Case Studies of 180 Water Disposal Fall-Off Tests in Alberta, Canada - Engineering Insights of Induced Seismicity

Abstract 180 case studies of water disposal fall-off tests are presented that provide permeability, reservoir pressure and identification of boundaries such as faults. Induced seismicity refers to earthquakes that are attributed to human activities. Critically stressed faults in the subsurface may be activated by fluid disposal operations. Changes in reservoir pressure and stress caused by fluid disposal operations may allow critically stressed faults to slip and generate seismicity. Results are provided which allow engineering insights extraction. The newly developed approach is based on pressure transient analysis (PTA) analyzing submitted high frequency, and high-resolution shut-in data. The data is captured during well-dedicated test operations such as fall-off tests or during routine operational shut-ins. The pressure response from these shut-ins can be used to provide information about the reservoir within the radius of investigation for radial flow or the area of investigation for more complex geometries. A numerical method description is provided for several case studies. Complete governing equations are provided, and the method is described in detail to permit readers to replicate all results The engineering information and results extracted from the water disposal fall-off tests are visualized in a data-analytics-based dashboard with the intent of locating information geospatially related to induced seismicity / earthquakes in Alberta, Canada. Arrival-times of P-primary and S-secondary waves at seismicity stations are utilized to estimate the location of earthquakes. The most significant new finding is that year over year monitored reservoir pressure trends can be visualized and linked to wellbore and earthquake locations with advantage of locating boundaries such as faults. In addition, recommendations to upgrade regulator data intake and update regulatory instruments such as directives and manuals will allow the regulator to act quickly and swiftly when needed. This is important because, much of the time, fault activation will not be perceptible on the surface. Induced seismicity protocols and disposal scheme engineering-related conditions are intended to limit the magnitude and frequency of induced earthquakes from fluid disposal operations The novelty of the newly developed approach is for industry to extract engineering insights from more than hundreds case studies, compare with their databases to react accordingly and for the regulator to improve the regulator's ability to mitigate water disposal induced seismicity related operations in a timely and science-based or technical manner by synchronizing location and engineering data.