This invention relates to a process for injecting a mixture into the ground to act as a containment/isolation barrier for fluids or gases or to act as an in situ waste remediation process either by biological or chemical means.

The contamination of ground water and subterranean formations are serious environmental problems. There are numerous sites containing toxic substances which are spreading in the ground and into ground water systems. Conventional methods of containing the spreading of these contaminants have involved construction of slurry trenches and pumping/withdrawal of ground water. An object of the present invention is an improved process to contain the spreading of contaminants in the ground and in the ground water systems.

The method of hydrofracing is well known for its use in stimulating petroleum and water wells in consolidated rock formations. The resulting orientation, shape and size of the fractures are not well controlled. An object of the present invention is an improved process to control the orientation, shape, size and aperture of induced fractures in the ground.

It is well known that many contaminants in the ground can be rendered innocuous by bioxidation. However, the mass transfer of oxygen into the ground is limited by the diffusion of oxygen gas, the permeability of the ground and the solubility of oxygen in water. Aqueous solutions of hydrogen peroxide have been used as a source of oxygen for bioxidation. However, the penetration of the hydrogen peroxide into the ground is limited and the release rates and concentration of oxygen in the ground are poorly controlled. Another object of the present invention is an improved process of delivering oxygen, nutrients and microbes to zones of contaminated ground.

Said process comprising the steps of:

pumping a mixture into the ground, so that the injected mixture penetrates from the injection source(s) and controlling the in situ geometry of the injected mixture in the ground by:

1) the shape and type of the injection apparatus,

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2) by interactively modifying the injection pressures and flow rates according to the feedback response from detection monitors, and

3) the physical and chemical composition of the mixture.

In one form of the invention the mixture is injected into the ground by a pneumatic or hydraulic operated pressure vessel; while in another form of the invention the mixture is pumped by a slurry type pump into the ground.

In one form of the invention the mixture is injected into the ground through a borehole; while in another form of the invention the mixture is injected through a lance type system.

Isolation of the injected source(s) in the borehole or lanced ground is made by the means of inflatable packers and/or packed earth.

The mixture is injected into the isolated section of the ground by either single or multiple outlet ports. Each outlet port is attached to a separate inflow line in which the injected pressures and flow rates can be controlled independently. Directional vanes and flexible diaphragms may be installed around each outlet port to isolate the section of the borehole wall or ground each outlet port injects into and to assist in control of injecting the mixture into the ground.

In one form of the invention the mixture would consist of clays or chemical mixtures of extremely low permeability. These mixtures would be injected so that their in situ geometry would provide a hydraulic and contaminant barrier(s) to limit the migration of fluids or gases in the ground. In another form of the invention which may or may not be combined with the one previously mentioned, the injected mixture would consist of oxidants and/or microbes and/or nutrients which may promote the in situ remediation of certain contaminants in the ground.

In another form of the invention the injected mixture would consist of material(s) with adsorptrve/absorptive properties for various contaminants and thus limit their migration in the ground. For ground containing organic contaminants the mixture in one form would contain activated carbon; while for other contaminants alternate substances such as clays and chemicals would be contained in the mixture. The composition of the injected mixture would be adapted to suit the application and/or geological environment and/or the desired in situ geometry of the injected mixture in the ground.

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The mixture in its various forms could be injected either directly or by mixing with water and/or air and injected into the ground either above or below the ground water regime.

Single or multiple injections made in the same borehole or lance at different depths and in neighbouring boreholes provide an overlap and or continuity of the injected mixtures in the ground. Repeated injections in the borehole or lance can extend the injected regime or replenish expended mixture.

In its most common embodiment it is envisaged that various forms of the invention as described in above would be combined to create a complete containment/remediation process for the treatment of contaminated ground.

Other applications for the process may include:

1) the creation of artificial perched water tables, and

2) limiting the up welling of saline waters and providing a contained hydraulic regime for rehabilitation of near surface saline soils.

There are numerous other applications of the invention and the above examples are included to indicate the diversity of the possible applications of the injection process.

The process requires the automatic monitoring of detection devices placed on and/or within the ground around the injection source(s), the monitoring of injection pressures and flow rates; and from inverse calculations the in situ geometry of the injected mixture (size, shape, extent and rate of propagation) is calculated resulting in a computer generated feedback signal to modify the injection pressures and flow rates, and thus develop an injected geometry optimum for the containment or remediation application.

In one form of the invention the detection devices are surface or borehole mounted high precision tiltmeters with an analog or digital output signal depending on the degree of tilt of the device. The tiltmeters are monitored to enable the integration of tilt with time and computation of ground movement. In another form of the invention, the detection devices are electrical probes monitoring the induced voltages from current source electrodes, which are placed in the ground around the injection source(s). In another form of the invention, the detection devices are surface and/or borehole mounted accelerometers providing an output analog or digital signal of

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ground motion in either two horizontal and/or the vertical direction(s). The accelerometers monitor the seismic response of the ground from active seismic sources, such as sparkers or magnetostrictive type sources placed in the ground around the injection source(s), or from active pulsating of the injected mixture in the ground.

Injection flow rates are monitored by appropriate flow rate devices depending on the mixture being injected and the method of injection. In one form of the invention the flow rate devices are direct in tube flowmeters; while in alternate forms the flow rate devices are external sonic or magnetic flowmeters. Irrespective of the form of the flowmeters, the flow rate devices output an analog or digital signal dependent on the flow rate. Flow rate devices are monitored to enable the injected volumes to be calculated by integrating the flow rates with time. Injection pressures are monitored by appropriate pressure devices either of the fluid, gas or inert type depending on the injected mixture and method of injection. The injection pressure devices output an analog or digital signal dependent on injection pressure.

In the case of tiltmeter detection devices, an inverse method using ground movement influence functions is used to compute the injected mixture in situ geometry. Ground movement influence functions relating the influence of an elementary area of injected mixture lying in a horizontal or inclined plane of a particular thickness to ground tilt and movement can be formulated from the ground deformational behaviour. From monitored ground tilts and injected flow rates and volumes, the in situ geometry and the rate of propagation of the injected mixture in the ground can be calculated by an inverse method of the influence functions constrained by the monitored injected flow rates and injected volumes.

In the case of electrical probe detection devices, an inverse and or tomographic method using ground potential influence functions is(are) used to compute the in situ geometry of the injected mixture. While in the case of accelerometer detection devices, an inverse and/or tomographic method using ground seismic wave influence functions is(are) used to compute the in situ geometry of the injected mixture. For whatever type of detection device, the in situ geometry of the injected mixture must be computed during the injection process to enable a feedback response to the injection system to modify the injected pressures and flow rates.

From the inverse and/or tomographic method described above, the injection pressures and flow rates required to modify the in situ injected geometry are calculated

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and controlled by feedback signals to the injection system and/or operator. The type of in situ injected geometry required, greater thickness or greater lateral extent or vertical/horizontal propagation, is achieved by appropriate injection pressures and flow rates depending on ground behaviour, mixture type and characteristics and injection method. The calculation of these injection pressures and flow rates involves the sequential calculations of the in situ geometry of the injected mixture during the injection process.

To assist with understanding the invention, reference will now be made to the accompanying drawings which show one example of the invention.

In the drawings:

Figure 1 shows one example of a system for the installation of an injected mixture according to this invention;

Figure 2 illustrates the form of a near horizontal injected geometry extending radially from a section of the borehole isolated by packers.

Figure 3 illustrates the method of overlapping and/or intersecting injected geometries to confine or remediate the contaminated ground;

Figure 4 illustrates the form of intersecting and/or overlapping injected geometries from vertical boreholes.

Figure 5 illustrates the form of intersecting and/or overlapping injected geometries from horizontal boreholes.

Figure 6 shows the computer control and monitoring instrumentation to control the injected geometry rate of propagation, its size, shape and extent.

Referring to Fig. 1 it can be seen that a vertical borehole is sectioned off by a system of inflatable packers 1, between these packers are the injection outlet ports 2, shown in this example as four ports, with radial isolation vanes 3, and flexible diaphragms 4, for independent control of injection pressures and flow rates in different directions. These injection outlet ports are connected to the pumping system 5 by flow lines 6, with pressure and flow rate monitoring devices

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6 PCI7AU93/00104

7 mounted on the flow lines and connected to a computer 8, surface or borehole mounted tiltmeters 9 are connected to the computer, and the computer provides a display of the barrier geometry and feedback control 10 to the pumping system 5, and control values 11 , to control pressures and flow rates and thus control the geometry of the injected mixture in the ground. An alternate down the hole injection system is shown with multiple outlet ports 12, connected to the pumping system 5 by flow lines 6, with a flexible flange 13 embedded into the ground by packed earth 14.

The pressures in the injection system are raised to initiate the fracture of the ground thus forming a crack for the mixture to propagate along. The tiltmeters and injection pressures and flow rates are monitored and from inverse calculations of these responses and their integration with time; the rate of propagation, size, shape and extent of the injected regime is determined and the injected geometry is controlled by computer generated feedback response to the operator and the pumping system to modify the injection pressures and flow rates.

Referring to Fig 2. it can be seen that a region of the borehole 1 is isolated by inflatable packers 2. The mixture is injected into this region 1 by flow lines 3. The injection pressure is raised to initiate a fracture in the borehole wall and injection pressures and flow rates modified to control the rate of propagation and geometry of the in situ injected regime 4. The extent, orientation and thickness of the injected regime can be altered by appropriate variations of injection pressures and flow rates resulting in near horizontal type geometry as shown in Fig.2.

Referring to Fig.3 it can be seen that by developing injected geometries at neighbouring boreholes 1 , either overlapping 2 or intersecting injected regimes 3 can be formed in the ground. Multiple injected regimes at different depths can be formed to enhance the confining or remediation applications of the invention.

Referring to Fig.4 vertical injected geometries 1 , are injected from vertical boreholes 2 to form an overlapping and/or intersecting vertical injected geometry. Horizontal injected geometries 3, are injected from vertical boreholes 4, to form an overlapping and/or intersecting horizontal injected geometry.

Referring to Fig.5 vertical injected geometries 1, are injected from a horizontal borehole 2, to form an overlapping and/or intersecting vertical injected geometry.

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Horizontal injected geometries 3, are injected from horizontal boreholes 4, to form an overiapping and/or intersecting horizontal injected geometry.

Referring to Fig. 6 high precision tiltmeters 1 are installed on the surface and/or mounted in boreholes and connected by signal conditioning circuitry 2 and 3 to a high speed analog to digital interface board 4 installed into a field computer 5. Pressure and flow rate monitoring devices 6 and 7 are connected to the computer by signal conditioning circuitry 8 and 9 and the high speed analog to digital interface board. Software installed on the computer automatically scans and monitors these devices and from their response; the software calculates and displays the injected regime's rate of propagation, size, shape and extent and then computes the changes required in pressures and flow rates to achieve a particular injected geometry. These changes in pressures and flow rates are displayed to the operator and automatically interfaced 10 to the pumping system 11 and control values 12 by feedback analog signals from the computer's analog to digital interface board 4. These signals modify the pumping system to achieve the particular injected geometry and/or enable the operator to manually override the process.

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