Precambrian Crystalline Basement Properties From Pressure History Matching and Implications for Induced Seismicity in the US Midcontinent. (3rd August 2021)

• Record Type: Journal Article
• Authors: Ansari, Esmail; Bidgoli, Tandis S.
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 22:Number 8(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-03
• Subjects: Arbuckle aquifer -- crystalline basement -- induced seismicity -- Kansas and Oklahoma earthquakes -- wastewater injection; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1029/2021GC009660
• Languages: English
• ISSNs: 1525-2027

Abstract

Abstract: Injection‐induced seismicity across the US midcontinent has almost exclusively occurred in the crystalline basement that underlies the Arbuckle Group aquifer and its equivalents, the primary wastewater disposal zone in this region. However, the properties of the basement are not well known. Newly compiled data, from Class I wells in Kansas, provide a unique record of pressures in the Arbuckle and an opportunity to constrain the reservoir‐scale properties of the basement such as permeability, diffusivity, and specific storage. Constraints on these parameters are critical for modeling fluid flow and pressures across the entire Arbuckle‐basement system, and are necessary for accurate evaluation and prediction of injection‐induced earthquakes. Here, we present a detailed, three‐dimensional geological and pressure history‐matched numerical model for the Arbuckle and basement, based on data from >400 wells covering a large region in south‐central Kansas, where injection‐induced seismicity has been concentrated since 2014. Simulations of dynamic data from 319 wells indicate that Arbuckle pressures have increased by 1.1 MPa in high injection rate areas and an overpressure of <0.1 MPa may be the cause of seismicity in the basement. Pressure‐history matching also yields the likely range in porosity (0.3%–7%), permeability (0.1–0.7 mD), and diffusivity (0.004–0.07 m 2 /s) for the basement. The resulting estimates suggest reservoir‐scale properties of the basement are enhanced by faults and fractures. Importantly, the diffusivities determined in this study are lower than estimates derived from Kansas earthquake triggering fronts, and suggest that such seismicity‐based techniques may have limitations, particularly where space‐time patterns between injection and seismicity are complex. Plain Language Summary: Wastewater injection tied to oil and gas development has induced earthquakes across a broad swath of the central US. These earthquakes have almost exclusively occurred in the crystalline rocks, many kilometers below the main disposal zone in this portion of the country, the Arbuckle Group aquifer. However, the hydrologic properties of these deep crystalline rocks are not well known and are needed to accurately model pressure transmission from injection wells to faults in the deep basement and related earthquake hazards. Newly compiled pressure data, from wastewater disposal wells in Kansas, provide an opportunity to constrain these properties. In this study, we construct a detailed, three‐dimensional geological model for the Arbuckle and basement, based on data from >400 wells covering south‐central Kansas. We use the model to simulate injection and pressures from more than 300 wells. The model indicates that Arbuckle pressures increased by 1.1 MPa in high injection rate areas and overpressures of <0.1 MPa may be the cause of seismicity in the basement. The simulation results also yield the likely range in hydrologic properties for the crystalline basement and suggests large‐scale properties of the basement are enhanced by hidden networks of faults and fractures. Key Points: A three‐dimensional geological and history‐matched numerical model for south‐central Kansas constrains the hydrological properties of the basement Basement properties from pressure history matching account for distributed fault and fracture networks Basement diffusivities are substantially lower that those derived from earthquake triggering fronts across the model area