Patent Application
20120063264
This disclosure relates generally to the sensing of seismic activity. More particularly, this disclosure relates to a method for the emplacement of a sensor in soil for sensing seismic activity.
The sensing of seismic activity is an area of ever-growing importance with the growing need to be able to reliably emplace sensors in soil for accurate sensing. Typically, the sensing of seismic activity is accomplished by way of a sensor being emplaced in the soil such that it can sense subterranean vibrations through pressures waves traveling through the ground. The key to such sensing of seismic activity is the ability to emplace a sensor properly in the soil so that it's not damaged during installation and that it's properly coupled to the surrounding soil so to accurately sense the subterranean activity. There are various known ways of emplacing sensors in the ground today such as, for example, emplacing temporary seismic sensors in vertical seismic profiling (VSP) applications wherein a clamping device is used to couple geophones to the interior of vertical well pipes. Another example is the emplacement of hydrophones in flooded vertical well pipes. Overall, the majority of permanent deep hydrophone or geophone sensor emplacements performed today in the industry use either vertical boreholes or deep trenches.
However, deep trenches often times result in the formation of voids, gaps and other cavities around the sensor which all serve to degrade the sensitivity and overall accuracy of the system. Further, open trench excavation is often times too disruptive to the surrounding area and is, hence, not preferred in many applications. Typically, open trench excavation is better suited for applications where space is limited and/or the required depth of the sensor emplacement is fairly shallow such as, for example, with depths ranging from several feet to 20 feet.
On the other hand, trenchless technologies are also known and used today as an alternative to open trench excavation. Trenchless technologies are such that create a borepath into which a sensor (or a sensor array) can be inserted. One form of trenchless technology is known as horizontal directional drilling (HDD). HDD is a steerable trenchless technology for installing underground pipes, conduits and cables in a shallow arc along a prescribed borepath by using drilling pipe launched from surface drilling rigs. HDD presents a minimal impact on the surrounding area. HDD is a typical approach taken when digging open trenches is impractical or the depth of the required emplacement is too deep. It is suitable for a variety of soil conditions and jobs including road, landscape and river crossings. Installation lengths up to 6,500′ (2,000 m) have been completed, and diameters up to 56″ (1,200 mm) have been installed in shorter runs. Pipes placed in the borepath can be made of various materials such as PVC, polyethylene, ductile iron, and steel if the pipes have the tensile strength to be pulled through the borepath.
The HDD drilling begins with first viewing the geological surroundings to see if HDD is a viable option. HDD is not favored when there are voids in the rock or incomplete layers of rock. The best material is solid rock, sedimentary material, or consolidated soils. However, trenchless technologies such as HDD also have a number of limitations and shortcomings. For example, HDD requires the use of very rugged sensors in order for the sensors to be reliably pulled through a borepath. Further, HDD has typically exhibited an inherent limited ability to effectively couple the sensor to the walls of the borepath and, hence, has exhibited poor performance at times. Further, sensors can be damaged during installation when using HDD methods by the significant pressures placed on the sensor (or the sensor array) by the borepath itself as the sensor is pulled through the borepath into place.
The sensors typically used in HDD applications for sensing seismic activity are in the form of one or more hydrophones or geophones aligned in an array placed within the borepath. However, due to their fragile nature and critical coupling requirements, difficulties often arise with their use in HDD applications.
Accordingly, there exists a long felt need for an improved method for the emplacement of a sensor in soil for sensing seismic activity that overcomes and alleviates the inherent problems known with the sensor emplacement methods currently being employed in the seismic sensing industry today.
According to one embodiment of the present disclosure, a method for the emplacement of a sensor in soil for sensing seismic activity is presented having a series of steps that comprise using a drillstring pipe to create a borepath having opposing ends, attaching a reamer to the drillstring pipe and pulling it back through the borepath to enlarge the diameter of the borepath, pulling a longitudinal housing and a grout pipe into the borepath extending from one opposing end to the other and with the longitudinal housing having a sensor encapsulated within, anchoring the longitudinal housing at one of the opposing ends, pulling the grout pipe longitudinally within the borepath to position its grouting end within the borepath between the opposing ends, and conducting a grout through the grout pipe into the borepath at the grouting end while continuing to pull the grout pipe through the borepath until the grouting end is positioned adjacent to one opposing end to encase the longitudinal housing within the borepath thereby facilitating emplacement of a sensor in soil for sensing seismic activity. Emplacement of a sensor in accordance with the teachings of the present disclosure may serve to alleviate some of the pressures that are otherwise exerted on the sensor when filling the borepath with grout. Further, the voids and gaps that might otherwise form around the longitudinal housing conventional methodologies may be substantially avoided using the emplacement method as taught by the present disclosure.
In one embodiment of the present disclosure, multiple grout pipes may also be used to conduct the grout into the borepath for encasing the sensor. Using multiple grout pipes provides for even more relief of the pressures felt by the sensor due to less grout needing to be pushed through the borepath from a single point. The use of multiple grout pipes also provides for improved grout coverage of the longitudinal housing.
Accordingly, some embodiments of the disclosure may provide numerous technical advantages. Some embodiments may benefit from some, none or all of these advantages. For example, a technical advantage of one embodiment of the disclosure may be improved sensor coupling to the soil. Furthermore, improved sensor coupling will result in higher sensor sensitivity and accuracy. Another embodiment may provide for an alternative grouting method that may provide even further benefit with regard to pressures seen at the sensor within the borepath.
Another example of a potential technical advantage of one embodiment of the present disclosure is that it may alleviate some of the inherent problems associated with the emplacement of sensor arrays regarding difficulties in maintaining proper sensor spacing within the borepath. For example, a technical advantage of one embodiment of the disclosure may be that the entire sensor array may be wholly contained and fixed in a position within a longitudinal housing before being installed in a borepath.
Although specific advantages have been disclosed hereinabove, it will be understood that various embodiments may include all, some, or none of the disclosed advantages. Additionally, other technical advantages not specifically cited may become apparent to one of ordinary skill in the art following review of the ensuing drawings and their associated detailed description. The foregoing has outlined rather broadly some of the more pertinent and important advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood so that the present contribution to the art can be more fully appreciated. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the present disclosure as set forth in the appended claims.
For a fuller understanding of the nature and possible advantages of the present disclosure, reference should be had to the following detailed description taken in connection with the accompanying drawings in which:
Similar reference characters refer to similar parts throughout the several views of the drawings.
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The longitudinal housing 22 in one embodiment is in the form of flexible pipe made from High-Density-Polyethylene (HDPE). HDPE pipe is preferable for many applications in that it has acoustical properties very similar to that of the surrounding soil 6. The longitudinal housing 22 which encapsulates the sensor 26 surrounded by the material 28 is further acoustically matched to the surrounding soil 6 by grout 30 which encases the longitudinal housing 22 within the borepath 12. The grout 30 serves to completely surround the longitudinal housing 22 and cure to securely fix the longitudinal housing 22 in place within the borepath 12. The grout 30 in one embodiment is preferably formed of a mixture of water, Portland cement and bentonite, the ratios of which are varied depending on the nature of the soil 6 that is to be acoustically matched. Further, the grout 30 has expansive properties such that it expands while curing in the borepath 12 to promote a reliable coupling between the longitudinal housing 22 and the surrounding soil 6. The relative expansiveness of the grout 30 can be controlled by the ratio of bentonite to water as well as by the type of bentonite used (i.e., granular versus powder).
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At step 110, the grout pipe 24 is pulled through the borepath 12 to position the grouting end within the borepath 12 between the opposing ends 16 and 18. From step 110, the process moves to step 112. At step 112, grout 30 is conducted through the grout pipe 24 into the borepath 12 at the grouting end while continuing to be pulled longitudinally through the borepath 12 until the grouting end is positioned adjacent to one opposing end of the borepath 12. At this point, the emplacement of the sensor 26 within the soil 6 is complete with the acoustically matched grout 30 left to expand and cure within the borepath 12. From step 112, the process moves to step 114 where the process ends.
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From step 206, the process moves to step 208. At step 208, a longitudinal housing 22 and a plurality of grout pipes 24 are attached to the drillstring pipe 4 and pulled into the borepath 12 extending from one opposing end 16 to the other opposing end 18. The longitudinal housing 22 includes a sensor 26 surrounded by material 28 encapsulated within it. In one embodiment, the plurality of grout pipes 24 may comprise three grout pipes 24. From step 208, the process moves to step 210. At step 210, the longitudinal housing 22 is anchored at one of the opposing ends 16 and 18. From step 210, the process moves to step 212. At step 212, the plurality of grout pipes 24 are pulled back longitudinally through the borepath 12 to the extent that their respective grouting ends are staggered within the borepath 12. From step 212, the process moves to step 214. At step 214, grout 30 is conducted through the plurality of grout pipes 24 simultaneously into the borepath 12 at the grouting ends until the borepath 12 is full of grout 30. The plurality of grout pipes 24 are left grouted in place within the borepath 12. At this point, the emplacement of the sensor 26 within the soil 6 is complete with the acoustically matched grout 30 left to expand and cure within the borepath 12 in accordance with the teachings of one embodiment of the present disclosure. From step 214, the process moves to step 216 where the process ends.
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From step 306, the process moves to step 308. At step 308, a longitudinal housing 22 and at least two grout pipes 24 are attached to the drillstring pipe 4 and pulled into the borepath 12 extending from one opposing end 16 to the other opposing end 18. The longitudinal housing 22 includes a sensor 26 surrounded by material 28 encapsulated within it. From step 308, the process moves to step 310. At step 310, the longitudinal housing 22 is anchored at one of the opposing ends 16 and 18. From step 310, the process moves to step 312. At step 312, the at least two grout pipes 24 are pulled back longitudinally through the borepath 12 in opposite directions until respective grouting ends of the grout pipes 24 are positioned adjacent each other at the longitudinal midpoint of the borepath 12.
From step 312, the process moves to step 314. At step 314, grout 30 is conducted through the at least two grout pipes 24 simultaneously into the borepath 12 at the grouting ends while the at least two grout pipes 24 are further simultaneously pulled in opposite directions toward respective opposing ends 16 and 18 of the borepath 12 until positioned adjacent the opposing ends 16 and 18. At this point, the emplacement of the sensor 26 within the soil 6 is complete with the acoustically matched grout 30 left to expand and cure within the borepath 12 in accordance with the teachings of one embodiment of the present disclosure. From step 314, the process moves to step 316 where the process ends.
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At step 406, another reamer 20 of a larger size and a grout pipe 24 are attached to the first drillstring pipe and pulled back through the borepath 12 to further enlarge the diameter 14 of the borepath 12 so to accommodate the pulling of additional materials through the borepath 12. From step 406, the process moves to step 408. At step 408, a second drillstring pipe that is smaller in size to the first drillstring pipe is pushed longitudinally through the center of the first drillstring pipe extending from one opposing end of the borepath 12 to the other. From step, 408, the process moves on to step 410. At step 410, a sensor 26 is attached to the second drillstring pipe and then pulled longitudinally through the center of the first drillstring pipe until centered in the first drillstring pipe and centered within the borepath 12. It should be understood, however, that steps 408 and 410 could alternatively use a mule tape, a wire, a rope or other similar devise in place of the second drillstring pipe to pull the sensor 26 into the first drillstring pipe.
From step 410, the process moves on to step 412. At step 412, the sensor is anchored to one of the opposing ends 16 and 18 of the borepath 12. From step 412, the process moves on to step 414. At step 414, grout 30 is conducted through the grout pipe 24 into the borepath 12 while simultaneously withdrawing the first drillstring pipe and the grout pipe 24 from the borepath 12 in the direction opposite to the opposing end 16 or 18 where the sensor 26 is anchored. At this point, the emplacement of the sensor 26 within the soil 6 is complete with the acoustically matched grout 30 left to expand and cure within the borepath 12 in accordance with the teachings of one embodiment of the present disclosure. From step 414, the process moves on to step 416 where the process ends.
In referring now to
From step 506, the process moves to step 508. At step 508, the grout pipe 24 is pulled back longitudinally through the borepath 12 so to position the grouting end within the borepath 12 between the opposing ends 16 and 18. From step 508, the process moves on to step 510. At step 510, grout 30 is conducted through the grout pipe 24 into the borepath 12 to encase and fixedly secure the longitudinal housing within the borepath 12. From step 510, the process moves on to step 512. At step 512, the sensor 26 is attached to the mule tape and pulled into place by the mule tape positioning the sensor 26 within the longitudinal housing. From step 512, the process moves on to step 514. At step 514, a material 28 is conducted into the longitudinal housing to surround the sensor 26 and acoustically match and couple the sensor 26 to the longitudinal housing. The longitudinal housing is then sealed to retain the material 28 within. At this point, the emplacement of the sensor 26 within the soil 6 is complete with the acoustically matched grout 30 left to expand and cure within the borepath 12 in accordance with the teachings of one embodiment of the present disclosure. From step 514, the process moves to step 516 where the process ends.
The present disclosure includes that contained in the appended claims, as well as that of the foregoing description. Although this disclosure has been described in its preferred form in terms of certain embodiments with a certain degree of particularity, alterations and permutations of these embodiments will be apparent to those skilled in the art. Accordingly, it is understood that the above descriptions of exemplary embodiments does not define or constrain this disclosure, and that the present disclosure of the preferred form has been made only by way of example and that numerous changes, substitutions, and alterations in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.
