Field:

The invention relates to wellbore imaging tools and methods and, in particular, for improving wellbore imaging operations where there is water in the wellbore.

Background:

The present applicant, Novamera Inc., is developing tools to enable commercial adoption of various surgical mining, also known as mining by drilling, methodologies. Reference is made for example to the applicant's earlier applications WO 2020/172736 and WO 2021/168591.

To enable surgical mining, it is critical to be able to identify and accurately define the boundaries of an orebody prior to its extraction. Defining the boundaries of an orebody can be done using geophysical tools. One such geophysical tool primarily uses down hole electromagnetic technologies.

Some geophysical methods, such as those employing electromagnetic technologies, are impacted by the presence of a liquid, such as water, with a different dielectric permittivity than the lithology. One such impact is the ability to acquire usable inform ation/data due to the interference and noise generated by water or water-based drilling fluids present in a borehole.

To overcome the problems of geophysical analysis in a water-filled hole, current methodologies include dewatering the hole prior to capturing images with the geophysical tool. However, this dewatering operation can have problematic safety and environmental impacts. Removing and transporting groundwater can present environmental concerns and is labor-intensive work in and around the drill rig.

Dewatering is also impractical. There is a large amount of water to remove in order to empty a borehole and there are physical depth constraints on maximum depth possible for pumping. If natural ground water exists, then the hole will quickly refill as soon as pumping stops.

Summary:

In accordance with a broad aspect of the present invention, there is provided: a water exclusion apparatus for a geophysical imaging tool, the water exclusion apparatus configured to be placeable around an exterior surface of the geophysical imaging tool and being operable to force at least some water away from the exterior surface of the geophysical imaging tool.

In accordance with another broad aspect of the present invention, there is provided: a method for preparing a geophysical imaging tool for operation in a borehole, the method comprising: positioning a geophysical imaging tool in a well and removing water from an annular area around the tool, without removing all the water in the borehole above the tool.

In one embodiment, removing the water may include operating a water exclusion apparatus that is positioned in the annular area to force at least some water away from the exterior surface of the geophysical imaging tool.

In another embodiment, removing the water may include positioning a seal in the annular area at or above an upper end of the tool and pumping out water from below the annular seal.

In accordance with another broad aspect of the present invention, there is provided: a water exclusion apparatus for a geophysical imaging tool, the water exclusion apparatus configured to be placeable around an exterior surface of the geophysical imaging tool and being operable to force at least some water away from the exterior surface of the geophysical imaging tool.

In accordance with another broad aspect of the present invention, there is provided: a method for preparing a geophysical imaging tool for operation in a borehole, the method comprising: positioning a geophysical imaging tool in the borehole and manipulating a water exclusion apparatus to remove water from an annular area around the geophysical imaging tool, without removing all the water in the borehole above the tool.

In accordance with another broad aspect of the present invention, there is provided: a wellbore tool for geophysical survey comprising: a geophysical imaging tool including a housing with an interior chamber and an exterior surface radially outwardly of the interior chamber; geophysical survey equipment within the interior chamber; and a water exclusion apparatus coupled to the housing, the water exclusion apparatus being operable to force at least some water away from the exterior surface of the geophysical imaging tool.

It is to be understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments of the invention are shown and described by way of illustration. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modification in various other respects, all within the present invention. Furthermore, the various embodiments described may be combined, mutatis mutandis, with other embodiments described herein. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

Brief Description of the Drawings:

Referring to the drawings, several aspects of the present invention are illustrated by way of example, and not by way of limitation, in detail in the figures, wherein:

Figures 1A and 1 B are schematic side views of a water mitigation solution in a wellbore using an upper seal to create an air gap in which a downhole imaging tool can operate. Figure 1A shows the upper seal in an annulus between a downhole tubular structure and the wellbore wall. Figure 1 B shows the upper seal in an annulus between an imaging tool and a downhole tubular structure.

Figure 2A, 2B and 2C are schematic views of a water exclusion apparatus in the form of an expandable sleeve on a downhole assembly for an imaging tool. Figure 2A shows a side view of the expandable sleeve in place on the end of a downhole imaging assembly. The sleeve in Figure 2A is not yet expanded. Figure 2B shows the expandable sleeve expanded by insertion of the imaging tool therein. Figure 2C is an orthogonal section through an expandable sleeve expanded by insertion of the imaging tool therein.

Figure 3A and 3B are schematic side views of a water exclusion apparatus in the form of an oil-filled expandable sleeve on a downhole imaging assembly. Figure 3A shows the expandable sleeve in place on the end of a downhole imaging assembly ready for expansion and Figure 3B shows the expandable sleeve expanded by insertion of the imaging tool therein.

Figures 4A and 4B are perspective views showing a water exclusion apparatus including a spring. Figure 4A depicts the imaging tool and spring in the run in position and Figure 4B is the imaging tool and spring in the water-excluding position.

Figure 5A and 5B are schematic side views of a borehole that includes a downhole imaging tool in place therein. The imaging tool has a water exclusion apparatus in the form of an inflatable packer. Figure 5A shows the inflatable packer in place as part of a downhole imaging assembly but not yet inflated and Figure 5B shows the inflatable packer of Figure 5A inflated and acting to exclude water from the annular area around the imaging tool sensors.

Figures 6A to 6C are side views of a downhole imaging tool with a water exclusion apparatus in the form of an inflatable packer. Figure 6A shows the inflatable packer on the imaging tool but not yet inflated. Figure 6B shows the inflatable packer in place in a borehole as part of a downhole imaging assembly, but the packer is not yet inflated. Figure 6C shows the installation of Figure 6B with the packer inflated and acting to exclude water from the annular area around the imaging tool sensors.

Figure 7 shows results from Example I, which is a graph showing signal-to-noise ratio for different borehole scan conditions referenced against scans in air.

Figure 8 shows results from Example I, which is a graph showing energy at the borehole/formation interface for different borehole scan conditions.

Detailed Description:

The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

To address the problems with geophysical survey in an environment containing a liquid with a different dielectric permittivity than the lithology, methods and apparatus have been invented to remove the liquid in the hole at the location where the imaging, such as an electromagnetic, tool is operating. While other liquids may be present that have a different dielectric permittivity than the lithology, typically the liquid is water, including introduced or naturally occurring fresh or salt water or water-based drilling fluids. In the following description, therefore reference to water is intended to encompass any liquid that has a different dielectric permittivity than the lithology.

In such a solution, water may remain in the borehole below and above the tool. For example, while water is removed from an annular space between the imaging tool and borehole wall, water may remain between the tool and the surface of the borehole, which is often referred to as the borehole above, or uphole of, the imaging tool.

These solutions can be adapted to work for all drilling methodologies i.e., core drilling, rotatory drilling and percussion drilling, including those useful for surgical mining. A common approach for surgical mining, as described in applicant's above noted international patent applications, is to deploy an imaging tool via a drill pipe. In one embodiment, the borehole may be drilled with a core bit installed on the end of a core barrel, which is installed on the end of a drill pipe. In such an embodiment, when it is desired to image the borehole, the imaging tool can be run in through the drill pipe inner diameter and operated at an end of the core barrel. In one embodiment, the imaging tool is extended through the open port of the core bit. While this drilling assembly and method is described below, it is to be appreciated that the methods and tools described herein may be applicable to other drilling assemblies, imaging assemblies and methods. In this description, sometimes, core barrel, drill string and drill pipe are used interchangeably.

With reference, for example, to Figures 1A and 1 B, in one embodiment, the water W is removed for imaging by positioning a seal 10a, 10b in an annular area at or above an upper end of a signal generating/receiving portion of an imaging tool 12 and pumping out water from below the annular seal. This permits the formation of an air gap 14a, 14b in which the imaging tool can operate.

For example, Figure 1A illustrates that annular seal 10a may be positioned to form a seal between a wellbore wall 16 and a structure within the wellbore, such as for example, a drill pipe 18 on which or below which the imaging tool 12 is positioned. While the seal is illustrated on the drill pipe, it could be on the imaging tool. This solution includes sealing the annular area between the drill pipe and borehole wall around the area of the drill bit and then pumping the water from below the seal upwardly to a position in the well above the seal or to surface. This solution creates air gap 14a in which the sensors of the imaging tool can operate. Depending on how much water is pumped out, the air gap 14a will be below seal 10a and above a surface level W or the bottom of the hole. Water W remains in the wellbore above seal 10a. The tool 12 can be protruded from the end of the drill pipe 18, through an open passage 20 of a core bit 22 and can be operated in the air gap. Figure 1 B illustrates that the annular seal 10b may be positioned to form a seal while the imaging tool 12 remains positioned within another structure such as a drill pipe 18.

In this solution, the imaging tool 12 can be maintained completely inside the drill pipe and the air gap 14b can be created inside the drill pipe. In particular, an upper seal 10b can be set in the drill pipe above the imaging sensors 12a portion of tool 12. To prevent water from reversing to fill the air gap, a lower seal 10c can be set in the drill pipe below the tool, for example at a lower end of the imaging tool or at the drill bit. Then the water is pumped out of the drill pipe in the space between upper and lower seals 10b, 10c.

This solution requires a section 18a of drill pipe 18, for example a section at or near the core barrel when core drilling, to be made out of a mostly nonmagnetic and mostly nonconductive material such as fiberglass.

This solution would create an air gap 14b for the sensors of the imaging tool to operate inside the drill pipe between the lower and upper seals.

In another embodiment, a water exclusion apparatus may be employed to remove water from the hole around the imaging tool. In one embodiment, the water exclusion apparatus is an expandable member, for example, a member that can expand by swelling, inflation, physical force such as compression, insertion or sleeving, etc. The expandable member can be an inflatable packer (sometimes herein referred to as a bladder), an expandable sleeve or a coil spring.

In a method using a water exclusion apparatus, the water exclusion apparatus is positioned around the tool. The apparatus may already be in position on the tool when the tool is deployed, or the apparatus and imaging tool may be manipulated to position the apparatus around the tool when the tool is already downhole.

When it is desired to operate the tool to make a geophysical survey, the water exclusion apparatus is operated to remove water from the hole around the tool. Operation may include expanding the apparatus to displace water from the area accommodated by the operation of expansion. Expansion may be various means depending on the type of apparatus being employed and for example, may include swelling, inflation, compression, filling or sleeving.

To facilitate operations, it is useful if the water exclusion apparatus is not normally expanded, but has a normal diameter smaller than the borehole in which the survey tool is to be used. It is submitted that the water exclusion apparatus can be expanded to a large diameter that forces water away from the outer diameter of the tool when the tool is going to conduct a survey. Then, after the survey, the water exclusion apparatus can be returned to a smaller diameter, which is smaller than the large diameter and possibly about the same as the normal diameter. In this way, the presence of water around the imaging tool is only impacted during operation, for example expansion, of the water exclusion tool. Also, the normal diameter of the water exclusion tool is normally small enough to readily pass through the borehole and possibly even pass through a string in the borehole.

In one embodiment, the large diameter is slightly smaller than the borehole diameter. As such, the water exclusion apparatus excludes most of the water around the imaging tool, but the water exclusion apparatus remains free of engagement against the borehole wall.

In another embodiment, the large diameter is about the same as the borehole. In such an embodiment, the water exclusion apparatus, when expanded can engage against the borehole wall. This means that the water exclusion apparatus may be fixed against rotation and axial movement relative to the borehole wall. In such an embodiment if desired, a coupling, if any, between the water exclusion apparatus and the imaging tool can be configured to permit the imaging tool to rotate within the water exclusion apparatus.

One example of a water exclusion apparatus, is illustrated in Figures 2A to 3B. In this embodiment, the water exclusion apparatus is an expandable sleeve 26. This expandable sleeve 26 is positioned relative to the imaging tool 12 such that the sleeve can be expanded by inserting the imaging tool into the sleeve. The expandable sleeve 26 can be, for example, an elastomeric tube, for example, formed of rubber.

With reference to Figures 2A to 2C, for example, in operation, expandable sleeve 26 is positioned in the well ahead of or along with the imaging tool 12. When it is desired to conduct an imaging routine, at least the portion of imaging tool 12 that includes the imaging emitters/receivers 12a is inserted into the inner diameter of the expandable sleeve 26. This insertion operation forces the expandable sleeve to expand (Figures 2B and 2C) and the expansion displaces the water from around the expanded sleeve and thereby from around the tool imaging electronics 12a within the sleeve.

The expandable sleeve can be run in separately from the tool or in one embodiment, the expandable sleeve is coupled to the end of the imaging tool and together they are run in to the position where the imaging tool is to be operated.

In the method, as described above, where the imaging tool is inserted out through the end of the drill string, the rubber sleeve, which may be coupled to the end of the overall imaging tool, is lowered down the drill pipe 18 until it reaches the bit 22. The sleeve 26, which is ahead of and extends beyond the end of the imaging tool 12, is the first to pass through the bit (Figure 2A). Once the sleeve/tube passes through the bit, the top of the sleeve is retained by the bit and the tool is then forced into the inner diameter of the sleeve/tube. The action of the tool being forced into the sleeve/tube expands the sleeve/tube, which then displaces the water from around the tool (Figures 2B and 2C). The tool sensors 12a are positioned within the sleeve below the drill pipe. When the imaging process is complete, the imaging tool can be pulled out of the sleeve, thereby allowing it to retract. The tool and the empty sleeve can be pulled out of the hole.

With respect to the embodiment of Figure 2C, sleeve 26 has two elongate parts with an inner opening between them. Some imaging tools have sensors that emit and receive outwards perpendicular to the hole mostly in one direction. In such an embodiment, it is not necessary to displace the whole annulus of water around the tool. Therefore, the sleeve may include a plurality of spaced apart elongate parts that are configured to be positioned on at least either sides of the tool just to keep it mechanically stable, the sensor images through only at least one of the parts. In such an embodiment, there may be an alignment mechanism to ensure that the imaging tool can only go into the sleeve in a position the sensor emitting direction is radially aligned with the sleeve part.

As shown in Figures 3A and 3B, another expandable sleeve 26 may be filled with a lubricant such as oil 28. The oil may facilitate handling of the sleeve, as it may be heavier and may be more rigid than an empty elastomeric sleeve. The method of use is substantially similar to the description above in respect of Figures 2A to 2C, but insertion of tool 12 into the inner diameter of expandable sleeve 26 moves the oil out to an annular area between the tool 12 and the sleeve.

The oil can be any of petroleum oils or plant oils, provided they do not significantly degrade electromagnetic signals. In one embodiment, the oil has a relative dielectric permittivity of between 2 and 5. In one embodiment, the oil is a plant-based oil such as canola oil, which has a relative dielectric permittivity of around 2.5 to 2.7. In one embodiment, the oil is castor oil, which has a relative dielectric permittivity of around 4.1 to 4.3. While other plant based oils could be used, it is the dielectric constant of the oil that is to be considered. Canola and castor oils have a good dielectric constant at borehole conditions.

Regardless, deployment of this solution is similar to that of Figure 2 where the action of imaging tool 12 being forced into the sleeve, as it is retained against movement, expands the sleeve downhole of the bit and displaces the water out of the annular area that is laterally about the side walls of the sleeve. The sleeve's expansion, therefore, excludes at least some and possibly all of the water from between the tool and the borehole wall 16.

Another embodiment of a water exclusion apparatus is illustrated in Figures 4A and 4B. In this embodiment, the water exclusion apparatus is a spring 30. The spring can be for example a coil spring with an open inner diameter. An imaging tool 12 can be aligned with or positioned within the open inner diameter. When the spring is uncompressed as in Figure 4A, it has a normal diameter smaller than the borehole in which the imaging tool is to be used and possibly even small enough to pass through a string in the borehole, such as drill pipe 16. Spring 30 can be expanded to a larger diameter by compression, for example by compressing at least one of the spring's ends towards the other (arrow A).

Spring 30 can be formed of a material that is transparent to imaging signals such as an elastomer and of course is plastically or elastically flexible.

As with the expandable sleeve, spring 30 is installed around the imaging tool at least while imaging. So the spring can be positioned downhole near to the imaging tool or coupled onto the imaging tool, for example coupled to an end of the overall imaging tool.

In operation where a drill string 16 is employed, the imaging tool 12 and spring 30 are lowered down the drill pipe, with the spring in an uncompressed, stretched state, until they reach the bit. The spring, which remains in a stretched state, and the tool are moved to protrude through the end of the drill string 16. The spring may then be compressed from its stretched state (Figure 4A) to a compressed state (Figure 4B) where the turns are compressed close one against the other. When compressed, the imaging tool is in the inner diameter of the coil spring, with the spring coils wrapped about the outer cylindrical surface of the imaging tool. When in the compressed state, the spring coils compress together to displace water away from the exterior of the tool.

The spring can be driven to compress in various ways. In one embodiment, for example, the spring is coupled to the imaging tool such that the imaging portion of the imaging tool is aligned with or installed within the interior of the coil spring, but the spring in the relaxed, stretched state extends beyond the distal end of the imaging tool. The spring, therefore, is the first to pass through the bit and then the imaging tool, aligned with or within an upper end of the spring, passes through the drill bit.

Then, the spring is compressed, which forces the imaging tool into the inner diameter, if it is not already there, between the closed coils of the spring 30.

The compression action is by forcing at least one end axially toward the other. In one embodiment, there may be a driver for driving one or both retainers 32a, 32b at the ends of the spring axially towards the other. In another embodiment, once the end of the tool starts passing through the bit, the end of the spring contacts the bottom of the drilled hole. The action of the tool being forced further through the bit then compresses the spring, which in turn compresses and expands the spring around the tool.

The fully compressed spring circumferentially surrounds the imaging portion of the tool and displaces the water from around the tool.

If desired, after the survey operation, the coil spring 30 can be uncompressed and the imaging tool and the spring can be pulled out of the borehole.

Another embodiment of an imaging tool with a water exclusion apparatus, is illustrated in Figures 5A and 5B, where the water exclusion apparatus is an inflatable packer. An inflatable packer includes an inflatable and expandable bladder 40, also called a packer element. The bladder is a cylindrical length of flexible material, closed at the ends and which is inflatable with an inflation fluid from an inflation system. The illustrated packer has a closed loop inflation system with a fluid chamber 44. Bladder 40 has an inner space that is configured to receive the portion of a downhole imaging tool 12 that contains the sensor electronics 12a. Bladder 40 surrounds the outer diameter of imaging tool 12 and is substantially coaxially arranged at the location of the sensor electronics. The bladder 40 may be coupled to the imaging tool and the fluid system 42 may be coupled to, for example, integrated into a housing body 46 of the overall down hole imaging tool 12.

The inflation fluid system may be manipulated downhole to inflate the bladder. For example, the inflation fluid system may be manipulated by adjusting fluid pressure in the wellbore, for example, by applying a fluid pressure to a fluid pressure responsive driver such as an inflation piston 48 or diaphragm. Inflation piston 48 can be contained with housing 46 and is in communication to wellbore pressure via fluid ports 49. When the fluid pressure responsive driver is actuated by fluid pressure, it reduces the volume of chamber 44 and inflation fluid 45 is then communicated for example forced through fluid channels 50 that open within bladder 40. The fluid is introduced into the annular space between the bladder and the tool 12. This operation inflates the bladder. The inflation fluid can be any of various incompressible fluids that do not significantly degrade electromagnetic signals. In one embodiment, the inflation fluid is an oil, such as a plant-based oil. As noted above, castor oil or canola oil is a good inflation fluid.

The material of the packer bladder as well is selected not to significantly degrade electromagnetic signals. Therefore, metallic or conductive reinforcements, etc. should be avoided.

Piston 48 may be biased into the deflated position, if desired. Regardless, the fluid system is closed loop so that the inflation fluid 45 remains in the tool before, during and after inflation.

Other forms of manipulation may be of interest, such as electric drivers, but fluid pressure actuated systems are reliable.

The illustrated tool of Figures 5A and 5B is configured for running in and operating at a distal end of a drill string, such as for example in a drill pipe or core barrel 18. The tool may have a locking mechanism 52 for locking the tool in the drill pipe. If so, the locking mechanism may be selected depending on the locking installation already in the drill pipe.

The tool may be configured to receive fluid pressure signaling. For example, the tool 12 may include an annular landing seal 54 for landing on and sealing in the opening 20 through the core barrel. Thus, any fluid introduced to the drill string is sealed within the core barrel and a pressure within the core barrel can be elevated to actuate the inflation fluid system.

The imaging tool 12 may also be configured to move with the drill string. For example, there may be a connection, such as a faceted (i.e. splined, hex, latched) connection, at locking mechanism 52 or at the tool near landing seal 20 for rotationally locking the tool body in bit 22 to move with the drill string 18.

In one drilling system embodiment, as illustrated, an imaging tool may be operable by running in through a drill pipe 18 that is in a bore hole 16. Specifically, in such a drilling system, the imaging tool is lowered down the drill pipe until it reaches a core barrel where it is mechanically locked in place with part of the tool protruding through the drill bit and out through the end of the drill pipe.

The electromagnetic sensors 12a are in the section of the tool that protrudes out beyond the end of the drill bit.

The packer bladder 40 is a cylindrical, flexible membrane coupled about the imaging tool. For example, the sensor carrying portion of the tool can be fully encased by the packer bladder. During run in, the bladder is deflated so that it has an outer diameter, just larger than the outer diameter of tool at sensors 12a. This diameter is small enough to pass through the drill string inner diameter and through the opening 20 at the end of the drill string.

Once the imaging tool is locked in place and the landing seal 54 is sealed against the inside of the drill bit (Figure 5A), fluid pressure is increased in the inside of the drill pipe by the driller on surface, as by water or drilling fluid introduction. The fluid pressure rises inside the drill pipe and is communicated to the piston 48 via ports 49. This pressure compresses the piston and therefore injects the fluid 45 from the imaging fluid chamber 44 into the packer bladder 40 (Figure 5B).

As the fluid enters the packer bladder, it will stretch and expand the outer diameter of the packer bladder as far as the bladder materials and fluid system is designed to allow. This inflation displaces the water from around the tool and up the hole.

Once the packer has been inflated, the electromagnetic imaging sequence can occur using sensors 12a in cooperation with processing and communication electronics 56. There is less, and possibly little to no water around, for example radially between the sensors 12a and borehole wall 16. Therefore, the scan results are improved over a water scan where the water remains around the tool sensors 12a. If there is little to no water, there are minimal effects to the data captured by the sensor compared to a scan done in air. The degree to which the bladder is inflated may be selected based on the desired operations of the tool. In one embodiment, for example, the bladder, the fluid system and/or the method of operation control the degree to which the bladder can be inflated. In one embodiment such as that illustrated in Figure 5B, the inflated diameter is slightly smaller than the borehole inner diameter. As such, the packer excludes most of the water around the imaging tool sensors 12a, but the water exclusion apparatus remains free of engagement against the borehole wall. The packer or method may be selected such that a space of less than 1cm, such as less than 5mm, remains between the bladder 40 and the borehole wall 16. One way to achieve this is by controlling the volume of inflation fluid in the imaging tool. If more oil is added to the system, then the packer will inflate to a larger diameter. The final diameter of the packer bladder can be tuned by adding or removing oil from the system before sending the tool down hole.

In such a method, even after the bladder is fully inflated, the drill string 18, and thereby the attached imaging tool 12, can be moved axially or rotationally within the borehole. Thus, the imaging tool can be rotated to obtain a scan along a particular direction, and/or the tool can conduct rotational scans, sometimes called lighthouse scans, and/or scans at a number of axially spaced apart locations or while axially moving the tool and sensors 12a.

In another embodiment, the inflated diameter can be about the same or greater than the borehole inner diameter. In such an embodiment, the packer bladder, when expanded, can touch, for example engage against, the borehole wall. This engagement means that the packer bladder may be fixed against rotation and against axial movement relative to the borehole wall. In such an embodiment if desired, there may be annular bearings 58, between the bladder 40 and housing 46 that are configured to permit the imaging tool to rotate within the bladder. With such bearings 58, when the bladder is fully inflated, the drill string 18, and thereby the attached imaging tool 12, can be moved rotationally within the borehole tool, while the bladder remains fixed in its rotational and axial location. Thus, the imaging tool can be rotated to obtain a scan along a particular direction, and/or the tool can conduct rotational scans, sometimes called lighthouse scans. Once the imaging sequence has been completed, the driller on surface can remove the pressure in the drill string, which causes the fluid to be drawn back into the imaging fluid chamber. Therefore, the outer diameter of the packer will reduce back to its starting size.

The tool can then be unlocked and the tool and the deflated packer can be removed from the drill pipe string as normal.

Major benefits of this solution when compared to the above-described background art are as follows:

- Very fast to inflate packer and displace all water from around the electromagnetic tool. Deflation is also very fast, so that the well circulation can be reinstated quickly;

- Very practical and safe to use as it requires little, if any, additional equipment or activities on surface around the drill rig;

- Can be a very simple mechanical design that requires no electronics to deploy and to carry out water exclusion, although electronics could be employed if desired; and

- Little chance of adverse environmental impacts as all inflation fluid remains in a closed loop system and is never discharged into the environment. If desired, an inflation fluid can be selected that is environmentally neutral and possibly one that has good signal transmission.

With reference to Figures 6A to 6C, another imaging tool with an inflatable packer is shown. The imaging tool 112 of Figures 6A to 6C is similar to that of Figures 5A and 5B, but a few optional features are noted.

For example the tool of Figures 6A to 6C includes a fluid pressure responsive driver in the form of a diaphragm 148 in chamber 44. Diaphragm 148 acts like a balloon and is expanded by fluid pressure communicated from the exterior of the tool through ports 49 to reduce the volume of chamber 44. When diaphragm 148 is expanded, it operates in the same way as piston 48 described above, to expel fluid 145 from chamber 44, move it through channels 50 to inflate bladder 40.

The landing seal 154 is mounted via a shock absorber spring 155 to housing 146. Spring 155 is a coil spring through which landing seal 154 can move axially along the outer surface of the tool. The spring is configured to reduce shocks when landing seal lands against the bit opening 20 and when pressuring up the drill string inner diameter. Spring 155 also biases the landing seal to remain pressed against the bit to ensure a tight seal is maintained.

The tool 112 includes a fluid bypass 160 to facilitate operations of the tool in the well. Fluid bypass 160 is a fluid conduit extending through the tool housing 146 with an inlet 160a below and an outlet 160b above landing seal 154. A check valve 162 is positioned in the bypass conduit between the inlet and the outlet. The check valve permits flow through the conduit from inlet 160a to outlet 160b, but can stop reverse flow, for example, beyond a predetermined pressure. Therefore, when landing seal 154 creates a seal against core barrel 18, fluid can flow from outlet 160b to 160a if the pressure P1 is below the predetermined pressure. For example, natural gravity equalization (P1 =P2) can occur across valve 162 (Figure 6B). However, pressures P1 above the predetermined pressure above can be stopped by valve 162 from passing down through the bypass conduit (Figure 6C). However, fluid pressure and excess water P2 below the landing seal can be relieved by passing up through bypass 160. This facilitates movement down of the drill string and alleviates overpressure situations, while still permitting drill string fluid pressure manipulations.

For example, in one embodiment when a driller communicates water pressure on surface and a curtain flow is reached, the check valve will block the flow and then the pressure in the pipe will start to rise until it reaches a max pre-determined value. At a certain pressure, the inflation system will inflate the packer. Once the imaging is done and the tool needs to be removed, the driller turns off the water on surface then the valve will pop and allow pressure inside and outside the drill pipe to equalize so that the whole tool can be pulled out.

The portion of the tool housing that carries the sensors is formed as a mandrel 146a with cavity that accommodates a core 112a that houses the sensors. The core may be water tight and substantially transparent to electromagnetic signal, such as of fiberglass. Wire ways 164 connect the sensors and electronics within core 112a to electronics nearer an upper end of the tool.

Bladder 40 is secured to encircle the mandrel 146a via a top sub 166a and a bottom sub 166b. When the bladder is inflated via fluid passing through channel 50, bottom sub 166b slides along the mandrel to accommodate the bladder expansion. Seals 168a, 168b seal the inflation fluid within the bladder. Top sub 166a and bottom sub 166b are each rotatable about mandrel 146a, while seals 168a, 168b maintain the oil sealed within the interior of bladder.

While various tool and method embodiments have been described, elements thereof can be combined in various ways.

The following examples are not intended to be limiting, but simply illustrate aspects and benefits of the invention.

Example I - Field Tests with Ground Penetrating Radar

At a private site in Newfoundland, Canada, tests were conducted in a borehole drilled in mafic/quartz rock. The borehole was 75.7mm in diameter. The ground penetrating radar sensor measured 47 mm outer diameter and was housed in a polyvinylchloride plastic pipe of outer diameter 60.33 mm. The tool had a 500 MHz ground penetrating radar sensor configuration.

The tool as described above was used to obtain results without any water exclusion apparatus (Tool A). A tool as described above was further wrapped with a 3 mm thickness of polyvinylchloride plastic film to provide an outer diameter of 71.01 mm (Tool B). The interface between the sensor and the interior of the plastic wrap was filled first with air and then with canola oil.

Two further test tools (Tool C) were constructed as above, but the tools were wrapped with 6mm of the plastic wrap instead of 3mm.

All tools were tested at the same depth in the same borehole. The borehole at the test depth was naturally filled with fresh ground water. For some tests, the borehole was evacuated of all liquids such that the borehole contained only air.

Tests were conducted using static scans. Static scans are where the data collection is along the same direction. In particular, once in place, the tool is not moved and the signal receiving component acquires data only along one direction.

Based on the borehole having a diameter of 75.7mm, during the tests the Tool A (the without any plastic wrap) is surrounded in the borehole by an annular space with a radial measurement of 7.7mm - either filled with air or filled with water, depending on the test. The tools with a 3mm wrap have a radial measurement of 4.7mm external to the plastic wrap and the tools with a 6mm have a radial measurement of 1.7mm between the tool and the borehole wall.

The following tests were conducted:

• Tool A in water filled borehole (full water);

• Tool A in air filled borehole (full air);

• Tool B with air fill - in water (air - 2mm water);

• Tool B with oil fill - in water (oil - 2mm water);

• Tool C with air fill - in water (air - 5mm water); and

• Tool C with oil fill - in water (oil - 5mm water).

The data for Tool A full water and all data for Tools B and C were analyzed against the Tool A air filled data for signal to noise ratio (SNR entire data space, SNR v. water thickness - Ref. signal: Air). Results are shown in Figure 7, wherein the significant improvement of Tools B and C over Tool A full water is readily appreciated. 'First Arrivals' is the portion of the signal that goes directly from transmitter to receiver and/or the signal that reflects off the immediate interfaces around the sensor i.e. the plastic pipe or the hole wall. The first arrivals are, therefore, not considered to be signal that goes out into the geology and back to the receiver. The "First Arrivals" data is, therefore, ignored.

The data was also analyzed for energy strength at the detected interface with the formation. The energy strength at the interface is calculated considering a window 5ns above and 5ns below the maximum energy peak. Because the scan acquired for Tool A air filled is considered the baseline, this metric serves to quantitatively visualize the performance of other conditions in terms of imaging relative to Tool A air filled. Ideally, the strength at the interface is close to that of the air scan (i). Figure 8 shows the energy profiles of the six tool conditions. The decay in energy strength of Tools B and C are each less than 30% compared to Tool A full air. The scan Tool A full water differs 230% from the scan Tool A full air.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article "a" or "an" is not intended to mean "one and only one" unless specifically so stated, but rather "one or more". All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 USC 112, sixth paragraph, unless the element is expressly recited using the phrase "means for" or "step for".