Patent Publication Number: US-8534124-B2

Title: Sensor housing apparatus

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/243,259 filed Sep. 17, 2009 under U.S.C. §119(e) which application is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     As is known in the art, there are many reasons for placing sensors, probes, and various kinds of detection instrumentation in subterranean environments. For example, the petroleum industry may use subterranean sensor arrays to study geophysical properties of the deep earth to assist in crude oil exploration and extraction. Construction teams drill boreholes into the earth and install sensor arrays, typically encased in a protective jacket. Once the sensory array is in place, grout may be injected into the borehole cavity to surround the sensor array and to attempt to uniformly couple the sensor array with the surrounding earth. One of the main goals of a drilling operation is to maximize sensor array accuracy and sensitivity by forming a tight acoustical and/or seismic coupling between the sensor array and the surrounding earth. 
     As is also known in the art, many sensor arrays lack both the strength and ruggedness to survive horizontal directional drilling (HDD) operations. To accommodate these weaker sensor arrays, drilling teams may excavate an open trench, dispose the sensor array at the bottom of the trench, and backfill the trench with grout and/or soil to cover the sensor array. However, open trench excavation may result in voids and air cavities in the surrounding earth, which can significantly impede sensor array performance. Furthermore, open trench excavation often involves moving relatively large amounts of earth, which can be expensive, time-consuming, and is disruptive of the surrounding area. 
     Open trench excavation may be useful under certain conditions, such as when space is limited or for shallow-depth applications. These installations are often limited to depths of 20 feet or less, and more typically involve depths of ten, five, or even fewer feet. Sensor arrays have limited application at such shallow depths, although construction teams can use them to detect vibrations in manholes and other underground tunnels near the surface. 
     As is also known in the art, directional boring (so-called “horizontal directional drilling” or HDD) is another technique that industry uses to install sensor arrays and other subterranean devices. Drilling operations often employ HDD where direct-cut open trenching is undesirable or too disruptive. Also, HDD may involve drilling at relatively large depths, such as to install piping under a canal and or to assist in oil exploration. 
     HDD is a steerable, trenchless method in which teams install devices in a three-stage process including drilling a pilot hole, enlarging the hole, and depositing the device within the larger hole. Drilling teams uses a viscous fluid to help cool the drill bit, remove loosened soil, and to stabilize the hole. To help stabilize the device and to attempt to fill all voids and produce a tight coupling, teams often introduce a grout through one end of a tube or conduit which also contains the installed device. The tube may be retreated back up the opening or pulled through the entire borehole when the team determines (e.g., using sensors) that they have deposited a sufficient amount of grout to stabilize the borehole cavity and/or crevices in the earth. 
     For example, HDD may be used to install high-power electrical cable which must be uniformly coupled to the surrounding medium, such as the earth, to promote heat transfer from the cables. One suitable material used to protect the cable includes high-density polyethylene (HDPE) plastic. HPDE offers an acoustical impedance similar to that of compact soil or soft rock. HPDE is also rugged, abrasion resistant, waterproof, and relatively inexpensive. 
     SUMMARY 
     In general overview, the inventive concepts, systems, and techniques described herein provide a sensor apparatus including a rugged, high-strength sensor housing to house sensors and a material delivery housing to conduct a material into an area about the sensor apparatus to secure and/or couple the sensors to surrounding medium. The inventors realized that integrating the sensor housing with the material delivery housing can facilitate the uniform distribution of coupling material along a length of the sensor apparatus. Moreover, the sensor apparatus has improved tensile strength and ruggedness, making it particularly useful for horizontal directional drilling installations. For example, the sensor apparatus may resist kinking and tangling, and may minimize sensor hardware breakage during installation. 
     Optionally, a strength member may be included to further increase ruggedness and tensile strength of the sensor apparatus. A lumen may be formed in the strength member and communications devices disposed therein to enable communications between a first portion and a second portion along the length of the sensor apparatus. 
     The material delivery housing wall defines radial ports to conduct a material about the sensor apparatus. The radial ports distributed about the material delivery housing can help produce an intimate coupling of the sensors to the surrounding soil and can be configured to produce fluid/backfill pressure gradients to suite soil/rock fluid-permeability characteristics. In some applications, the density of radial ports along a length of the material delivery housing may be either varied or held constant to control material flow into a surrounding bore hole. The density of radial ports may be expressed as a total radial port cross-sectional area per linear foot of material delivery housing. Other design factors, such as radial port size, shape, and number may be configured to uniformly distribute the material and/or to accommodate material viscosity, density, and other properties. Such other properties may include variation in fluid pressures anticipated due to installation of portions of the sensor apparatus at different depths along a curved borehole path. Lower portions subject to higher fluid pressures may have a lower total cross-sectional area of radial ports to equalize the flow rate of a material with that of sensor apparatus portions disposed at shallower depth, where fluid pressure may be lower. 
     In one aspect, a sensor apparatus includes a first elongated housing to at least partially enclose a sensor device and a second elongated housing generally parallel to the first elongated housing. The second elongated housing defines at least one radial port extending from an inner surface to an outer surface of the second elongated housing adapted to conduct a material through the second elongated housing and out the radial port about the sensor apparatus. 
     In a further embodiment, the sensor apparatus includes one or more of the following features: the first elongated housing has a generally circular cross-sectional area and the second elongated housing has a generally circular cross-sectional area and the outer surface of the second elongated housing is coupled along a length of the sensor apparatus to an outer surface of the first elongated housing; the first elongated housing has a first radius and the second elongated housing has a second radius, wherein the first radius is larger than the second radius; the first elongated housing has a wall having a first thickness and the second elongated housing has a wall having a second thickness, the second thickness larger than the first thickness; the first elongated housing has a generally triangular cross-sectional area and the second elongated housing has a generally triangular cross-sectional area; the first elongated housing has a wall having a first thickness and the second elongated housing has a wall having a second thickness, the second thickness larger than the first thickness; the sensor apparatus has a generally oval-shaped cross-sectional area, the first elongated housing disposed within a first portion of the oval-shaped cross-sectional area and the second elongated housing disposed within a second portion of the oval-shaped cross-sectional area; the sensor device includes a sensor string at least a portion of which is coupled to an inner surface of the first elongated housing to enhance sensor sensitivity, the sensor string including at least one of: a plurality of acoustic sensors and a plurality of seismic sensors; a coupling material formed about the sensor device couples the sensor device to the inner surface of the first elongated housing; the coupling material includes a fluid material; an inner surface and an outer surface of the first elongated housing form a first wall having a thickness configured to enhance sensor sensitivity and an inner surface and an outer surface of the second elongated housing form a second wall having a thickness to enhance tensile strength of the sensor apparatus; the at least one radial port includes a plurality of radial ports arranged in a helical pattern along a length of the second elongated housing; the at least one radial port includes a plurality of radial ports arranged at a density along a length of the second elongated housing to support uniform distribution of the material; the at least one radial port includes a plurality of radial ports, further including an inner housing disposed within at least a portion of the second elongated housing to block distribution of the material through at least one of the radial ports; further including an elongated member coupled longitudinally to at least one of the first and second elongated housings; the first elongated housing has a generally triangular cross-sectional area and the second elongated housing has a generally triangular cross-sectional area and the elongated member is housed within one of the first and second elongated housings; the sensor apparatus has a generally oval-shaped cross-sectional area, first elongated housing disposed within a first portion of the oval-shaped cross-sectional area, the second elongated housing disposed within a second portion of the oval-shaped cross-sectional area, and the elongated member disposed within at least one of the first and second portions; electronics are disposed in a lumen formed within the elongated member. 
     In another aspect, a sensor apparatus includes an elongated sensor body forming a first lumen into which a sensor device may be inserted and a second lumen having a portion parallel to the elongated sensor body and a radial port portion extending from the portion parallel to the elongated sensor body to an outer surface of the elongated sensor body. The second lumen acts to conduct a material through the parallel portion of the second lumen and through the radial port portion of the second lumen to a position about the sensor apparatus. 
     In a further embodiment, the sensor apparatus includes one or more of the following features: the first lumen has a generally circular cross-sectional area and the second lumen has a generally circular cross-sectional area; the sensor device includes a sensor string at least a portion of which is coupled to an inner surface of the first lumen to enhance sensor sensitivity, the sensor string including at least one of a plurality of acoustic sensors and/or a plurality of seismic sensors; a coupling material formed about the sensor string couples the sensor to the inner surface of the first lumen, the coupling material including a fluid material; an inner surface and an outer surface of the first lumen form a first wall having a thickness configured to enhance sensor sensitivity and an inner surface and an outer surface of the second lumen form a second wall having a thickness to enhance tensile strength of the sensor apparatus; the radial port portion includes a plurality of radial port portions arranged in a helical pattern along a length of the second lumen; the radial port portion includes a plurality of radial port portions, further including an inner member disposed within at least a portion of the second lumen to block distribution of the material through at least one of the radial port portions; the elongated sensor body further forms a third lumen and further including a strength member located within the third lumen. 
     In another aspect, a method for installing a sensor apparatus includes providing a first elongated housing to at least partially enclose a sensor device and providing a second elongated housing coupled longitudinally to the first elongated housing. The second elongated housing includes at least one radial port extending from an inner surface to an outer surface of the second elongated housing and conducting a material through the at least one radial port about the sensor apparatus, the material received through an opening of the second elongated housing. 
     In further embodiments, the method includes one or more of the following features: coupling the sensor device to an inner wall of the first elongated housing, and; forming an opening in a wall of the first elongating housing to insert at least a portion of the sensor device within the first elongating housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features of this invention, as well as the invention itself, may be more fully understood from the following description of the drawings in which: 
         FIG. 1A  is a pictorial representation of a sensor apparatus in accordance with the inventive systems, techniques, and concepts; 
         FIG. 1B  is a cross-sectional view of a further embodiment of the sensor apparatus shown in  FIG. 1A  at line AA′; 
         FIG. 2A  is a pictorial representation of a sensor apparatus installed in an exemplary subterranean environment; 
         FIG. 2B  is a cross-sectional view of the sensor apparatus shown in  FIG. 2A  at line BB′; 
         FIG. 2C  is a pictorial representation of a sensor apparatus embodiment including an inner housing; 
         FIG. 3  is a pictorial representation of a border security operation which may incorporate a sensor apparatus described herein; 
         FIG. 4  is a pictorial representation of a sensor apparatus embodiment including a strength member; 
         FIG. 5  is a pictorial representation of exemplary cross-sectional configurations of a sensor apparatus described herein; 
         FIG. 6  is a pictorial representation of another embodiment of a sensor apparatus described herein; and 
         FIG. 7  is a block diagram of an embodiment of a method for installing a sensor apparatus as described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1A , in one aspect the inventive systems, techniques, and concepts includes sensor apparatus  100  including first elongated housing  110  to at least partially enclose sensor device  150  and second elongated housing  120  generally parallel to first elongated housing  110 . Second elongated housing  120  defines at least one radial port  122  extending from inner surface  121 A to outer surface  121 B of second elongated housing  120  which allows material  105  received through opening  124  of second elongated housing  120  to flow along the interior of second elongated housing  120 . Material  105  flows out radial port  122  and at least partially fill in voids created between first elongated housing  110  (with sensor device  150  therein) and second elongated housing  120  and surrounding medium  195  as well as the void defined by second elongated housing  120  such that sensor apparatus  100  is coupled to surrounding medium  195 . 
     In a further embodiment, first elongated housing  110  has a generally circular cross-sectional area and second elongated housing  120  has a generally circular cross-sectional area. It will be understood by one of ordinary skill in the art that different cross-sectional areas may be used for at least one of first and second elongated housings  110 ,  120  depending on the sensor application. Exemplary cross-sectional embodiments will be described further below. It should also be noted that the sensor apparatus  100  is not limited to first elongated housing  110  and second elongated housing  120 , any may include two, three, four, or more first elongated housings  110 , as may be the case to provide multiple sensor devices  150 , and/or two, three, four, or more second elongated housings  120 , as may be beneficial to fine-tune the conducting of material  105  about sensor apparatus  100 . 
     First and second elongated housings  110 ,  120  are coupled at outer surface  111 B of first elongated housing  110  and outer surface  121 B of second elongated housing  120  along a length of sensor apparatus  100 , which may include the entire length of sensor apparatus  100 . Various methods may be used to couple housings  110 ,  120 , including, but not limited to, epoxy and/or adhesive tape disposed along outer surfaces  111 B,  121 B to fixedly couple housings  110 ,  120 . In still other embodiments, first and second elongated housings  110 ,  120  are extruded together as part of an extrusion process which may involve melting raw plastic materials and forming them into a continuous profile as may be similar to that shown in the sensor apparatus embodiment of  FIG. 1A . 
     It will be understood to one of ordinary skill in the art that first and second elongated housings  110 ,  120  may be coupled longitudinally in other ways. As by way of a non-limiting example, at least one coupler body (an example of which is designated by reference numeral  103 ) may be disposed crosswise about sensor apparatus  100  along outer surface  111 B of first elongated housing  110  and outer surface  121 B of second elongated housing to fixedly join housings  110 ,  120 . One method for fixing housings  110 ,  120  in this way includes positioning unformed coupler body  103  loosely around sensor apparatus  100  and heat shrinking coupler body  103  until it tightly wraps around housings  110 ,  120 , forming a secure bond. In a further embodiment, coupler body  103  is a band of material that can further strengthen sensor apparatus  100 , such as by resisting unwanted folding and twisting which may affect the uniform distribution of material  105  about sensor apparatus  100 . 
     A suitable material for at least one of the first and second elongated housings  110 ,  120  includes, but is not limited to, high-density polyethylene (HDPE). HDPE is a low-cost, flexible, waterproof, abrasion-resistant material that can be readily cut, drilled, and thermally fusion-welded using conventional tools and existing commercial off-the-shelf equipment. HPDE has an acoustical impedance that can match that of a typical soil and/or rock (for example, an impedance in the range of about 1 mega-rayleigh (Mrayls) to about 10 Mrayls, and in particular, from about 1 Mrayls to about 3 Mrayls). It will be understood by one of ordinary skill in the art that higher impedances greater than 10 Mrayls may be experienced, such as for hard rock, and that appropriate materials may be used to match such impedances. 
     As described above with reference to  FIG. 1A , first elongated housing  110  at least partially encloses sensor device  150 . Sensor device  150  includes, but is not limited to, a hydrophone, geophone, accelerometer, magnetometer, electromagnetic radio-frequency receiver and transceiver, and/or another type of sensor that detects vibrations, pressure, and/or stress about sensor apparatus  100 . Still other type of sensor devices  150  include those capable of measuring and/or monitoring on a periodic or continuous basis pressure, voltages/currents, gravitational forces, gamma rays, and magnetic fields and resonances. In other embodiments, sensor device  150  is a sensor string which includes one or more of the above sensors or a combination thereof. 
     In a further embodiment, sensor device  150  is coupled to inner surface  111 A of first elongated housing  110 . The method of coupling sensor device  150  depends on factors such as the type of sensor  150  and the characteristics of surrounding medium  195 . For example, in some applications, a pressure or stress sensor such as a hydrophone must be capable of detecting minute compression and rarefaction variations in medium  195  about sensor apparatus  100 . This can be achieved by potting a hydrophone sensor in adhesive or elastomeric substance (a portion of which is designated by reference numeral  151 ), filling substantially all of the volume between the hydrophone sensor and inner surface  111 A of first elongated housing  110 . Non-limiting examples of an adhesive or elastomeric substance include urethane rubber, silicone oil, gel, or other suitable dielectric fluids such as deionized water. 
     As is known in the art, potting is a process of filling a completed electronic assembly with a solid compound for resistance to shock and vibration, and for exclusion of moisture and corrosive agents. Thermosetting type plastics are often used in this process. Conformal coating is another method which may be used to, for example, coat circuit board assemblies with a layer of transparent conformal coating. Advantageously, conformal coating provides many of the benefits of potting, yet can be lighter and easier to inspect, test, and repair. 
     In other embodiments, a pressure/stress sensor such as a hydrophone can be coupled to inner surface  111 A of first elongated housing  110  by mechanically wedging or fastening the hydrophone firmly into place within first elongated housing  110 . Still another method of pressure/stress sensor coupling includes filling the inner area of first elongated housing  110  with a gel or a fluid such as water or oil (e.g., silicone or castor). 
     Advantageously, fluid coupling of sensor devices may offer enhanced coupling and higher signal amplitudes due, in part, to a combination of fluid resonance effects and mechanical mode conversions. Furthermore, fluid coupling may enable higher received signals in comparison to solid coupling (e.g. solid coupling using a cured cementatious material) and may provide more intimate coupling of sensor device having complex surfaces. 
     In other embodiments in which sensor device  150  is a geophone or an accelerometer, sensor device  150  may be fastened or adhered to one portion of inner surface  111 A of first elongated housing  110  using, for example, a screw, rivet, epoxy, and/or other types coupling devices and/or methods. 
     Embodiments of radial port  122  will now be described in more detail. In general overview second elongated housing  120  defines a port which may be a variety of shapes and extends generally through second elongated housing  120  and is herein referred to as radial port  122 . Radial port  122  is configured to conduct material  105  from the interior of second elongated  120  housing to flow about both first and second elongated housings  110 ,  120  and consequently about sensor apparatus  100 . Material  105  includes, but is not limited to, a grout material that can be configured to match the impedance characteristics of the surrounding medium  195  such as surrounding soil and/or subsurface materials. Material  105  may include various fluids and compounds with different viscosities. For example, material  105  may include a cement slurry or a chemical compound. 
     Referring now to  FIG. 1B  in which a cross-sectional view of sensor apparatus  100  of  FIG. 1A  at line AA′ is shown, and in which like elements of  FIG. 1A  are shown with like reference numerals, material  105  is conducted within second elongated housing  120  through radial ports  122 A,  122 B,  122 C and about sensor apparatus  100 . As can be seen in  FIG. 1B , material  105  flows into area  190  defined by outer surface  161  of sensor apparatus  100  and a cavity, which may be borehole  163  drilled during horizontal-directional drilling (HDD) operations described above. The cavity may further include crevices and other natural or manmade volumes formed about the borehole, such as cracks and fissures in bedrock and other tunnels and voids that may intersect with borehole  163 . In such instances, it may be desired to conduct material  105  into these other areas as well so that material  105  is distributed uniformly about sensor apparatus  100  for optimal sensor sensitivity, accuracy, and reliability. 
     Radial ports  122 A,  122 B,  122 C may be configured in a multitude of ways depending on the particular needs of the sensor application. For example, as shown in  FIG. 1B , radial port  122 A may be formed on one side  123 A of second elongated housing  120 , and radial ports  122 B,  122 C may be formed on an opposing side  123 B of second elongated housing  120 . Such a configuration enables material  105  to flow at disparate rates into area  190  about sensor apparatus  100 . 
     Material  105  improves the coupling between surrounding medium  195  and sensor device  150 . Surrounding medium  195  may include different medium types, such as solid bedrock  195 A and sandy loam material  195 B. The improved material coupling can provide an impedance matching that is better than that of a void in which no material is disposed. 
     Advantageously, improved impedance matching between material  105  and surrounding medium  195  can significantly improve sensor accuracy and reliability. For example, seismic impedance depends on both mass-density and speed of sound. The mass-density of material  105  can be configured to approximate (or substantially equal) that of the mass-density of surrounding medium  195 . In this way, material  105  better couples seismic energy between t surrounding medium  195  and t sensor device  150  than air voids in which no material is disposed. 
     Referring again to  FIG. 1A , in the same or different embodiment, radial port  122  may be configured in other ways, such as by varying the density and/or number of radial ports. Still further, the shape and/or size of one or more of radial ports  122  may be configured depending on the needs of the sensor application. For example, the shape of radial port  122  may include, but is not limited to, a generally circular shape, a triangular shape, and/or a slotted shape in order to favor flow of material into the adjacent area in one dimension. In another example, the diameter of a radial port may be made larger or smaller to respectively increase or decrease the flow rate of material into an area adjacent to the radial port. 
     Referring now to  FIG. 2A , in operation, sensor apparatus  200  may be disposed within pre-drilled subterranean borehole  280  (such as that generated by a HDD operations or surface trenching operations) from one end  280 A of borehole  280  to another end  280 B of borehole  280 . Sensor apparatus  200  may be unwound from spool  281  and guided through borehole  280  by string  282 . As shown in  FIG. 2A , sensor apparatus  200  includes sensor device  250 , as may be similar to sensor device  150  described in conjunction with  FIG. 1A , disposed at least partially within first elongated housing  210 . Sensor device  250  may include sensor string  250  disposed across the entire length of sensor apparatus  200 . 
     Sensor apparatus  200  also includes second elongated housing  220  having a wall defining at least one radial port  222  for conducting material into bore hole  280 . A pump (not shown) may be used to pump material into open end ( 224 ) of second elongated housing  220 . In sensor apparatus  200  of  FIG. 2A , radial ports (generally designated by reference numeral  222 ) are formed across the entire length of second elongated housing  220  to conduct material, such as a grout material, about sensor apparatus  200 . Radial ports  222  may be arranged in other patterns, such as a helical pattern along a length of the second elongated housing  220 , to promote the uniform distribution of material. 
     Referring now to  FIG. 2B , in which a cross-section of sensor apparatus  200  of  FIG. 2A  is shown at line BB′ and in which like elements of  FIG. 2A  are shown with like reference numerals, grout material  205  may be conducted via radial ports  222 A,  222 B,  222 C into borehole area  290  about sensor apparatus  200 . Sensor device  250  may be used to determine when bore area hole  290  is sufficiently filled with grouting material, such as to form a uniform coupling between sensor apparatus  200  and surrounding medium, a portion of which is designated by reference numeral  295 . In one embodiment, sensor device  250  is configured to detect a predetermined pressure gradient according to predetermined sensor application design standards. 
     Referring now to  FIG. 2C , in some sensor apparatus embodiments  200 ′, inner housing  275  may be disposed within second elongated housing  220  to suit one or more needs of the sensing application. For example, inner housing  275  may be disposed within second elongated housing  220  and withdrawn or displaced within second elongated housing  220  during installation (as shown by line designated by reference numeral  276 ) as grout material  205  is pumped into second elongated housing  220 . This can allow grout material  205  to be conducted at precise portions about sensor apparatus  200 ′. As can be seen in  FIG. 2C , in one particular example, inner housing  275  is disposed within second elongated housing  220  along first portion  280 A to prevent grout material  205  from flowing through one or more blocked radial ports (an example of which is designated by reference numeral  222 A) along first portion  280 A, while permitting grout material  205  to flow through one or more unblocked radial ports (an example of which is designated by reference numeral  222 B) along second portion  280 B of second elongated housing  220 . 
     In the same or different embodiment, inner housing  275  is pushed through second elongated housing  220  after grout material  205  has been conducted about sensor apparatus  200 ′, which may assist in sealing and seating grout material  205  and may prevent backflow and pressure when hardening. 
     Referring now to  FIG. 3 , an exemplary application of a sensor apparatus described herein, although not limited to such an application, includes border security and surveillance. Border security personnel  301 , such as those employed by the United States Department of Homeland Security, use sensor apparatus  300 , shown in cross-sectional view, to monitor illegal activities which may occur at or near the United States border (here represented by a border security fence  303 ). For example, smugglers  304  may attempt to smuggle illegal materials  306  across the border via underground tunnel  307 . Sensor apparatus  300  installed at or near border may detect vibrations  309  generated by the illegal activity and transmitted through surrounding soil  395 . Sensor apparatus  300 , and in particular sensor device  350  is configured to detect vibrations  309 . Sensor device  350  is coupled by connector  391  to external system  393  to enable rendering of vibrations  309  to border security personnel  301 . 
     In a further embodiment, sensor apparatus  300  includes electronics that are coupled to sensor device  350  and configured to process the vibrations (or any other type of sensor output) for output to external systems. For example, electronics may be coupled electronically and/or mechanically (such as by a vibrating membrane) to sensor device  350  and may amplify, filter, and/or digitize the sensed vibrations for output. Pre-amplifiers, power conditioning components, and other system components may be used for these purposes. 
     One of ordinary skill in the art will readily understand that the sensor apparatus described herein is not limited to border security operations, and may find use in subterranean exploration operations, such as oil and gas exploration, tunnel boring operations and surveillance, such as during the construction and monitoring of underground facilities, and subterranean infrastructure construction and maintenance, such as for fiber-optic networks and power transmission networks. 
     Referring now to  FIG. 4 , in further embodiments a sensor apparatus  400  includes integral strength member  430  running a substantial length of sensor apparatus  400 . Strength member  430  can handle high-tensile loads during sensor installation. Suitable materials for strength member  430  include, but are not limited to, steel, aromatic polyamide (also known as aramid), and/or other high-tensile materials. Strength member  430  is coupled longitudinally to at least one of first and second elongated housings  410 ,  420 . In the exemplary sensor apparatus embodiment  400  of  FIG. 4 , strength member  430  is shown longitudinally coupled to outer surfaces of first and second elongated housing  410 ,  420  and adjacent to coupled surfaces of first and second elongated housing  410 ,  420 . 
     In further embodiments, lumen  432  is formed within strength member  430  to at least partially enclose devices such as electronics to enable certain useful functionality, such as to enable communications from a first end of sensor apparatus  400  to a second end of sensor apparatus  400 . In military applications, for example, such a configuration enables communications, such as those between a command post and one or more field posts on opposite ends of a demilitarized zone traversed by sensor apparatus  400 . 
     Referring again to  FIG. 4 , in a further embodiment, sensor device  450  may be inserted and disposed within first elongated housing  410  via one or more openings, an example of which is designated by reference numeral  452 , defined by first elongated housing  410  at a portion of wall  455  of first elongated housing  410 . As can be seen in  FIG. 4 , sensor device  450  is inserted into first elongated housing  410  through opening  452 . In still further embodiments, one or more other openings are formed to enable sensor device  450  to be pulled or pushed out of first elongated housing  410 . After insertion of sensor device  450 , opening  452  of wall  455  may be fusion-welded with first elongated housing  410  at the edges of opening  452 . In still other embodiments, another material may be used to cover opening  452 , such as a patch piece of material that is of the same or similar composition as first elongated housing  410  material. 
     Referring now to  FIG. 5 , various cross-sectional configurations of sensor apparatus  501 ,  502 ,  503 ,  504 ,  505 ,  507 ,  508  are shown and will now be described in more detail. Sensor apparatus  501  (shown in cross-sectional view as are all of the sensor apparatus embodiments  501 - 508 ) is an example of first elongated housing  510  and second elongated housing  512  coupled along respective outer surfaces  510 A,  512 A. As can be seen in  FIG. 5 , first and second elongated housings  510 ,  512  may have different respective wall thicknesses t 1  and t 2  to accommodate various design constraints and needs of the sensor application. For example, thickness t 1  may be greater than thickness t 2  to accommodate pullback strength requirements of sensor apparatus  501  during installation and reduced grout pressure. 
     In another embodiment, sensor apparatus  502  includes first elongated housing  520  with a relatively thin wall for enhanced sensor device sensitivity and second elongated housing  522  having a smaller radius r 2  than the radius r 1  of first elongated housing  520  and a relatively thick wall to accommodate higher grout material pressure. 
     In a further embodiment, sensor apparatus  503  includes first elongated housing  530  and second elongated housing  532  having triangularly-shaped cross-sectional areas. Such triangularly shaped cross-sectional areas may impart higher tensile strength and/or crush resistance due to the inherent strength of triangularly shaped structures. Here, first and second elongated housing  530 ,  532  have sides of substantially equal lengths (forming equilateral triangles) however the sides need not be of the same length. Furthermore, first and second elongated housings  530 ,  532  are coupled longitudinally along a substantial portion of respective sides  530 A,  532 A. In another embodiment, sensor apparatus  504  similar to sensor apparatus  503  includes first and second elongated housings  540 ,  542  with different respective wall thicknesses t 3  and t 4 . 
     In another embodiment, sensor apparatus  505  has an oval-shaped cross-sectional area which is split in half to form first elongated housing  550  and second elongated housing  552 . The oval shape may impart increased resistance to tangling of sensor apparatus  505 , as may occur during installation and/or due to shifting ground during the lifetime of the sensor. It will be understood that sensor apparatus  505  may be divided in other ways, such as toward one end of the oval or the other end of the oval and/or diagonally. 
     In a further embodiment, sensor apparatus  506  similar to sensor apparatus  501  includes strength member  564 , as may be similar to strength member  430  described in conjunction with  FIG. 4 . 
     In another embodiment, sensor apparatus  507  similar to sensor apparatus  503  and  504  includes strength member  574 . Here, strength member  574  occupies an inner area and is coupled to inner surface  572 A of second elongated housing  572 ; however, one of ordinary skill in the art will recognize that strength member  574  may be coupled to other portions of sensor apparatus  507 , such as inner surface  570 A of first elongated housing  570 . 
     In a further embodiment, sensor apparatus  508  similar to sensor apparatus  505  includes strength member  584 . Here, strength member  584  occupies substantially equal inner areas of first elongated housing  580  and second elongated housing  582 . Containing strength member  584  within the inner areas instead of along the outer surfaces of the housings results in a smaller cross-sectional area of sensor apparatus  508  and may simplify extrusion of sensor apparatus  508 . 
     Referring now to  FIG. 6 , in another aspect, the inventive techniques, systems, and concepts include sensor apparatus  600  (shown in  FIG. 6  in perspective view) including elongated sensor body  602  forming first lumen  610  to at least partially enclose sensor device  650  and second lumen  620  having portion  621  parallel to elongated sensor body  602  and radial port portion  622  extending from parallel portion  621  of second lumen  620  to outer surface  611 B of elongated sensor body  602 . Second lumen  620  acts to conduct material  605  through parallel portion  621  and through radial port portion  622  to a position about sensor apparatus  600 . As can be seen in  FIG. 6 , sensor apparatus embodiment  600  has smooth outer surface  608  which can reduce interference and/or entanglement with other objects and devices in borehole  690  (shown in  FIG. 6  in cutout perspective view). In a further embodiment, sensor apparatus  600  includes third lumen  632  at least partially enclosing strength member  630 , which may be similar to strength member  430  described in conjunction with  FIG. 4 . 
     Referring now to  FIG. 7 , a method  700  of installing a sensor apparatus includes providing a first elongated housing to at least partially enclose sensor device  702 , and providing a second elongated housing coupled longitudinally to first elongated housing  704 . The second elongated housing includes at least one radial port extending from an inner surface to an outer surface of the second elongated housing. The method  700  further includes displacing a material through the second elongated housing and out at least one radial port in the second elongated housing to allow material to be positioned near the sensor device. 
     In a further embodiment, the method  700  further includes coupling the sensor device to an inner wall of first elongated housing  708  and/or forming an opening in a wall of the first elongating housing to insert at least a portion of the sensor device within the first elongating housing  710 . 
     Having described exemplary embodiments of the invention, it will now become apparent to one of ordinary skill in the art that other embodiments incorporating their concepts may also be used. The embodiments contained herein should not be limited to disclosed embodiments but rather should be limited only by the spirit and scope of the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.