Abstract:
A biodegradable ground contact sleeve for a seismic data acquisition node includes a ground contact sleeve having a substantially tubular shaped body insertable into the surface of the earth and having an internal opening at one longitudinal end for receiving a seismic data acquisition node and making acoustic coupling thereto. The ground contact sleeve is formed of biodegradable material.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation of International Application No. PCT/US15/53083 filed on Sep. 30, 2015. Priority is claimed from U.S. Provisional Application No. 62/058,089 filed on Sep. 30, 2014. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    Not Applicable. 
       BACKGROUND 
       [0004]    The present disclosure relates in general to seismic data acquisition, and in particular to mounting of seismic data acquisition nodes to and into earth surfaces. 
         [0005]    Seismic data acquisition nodes have been used for acoustically coupling seismic sensors to earth surfaces, both above the ground and mounted into the ground. A sensor node is a self-contained device that comprises one or more sensors and sensor signal processing and recording devices. The nodes may be deployed individually or arranged in an array and then used for acquiring seismic data resulting from seismic energy imparted into the earth or seismic energy that occurs naturally or from other subsurface phenomena. The acquisition nodes are conventionally mounted in holes formed into the earth, and ground contact sleeve devices formed into the housing of the nodes or affixed to the nodes have been used to acoustically couple the acquisition nodes to the ground. The acquisition nodes and the ground contact sleeve devices are removed from the ground and collected after use. Removing acquisition nodes having ground contact sleeve devices from the ground is time consuming and expensive, especially for those devices which are wedged into the ground. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is perspective view of a biodegradable ground contact sleeve and a seismic data acquisition node, showing the node mounted in the ground contact sleeve. 
           [0007]      FIG. 2  is an exploded view showing the seismic data acquisition node removed from the ground contact sleeve. 
           [0008]      FIG. 3  is bottom view of the ground contact sleeve and acquisition node of  FIGS. 1 and 4 . 
           [0009]      FIG. 4  is side elevation view of the ground contact sleeve with the acquisition node mounted within the ground contact sleeve. 
           [0010]      FIG. 5  is longitudinal section view of the ground contact sleeve and acquisition node, taken along section line  5 - 5  of  FIG. 4 . 
           [0011]      FIG. 6  is side elevation view of the ground contact sleeve after removal of the acquisition node. 
           [0012]      FIG. 7  is cross-sectional view of the ground contact sleeve, taken along section line  7 - 7  of  FIG. 6 . 
           [0013]      FIG. 8  is an enlarged view of a portion of the sectional view of the ground contact sleeve of  FIG. 7  showing a squared geometric configuration for the internal ribs of the ground contact sleeve. 
           [0014]      FIG. 9  is cross-sectional view of an alternative embodiment of the ground contact sleeve, taken along section line  7 - 7  of  FIG. 6 . 
           [0015]      FIG. 10  is an enlarged view of a portion of the sectional view of another embodiment of ground contact sleeve of  FIG. 9 , showing an angular directional gripping configuration for the internal ribs of the ground contact sleeve having a rotational collapsing feature to provide for release of the acquisition node from within the ground contact sleeve with rotation of the node in a first angular direction and to provide for gripping of the acquisition node when the node is rotated in a second angular direction. 
           [0016]      FIG. 11  is side elevation, exploded view of the ground contact sleeve with a pin cap and pin flag to assist in a user locating the ground contact sleeve in the field. 
           [0017]      FIG. 12  is cross-sectional view of the ground contact sleeve, pin cap and pin flag of  FIG. 11 , taken along section line  12 - 12 . 
           [0018]      FIG. 13  is detail view of an upper portion of the ground contact sleeve and the pin cap of the cross sectional view of  FIG. 12 . 
           [0019]      FIG. 14  is a schematic view of an open-ended ground contact sleeve mounted in the earth, with the ground contact sleeve shown in a longitudinal cross-section. 
           [0020]      FIG. 15  is a schematic view of a flute-ended ground contact sleeve mounted in the earth, with the fluted ended ground contact sleeve shown in a longitudinal cross-section. 
           [0021]      FIG. 16  is a schematic view of a closed-ended ground contact sleeve mounted in the earth, with the closed ended ground contact sleeve shown in a longitudinal cross-section. 
           [0022]      FIG. 17  is a schematic view of a second closed-ended ground contact sleeve mounted in the earth, with the second closed-ended ground contact sleeve shown in a longitudinal cross-section and with the closed end being ribbed, or having a grooved lower surface to allow penetration of the acquisition node through the closed end and into soil/earth after installation of the ground contact sleeve into the ground. 
           [0023]      FIG. 18  is side elevation view of an insertion tool with the ground contact sleeve mounted thereto for insertion into the terrain. 
           [0024]      FIG. 19  is longitudinal section view of the insertion tool and the ground contact sleeve, taken along section line  19 - 19  of  FIG. 18 . 
           [0025]      FIG. 20  is a detail view of an intermediate portion of the insertion tool and the ground contact sleeve  FIG. 21  is an enlarged view of a portion of  FIG. 18 , showing the two rotary extending cutting cam pawls at the lowermost end of the insertion tool. 
           [0026]      FIG. 22  is a perspective view of the lower end of the insertion tool, showing the two rotary extending cutting cam pawls. 
           [0027]      FIG. 23  is a cross-sectional view taken along section line  23 - 23  of  FIG. 22 , and shows the retractable cutter located in the lower end of the insertion tool. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]      FIG. 1  is perspective view of a biodegradable ground contact sleeve  12  and a seismic data acquisition node  10 , showing the seismic data acquisition node  10  mounted in the ground contact sleeve  12 . The ground contact sleeve  12  may have a tubular shaped body  14  and an upper end defining a stop or flange  16 . The flange  16  may have an arcuate shaped profile with a concave-shaped lower surface and a convex shaped upper surface. The ground contact sleeve  12  has a lower end  18  wherein longitudinally extending, vertical slots  22  define finger-like tabs  20 . The tables  20  may be angularly spaced apart about a longitudinal axis  30  of the ground contact sleeve  12  and the acquisition node  10 . 
         [0029]      FIG. 2  is an exploded view showing the seismic data acquisition node  10  removed from the ground contact sleeve  12 . The seismic data acquisition node  10  is shown having a housing  24  which may have a cylindrically shaped exterior profile, a head  26  which may house a wireless transceiver (not shown), and a lower end having a nose  28 . 
         [0030]      FIG. 3  is bottom view of the ground contact sleeve  12  and seismic data acquisition node  10  of  FIGS. 1 and 4 . 
         [0031]      FIG. 4  is a side elevation view of the ground contact sleeve  12  with the acquisition node  10  mounted within the ground contact sleeve  12 . 
         [0032]      FIG. 5  is longitudinal section view of the ground contact sleeve  12  and acquisition node  10 , taken along section line  5 - 5  in  FIG. 4 .  FIG. 6  is a side elevation view of the ground contact sleeve  12  after removal of the seismic data acquisition node  10 . 
         [0033]      FIG. 7  is a cross-sectional view of the ground contact sleeve  12 , taken along section line  7 - 7  in  FIG. 6 . The ground contact sleeve  12  may have an interior passage  34  with ribs  36  protruding inwardly from the inner wall of the tubular body  14  to provide spacers and grip protrusions for securing and acoustically coupling the seismic data acquisition node  10  within the ground contact sleeve  12 . 
         [0034]      FIG. 8  is an enlarged view of a portion of the sectional view of the ground contact sleeve  12  of  FIG. 7 , showing a squared geometric configuration for the internal ribs  36  of the ground contact sleeve  12 . 
         [0035]      FIG. 9  is cross-sectional view of another embodiment of the ground contact sleeve  12 , taken along section line  7 - 7  of  FIG. 6 , showing another configuration of ribs  38  for acoustically coupling the seismic data acquisition node  10  within the ground contact sleeve  12 . 
         [0036]      FIG. 10  is an enlarged view of a portion of the sectional view of the embodiment of the ground contact sleeve  12  of  FIG. 9 , showing an angular directional gripping configuration for the internal ribs  38  of the ground contact sleeve  12  having a rotational collapsing feature to provide for release of the acquisition node  10  from within the ground contact sleeve  12  with rotation of the seismic data acquisition node  10  in a first direction  42  and to provide for gripping of the acquisition node  10  when the node  10  is rotated in a second direction  43  opposite to the first direction  42 . To provide such directional features on the ribs  38 , a longitudinally extending recess  40  may be provided by a slot or a channel which extends the full longitudinal length of respective ones of the ribs  38 , parallel to the longitudinal axis  30  (shown in  FIGS. 1 and 2 ). The ground contact sleeve  12  may mounted in the ground such that the ribs  38  and the respective recesses  40  extend substantially vertically. The inward edge of the recess  40  may have an arcuate shape. 
         [0037]      FIG. 11  is side elevation, exploded view of the ground contact sleeve  12  with a pin cap  52 , a pin  54 , and pin flag  56  to assist in a user locating the ground contact sleeve  12  when it is deployed in the ground. 
         [0038]      FIG. 12  is cross-sectional view of the ground contact sleeve  12 , pin cap  52 , the pin  54 , and the pin flag  56  of  FIG. 11 , taken along section line  12 - 12  in  FIG. 11 . 
         [0039]      FIG. 13  is detail view of an upper portion of the ground contact sleeve  12  and the pin cap  52  of the cross-sectional view of  FIG. 12 . 
         [0040]      FIG. 14  is a schematic view of an open-ended ground contact sleeve  62  mounted in the earth, with the ground contact sleeve  62  shown in a longitudinal cross-section. The ground contact sleeve  62  may have a fully open lower end  64 . 
         [0041]      FIG. 15  is a schematic view of a flute-ended ground contact sleeve  12  mounted in the ground, with the fluted-ended ground contact sleeve  12  shown in longitudinal cross-section. The ground contact sleeve  12  has a fluted lower end  18  as described above. 
         [0042]      FIG. 16  is a schematic view of a closed-ended ground contact sleeve  66  mounted in the earth, with the closed-ended ground contact sleeve  66  shown in longitudinal cross-section. The ground contact sleeve  66  may have an enclosed lower end  68 . 
         [0043]      FIG. 17  is a schematic view of a second closed-ended ground contact sleeve  70  mounted in the ground with a second closed-ended ground contact sleeve  70  shown in a longitudinal cross-section and with the closed end  72  being ribbed, or having recesses  74 , grooves, or an otherwise thinned lower end  72  to allow penetration of the seismic data acquisition node  10  through the closed end and into the ground after installation of the ground contact sleeve  70  into the ground. 
         [0044]      FIG. 18  is side elevation view of a insertion tool  82  with the ground contact sleeve  12  mounted thereto for insertion into the ground, and  FIG. 19  is longitudinal section view of the insertion tool  82  and the ground contact sleeve  12 , taken along section line  19 - 19  of  FIG. 18 . 
         [0045]      FIG. 20  is a detail view of an intermediate portion of the insertion tool  82  and the ground contact sleeve  12 . The insertion tool  82  has a centrally disposed insertion pole  84 , a grip handle  86  and a stop  88  which preferably fits flush against the upper end of the flange  16  of the ground contact sleeve  12 . When the insertion tool  82  is used manually by a person, the person may place his foot on the stop flange  88  to use his weight to push the panting tool and the ground contact sleeve into the ground. The insertion tool  82  may also be mechanized for automatic use as part of a mobile insertion unit. The lower end  92  of the insertion tool  82  has a retractable cutter  94 . 
         [0046]      FIG. 21  is an enlarged view of a portion of  FIG. 18 , showing the two rotary extending cutting cam pawls  96  at the lowermost end  92  of the insertion tool  82 .  FIG. 22  is a perspective view of the lower end  92  of the insertion tool  82 , showing the two rotary extending cutting cam pawls  96 . 
         [0047]      FIG. 23  is a cross-sectional view taken along section line  23 - 23  of  FIG. 22 , and shows the cutting tool retractable cutter  94  located in the lower end  92  of the insertion tool  82 . Friction of the lower end  92  of the insertion tool  82  rotating in the ground will cause the cam pawls to extend and retract, depending upon the direction of rotation of the insertion tool  82  in the ground. The lowermost end of the insertion tool  82  may have a cutting tool  104  which preferably has sharpened edges for cutting into the ground surface. The rotary cutting pawls  96  and  98  are pivotally mounted to two pins  100 , and a stop pin  102  is provided proximately between the two pins  100  to provide a stop for the cutting pawls  96  and  98  when in the fully extended position. 
         [0048]    In one example embodiment, a geometric pattern of ridges on an exterior surface of the ground contact sleeve  12  may include such features as diamonds, ovals, squares and/or other geometric shapes that increase the surface area of contact between the ground contact sleeve and the surface soil from 100 mm 2  to 1000 mm 2 , with a preferred range of 500 to 750 mm 2 . The configuration of external features and ground contact surface area for any example ground contact sleeve may be optimized for a particular soil type. For example for sandy soil, squares that increase the surface area by 750 mm 2  may provide optimal contact between the ground contact sleeve and the surface soil. 
         [0049]    In another example embodiment, the exterior of the ground contact sleeve may comprise a feature on an upper end thereof capable of affixing a cap to deter contamination of the interior of the ground contact sleeve with sediment and debris. 
         [0050]    In another example embodiment, the interior surface of the ground contact sleeve may include inward protrusions of various configurations explained further below that provide increased contact surface area with the seismic data acquisition node ( 10  in  FIG. 1 ), while providing space for the ejection of debris upon insertion of a node ( 10  in  FIG. 1 ) into the ground contact sleeve ( 12  in  FIG. 1 ). 
         [0051]    A ground contact sleeve left in place in the ground to provide an identical sensor position for 4D seismic imaging may accumulate sediment or debris in the interior over time, even when a using a cap. By using inward protrusions, such embodiments may enable a sensor to be inserted into the ground contact sleeve even when the interior of the ground contact sleeve is partially or completely filled with liquid and debris. 
         [0052]    In another embodiment, features such as splines on an interior wall or the top surface of the ground contact sleeve  100  may be in the form of longitudinal lines separated by at least 2 mm and up to 10 mm. The longitudinal lines should provide acoustic coupling to the sensor and allow for ejection of debris or sediment when the sensor is inserted into the ground contact sleeve. The height of the splines may be selected to provide an interference fit between the splines and the sensor housing ( 105  in  FIG. 4 ) for good acoustic coupling. 
         [0053]    To achieve the optimum coupling of a seismic wave sensor to composite-material, biodegradable device, feature components must simultaneously aid the transmission of seismic waves, while also comprising chemically labile groups. [Labile is generally defined as chemical groups that react with common environmental compounds such as water and oxygen in the presence of sunlight to bring about the scission or oxidation of groups that lead to decomposition of chemical species]. Those skilled in the art would recognize that in a generic sense, the quality of recorded data, is directly related to the contact of the sensor, sleeve for sensor insertion into the earth, and the soil surrounding the device. It is generally accepted that rigid materials achieve that principle, while elastomeric materials would absorb some of this energy. Further, since seismic transmission largely derives from the particle displacement, materials capable of absorbing such energy tend to polymers with long chains, well aligned chains or elastomers that distribute the energy by molecular vibrations of the chain. By contrast, polymers with rigid structures whose internal degrees of freedom is restricted, would general be better at transmitting such seismic energy. 
         [0054]    Selection of a material that is biodegradable may take account of a number of different physical requirements for the ground contact sleeve. Physically, rigid, full surface area contact between the ground contact sleeve with any form of acoustic sensor would provide better acoustic coupling between the ground and the sensor than a contact arrangement comprising large air gaps. A multitude of raised ridges as in various embodiments described above in principle would have greater surface area than a smooth surface and such ridges would have greater contact, and therefore, greater data fidelity due to the increased number of rigid contacts, as described above. 
         [0055]    Generally, materials that are more favorable for environmental degradation, i.e., biodegradability, often have mechanical properties that tend to attenuate acoustic energy, thus reducing the effectiveness of the ground contact sleeve. 
         [0056]    In some embodiments of a ground contact sleeve according to the present disclosure, composite materials comprising biodegradable components such as cellulose, while also comprising biodegradable thermoplastics may provide both good acoustic coupling between the ground contact sleeve and the sensor node while having the desired biodegradability. 
         [0057]    One type of plastic that may be used in some embodiments is polylactic acid (PLA). PLA decomposes in the presence of water and oxygen into carbon dioxide and water. Such decomposition processes, encompassed by the term “hydrolysis”, occur at rates that are related to temperature, time, water, and soil composition. Physical impregnation of cotton fiber (cellulosic polymers) by a water labile thermoplastic such as PLA may affect the stability of a composite material depending on the thickness of and the numbers of and layers of thermoplastic accessible to water. In one embodiment, the PLA is prepared with long carbon fiber to improve acoustic performance. 
         [0058]    In some embodiments the material for the ground contact sleeve may be made in layers by rastering molten plastic (e.g., PLA) over a sheet of canvas (e.g., made from cotton or cellulose). In other embodiments, canvas sheet may be dipped into molten PLA, rolled and dried around a mold to achieve the desired shape. 
         [0059]    In other embodiments, PLA thermoplastic may be stabilized by additives that microscopically reverse the first steps of hydrolysis by catalytic protection. Such additives can be added during the original synthesis of the polymer, or added during the thermal processing into the canvas. Examples of such additives may include inorganic salts such as silicates, or aluminates. Solid polysaccharide polymers such as cellulosics and galactomannans are known to absorb water, so as to protect the polylactic acid from hydrolysis, thus increasing the useful lifetime of the ground contact sleeve. 
         [0060]    The mechanical properties of the PLA may be adjusted by the addition of rigid comonomers. Such comonomers may also affect the hydrolysis rate. Examples of comonomers may include phenyl subunits, such as benzene dicarboxylic acids, [terephthalic acid, CAS 100-210, isophthalic acid, CAS 121-91-5, and phthalic acid, CAS 88-99-3] or naphthalene dicarboxylic acids, such as 2,3-naphthalenedicarboxylic acid CAS 2169-87-1 or 1,4-naphthalenedicarboxylic acid, CAS 605-70-9. One skilled in the art will recognize that carboxylic acid derivatives of the foregoing compounds may also be used. The foregoing examples are therefore illustrative and not limiting as to the scope of the present disclosure. Such derivatives may include aldehydes, ester, anhydride and/or acid chlorides. In other embodiments, intramolecular ester hydrolysis of rings or macrocylic rings may be used. The common element of these derivatives would follow the synthetic route of condensation polymerization and copolymerization. The particular rigid comonomers used may be selected to cause the ground contact sleeve to have acoustic impedance selected to match local soil conditions and to provide a desired time through which the ground contact sleeve would maintain stability before biodegradation. For example, soil pH will vary depending on the minerals present in the soil. The soil pH will buffer or accelerate the hydrolysis. 
         [0061]    Composite materials comprising canvas/PLA can also be thermally molded with a hot iron that uses the thermoplastic properties mold the composite to possess raised indentations on the interior surface to increase the rigid coupling surface area. 
         [0062]    For time-lapse seismic surveying, the duration of the interval between seismic surveys will determine the length of time the biodegradable ground contact sleeve should maintain its mechanical integrity. To that end, the choice of additives to the PLA would be chosen to meet the interval described. 
         [0063]    A ground contact sleeve for a seismic data acquisition node according to the present disclosure may provide a ground contact sleeve for coupling a seismic data acoustic node to the ground, wherein the ground contact sleeve is biodegradable and may be left in the ground indefinitely when the seismic data acquisition node is removed after use. In some embodiments, the biodegradable material may comprise seeding material to provide plant growth after use and abandoning of the ground contact sleeve. 
         [0064]    While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.