confirm the quantitative relationship between common logs and lithofacies. Seismic data, and interpreted sequence stratigraphy and depositional environments were used as soft data to constrain deterministic and stochastic 3D lithofacies models.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California