Hydrophone gain design for array noise tool

A system for leak detection. The system may comprise an acoustic logging tool that includes a hydrophone array with a plurality of hydrophones. The system may further include an information handling system communicatively connected to the acoustic logging tool and wherein the information handling system chooses three or more hydrophones from the plurality of hydrophones to operate during measurement operations.

BACKGROUND

For oil and gas exploration and production, a network of wells, installations and other conduits may be established by connecting sections of metal pipe together. For example, a well installation may be completed, in part, by lowering multiple sections of metal pipe (i.e., a casing string) into a wellbore, and cementing the casing string in place. In some well installations, multiple casing strings are employed (e.g., a concentric multi-string arrangement) to allow for different operations related to well completion, production, or enhanced oil recovery (EOR) options.

A growing concern in the life of an oil or gas well is the pressure buildup in its annuli. Pressure buildup may fatigue conduits within the annuli. Eventually, the conduit may fail and lead to a leak, in which fluid from outside the conduit flows to the inside of the conduit. This may lead to the recovery of undesirable fluids, additional corrosion, and/or catastrophic failure of multiple conduits. The first challenge for a petroleum engineer is to identify the source of the leak to enable design of an effective remedial activity. Identification of the source of pressure communication between well tubing-casing and casing-casing annuli presents an enormous challenge to petroleum engineers.

There are many methods to identify the source of leaks in a well by capturing acoustic noise with hydrophones. Currently, when utilizing hydrophones, a reoccurring problem is the saturation of either high gain channels or low gain channels that are both disposed on an acoustic logging tool. For example, for high amplitude leak noise, a low-gain hydrophone is able to record and measure this noise, however, high-gain hydrophones disposed on the acoustic logging tool become saturated. The opposite is true for low amplitude leak noise. High-gain hydrophones are able to record low frequency leak noise, but low-gain channels disposed on the acoustic logging tool become saturated.

DETAILED DESCRIPTION

This disclosure may generally relate to methods and systems for capturing and recording both a high leak noise and a low leak noise using an acoustic logging tool. To record both the high leak noise and the low leak noise, a hydrophone array of at least three hydrophones may be utilize for beamforming. A two-level gain configuration is designed to have selected channels (minimum three hydrophones in a group) with high gain and other channels with low gain. A two-level gain configuration is defined as at least one low gain channel on a hydrophone and at least one high gain channel on a second hydrophone disposed on the acoustic logging tool. In examples, there may be a plurality of low gain channels and a plurality of high gain channels. The two groups (high and low gain channels) are designed to create a larger aperture for both groups, which may optimize beamforming results.

FIG.1illustrates an operating environment for an acoustic logging tool100as disclosed herein in accordance with particular embodiments. Acoustic logging tool100may comprise a hydrophone104. In examples, there may be any number of hydrophones104, which may be disponed on acoustic logging tool100. Acoustic logging tool100may be operatively coupled to a conveyance106(e.g., wireline, slickline, coiled tubing, pipe, downhole tractor, and/or the like) which may provide mechanical suspension, as well as electrical connectivity, for acoustic logging tool100. Conveyance106and acoustic logging tool100may extend within casing string108to a desired depth within the wellbore110. Conveyance106, which may include one or more electrical conductors, may exit wellhead112, may pass around pulley114, may engage odometer116, and may be reeled onto winch118, which may be employed to raise and lower the tool assembly in the wellbore110. Signals recorded by acoustic logging tool100may be stored on memory and then processed by display and storage unit120after recovery of acoustic logging tool100from wellbore110. Alternatively, signals recorded by acoustic logging tool100may be conducted to display and storage unit120by way of conveyance106. Display and storage unit120may process the signals, and the information contained therein may be displayed for an operator to observe and stored for future processing and reference. Alternatively, signals may be processed downhole prior to receipt by display and storage unit120or both downhole and at surface122, for example, by display and storage unit120. Display and storage unit120may also contain an apparatus for supplying control signals and power to acoustic logging tool100. Typical casing string108may extend from wellhead112at or above ground level to a selected depth within a wellbore110. Casing string108may comprise a plurality of joints130or segments of casing string108, each joint130being connected to the adjacent segments by a collar132. There may be any number of layers in casing string108. For example, a first casing134and a second casing136. It should be noted that there may be any number of casing layers.

FIG.1also illustrates a typical pipe string138, which may be positioned inside of casing string108extending part of the distance down wellbore110. Pipe string138may be production tubing, tubing string, casing string, or other pipe disposed within casing string108. Pipe string138may comprise concentric pipes. It should be noted that concentric pipes may be connected by collars132. Acoustic logging tool100may be dimensioned so that it may be lowered into the wellbore110through pipe string138, thus avoiding the difficulty and expense associated with pulling pipe string138out of wellbore110.

In logging systems, such as, for example, logging systems utilizing the acoustic logging tool100, a digital telemetry system may be employed, wherein an electrical circuit may be used to both supply power to acoustic logging tool100and to transfer data between display and storage unit120and acoustic logging tool100. A DC voltage may be provided to acoustic logging tool100by a power supply located above ground level, and data may be coupled to the DC power conductor by a baseband current pulse system. Alternatively, acoustic logging tool100may be powered by batteries located within the downhole tool assembly, and/or the data provided by acoustic logging tool100may be stored within the downhole tool assembly, rather than transmitted to the surface during logging (corrosion detection).

As illustrated, one or more hydrophones104may be positioned on the acoustic logging tool100. It should be understood that the configuration of acoustic logging tool100shown onFIG.1is merely illustrative and other configurations of acoustic logging tool100may be used with the present techniques. Hydrophone104may include any suitable acoustic receiver suitable for use downhole, including piezoelectric elements that may convert acoustic waves into an electric signal or hydrophones. Additionally, hydrophone104may be able to record any waves generated by leakage or other flow event inside and/or outside of the borehole. In examples, hydrophone104may be disposed at any suitable location on acoustic logging tool100. For example, hydrophones104may be disposed along the outer edge of acoustic logging tool100or within acoustic logging tool100. Additionally, hydrophones104may be stacked along the longitudinal axis of acoustic logging tool100and/or one or more hydrophones104may be disposed circumferentially in a plane perpendicular to the longitudinal axis of acoustic logging tool100.

Referring back toFIG.1, the recordation of signals by hydrophones104may be controlled by display and storage unit120, which may include an information handling system144. As illustrated, the information handling system144may be a component of the display and storage unit120. Alternatively, the information handling system144may be a component of acoustic logging tool100. An information handling system144may include any instrumentality or aggregate of instrumentalities operable to compute, estimate, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system144may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. Information handling system144may include a processing unit146(e.g., microprocessor, central processing unit, etc.) that may process EM log data by executing software or instructions obtained from a local non-transitory computer readable media148(e.g., optical disks, magnetic disks). The non-transitory computer readable media148may store software or instructions of the methods described herein. Non-transitory computer readable media148may include any instrumentality or aggregation of instrumentalities that may retain data and/or instructions for a period of time. Non-transitory computer readable media148may include, for example, storage media such as a direct access storage device (e.g., a hard disk drive or floppy disk drive), a sequential access storage device (e.g., a tape disk drive), compact disk, CD-ROM, DVD, RAM, ROM, electrically erasable programmable read-only memory (EEPROM), and/or flash memory; as well as communications media such wires, optical fibers, microwaves, radio waves, and other electromagnetic and/or optical carriers; and/or any combination of the foregoing. Information handling system144may also include input device(s)150(e.g., keyboard, mouse, touchpad, etc.) and output device(s)152(e.g., monitor, printer, etc.). The input device(s)150and output devices)152provide a user interface that enables an operator to interact with acoustic logging tool100and/or software executed by processing unit146. For example, information handling, system144may enable an operator to select analysis options, view collected log data, view analysis results, and/or perform other tasks.

FIG.2illustrates acoustic logging tool100with a hydrophone array200in accordance with particular embodiments. Without limitation, there may be any number of hydrophones104. As illustrated, the hydrophone array200includes a plurality of the hydrophones104arranged longitudinally along the acoustic logging tool100. During measurement operations, acoustic logging tool100may detect the depth and radial location of leak202and/or flow of fluid204in wellbore110. In examples, acoustic logging tool100may be deployed with one or more stabilizers206installed above or below acoustic logging tool100. As illustrated inFIG.2, and discussed above, acoustic logging tool100may be disposed in pipe string138, which may be disposed in a first casing134. During operations, each hydrophone104of hydrophone array200may sense and record any number of acoustic signals and/or vibrations continuously as acoustic logging tool100moves up or down wellbore110within pipe string138. The recorded acoustic signals and/or vibrations may be formed into acoustic data. The acoustic data may be transmitted to information handling system144(e.g., referring toFIG.1), which may process each recorded acoustic signal with a beamforming algorithm to identify the location of the acoustic source. Without limitation, information handling system144may be disposed at the surface or on acoustic logging tool100. Still further, multiple information handling systems144may be utilized, where at least one information handling system144is disposed at surface and at least another information handling system144is disposed on acoustic logging tool100, where every information handling system144is in communication with each other. In examples, the acoustic source may be a leak202caused by flow of fluid204in leak202. Fluid204may be flowing from outside pipe string138and into pipe string138, or vice versa. Likewise, fluid204may be moving from outside of first casing134and into first casing134, or vice versa. This is true for any casing that may be outside of first casing134. To properly process acoustic noise, beamforming may be used. Beamforming is a signal processing technique used in hydrophone array200for directional signal transmission or reception. This is achieved by combining waveforms by a phased array in such a way that signals at particular angles experience constructive interference while others experience destructive interference. Utilizing this concept, personnel may be able to determine the location of leak202and/or the source of acoustic noise.

With continued reference toFIG.2, acoustic noise may be captured and recorded by hydrophones104. Hydrophones104are commonly built with pre-amplifiers to increase the output voltage by a gain value. The gain value may be as understood as the gain value of the pre-amplifier connected with hydrophone104. If there are other electronics built in with hydrophone104, the gain values are considered. For example, if there are a pre-amplifier and a filter board, the gain value equals the pre-amplifier gain value multiplied by the filter board gain value. Hydrophones104with a high gain value (i.e., a high gain channel) may be sensitive and able to pick up low-amplitude acoustic noises. However, a hydrophone104with a high gain value may become saturated when there is a high-amplitude acoustic noise. With a low gain value, hydrophone104may be able to detect high-amplitude acoustic noises, but low-amplitude acoustic noises may be below the noise floor of hydrophone104and undetectable. To capture and record a range of noise amplitude levels (e.g., both high and low), hydrophone array200may be designed to have a selected number of hydrophones104designed with a high gain and the others with a low gain.

However, there is often a problem that the range of hydrophones104are not sufficient to cover both low leak noise and high leak noise. Generally, there is a threshold noise level below which acoustic noise is undetectable. The noise level is related to the electrical or baseline noise of a hydrophone104. When electrical signal generated by the noise is below the baseline noise of hydrophone104, the noise is undetectable.

The noise level is related to different gains a hydrophone104may be created for. As discussed below, systems and methods may utilize a high gain and a low gain hydrophone104for measurement operations. Low-gain hydrophones104may not be able to detect low leak noise (because it falls below its low threshold). Similarly, high-gain hydrophones104may not be able to detect high leak noise (because the noise level is above its high threshold). For high leak noise, there is a maximum threshold for an electric signal in which hydrophone104may be designed. If the electrical signal is above the maximum threshold, the signal will saturate hydrophone104. This may effectively place a high ceiling on hydrophone104and prevent it from recording higher acoustic signal amplitudes.

For high leak noise, low-gain hydrophones104(i.e., a low gain channel) are able to capture and record high leak noise, but high gain channels are saturated. For low leak noise, high-gain hydrophones104are able to capture and record low leak noise, but low-gain hydrophones104cannot.

Additionally, there me be times during measurement operations in which only a selected number of hydrophones104may be in working condition. In order to optimize beamforming results during measurement operations, a method of individual selecting hydrophones104at any given time may be performed. Optimization for this matter is the best selection of hydrophones104to produce the clearest images and measurements.

For example, the method may be performed with at least three viable hydrophones104. During measurement operations, at least three hydrophones104may be utilized for beamforming and an aperture of hydrophone array200may be as large at acoustic logging tool100(e.g., referring toFIG.1) may allow for an optimized beamforming result. Generally, in examples, the number of hydrophones104and their spacings are fixed. The selection of hydrophone104may be 1, 2, 3 low gain and 4, 5, 6 high gain. In this example, the aperture is reduced as the spacing only has two hydrophones104. In another example, the selection of hydrophones104are 1, 3, 5 low gain and 2, 4, 6 high gain. The aperture in this case has a spacing of four hydrophones104. In this example, a two-level gain configuration for hydrophone array200disposed on acoustic logging tool100is designed to a first group of channels with high gain and another group of channels with low gain. The two groups (high and low gain channels) are designed to be spaced out, or not adjacent to each other, to create a larger aperture for both groups, which may give optimal beamforming results. In examples, hydrophones104in a group (low or high gain) may be adjacent to each other. This may be considered as minimum length of separation, which is no separation between hydrophones104. Thus, hydrophones104may be separated from each other in other examples by about one inch (about 2.5 centimeters), about six inches (about 15 centimeters), about a foot (about 0.3 meters), about one foot to six feet (about 0.3 meters to about 2 meters), or about five feet to about ten feet (about 1.5 meters to about 3 meters). A channel represents a single hydrophone104. In examples, the high gain channel and low gain channels may be adjacent to each other. During measurement operations, chosen hydrophones104from hydrophone array200are selected by personnel utilizing information handling system144, which is communicatively coupled to acoustic logging tool100(e.g., referring toFIG.1).

Generally, there may be about seven hydrophones104in hydrophone array200.FIGS.3A-3Fshows different beamforming results with different hydrophone selections based on laboratory test data. In these tests, hydrophone array200was located in the center of first casing134(with 3.5-inch radius), and there is a leak202outside pipe string138.FIGS.3A and3Billustrate when four consecutive hydrophones104are selected (e.g., 1-4 or 4-7), the aperture is not maximized, and the beamforming result shows large artifacts300both inside and outside first casing134. For this disclosure, maximized is defined as largest possible distance between a topmost hydrophone104and bottommost hydrophone104in a group (either high gain or low gain). The largest possible distance is generally length of the entire hydrophone array200minus the distance between two adjacent hydrophones104. Additionally, large artifacts300is identified by a lighter color, which may indicate possible location of leak202(e.g., referring toFIG.2). InFIGS.3A and3B, a possible leak202is identified by large light-colored area near (2,2) in and (5, −3) in. The potential area for leak202is not focused, thus the area is considered a large artifact300.

FIG.3Cshow when hydrophones104are spaced out to cover a large aperture (e.g., 1, 3, 5, 7), the beamforming result shows leak202outside first casing134. As shown inFIG.3C, a lighter color indicates possible location of leak202. InFIG.3C, as the lighter color is focused, a leak202is presumed to be near (6, −2) in. Similarly, with three hydrophones104selected, as illustrated inFIGS.3D and3E, large artifacts300are observed when hydrophones104are closely together (e.g., 1-3 or 5-7). InFIGS.3D and3E, the lighter area indicating a location of leak202is not focused. InFIG.3D, there are large light color area near (2,2) and (5, −4). InFIG.3E, the light color area is near depth location −4. InFIGS.3D and3E, the location of leak202cannot be identified, thus it is identified as large artifacts300. InFIG.4F, the light color area is focused at (5, −2), indicating a possible location of leak202. When hydrophones104, as illustrated inFIG.3F, are spaced out (e.g., 1, 4, 7), leak202outside first casing134may be shown. Hence, hydrophone 1, 3, 5, 7 (e.g.,FIG.3C) and hydrophone 1, 4, 7 (e.g.,FIG.3F) may be the best configurations when utilizing four hydrophones104and/or three hydrophones104, respectively.FIGS.4A-4Fis actual field data that verifies the lab data seen inFIGS.3A-3F. At this depth, there is a leak202at 1.75-inch radially. When hydrophones104are closely together (e.g., referring toFIGS.4A,4B,4D, and4E), the light color areas are spread out and not focused, large artifacts300. When the aperture is maximized (FIGS.4C and4F), a light area is focuses an indicates a leak202. This is located at 4 in depth within pipe staring138(e.g., referring toFIG.2). The radius of pipe string138is 1.75 in. When hydrophones104are spaced out (e.g.,FIGS.4C and4F) to maximize the aperture, the beamforming result is the best.

In other examples, a hydrophone gain design for an eight-hydrophone array200(e.g., referring toFIG.2) is shown inFIGS.5A-5D. The eight-hydrophone array200has channels 1, 4, and 7 with high gain and channels 2, 3, 4, 5, 8 with low gain. The beamforming results are generated from synthetic data with the true leak location at (4,1) inch.FIGS.5A and5Bare generated with a signal-to-noise ratio of 0.002:1. With a low noise level, only channels designed for high gain produce reliable measurements. Thus, only the beamforming map generated with channels 1, 4, and 7 shows the correct location of leak202.FIGS.5C and5Dare generated with a signal-to-noise ratio of 10:1. With a high signal amplitude, channels 1, 4, and 7 are saturated while channels 2, 3, 5, 6, and 8 produce reliable measurements. Saturation is illustrated inFIG.6Aon a time domain andFIG.6Bin a frequency domain. Beamforming results show that both groups of hydrophones104show the correct location of leak202. This is because although channels 1, 4, and 7 are saturated, and the signal amplitude is truncated, the phase information is preserved (e.g., as illustrated inFIGS.6A and6B). The beamforming algorithm only uses phase information. However, these hydrophones104do not show the correct signal amplitude and the two-gain design is still necessary.

Improvements over the current technology are found in that compared to a single gain design, the proposed two-gain design allows the beamforming to perform at lower or higher noise level. The solution to maximize hydrophone aperture helps to optimize beamforming result at lower or higher noise level when not all hydrophones are viable and/or working. The systems and methods may include any of the various features disclosed herein, including one or more of the following statements.

Statement 1: A system for leak detection may comprise an acoustic logging tool. The acoustic logging tool may comprise a hydrophone array with a first group of hydrophones and a second group of hydrophones. The system may further comprise an information handling system communicatively connected to the acoustic logging tool and wherein the information handling system chooses three or more hydrophones from the first group of hydrophones and the second group of hydrophones.

Statement 2. The system of statement 1, wherein the first group of hydrophones are low gain hydrophones.

Statement 3. The system of statement 2, wherein the low gain hydrophones are saturated from high amplitude acoustic noise.

Statement 4. The system of statement 2, wherein the second group of hydrophones are high gain hydrophones.

Statement 5. The system of statement 4, wherein the high gain hydrophones do not sense low amplitude acoustic noise.

Statement 6. The system of statement 4, wherein at least one high gain hydrophone and at least one low gain hydrophone are adjacent to each other.

Statement 7. The system of statement 4, wherein two or more high gain hydrophones are disposed adjacent to a low gain hydrophone.

Statement 8. The system of statement 4, wherein two or more low gain hydrophones are disposed adjacent to a high gain hydrophone.

Statement 9. The system of statement 4, wherein each of the low gain hydrophones are spaced apart from each other.

Statement 10. The system of statement 4, wherein each of the high gain hydrophones are spaced apart from each other.

Statement 11. A method for leak detection may comprise disposing an acoustic logging tool into a wellbore. The acoustic logging tool may comprise a hydrophone array with a first group of hydrophones and a second group of hydrophones. The method may further comprise selecting three or more hydrophones from the hydrophone array using an information handling system that is communicatively connected to the acoustic logging tool and performing measurements with the three or more hydrophones chosen from the hydrophone array.

Statement 12. The method of statement 11, wherein the first group of hydrophones are low gain hydrophones.

Statement 13. The method of statement 12, wherein the low gain hydrophones are saturated from high amplitude acoustic noise.

Statement 14. The method of statement 12, wherein the second group of hydrophones are high gain hydrophones.

Statement 15. The method of statement 14, wherein the high gain hydrophones do not sense low amplitude acoustic noise.

Statement 16. The method of statement 14, wherein at least one high gain hydrophone and at least one low gain hydrophone are adjacent to each other.

Statement 17, The method of statement 14, wherein two or more high gain hydrophones are disposed adjacent to a low gain hydrophone.

Statement 18. The method of statement 14, wherein two or more low gain hydrophones are disposed adjacent to a high gain hydrophone.

Statement 19. The method of statement 14, wherein each low gain hydrophone are spaced apart from each other.

Statement 20. The method of statement 14, wherein each high gain hydrophone are spaced apart from each other.