Patent Description:
Reference to background art herein is not to be construed as an admission that such art constitutes common general knowledge in Australia or elsewhere.

Drilling and blasting is the controlled use of explosives to break rock for excavation. It is practised most often in mining, quarrying and civil engineering applications such as dam and road construction.

Typically, a drill crew will undertake a campaign of drilling the blast holes to a predetermined depth and in a predetermined pattern. The depth of each hole and the blast hole pattern is designed with particular care by the drill and blast engineering team to obtain the desired excavation of ground.

After the drill crew has completed its campaign the blast crew then load each hole with explosives. It is extremely important that the correct amount of explosives are loaded into each hole. Poor outcomes in drill and blast operations can lead to significant additional excavation costs due to poor fragmentation of the ground after blast.

However, despite due care by the drilling crew there is a divergence from the desired hole depth of each blast hole and also a divergence from the location of each hole from the plan developed by the drill and blast engineering team. Furthermore, some drilling patterns may consist of several holes that could take days or weeks to be logged and charged with explosives. During this time, the borehole is exposed to the elements and may be partially filled with water.

Furthermore, cave ins can occur in the borehole thus reducing the effective depth of the borehole for the purpose of blasting.

These variations need to be accounted for when selecting the amount of explosives to be loaded in each hole. As such, prior to the explosives being loaded into the hole a process referred to as hole dipping occurs. Traditionally, this process has involved a member of the blast crew dropping a tape measure or a line with a weight at the end of it to determine the actual depth of the borehole and also to assess for the presence of water as well as the depth of the water when water is present.

That process is conducted manually for each hole and the results are then passed to the blast engineer. The blast engineer then calculates the amount of explosives to load into each hole in order to achieve the desired blast effect.

This process is very time consuming, subject to error and involves a large amount of manual effort from mine site personnel.

<CIT> discloses a communication system comprising: a first transmitter that is acoustically coupled to a column of fluid located within a wellbore of an oil, gas, or water well, wherein the first transmitter transmits sound waves wirelessly through the column of fluid located within the wellbore, and wherein the sound waves are encoded with data; and a first receiver that is acoustically coupled to the column of fluid located within the wellbore, wherein the first receiver receives the data-encoded sound waves, wherein the data-encoded sound waves communicate information about the well or a component of the wellbore.

<CIT> discloses a method and device for obtaining measurements of downhole properties in a subterranean well, in which an untethered apparatus includes a housing and one or more sensors configured to measure data along the subterranean well, the data including one or more physical, chemical, geological or structural properties in the subterranean well.

It is an aim of this invention to provide a device, method and/or system which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides a useful alternative.

In accordance with the invention, there is provided a borehole sensing device as defined by the appended claims.

Further features and advantages of the present invention will become apparent from the following detailed description.

By way of example only, preferred embodiments of the invention will be described more fully hereinafter with reference to the accompanying figures.

Elements of the invention are illustrated in concise outline form in the drawings, showing only those specific details that are necessary to understanding the embodiments of the present invention, but so as not to clutter the disclosure with excessive detail that will be obvious to those of ordinary skill in the art in light of the present description.

<FIG> shows a schematic view of a system for determining borehole conditions <NUM> according to an embodiment of the invention. Also show in <FIG> is a schematic view of a borehole sensing device <NUM> and a receiving device <NUM> forming part of system <NUM>.

Borehole sensing device <NUM> is adapted to be deployed within a borehole and has a sensing module <NUM>, a processing module <NUM> and a communications module <NUM>. Borehole sensing device <NUM> may be deployed within a borehole by being dropped into the borehole by a person, by a UAV or other similar deployment methods.

Sensing module <NUM> is adapted to sense conditions of the borehole which, in a preferred embodiment, is used to calculate the absolute depth of the borehole, the presence or absence of moisture and/or water within the borehole and the depth of water from the bottom of the borehole. Other conditions may optionally include temperature of the bore hole and the like.

In a preferred form, the sensing module <NUM> includes a pressure sensor configured to determine the depth of the borehole by determining the pressure differential between the top of the borehole and the surface of water in the borehole to thereby determine the distance between those two points.

Furthermore, in a preferred form, the borehole sensing device <NUM> is adapted to sink in the water of the borehole. As such, the sensing device is also able to determine the pressure differential between the surface of the water and the bottom of the borehole to thereby calculate the depth of the water and also the absolute depth of the borehole.

A skilled addressee will appreciate that the three pressure readings taken: at the mouth of the hole, at the bottom of the hole under a body of water, if any, and at the top of the body of water, can be used to calculate the absolute depth of the borehole and also the height of the column of water by using well known relative pressure differential equations to calculate that data.

In a preferred form, the sensing module <NUM> is in the form of a bathymetry sensor as is known in the art. The sensing module <NUM> may also include temperature sensors, moisture sensors and other such sensors to determine conditions of the borehole.

Processing module <NUM> is adapted to receive data associated with the conditions of the borehole from the sensing module <NUM> and communicate that data to communications module <NUM>. Communications module <NUM> is adapted to communicate data associated with conditions of the borehole out of the borehole.

In the embodiment, this communication takes the form of an audio transmission that has a protocol for communicating the data associated with conditions of the borehole. As such, in the embodiment, communications module <NUM> takes the form of a speaker. Other communication forms may be used such as radio waves, optical signals or the like. In a preferred form the communications module <NUM> communicates the data associated with the conditions of the borehole continuously in a looped data sequence. Suitably, that data includes a unique borehole identifier.

In some embodiments of the invention, communications module <NUM> may provide for two way communications such that the data associated with conditions of the borehole is communicated from communications module <NUM> in response to receiving a request message to do so.

Preferred embodiments of the sensing device <NUM> will be described in greater detail below.

Receiving device <NUM> is located distal from the borehole sensing device. Preferably, the receiving device <NUM> is located out of the borehole and includes a receiving module <NUM> a processing module <NUM> and a data store <NUM>. Receiving module <NUM> is adapted to receive the data associated with the conditions of the borehole transmitted by the communications module <NUM> of the borehole sensing device <NUM>. In the embodiment, receiving module <NUM> takes the form of an audio receiver such as a microphone or the like.

The processing module processes the data received from the receiving module and stores that data in data store <NUM>. Optionally, data store <NUM> may be located remote from the receiving device <NUM>.

Receiving device <NUM> may take the form of a handheld unit operable by a person, a station on the ground, a ground vehicle or an unmanned aerial vehicle (UAV) or the like or be deployed in such a device. Alternatively, the receiving device <NUM> may be located at a central location remote from the borehole and the borehole sensing device <NUM>. In all embodiments, the receiving device <NUM> is located out of the borehole whilst, in use, the borehole sensing device is located within the borehole.

Preferred embodiments of receiving device <NUM> will be discussed in greater detail below.

<FIG> shows a perspective view of an embodiment of the borehole sensing device <NUM> shown in schematic as part of the system for determining borehole conditions <NUM> shown in <FIG>. <FIG> shows a side view of the borehole sensing device <NUM>, <FIG> shows a top view of the borehole sensing device <NUM>, <FIG> shows a bottom view of the borehole sensing device <NUM> and <FIG> shows an exploded perspective view of the bore hole sensing device <NUM>.

Borehole sensing device <NUM> has a casing <NUM>. Casing <NUM> has a Gömböc shaped exterior in this embodiment of the borehole sensing device <NUM>. This shape allows the borehole sensing device <NUM> to remain in a preferred orientation during its deployment in the borehole and passage down the borehole as will be described in further detail below. Suitably, the shape of the casing may be any monostatic polytope geometry.

Casing <NUM> has a hollow interior. A communications aperture <NUM> extending from an outer side of casing <NUM> into hollow cavity. Casing <NUM> also has a number of fluid ingress apertures <NUM> extending from an outside of casing <NUM> to within hollow cavity to allow the ingress of water to or egress of gas from within the hollow cavity in circumstances when the borehole sensing device <NUM> is deployed within the borehole and water is present in the borehole.

Borehole sensing device <NUM> also has a power ignition device <NUM> in the form of an aperture extending through the casing <NUM> in the hollow interior and a tab that is operable upon extraction through the aperture to provide power to the borehole sensing device <NUM> as will be discussed in greater detail below.

Power ignition device <NUM> may take the form of a switch or other like power ignition mechanisms in certain embodiments of the invention.

A blind bore <NUM> is located at an end of borehole sensing device <NUM> distal to the communications aperture <NUM>. Blind bore <NUM> extends within casing <NUM> as shown and has located therein a ballast member <NUM>. Optionally, blind bore <NUM> may also include apertures extending therethrough in hollow cavity to allow ingress of water and egress of gas.

A cap <NUM> releasably retains ballast member <NUM> within blind bore <NUM>. Cap <NUM> is formed from a material such as citric acid, bicarbonate soda, sugar or the like or combinations thereof that is dissolvable in fluid at a predictable rate. Alternatively, cap may be secured to casing by a binding agent that is dissolvable in a fluid. A skilled addressee will appreciate that vents and the like may be included around the casing proximal the cap so as to better allow water to access the cap.

In the event that cap <NUM> dissolves as a result of the presence of fluid, such as water, ballast member <NUM> is free to move out of blind bore <NUM> as will be discussed in greater detail below.

Sensing module <NUM>, processing module <NUM> and communications module <NUM> are located within hollow cavity of casing <NUM> of borehole sensing device <NUM>. These components have functions as previously described.

Power module <NUM> is also located within housing <NUM> to provide power to sensing module <NUM>, processing module <NUM> and communications module <NUM>. Power module <NUM> is operable by way of power ignition device <NUM>.

Floatation members <NUM> are located within hollow cavity of casing <NUM> of borehole sensing device <NUM>. Floatation members <NUM> are selected to have a buoyancy force that is less than the sinking force provided by the ballast member <NUM> such that when ballast member <NUM> is located within blind bore <NUM>, the borehole sensing device <NUM> sinks within a fluid. Furthermore, the buoyancy force provided by floatation members <NUM> is of sufficient force such that when ballast member <NUM> exits blind bore <NUM> after cap <NUM> has dissolved in fluid the buoyancy force provided by flotation members <NUM> is such that borehole sensing device <NUM> floats to the surface of the fluid.

Whilst two floatation members <NUM> are shown in the embodiment described, it will be appreciated that there may be more or less floatation members provided such that the buoyancy force provided is as described above.

Also located within hollow cavity of casing <NUM> are weight sin the form of washers <NUM>. A skilled addressee will appreciate that the weights may take a form other than a washer shape.

Whilst, casing <NUM> of borehole sensing device <NUM> has a Gömböc shape, the borehole sensing device <NUM> is formed so that the centre of buoyancy is above the centre of mass such that borehole sensing device <NUM> is orientated in use such the communications aperture <NUM> is directed to the month of the borehole within which the borehole sensing device <NUM> is deployed. As such, a skilled addressee will appreciate that casing <NUM> may have other shapes that perform this function and/or the components of the borehole sensing device <NUM> may be arranged in a different manner to the embodiment described to still nevertheless perform this function.

<FIG> show borehole sensing device <NUM> in use. In use, borehole sensing device <NUM> is deployable within a borehole <NUM> and is configured to communicate data associated with conditions of the borehole <NUM> to receiver module <NUM>. In the embodiment, that data includes the temperature of the borehole, data that is indicative of the presence or absence of any fluid present in the borehole, data associated with the absolute depth of the borehole and, in circumstances where there is fluid present, data associated with the depth of water in the borehole.

As shown in <FIG>, bore hole sensing device is deployed in borehole <NUM> by dropping the borehole sensing device <NUM> within borehole <NUM>. Prior to being deployed, the power module <NUM> of borehole sensing device <NUM> is activated by a user activating power ignition device <NUM>. AS such, the processing module <NUM>, the sensing module <NUM> and the communications module <NUM> are thus powered.

In alternative embodiments, the borehole sensing device <NUM> may be dropped from a UAV that has a set of location data in the form of GPS co-ordinates representative of the location of a plurality of boreholes and is configured to drop a borehole sensing device in each borehole.

The pressure at the mouth of the borehole <NUM> is, in the preferred embodiment, known and stored in the data store of the receiving device <NUM>. Alternatively, the pressure is measured by the sensing module <NUM> of the borehole sensing device <NUM> prior to it being deployed in the borehole <NUM>.

In the example shown, borehole <NUM> has water <NUM> located therein. As shown in <FIG>, due to the sinking force provided by ballast member <NUM> being greater than the buoyancy force provided by the floatation members <NUM>, the borehole sensing device <NUM> strikes the water and proceeds to sink to the bottom of the borehole. As the borehole sensing device <NUM> sinks water enters the hollow cavity created by the casing through water ingress apertures <NUM> and communications aperture <NUM>. Once borehole processing device <NUM> reaches the bottom of the borehole <NUM>, sensing module <NUM> takes a first pressure reading. A skilled addressee will appreciate that the sensing module may make continuous measurements and the first pressure reading will be the reading at which the pressure is the greatest.

In some embodiments, sensing module <NUM> also takes a temperature reading, a reading to detect the presence or absence of water in the borehole <NUM> or a further reading related to other conditions of the borehole at this position.

As previously mentioned, cap <NUM> is formed from a material that is dissolvable in fluid. As such, cap <NUM> dissolves within the water <NUM>. When cap <NUM> dissolves, ballast member <NUM> is no longer retained within blind bore <NUM> and exits blind bore <NUM>. As borehole sensing device <NUM> no longer has ballast member <NUM>, the force provided by floatation members <NUM> causes the borehole sensing device <NUM> to float to the surface of water <NUM> as shown in <FIG>. At this point, sensing module <NUM> of borehole sensing device <NUM> takes a second pressure reading.

Optionally, sensing module <NUM> also takes a temperature reading, moisture reading and/or, in embodiments where modules to sense other borehole characteristics are present, data associated with those other characteristics of the condition of the borehole may also be taken at this stage.

Processing module <NUM> of borehole sensing device <NUM> then communicates data associated with the conditions of the borehole <NUM>. In the embodiment, this data includes the first pressure reading and the second pressure reading. As previously discussed, other data may be communicated such as temperature data, moisture data and data uniquely identifying the borehole <NUM>.

In the embodiment, communications module <NUM> communicates the data associated with the condition of the borehole using the media of audible sound. A suitable communications protocol is used so as the sound carries the data. Such communication may be Morse code, pulse width coding, pulse position coding, frequency shift-keying coding or other such technique or a proprietary protocol to transmit data using sound, or other media. As such, in the embodiment, communications module <NUM> is in the form of a speaker and emits sound that defines the data associated with conditions of the borehole <NUM> out of the borehole sensing device <NUM> through communications aperture <NUM> and out of borehole <NUM>. That sound is emitted continuous in a loop until power module <NUM> runs out of power. In some embodiments the sound is emitted at intermittent periods or at predetermined times.

As shown in <FIG>, receiving device <NUM> then receives the data communicated by borehole sensing device <NUM> and processes and stores that data as previously described. The two pressure readings taken by the sensing module <NUM> from within the borehole <NUM>, together with moisture data, can then be used to calculate the absolute depth of the borehole and the depth of the water in the borehole which is then used by the blast engineer as previously described.

In a preferred form, this calculation is carried out by the receiving unit having received the first pressure reading, the second pressure reading and, optionally, the moisture reading and, having had already known the pressure reading at the mouth of the borehole <NUM> various depth calculations can occur, as will be well known in the art based on pressure differentials, to determine, the depth of the borehole, the height of the water column if any, within the borehole, the presence of absence of water, etc..

For example, if the first pressure reading is approximately equal to the second pressure reading and the moisture reading indicates that the borehole is dry then the borehole is dry and the depth can be calculated using pressure differential calculations.

If the first pressure reading is approximately equal to the second pressure reading and the moisture reading indicates that the borehole is wet then the borehole is muddy and the depth can be calculated using pressure differential calculations.

If the first pressure reading is greater than the second pressure reading and the moisture reading indicates that the borehole is wet then the borehole is filled with water and the depth of both the hole and the water level can be calculated using pressure differential calculations.

The skilled addressee will appreciate other logic conditions that may be accounted for such as fault detection and the like.

Optionally, the calculation translating the pressure readings to absolute depth of the borehole and depth of water, including its presence or absence in the borehole, may be undertaken at the processing module <NUM> and then the data associated with conditions in that form is communicated by the borehole sensing device <NUM> to the receiving device <NUM>.

In the embodiment, the receiving unit <NUM> is in the form of a UAV but may take other forms as previously described.

<FIG> shows a perspective view of a further embodiment of a receiving device <NUM> shown in schematic in <FIG> as part of the system for determining borehole conditions.

As in the previous embodiment, receiving device <NUM> is adapted to receive data communicated by embodiments of the borehole sensing device <NUM> and processes, stores and communicates that data as previously described. Receiving device <NUM> is a handheld unit and is adapted to be used by a mine worker who travels between the boreholes to receive the data communicated from respective borehole sensing devices <NUM> located in each.

Receiving device <NUM> has a main portion <NUM> and handle portion <NUM> extending from main portion <NUM>. Handle portion <NUM> has a series of finger grips <NUM> and is adapted to nest in the hand of a user. Handle portion <NUM> also has a trigger device <NUM> adapted to be activated by the user to commence data reception, complete data reception or to determine whether data is to be communicated.

In the embodiment shown, receiving module <NUM> has a microphone <NUM> adapted to receive the audible signal that communicates the conditions of the borehole transmitted by the communications module <NUM> of the borehole sensing device <NUM>. Receiving module also includes one or more communications modules which, in the embodiment, are an SD card reader <NUM>, WIFI transmitter and receiver <NUM>, SD card reader <NUM> all of which are in communication with a processing module <NUM> (not shown in the embodiment) and data store <NUM> (not shown in the embodiment) of the receiving device <NUM>.

A skilled addressee will appreciate that other communication and storage interfaces may be located on receiving module in communication with processing module and data storage such as ethernet, Bluetooth, GPS receiver, serial comport and the like.

Receiving module <NUM> also comprises a power source <NUM> for supplying power and/or recharging batteries to supply power to the various components of the receiving device <NUM>.

Main portion <NUM> has a display module <NUM> in the form of a screen and a receiving module <NUM>. Display module <NUM> provides feedback to the user of the receiving device an is able to provide visual indication of the conditions of the borehole, when data has been received and transmission is complete, when a signal carrying conditions of a borehole has been communicated and the like.

<FIG> shows a perspective view of a further embodiment of a borehole sensing device <NUM> shown in schematic in <FIG> as part of the system <NUM> for determining borehole conditions. <FIG> shows a sectional side view of the borehole sensing device <NUM> shown in <FIG>.

As in earlier embodiments, borehole sensing device <NUM> is adapted to be deployed within a borehole and has a sensing module <NUM>, a processing module <NUM> and a communications module located within a hollow cavity of casing <NUM>.

Casing <NUM> has a communications aperture <NUM> extending from an outer side of casing <NUM> into hollow cavity. Casing <NUM> also has a number of fluid ingress apertures <NUM> extending from an outerside of casing <NUM> to within hollow cavity to allow ingress of water into cavity.

A cap <NUM> releasably retains ballast member <NUM> within blind bore <NUM>. Cap <NUM> is formed from a material such as citric acid, bicarbonate soda, sugar or the like or combinations thereof that is dissolvable in fluid at a predictable rate. Alternatively, cap may be secured to casing by a binding agent that is dissolvable in a fluid. The cap and ballast member function as previously described.

Whilst remaining unlabelled for clarity reasons, borehole sensing device <NUM> has other features as described with reference to bore sensing device <NUM> as described in <FIG>.

Borehole sensing device <NUM> has a series of grooves <NUM> located in an outerface of casing <NUM>. Each groove <NUM> extend longitudinally from proximal communications aperture <NUM> and terminate proximal blind bore <NUM> and have at each terminal end an aperture 1149A extending from an outer face to an inner face of casing <NUM>.

The grooves <NUM> extend longitudinally at spaced circumferential intervals about casing <NUM>.

As before, sensing module <NUM> of borehole sensing device <NUM> has a pressure sensor adapted to read pressure as previously described. In the embodiment shown in <FIG> and <FIG>, sensing module <NUM> further comprises a moisture sensor in the form of a conductive member <NUM> located within each groove and extending through casing <NUM> and in communication with processing module <NUM>.

When the borehole sensing device <NUM> is located in the presence of moisture at the bottom of a borehole, the conductive members conduct electricity and thereby communicate to processing module <NUM> the presence of that moisture for processing as previously discussed.

The grooves and the conductive members are arranged such that faces of the casing are suitably covered so as to determine absence of moisture regardless of the orientation of the borehole sensing device <NUM> in the borehole.

A skilled addressee will appreciate that other arrangements and mechanisms may be used to detect and communicate the presence or absence of moisture and those may equally be implemented in the borehole sensing device of the invention.

<FIG> shows a perspective view of still a further embodiment of a borehole sensing device <NUM> shown in schematic in <FIG> as part of the system <NUM> for determining borehole conditions. <FIG> shows a sectional side view of the borehole sensing device <NUM> shown in <FIG>.

As in earlier embodiments, borehole sensing device <NUM> is adapted to be deployed within a borehole and has a sensing module <NUM>, a processing module <NUM> and a communications module <NUM> located within a hollow cavity of casing <NUM>.

Unlike previous embodiments, casing <NUM> has a disc shape formed from opposing upper surface 2140A and lower surfaces 2140B separated by a circumferentially extending edge surface 2140C. In the embodiment, the upper and lower surfaces 2140A and 2104B have a generally circular shape when each is viewed in plan.

The shape of the casing <NUM> advantageously allows for greater control over the orientation of the sensing device <NUM> once deployed within a borehole. Due to the particular aerodynamic nature of the shape there is a very high likelihood that the borehole sensing device will land and come to rest with either the upper surface or lower surface being orientated to face the mouth of the borehole.

Furthermore, the shape will cause the device to have lift and drag both slowing its descent down the borehole and also bringing it in contact with the walls of the borehole to further slow descent and to thereby minimising impact related damages at the bottom of the borehole. Preferably, circumferentially extending edge surface 2140C acts to dampen impacts.

A skilled addressee will appreciate that other shaped casing will have similar desirable affects providing that the shape has a high aspect ratio with respect to the thickness of the casing such as oblong shaped casings and the like.

As a consequence of the prospect of borehole sensing device <NUM> being locatable such that either upper face 2140A or 2140B may be orientated to face the mouth of the borehole, there is a communication aperture 2141A extending through upper face 2140A and also a communication aperture 2141B extending through lower face casing 2140B with each proximal communications module <NUM>. It will be appreciated that this is necessary in order that data associated with conditions of a borehole may be accurately transmitted from communications module <NUM> to receiving device. Optionally, borehole sensing device <NUM> includes an orientation sensor so that determination of the orientation of the borehole sensing device <NUM> may be made.

Furthermore, casing <NUM> has a single central bore <NUM> extending therethrough. Central bore <NUM> has an opening 2144A on upper face 2140A and an opening 2144B in a lower face 2140B. A cap 2146A is captively located in central bore <NUM> proximal opening 2144A and a cap 2146B is captively located within central bore <NUM> proximal opening 2144B.

A ballast member is located within central bore <NUM> between cap 2146A and cap 2146B. As before, each cap is dissolvable in water and ballast member is able to exit central bore through which ever cap is dissolved to function as previously described.

There are grooves and conductive members suitably located about casing which function as before to detect moisture.

<FIG> shows a perspective view of a repeater device <NUM> located on amplification member <NUM> forming part of a further embodiment of the system <NUM> for determining borehole conditions.

<FIG> shows a partial sectional view the repeater device <NUM> and the amplification member <NUM> shown in <FIG>.

Amplification member <NUM> is adapted to be located upon and cover the mouth of borehole <NUM> (not shown) and acts to amplify a signal communicated from the borehole sensing device carrying the data associated with conditions of the borehole.

As such, amplification device has a base <NUM> and a sidewall <NUM> terminating at a topwall <NUM>. Base has an opening (not shown) such that a cavity <NUM> is formed within by the sidewall <NUM> and the top wall <NUM> that opens at the bottom end of the amplification device.

In the embodiment, the sidewall is conical in shape thus forming a conical cavity. There is an opening <NUM> in top wall <NUM>. The amplification member acts to amplify audible signals and also prevent ingress of debris and water to within a borehole <NUM>.

Repeater device <NUM> located upon top wall <NUM> of amplification member. Repeater device <NUM> has mounting portion <NUM> which penetrates opening <NUM>. Mounting portion <NUM> has a conical side wall <NUM> open at a lower end forming a conical cavity <NUM>.

A receiving device <NUM> in the form of a microphone is located at the top of cavity <NUM> and is adapted to receive signals from the borehole sensing device in the borehole.

Repeater device <NUM> has a transmitting device <NUM> in the form of a speaker located on an upper surface and is adapted to retransmit the signal received by receiver device <NUM>.

A series of indication devices <NUM> are also located on upper surface. These suitably take the form of lights to indicate, for example, when signals are received and also to suitable indicate certain conditions of the borehole <NUM> such as temperature and the presence or absence of water. The systems, methods and devices of the invention provide for a low cost, autonomous and accurate process to identify certain conditions of a borehole such that the amount of explosive to be loaded in each blast hole can be accurately determined.

The above description of various embodiment of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment.

Embodiments of the borehole sensing device of the invention may further comprise a water-soluble coating located on an outer surface of the casing. That water-soluble coating may be in the form of gelatine or a different form of dissolvable coating including effervescent chemical material or other soluble organic or inorganic coating. The water-soluble coating located on the external surface of the casing is especially advantageous when the borehole sensing device is being deployed in boreholes that are especially muddy and/or filled with water. In such circumstances, the impact of the borehole sensing device as it reaches the bottom of the borehole may be of sufficient force that the device may become embedded in mud and underwater. The suction force of the mud and the impact may be such that the device is unable to break free and float to the surface of the water even after the ballast has been deployed. The water-soluble coating acts to allow water to penetrate along the interface between the coating and the outer surface of the casing to thereby breach the suction force. Advantageously, the coating also allows fluid to leach into the plug and allow the ballast to release.

Claim 1:
A borehole sensing device (<NUM>, <NUM>, <NUM>) for logging the depth of a borehole (<NUM>) and determining the presence or absence of water (<NUM>) therein prior to explosives being loaded into that borehole (<NUM>), the borehole sensing device (<NUM>, <NUM>, <NUM>) being adapted to be deployed within the borehole (<NUM>), the device (<NUM>, <NUM>, <NUM>) comprising:
a sensing module (<NUM>, <NUM>, <NUM>) adapted to sense conditions of the borehole (<NUM>), which includes a pressure sensor configured to:
take three pressure readings at the mouth of the borehole (<NUM>), at the bottom of the borehole (<NUM>) under a body of water (<NUM>), if any, and at the surface of the body of water (<NUM>);
determine the depth of the borehole (<NUM>) by determining the pressure differential between the mouth of the borehole (<NUM>) and the surface of the body of water (<NUM>) in the borehole (<NUM>) to thereby determine the distance between those two points; and
determine the absolute depth of the borehole (<NUM>) by determining the pressure differential between the surface of the body of water (<NUM>) and the bottom of the borehole (<NUM>) to thereby calculate the depth of the body of water (<NUM>) and the absolute depth of the borehole (<NUM>);
a processing module (<NUM>, <NUM>, <NUM>) in communication with the sensing module (<NUM>, <NUM>, <NUM>), the processing module (<NUM>, <NUM>, <NUM>) adapted to receive data associated with the conditions of the borehole (<NUM>) from the sensor module; and
a communications module (<NUM>, <NUM>, <NUM>) adapted to communicate out of the borehole (<NUM>) the data associated with the conditions of the borehole (<NUM>), wherein the communications module (<NUM>, <NUM>, <NUM>) is a speaker and the data associated with conditions of the borehole (<NUM>) is communicated by way of audio transmission.