Petro-Find Geochem Ltd very high-density soil gas surveys for light hydrocarbons and CO2 could play a significant role in the development of Enhanced Coalbed Methane (ECBM) and CO2 Miscible Flooding (EOR) projects in Canada. The ability to detect surface leakages from these projects can translate into more efficient operations with substantially reduced costs as well as provide a tool for measurement of environmental impacts.

Such surveys involve new approaches and methods and therefore, Petro-Find recommends that each survey be conducted in two stages: a PROOF OF CONCEPT followed by the application of lessons learned in a more extensive survey. The surveys would have two objectives: measurement of the concentration and patterns of CO2 and light hydrocarbons in soils (as expressed by contours) to determine efficiency of injection and production operations; and calculation of total flux to indicate possible environmental impact. Petro-Find is well-equipped to assess the concentration and pattern of CO2 leakage; new methods will be applied for the measurement of total flux.

It remains to be seen whether soil gas surveys can also be useful for coal bed methane projects (ie. without injection) as studies elsewhere have met with mixed results.

ECBM PROJECTS

Petro-Find soil gas surveys can be adapted for Enhanced Coalbed Methane (ECBM) Projects. Repetitive very high-density surveys for Methane could prove to be a major tool for showing the lateral extent and direction of gas flooding fronts extending from the central injection well to the production wells. The released Methane from gas flooding moves laterally along the coal bed in the direction of the highest permeability and lowest pressure. It is reasonable to expect that the Methane migrates upwards as well though the hanging wall of the coal seam to the surface where it can be detected by soil gas surveys. It should be noted that Methane is reported in surface water wells in Wyoming CBM projects.

The gas front composed of Methane and CO2 may exhibit an elliptical pattern with the long axis parallel with face cleats. Lineaments or faults may serve as either conduits or barriers for the gases. Facies changes in the coal seam are also mitigating factors. The directional (anisotrophic) permeability of the cleat system and its control of gas fronts as it moves laterally along the coal seam have major implications for the spotting and timing of production wells.

CO2 MISCIBLE FLOODING PROJECTS

Petro-Find technology can be applied to CO2 Miscible Flooding projects, which is finding increasing application for tertiary recovery of oil reservoirs. Repetitive very high-density surveys for CO2 and light hydrocarbons could prove to be a major tool for showing the lateral extent and direction of the CO2 flooding fronts extending from the central injection well to the production wells.

It is entirely reasonable to expect that CO2 injected under high pressure in an oil reservoir will exhibit vertical migration through micro-fractures. The molecular weight of CO2 is about the same as Propane, which can easily escape along with heavier Butane to the surface. With flooding, open fractures can act as major conduits for CO2 and light hydrocarbons from the oil reservoir to the surface. Alternatively, closed fractures can act as barriers to the sweeping action of CO2 and a damming effect is likely to be observed.

CO2 SEQUESTRATION

A major benefit from ECBM and EOR projects is CO2 sequestration, which could contribute in a major way to reducing GHG linked to Global Warming. A variation on carbon sequestration - EOR (enhanced oil recovery using CO2) - has been practiced by the petroleum industry, mainly in the USA, for more than 30 years. Therefore, it is likely that a large proportion of early-generation sequestration projects will be implemented in oil and gas fields, where additional oil and gas produced as a result of CO2 injection can offset the costs of injection.

In a carbon sequestration project, the goal is to keep the injected CO2 in the subsurface reservoir. However, improperly plugged wells and faulting/fracturing would cause leakage from a reservoir even before injection. If the reservoir is fractured/faulted, the leakage will be enhanced by pressurizing the reservoir with CO2. Therefore, to know if injection is causing leakage a background database should predate injection.

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