Modeling the Structure, Porosity, and Permeability of the Arbuckle Group in South-Central Kansas

Abstract

The Arbuckle Group includes the oldest and lower-most sedimentary formations in the midcontinent. Of vital economic importance in Kansas and the region, the Arbuckle is a primary oil-producing reservoir and also serves as the primary target for disposal of unwanted fluid waste. Despite its economic significance, the structure, porosity, and permeability of the Arbuckle is poorly understood. Recently, our need to understand the Arbuckle’s reservoir characteristics has intensified. A sudden and rapid increase of seismicity in the midcontinent correlates to rapid increase of Arbuckle wastewater disposal volumes. Additionally, the Arbuckle is being considered as a potential sink for long term storage of CO₂. Here, a 125km² geologic model of the Arbuckle Group in southern Kansas is developed from a dataset of 29,601 Kansas oil, gas, and disposal wells. Wireline logs from over 1,000 wells are used to correlate formation tops and ensure the accuracy of industry-provided tops (29,591 wells). A petrophysical analysis of porosity and permeability is performed by leveraging data from wireline logs, core, and drill-stem-tests. These properties are statistically up-scaled into a layered 3-D cellular wireframe resulting in multiple simulation-ready models. The model is used to perform simulations using two unique datasets: (1) wastewater injection volumes from 319 injection wells in the model area are used to simulate Arbuckle pressures and (2) UIC Class I wells within the model area provide long-term pressure data that is used to iteratively adjust petrophysical properties required for an accurate history match of observed pressures. The simulations are being used to explore spatial and temporal changes in the Arbuckle’s pressure by history matching to dynamic pressure data. Additionally, the simulations investigate pressures at depth in the Precambrian crystalline basement, where recent seismicity is concentrated. Initial simulation results indicate that permeabillity estimates originating from drill-stem-test analysis can match with Arbuckle dynamic pressure data while permeability estimates from wireline logs and core analysis are significantly under-representing the permeability. This result appears to be consistent with the nature of the Arbuckle Group which is dominated by secondary features in the form of fractures and vugular carbonate porosity.

AAPG Datapages/Search and Discovery Article #90350 © 2019 AAPG Annual Convention and Exhibition, San Antonio, Texas, May 19-22, 2019