Estimation of rock frame weakening using time-lapse crosswell: The Frio brine pilot project

Abstract

[Formula: see text] injection into subsurface reservoirs leads to pressure and saturation changes. Furthermore, [Formula: see text]-brine-minerals interaction could result in dissolution or reprecipitation of rock frame-forming minerals. Observed time-lapse seismic associated with [Formula: see text] injection into poorly consolidated sandstone at the Frio [Formula: see text] injection site (Texas, USA) could not be predicted using classical rock-physics models (i.e., models involving elastic changes in the rock frame due to saturations and/or pressures changes only, and assuming no changes in the rock microstructure). That, and the changes in the fluid chemistry after [Formula: see text] injection, suggests that the assumption of a constant rock microstructure might be violated. Using high-resolution time-lapse crosswell data, we have developed a methodology for estimating changes in the rock frame by quantifying the rock-frame drained moduli before and after [Formula: see text] injection. Based on rock microstructure diagnostics, we found that the changes in the drained frame elastic properties are due to the changes in the grain contact-cement percentage. The reduction in contact-cement percent is found to be variable throughout the reservoir, with a maximum near the injection well, down to 0.01% from the initial 0.1% contact cement; this results in more than 40% reduction in the drained frame shear and bulk moduli. [Formula: see text] saturation was estimated using this model for uniform and patchy saturation cases. Our rock-physics analysis may allow improved interpretation of time-lapse seismic for [Formula: see text] saturation in the context of other poorly consolidated sandstones with similar geomechanical properties. Having the P- and S-wave velocity time-lapse data is key to improve saturation estimates with this analysis method.

Elastic properties of unconsolidated sandstones of interest for carbon storage

“…Such transport was suggested by Al Hosni et al. (2016) in explaining why the magnitude of the time‐lapse effect due to the injection of CO 2 into the Frio C sand at the Frio CO 2 injection site was greater than predicted using conventional rock physics models.…”

“…This may make it easier for grain contacts to slip and for fluid flow to dislodge and transport grains in the Frio case than in the Paluxy sandstone, particularly if CO 2 acts to weaken any cement that may be present at the grain contacts. Such transport was suggested by Al Hosni et al (2016) in explaining why the magnitude of the time-lapse effect due to the injection of CO 2 at the Frio CO 2 injection site was greater than predicted using conventional rock physics models.…”

“…The laboratory data for dry sandstones shown in Figure 6 have been published by Han (1986), Han et al (1986) and Murphy et al (1991). Data for the Frio Brine Pilot Well have been published by Hovorka et al (2006), Sakurai et al (2006), Daley et al (2008) and Al Hosni et al (2016).…”

Numerical Simulation of Thermo‐Hydro‐Mechanical‐Chemical Response Caused by CO2Injection into Saline Geological Formations: A Case Study from the Ordos Project, China

“…In an acidic environment created by CO 2 injection, the impact of water -rock reaction on rock mechanical properties may be very obvious. For instance, at the Frio test site in the United States, a reduction of approximately 30% in rock shear modulus (characterized by P-wave velocity) was observed after CO 2 injection, much more than originally anticipated (Al Hosni et al, 2016). Subsequent analysis indicated that this was due to the reduction of aqueous pH by CO 2 injection, which triggered the dissolution of cementing minerals in the rock (Xu et al, 2010;Ilgen and Cygan, 2016).…”

Spatiotemporal changes of seismic attenuation caused by injected CO2 at the Frio‐II pilot site, Dayton, TX, USA

“…Time‐lapse seismic imaging has been shown to be an effective technique for subsurface CO 2 monitoring for both enhanced oil recovery [ Lazaratos and Marion , ; Majer et al ., ; White , ] and sequestration [ Arts et al ., ; Xue et al ., ; Daley et al ., ; Gareth and Chadwick , ; Ajo‐Franklin et al ., ]. For example, time‐lapse crosswell tomographic velocity estimates of the Frio‐I CO 2 plume demonstrated a seismic velocity decrease up to 500 m/s within the plume that were caused by the injection of supercritical CO 2 into the brine reservoir [ Hovorka et al ., ; Ajo‐Franklin et al ., ; Daley et al ., ; Al Hosni et al ., ]. For the expected advanced role of monitoring in the future, e.g., for the accounting of CO 2 emissions [ Benson , ], there is a demand for seismic monitoring to provide early detection of leaks and quantitative estimation of the amount of CO 2 in the storage zone.…”