In Situ Geophysical Sensing Apparatus Method And System

Abstract

An apparatus for in situ geophysical sensing includes a sensor for measuring geophysical data and a liquid absorbent member connected to the sensor that expands in response to contacting a liquid and thereby physically couples the sensor to a local sensing environment. The liquid absorbent member may be formed of beads or pellets or powder that includes a liquid absorbent material. The liquid absorbent member may also include a soluble binding agent for binding the beads or pellets or powder into an integral member such as a casing for containing the sensor. A method and system corresponding to the apparatus are also described herein. The apparatus, method and system described herein may be used to improve borehole sensor data quality without adding significant complexity to the borehole sensor deployment process.

Description

BACKGROUND

[0001] 1. Technical Field

[0002] Embodiments of the subject matter disclosed herein generally relate to the field of seismic sensing. In particular, the embodiments disclosed herein relate to devices, methods and systems for in situ borehole coupling for geophysical sensing applications.

[0003] 2. Discussion of the Background

[0004] Seismic sensors are often deployed in wells for geophysical data applications. The sensors need to make firm contact with the walls of the well in order to accurately record seismic data. However, the sensors often suffer from substandard coupling to the walls of the borehole resulting in poor data quality. Packing suitable filler material between the sensors and the walls of the well without leaving voids is difficult--particularly for applications where the borehole sensors are stacked. For example, grout densities are often too low to travel down a borehole and fully encompass a sensor. In such cases a larger borehole may be cut and a hose or pipe used to travel past one or more sensors and deposit grout from the bottom up. This may require specialized grout pumping equipment and a larger borehole. However, even a bottom up approach may leave unwanted gaps in the filler material.

[0005] Commonly assigned U.S. patent application Ser. No. 12/171,135, which is incorporated herein by reference, describes an alternative solution where an inflatable bladder can be used to fill in the space between the sensor and the borehole. While the quality of the geophysical data generated may be improved, implementing such a solution adds complexity to the borehole sensor deployment process.

[0006] What is needed is a borehole coupling solution that does not add significant complexity to the borehole sensor deployment process.

SUMMARY

[0007] As detailed herein an apparatus for in situ geophysical sensing includes a sensor for measuring geophysical data and a liquid absorbent member connected to the sensor that expands in response to contacting a liquid such as water and thereby physically couples the sensor to a local sensing environment. The liquid absorbent member may be formed of beads or pellets or powder comprising the liquid absorbent material.

[0008] In certain embodiments, the liquid absorbent member comprises a soluble binding agent for binding the beads or pellets or powder into an integral member such as a casing for containing the sensor. In other embodiments, the liquid absorbent member is coated with a soluble layer for temporary isolation of the liquid absorbent material from liquid that is in contact with the liquid absorbent member.

[0009] In some deployments, water may be naturally occurring within the borehole sensing environment. In other deployments, a borehole may be filled with water, some other liquid, or slurry in order to activate expansion of the liquid absorbent member.

[0010] A method and system corresponding to the above apparatus are also described herein. The apparatus, method and system described herein may be used to improve borehole sensor data quality without adding significant complexity to the borehole sensor deployment process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings:

[0012] FIG. 1 is a perspective schematic depicting a survey environment wherein an array of expandable geophysical sensors may be deployed;

[0013] FIG. 2 is an exploded perspective view drawing depicting a first embodiment of the expandable geophysical sensor;

[0014] FIGS. 3a and 3b are side view drawings depicting deployment of the first embodiment of the expandable geophysical sensor within a downhole pipe;

[0015] FIG. 4 is a flowchart diagram of an in situ geophysical sensing method;

[0016] FIGS. 5a and 5b are side view drawings depicting deployment of a second embodiment of the expandable geophysical sensor within a downhole pipe; and

[0017] FIG. 6 is a schematic block diagram of an in situ geophysical sensing and processing system.

DETAILED DESCRIPTION

[0018] The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

[0019] Reference throughout the specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[0020] As detailed herein, a novel apparatus for in situ geophysical sensing--referred to herein as an expandable geophysical sensor--includes a sensor for measuring geophysical data and a liquid absorbent member connected to the sensor that expands in response to contacting a liquid such as water and thereby physically couples the sensor to a local sensing environment.

[0021] FIG. 1 is a perspective schematic depicting a survey environment (100) wherein an array of expandable geophysical sensors (110) may be deployed. In the depicted deployment, multiple expandable geophysical sensors (110) are placed on each cable (112) to form a number of sensor strings (113) that are weighted with a weight (114) that helps pull the expandable sensors (110) into place within a borehole (120). A sensor string (113) may be suspended from a suspension fixture (not shown) located at the top of the borehole (120).

[0022] Once in place, the expandable geophysical sensors (110) may expand (not shown) in response to contacting a liquid and thereby physically couple to the sensing environment that is local to each sensor (110). Cable (112) may facilitate collecting geophysical data from the expandable geophysical sensors (110) and conducting analysis on that data.

[0023] FIG. 2 is an exploded perspective view drawing depicting a first embodiment (110a) of the expandable geophysical sensor (110). FIGS. 3a and 3b are side view drawings depicting deployment of the first embodiment (110a) of the expandable geophysical sensor (110).

[0024] As depicted in FIGS. 2, 3a and 3b, the first embodiment (110a) includes a sensor (210), a casing (220), a tip cap (230) with barbs (232), a tip bolt (240) and an end cap (250). The expandable geophysical sensor (110) expands to improve coupling to a local sensing environment. For purposes of simplicity, the depicted deployment is shown in FIGS. 3a and 3b within a downhole pipe. However, the expandable geophysical sensors (110) may also be deployed in a borehole without a pipe in order to couple directly to the wall of the borehole and the local sensing environment.

[0025] The sensor (210) measures and provides geophysical data such as seismic-related data or other data associated with a local environment. For example, the sensor may be a geophone, a hydrophone, an accelerometer, a fiber optic sensor, a temperature sensor, a strain sensor, a pressure sensor, a magnetic sensor, a chemical sensor, a tilt meter or the like.

[0026] The expandable geophysical sensor (110) may include a liquid absorbent member (215) that is connected to and/or proximate to the sensor (210). For example, the liquid absorbent member (215) may be attached (i.e., bonded, bolted, etc.), formed around, or deposited onto, the sensor (210), or otherwise arranged so that is proximate to the sensor (210). In one embodiment, the liquid absorbent member (215) comprises two sub-members (e.g., halves) that are mechanically attached to each other to form the casing (220) and enclose the sensor (210).

[0027] The liquid absorbent member (215) comprises a liquid absorbent material that expands in response to contacting a liquid and thereby physically couples the sensor to a local sensing environment. In one embodiment, the liquid absorbent material is a mined material such as bentonite. In another embodiment, the liquid absorbent material is a man-made material such as a super absorbent polymer.

[0028] The liquid absorbent member (215) may be formed of beads or pellets or powder comprising the liquid absorbent material. The liquid absorbent member (215) may also comprise a soluble binding agent for binding the beads or pellets or powder into an integral member such as the casing (220). In some embodiments, the liquid absorbent member (215) is coated with a soluble layer (not shown) for temporary isolation of the liquid absorbent material from a liquid that is adjacent to the liquid absorbent member (215). Using a soluble binding agent or a soluble layer may defer expansion of the liquid absorbent member (215) in the presence of a liquid and enable unimpeded deployment of the expandable geophysical sensor (110). In one embodiment, the liquid absorbent member (215) comprises pellets of less than 5 mm in diameter that are coated with a food-grade water-soluble binding agent. The use of a food-grade water-soluble binding agent may minimize the environmental impact of the binding agent.

[0029] In the depicted embodiment, the entire casing 220 is formed of the liquid absorbent member (215). However, in other embodiments the casing (220) is made of a solid material and encompassed partially or wholly by the liquid absorbent member (215). The casing (220) may contain the sensor when in an unexpanded state (300a), as shown in FIG. 3a, as well as the expanded state (300b), as shown in FIG. 3b. As shown in FIG. 2, the casing (220) may include one or more casing sections (222). In the depicted embodiment, the casing sections (222) are split along an axial dimension to provide a left casing section (222a) and a right casing section (222b). Each depicted casing section (222a and 222b) has casing cavity (224) for receiving and encompassing the sensor 210.

[0030] The casing (220) may also include the tip cap (230) and the end cap (250). The tip cap (230) and the end cap (250) may hold the axially split casing sections (222a and 222b) in place around the sensor (210). The tip cap (230) and the end cap (250) may also block vertical expansion of the liquid absorbent member (215) and thereby promote horizontal expansion of the liquid absorbent member (215) against a borehole wall or downhole pipe (310).

[0031] The tip cap (230) may include a number of barbs (232) that provide friction against the borehole wall or downhole pipe (310) and enable placement of the geophysical sensor (110a) during deployment. Specifically, the barbs (232) may prevent the expandable geophysical sensor (110a) from falling into the borehole or pipe while still allowing forward movement during deployment. For example, the barbs (232) may enable pushing the expandable geophysical sensor (110a) with a rod or other insertion tool to a desired position which is held by the barbs (232) until the liquid absorbent member (215) can expand and couple the geophysical sensor (110a) to the borehole wall or downhole pipe (310).

[0032] The sensor (210) may be connected to a cable (260) that runs vertically through the casing (220) and the end cap (250). A cable clamp (270) in combination with the tip bolt (240) may secure the members of expandable geophysical sensor (110a) to the cable (260). The cable (260) may comprise electrically conductive wires that enable uphole communication of the geophysical data provided by the sensor (210). The cable (260) may also facilitate insertion of the expandable sensor (110) into a hole (312). FIG. 3b illustrates the liquid absorbent member 215 in an expanded state, ensuring good coupling with the walls of the pipe 310. In one application, water or other liquids naturally occurring in the well are absorbed by member 215. In another application, water or another liquid is poured from the surface into the well in order to be absorbed by member 215.

[0033] FIG. 4 is a flowchart diagram of an in situ geophysical sensing method (400). As depicted, the method (400) includes boring (410) one or more holes, inserting (420) one or more expandable sensors (110), waiting (430) for a liquid absorbent member to expand, measuring (440) geophysical data, collecting (450) the geophysical data, processing (460) the geophysical data and analyzing (470) the geophysical data.

[0034] Boring (410) one or more holes may include using hole boring equipment to create an array of holes that are strategically placed to collect geophysical data.

[0035] Inserting (420) one or more expandable sensors (110) may include pushing or lowering one or more expandable geophysical sensors (110) into each hole created by the boring operation (410). Inserting (420) may also include ensuring that the expandable geophysical sensors (110) come in contact with a liquid such as water. For example, in some deployments water may be naturally occurring within the borehole sensing environment while in other deployments, a borehole may be filled with water, a slurry, or another liquid, (either before or after insertion of the sensors (110)) in order to activate expansion of the expandable geophysical sensors (110).

[0036] Waiting (430) for a liquid absorbent member to expand may include having a knowledge of the expected required expansion time for a particular borehole or pipe size and waiting the prescribed time. The expected required expansion time may be collected experimentally or by modeling the absorption rate of the liquid absorbent member.

[0037] Testing may also be conducted to determine if the liquid absorbent member has expanded sufficiently to provide physical coupling to the borehole or pipe wall. For example, in one embodiment a test shot is fired to determine the effectiveness of the physical coupling of the expandable geophysical sensors (110) to the borehole or pipe wall. In another embodiment, a cable connected to one or more expandable geophysical sensors (110) may be pulled with a selected force in order to determine if the expandable geophysical sensors (110) remain fixed in place and thereby determine if sufficient physical coupling has occurred with the walls of the borehole or pipe.

[0038] Measuring (440), collecting (450), processing (460) and analyzing (470) geophysical data may include conducting operations typically associated with geophysical data applications such as seismic analysis. For example, processing (460) may provide an image of a surveyed subsurface suitable for seismic analysis.

[0039] FIGS. 5a and 5b are side view drawings depicting a second embodiment (110b) of the expandable geophysical sensor (110) deployed within a downhole pipe (310). FIG. 5a depicts the second embodiment (110b) of the expandable geophysical sensor (110) in an unexpanded state (500a) while FIG. 5b depicts the second embodiment (110b) of the expandable geophysical sensor (110) in an expanded state (500b).

[0040] As depicted, the second embodiment (110b) includes a sensor (510), one or more liquid absorbent members (515), a tip (530), a cap (540) and a cable (550). One of skill in the art will appreciate that similar to first embodiment (110a), the depicted second embodiment (110b) is simply illustrative and that many other embodiments of the expandable geophysical sensor (110) may be realized that fit within the scope of the claims.

[0041] In many aspects, the depicted second embodiment (110b) is very similar to the first embodiment (110a). For example, similar to the sensor (210) the sensor (510) measures and provides geophysical data such as seismic-related data. Also, similar to the liquid absorbent member (215) the liquid absorbent members (515) comprise a liquid absorbent material (such as bentonite or an absorbent polymer) that expands in response to contacting a liquid and thereby physically couples the sensor to a local sensing environment.

[0042] In other aspects, the depicted second embodiment (110b) is different from the first embodiment (110a). For example, in contrast to the liquid absorbent member (215) of the first embodiment (110a), the liquid absorbent members (515) of the second embodiment (110b) provide physical coupling without functioning as a casing or enclosure for the sensor (510).

[0043] Furthermore, the depicted cable (550) extends upward and downward in the second embodiment (110b) which enables connecting multiple expandable sensors (110b) together into a sensing string as shown in FIGS. 1 and 6. For example, in the upward direction the cable (550) may be connected to another expandable sensor (110b) while in the downward direction the cable (550) may be connected to a weight that facilitates keeping the string of expandable sensors (110b) taut while lowering the expandable sensors (110b) into a borehole or pipe.

[0044] FIG. 6 is a schematic block diagram of an in situ geophysical sensing and processing system (600). As depicted, the in situ geophysical sensing and processing system (600) includes deployment equipment (605), an array (610) of expandable sensors (110) connected into sensing strings (113), a signal source (615), one or more data collections devices (620), data processing equipment (630) and one or more data analysis workstations (640). The in situ geophysical sensing and processing system (600) facilitates measuring and processing geophysical data over a selected geophysical volume (not shown).

[0045] The deployment equipment (605) may be used to deploy the sensors (110) of the array (610). The deployment equipment (605) may include hole boring equipment used to create one or more boreholes (120). The boreholes (120) may be created at selected locations on the surface of the geophysical volume in order to strategically cover a geophysical volume with the array (610) of expandable sensors (110). In order to achieve vertical differentiation over the geophysical volume, multiple expandable sensors (110) separated by selected distances may be connected into sensing strings (113). In order to achieve horizontal differentiation over the geophysical volume, the strings (113) may be lowered into the created boreholes (120) that are spaced laterally over the geophysical volume. The boreholes (120) may be located on land or on the floor of a body of water.

[0046] Once in place in the presence of water or another liquid, the expandable geophysical sensors (110) may expand and physically couple to the specific selected locations within the geophysical volume and provide geophysical data (not shown) corresponding to those selected locations. The geophysical data may include data recorded in response to a signal generated by the signal source (615). For example, the signal source (615) may be a seismic source and the geophysical data may be seismic data recorded in response to a shock wave generated by the seismic source.

[0047] The geophysical data provided by the expandable geophysical sensors (110) may be collected by one or more data collections devices (620), processed by the data processing equipment (630), and analyzed by geophysicists or the like at one or more data analysis workstations (640).

[0048] The embodiments disclosed herein provide an apparatus, method and system for in situ geophysical sensing. It should be understood that this description is not intended to limit the invention. On the contrary, the described embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the disclosed embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.

[0049] Although the features and elements of the disclosed embodiments are described in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.

[0050] This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.

Claims

1. An apparatus for in situ geophysical sensing, the apparatus comprising: a sensor for measuring geophysical data; and a liquid absorbent member proximate to the sensor, the liquid absorbent member including a liquid absorbent material that expands in response to contacting a liquid and thereby physically couples the sensor to a local sensing environment.

2. The apparatus of claim 1, wherein the liquid absorbent member is formed of beads or pellets or powder comprising the liquid absorbent material.

3. The apparatus of claim 2, wherein the liquid absorbent member further comprises a soluble binding agent for binding the beads or pellets or powder into an integral member.

4. The apparatus of claim 1, wherein the liquid absorbent member is coated with a soluble layer for temporary isolation of the liquid absorbent material from the liquid that is adjacent to the liquid absorbent member.

5. The apparatus of claim 1, wherein the liquid absorbent member is a casing configured to fully enclose the sensor.

6. The apparatus of claim 5, wherein the casing comprises a plurality of casing sections that are split along an axial dimension.

7. The apparatus of claim 5, wherein the casing comprises a tip portion having a tip cap for blocking vertical expansion of the liquid absorbent material.

8. The apparatus of claim 5, wherein the casing comprises an end portion having an end cap for blocking vertical expansion of the liquid absorbent material.

9. The apparatus of claim 1, wherein the sensor is connected to a cable.

10. The apparatus of claim 9, wherein the cable facilitates insertion of the sensor into a hole.

11. The apparatus of claim 9, wherein the cable enables uphole communication of the geophysical data provided by the sensor.

12. The apparatus of claim 9, wherein the cable is connected to another sensor.

13. The apparatus of claim 9, wherein the cable is connected to a weight.

14. The apparatus of claim 1, further comprising a plurality of barbs.

15. A method for in situ geophysical sensing, the method comprising: providing an expandable sensor including: a sensor for measuring geophysical data, and a liquid absorbent member proximate to the sensor, the liquid absorbent member comprising a liquid absorbent material that expands in response to absorbing a liquid and thereby physically couples the sensor to a local sensing environment; inserting the expandable sensor into a hole and providing a liquid to the expandable sensor; allowing the liquid absorbent member to expand in response to contacting the liquid and physically couple the sensor to a local sensing environment; and measuring geophysical data with the expandable sensor.

16. The method of claim 15, further comprising: processing the geophysical data to determine an image of a surveyed subsurface.

17. The method of claim 15, further comprising: boring a hole for the expandable sensor.

18. A system for in situ geophysical sensing and processing, the system comprising: a plurality of expandable sensors placed into one or more holes and expanded to physically couple to a local sensing environment each expandable sensor including: a sensor for measuring geophysical data, and a liquid absorbent member connected to the sensor, the liquid absorbent member comprising a liquid absorbent material that expands in response to absorbing a liquid and thereby physically couples the sensor to a local sensing environment; and data processing equipment for processing the geophysical data.

19. The system of claim 18, further comprising hole-boring equipment for boring the one or more holes.

20. The system of claim 18, wherein the plurality of expandable sensors are attached to each other along a wire and placed in a single well.