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Subsurface Impermeable Barriers


GeoSierra has pioneered the installation of trenchless subsurface permeable reactive barriers (PRBs) for groundwater remediation and has installed kilometers of PRBs at sites throughout the USA. The same technology is used to create a subsurface impermeable barrier, as a freeze wall, or impermeable by grout injection or the injection of a special swellable proppant. The imperable barrier can provide containment of hazardous wastes or as a fluid loss barrier for thermal enhanced oil recovery (EOR) using steam, such as in SAGD (Stream Assisted Gravity Drainage) operations. To view how we construct subsurface impermeable Barriers, view our construction and QA/QC verification testing video at Video.

The subsurface barrier constucted as a freeze wall will require continuous circulation of cold saline gelled water fluid throughout the wall. The formation pore water is frozen creating a substantial barrier. If the formation contains extremely high saline water or free methane then an alternate barrier should be considered. Either as a chemical injection in the wall, and upon setting of the chemical grout at an impermeable barrier is created, or alternatively, a swellable proppant is injected to construction the barrier and after a few days the proppant will swell filling all the void space in the wall, creating an impermeable barrier. Both the chemical grout and swellable proppant barrier walls can withstand high elevated temperatures up to 250°C.

 

SAGD operating close to outcrop can have significant fluid loss to the outcrop due to high fluid mobility. The operating pressure is normally reduced to reduce the fluid loss, and such reduction in fluid loss can be significant if the operating pressure is close to yielding a very low horizontal effective stresses. At or near zero horizontal effective stress, The McMurray formation experiences a ~70% increase in permeability.

Alternatives other than reducing the operating steam pressure are limited, namely a fluid loss subsurface barrier between the SAGD panels and the outcrop. Such a barrier would normally be extensive in length and its fluid loss efficiency needs to be extremely high in order to be effective. That is, the barrier has to have a high instrinsic integity, which generally limits the choice of barrier to a freeze wall.

Fluid Loss to Outcrop

   


 
 
 
 

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