Pressure Buildup During Supercritical Carbon Dioxide Injection From a Partially Penetrating Borehole into Gas Reservoirs

Abstract

Injecting CO 2 into a subsurface formation causes a buildup of pressure in the vicinity of the injection well. While a large injection rate can reduce the cost associated with injection, an indefinitely large injection rate can result in excessive formation damage. To obtain an optimal injection rate without exceeding the safe pressure limits, one will like to have some knowledge of the transient pressure buildup characteristics resulting from a particular injection rate. While elaborate numerical simulations can provide reliable pressure buildup predictions, they require extensive knowledge about the formation, which is normally not available at the start of an injection process. To alleviate this problem, using some simplifying assumptions, we have developed a solution to predict the transient buildup of pressure resulting from injection of supercritical carbon dioxide from a partially penetrating well into a gas reservoir. The solution in space and time is first obtained in the Fourier-Laplace transform space, and then inverted back into real space (in cylindrical coordinates) and time. We use the solution to study pressure transient characteristics for different formation permeabilities and anisotropy ratios. Results obtained using the solution compared well with those from numerical simulations.Keywords: carbon dioxide; storage; sequestration; pressure buildup; supercritical; analytical solution; gas reservoir IntroductionCapturing carbon dioxide from flue gases and injecting them into deep subsurface formations, a process commonly known as geologic storage, has been receiving increasing attention as a viable option for mitigating atmospheric emissions and reversing the global trends of rising surface temperatures (IPCC, 2005). Geologic storage aims to prevent CO 2 from entering the atmosphere by storing it permanently in three main subsurface formations -deep saline aquifers, unminable coal beds, and depleted natural gas reservoirs (Gunter et al., 1996;Bachu, 2000;Gale, 2004; IPCC, 2005;Hepple and Benson, 2005;Holloway, 2005;Oldenburg, 2006;Bachu, 2008; Zhou, 2009, Vilarrasa et al., 2010a Injection of CO 2 into deep geological formations is achieved by pumping it down into an injection well. While the actual geological storage zone can be quite thick (ranging from a few meters to tens of meters), only a small part of the injection well (typically, a few meters to 10 or 20 meters) within the storage zone is perforated to allow the injected CO 2 to enter the storage zone. The thickness of the perforated zone depends on the permeability and thickness of the formation. Injection raises the pressure in the immediate vicinity of the well, enabling CO 2 to enter the pore spaces initially occupied by the formation fluids. The spatial and temporal distribution of pressure buildup in the formation will obviously depend on the rate of injection, the permeability, porosity, and thickness of the storage formation, the perforation thickness, and other geological features (such as presence of faults or permeabi...

A model comparison initiative for a CO2 injection field test: an introduction to Sim-SEQ

“…These models must account for multiple physicochemical processes involving interactions between the injected CO 2 , the formation fluids (either brine or hydrocarbons), and the reservoir rocks (Kang et al, 2010). Depending upon the nature of the fluids already residing in the formation, these processes may include (but are not necessarily limited to) fluid flow under pressure gradients created by the injection process; buoyancy-driven flow caused by density difference between the injected and formation fluids; diffusion, dispersion and fingering (arising from formation heterogeneities and mobility contrast between the fluids); capillarity (resulting from different wetting characteristics of the fluids concerned); dissolution into the formation fluid, mineralization, and adsorption of CO 2 (Intergovernmental Panel on Climate Change, IPCC, 2005;Mukhopadhyay et al, 2011).…”

Heat transport and pressure buildup during carbon dioxide injection into depleted gas reservoirs

“…Mukhopadhyay et al (2012) identify this feature as a disadvantage. However, application of the pseudo-pressure concept in conjunction with the pseudo-time concept of Agarwal (1979) leads to a significant improvement.…”

“…Disregarding statements made in the previous section, following Mukhopadhyay et al (2012), consider the additional assumptions that (i) the difference between the CH 4 and CO 2 properties is negligible, (ii) temperature changes are negligible and (iii) the water and rock are incompressible. The mass conservation equations reduce to θ c ρ c α c ∂P ∂t = − 1 r ∂ ∂r (rρ c q c ) (3.14)…”

“…The above PDE is nonlinear because of the dependence of ρ c , α c and µ c on P. Mukhopadhyay et al (2012) linearize the above equation by imposing a Pitzer correlation for the relationship between ρ c and P. The linearized PDE is then solved in Laplace transform space and inverted back to the time domain to obtain an analytical solution for P in the form of an integral equation, which is evaluated numerically.…”

“…However, depleted gas reservoirs are often abandoned at pressures lower than 1 MPa. Mukhopadhyay, Yang & Yeh (2012) presented numerical simulations concerning CO 2 injection into a depleted gas reservoir at 0.5 MPa. However, they ignored thermal effects and considered the reservoir to be of infinite extent.…”