Gravity monitoring of C O2 movement during sequestration: Model studies

Abstract

Electromagnetic induction data parameterized in time dependent object intrinsic polarizabilities allow discrimination of unexploded ordnance (UXO) from false targets (scrap metal). Data from a cart-mounted system designed for discrimination of UXO with 20 mm to 155 mm diameters are used. Discrimination of UXO from irregular scrap metal is based on the principal dipole polarizabilities of a target. A near-intact UXO displays a single major polarizability coincident with the long axis of the object and two equal smaller transverse polarizabilities, whereas metal scraps have distinct polarizability signatures that rarely mimic those of elongated symmetric bodies. Based on a training data set of known 1 targets, object identification was made by estimating the probability that an object is a single UXO. Our test survey took place on a military base where both 4.2" mortar shells and scrap metal were present. The results show that we detected and discriminated correctly all 4.2" mortars, and in that process we added 7%, and 17%, respectively, of dry holes (digging scrap) to the total number of excavations in two different survey modes. We also demonstrated a mode of operation that might be more cost effective than the current practice.

Understanding the applications and limitations of time-lapse gravity for reservoir monitoring

“…Gasperikova and Hoversten (2008) successfully demonstrate this latter point by implementing a realistic model of the Schrader Bluff reservoir, where variations of rock properties and resulting spatial density variations are incorporated. In our demonstration, we will implement an algorithm that incorporates multiple dipping seismic surfaces directly into the 4D gravity inversion.…”

Evaluating time-lapse borehole gravity for CO2 plume detection at SECARB Cranfield

“…Ultimately this modeling provides not only survey design geometries, but likewise a means of managing the length of the operation and hence total field costs. Similar response modeling has been previously undertaken (Sherlock et al, 2006;Gasperikova and Hoversten, 2008), without corresponding field acquisitions to test their outcomes.…”

“…In most instances, the variations in density due to water floods or CO 2 plumes are not detectable from the surface. Consequently borehole deployed measurements have been proposed and modeled to assess their viability (Gasperikova and Hoversten, 2008;Sherlock et al, 2006). There are relatively few borehole deployable gravimeters in the world, and hence limited operating experience, although the capability has existed since the late 1950s.…”

Assessing the monitorability of CO2 saturation in subsurface saline aquifers

“…Several studies on geophysical monitoring of subsurface CO 2 storage have been published recently (e.g., Arts et al, 2004;Alnes et al, 2008;Daley et al, 2008;Gasperikova and Hoversten, 2008;Yordkayhun et al, 2009). Most of these focus on detecting the CO 2 plume and its spatial extent.…”