Data integration, reservoir response, and application

Abstract

The microseismic activity observed in and around a geologic formation undergoing carbon dioxide (CO 2) injection is a combination of natural, or "background", microseismicity plus that activity which is induced by injection operations. Since injection pressure within storage target formations are maintained safely below fracture pressure this induced activity typically originates at natural pre-existing zones of mechanical weakness presented by structural or stratigraphic features. The combination of mechanical properties and in-situ stresses dictate the focal mechanism for microseismic emissions, an understanding of which facilitates the use of observed microseismicity for regulatory compliance and project management. Under favorable conditions microseismic activity may be unambiguously correlated with structural and/or stratigraphic features directly observed in seismic data, thus providing strong constraints to interpretation of observed microseismicity for focal mechanisms. However, in many cases, such as at the Illinois Basin-Decatur Project (IBDP), this direct correlation is elusive and other indirect support is required. Analysis of microseismicity at IBDP has been performed within the context of the integrated reservoir and mechanical earth models developed as part of the site characterization and monitoring program. The IBDP integrated modeling workflow involved continuous and geotechnically consistent data integration for geologic modeling, calibrated flow simulation, three-dimensional (3D) Mechanical Earth Model, and coupled hydromechanical simulation. Using the coupled model, scenario-based forward modeling of microseismicity was performed for hypothetical focal mechanisms inferred from observed data. The experience gained at IBDP illustrates the importance of integrated modeling in the interpretation of microseismic activity for focal mechanisms and provides valuable insights into critical data gaps which could be the target of future basic research efforts.

Characterization of induced seismicity patterns derived from internal structure in event clusters

“…This can inhibit vertical flow and restrict the injected CO 2 to remain near the Lower Mount Simon injection horizon [ Bowen et al ., ], which has an average thickness of about 25 m locally. The impact of such vertical heterogeneity on development of the pressure and saturation plumes within the Lower Mount Simon formation is seen clearly monitoring well data where individual baffles in the reservoir interval can be distinguished [ Will et al, ]. The lowest portion of the Mount Simon Sandstone overlying the Precambrian rhyolite basement is the so‐called Argenta formation.…”

A review of geochemical–mechanical impacts in geological carbon storage reservoirs

“…CO 2 was injected at a rate of 1000 tons per day from November 2011 until November 2014. 19 The injection pressure rate was kept well below the fracture propagation pressure, as required by the regulatory framework for Underground Injection Control and determined by a step-rate test. For about 18 months, the preinjection seismicity was also measured; less than 10 events with a magnitude below 1.5 were recorded, and these events were attributable to the geologic formation, i.e., after industrial and distant natural earthquakes were removed from the data set.…”

“…a. CO 2 was injected at a rate of 1000 tons per day from November 2011 until November 2014 . The injection pressure rate was kept well below the fracture propagation pressure, as required by the regulatory framework for Underground Injection Control and determined by a step‐rate test.…”

Overview of microseismic response to CO2 injection into the Mt. Simon saline reservoir at the Illinois Basin-Decatur Project

“…All of the seismic lines and surveys, along with the multiple downhole geophysical investigations for formation properties, were incorporated to produce a series of static and dynamic models including, geologic, velocity and reservoir models (Senel et al, 2014;Will et al, 2016a). Also, inversion of the 3D seismic data along with reservoir properties acquired from well data were used to produce a reservoir flow simulation based on the integrated earth model.…”

“…12). Will et al (2016a) presents an in depth analysis of the data integration and reservoir response resulting in microseismicity.…”