Patent Description:
Operators may measure conditions of a flowline or a wellbore, conditions such as fluid flow, using a logging tool. Such tools are primarily used to measure the downhole pressure, temperature, and fluid velocity. Other properties can also be measured using logging tools, depending on the particular wellbore condition or problem being investigated. Well operators may also install permanent pressure and temperature gauges at specific locations within the wellbore, but this can be an expensive option since the gauges are often not retrieved, and information from the permanent gauge may diminish in value over the life of the well.

A known flowline inspection system is disclosed in <CIT>.

Embodiments of the invention are described with reference to the following figures. The same numbers are used throughout the figures to reference like features and components. The features depicted in the figures are not necessarily shown to scale. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form, and some details of elements may not be shown in the interest of clarity and conciseness.

The disclosed embodiments include improvements in processing the start time for a pressure pulse within a flowline.

Aspects of the present disclosure include improved time of flight measurements for the reflected pressure waves, for more accurate determination of the location of depositions or failures along the flowline. The time of flight measurements are improved, in part, by accurate selection of attributes associated with closure of a flowline valve, such as the start time of when the pressure pulse is generated. The improved accuracy in identifying the start time of the pressure pulse leads to better identifying the location of obstructions or failures along the flowline.

<FIG> depicts a schematic view of a pipeline inspection system <NUM> according to one or more embodiments. The pipeline inspection system <NUM> is used to detect and locate various obstructions in or failures associated with a flowline <NUM> such as a pipeline or any suitable flowline used to carry a fluid. A pressure sensor <NUM>, which may include a pressure gauge or transducer, is located immediately upstream or downstream from a valve <NUM> connected to the flowline <NUM>. A computer system <NUM> is in communication with the pressure sensor <NUM> to receive a pressure profile recorded by the pressure sensor <NUM>. The pressure profile may be received as a pressure signal having a value per a given time. The valve <NUM> is closed to generate a pressure pulse in the flowline <NUM>, and the pressure sensor records the pressure profile as the pressure value from the reflected pressure waves generated along the flowline <NUM>. The valve <NUM> may be closed mechanically (e.g., by an actuator), or may be closed by hand (e.g., by an operator).

The computer system <NUM> may include one or more processors <NUM> and memory <NUM> (e.g., ROM, EPROM, EEPROM, flash memory, RAM, a hard drive, a solid state disk, an optical disk, or a combination thereof) capable of executing instructions. Software stored on the memory <NUM> governs the operation of the computer system <NUM>. A user interacts with the computer system <NUM> and the software via one or more input devices <NUM> (e.g., a mouse, touchpad, or keyboard) and one or more output devices <NUM> (e.g., a screen or tablet). The computer system <NUM> is operable to analyze the pressure profile to identify a parameter of the pressure pulse, including a start time of the valve closure, an end time of the valve closure, a reference time of the pressure pulse, and a discard time of the pressure pulse.

The start time of the valve closure is the time at which valve closure is initiated. The reference time is the time at which the valve closure has closed to sufficiently generate an acoustical pulse for purposes of calculating the time of flight of the reflected pressure waves. The end time is the time at which valve closure is completed. The discard time is the time at which the pressure pulse reaches the end of the flowline or has attenuated to a degree that the pressure sensor can no longer adequately record the pressure value over a background level of the signal present within the flowline.

<FIG> shows a flowchart of an automated method <NUM> of inspecting the flowline <NUM> according to one or more embodiments. At block <NUM>, the pressure sensor <NUM> begins measuring the pressure inside the flowline <NUM> and the location of the sensor <NUM> is recorded. At block <NUM>, the valve <NUM> is actuated to a closed position or a partially closed position to generate a pressure pulse in the flowline <NUM>. As the pressure pulse travels along the flowline <NUM>, pressure waves may reflect back to the pressure sensor <NUM> when the pressure pulse encounters any obstructions or failures along the flowline. For example, <FIG> depicts a graphical view of an outlet type pressure profile <NUM> recorded by a pressure sensor attached to a flowline, and the pressure change <NUM> after <NUM> seconds demonstrates when the valve was closed to generate the pressure pulse. In the case of an outlet, the pressure sensor <NUM> is positioned upstream from the valve <NUM>. Referring to <FIG>, at block <NUM>, the pressure wave reflections are received at the pressure sensor <NUM> and recorded over time as the pressure profile.

The computer system <NUM> automates the analysis of the pressure profile to reduce the likelihood of misinterpreting the parameters in the pressure profile and improve the functionality of the processing method. The computer system <NUM> analyzes the pressure profile to identify parameters of the pressure pulse for use in identifying characteristics (e.g., valves, breaks, tools, solid/wax buildup) that may be present, or may develop in locations throughout the flowline <NUM>. At block <NUM>, the computer system <NUM> determines whether the valve closure is generated by an inlet or an outlet and whether the pressure pulse generates an adequate pressure change to analyze the pressure profile. The computer system <NUM> identifies pressure changes (drops or rises) that exceed threshold value (e.g., an increase of <NUM>%) relative to the ambient pressure (background noise) level of the flowline <NUM>. The ambient pressure of the flowline may be the average pressure observed during a time slice before a pressure pulse is generated in the flowline. The time slice may be about <NUM>-<NUM> seconds, or may be shorter or longer. If no pressure changes exist that exceed the threshold value, the flowline inspection may be repeated by returning to block <NUM> or flagged for review by an analyst, who is experienced at interpreting pressure profiles.

Upon identification of a pressure change, the first derivative and the second derivative of the pressure profile are calculated, at block <NUM>, to identify parameters of the pressure pulse as further described herein. A reference time, which is used to calculate the time of flight of the reflected pressure waves, is identified in the pressure profile. Furthermore, a leveled time may also be identified and used to calculate the time of flight of the reflected pressure waves. Referring to <FIG>, the first and second derivatives <NUM> of pressure profile <NUM> are the two curves that spike at the pressure change <NUM> and level out along the zero value of the right vertical axis. At block <NUM>, the reference time and/or the leveled time of the pressure pulse are identified by evaluating characteristics of the pressure profile <NUM>. The reference time is identified by finding the time associated with the peak value (i.e., highest value of a peak or lowest value of a trough) of the first derivative that occurs after the change in pressure used to identify a pressure pulse at block <NUM>. The leveled time is identified by finding the time associated with a return to the threshold value of ambient pressure level as detected during the time slice.

<FIG> shows a zoomed-in view of the pressure pulse depicted in <FIG>, and the reference time <NUM> is identified as the peak value of the first derivative <NUM> encountered after the pressure change formed from the valve closure. For an outlet as depicted in <FIG>, the peak value of the first derivative is a local maxima, whereas for an inlet the peak value of the first derivative is a local minima. At block <NUM>, the end time <NUM> is identified as the time associated with the peak of the second derivative <NUM> which occurs immediately after the reference time <NUM>. In addition, as described below with respect to <FIG>, the end time may be identified with respect to the leveled time. The leveled time is identified by determining when the pressure value has stopped changing (i.e., leveled off) after the disturbance due to the generation of the pressure pulse. For example, if the first and second derivatives are zero plus-or-minus a small range for at least a certain time period, then the leveled time may be used to identify the end time, particularly if the valve closure is not perfect. A valve closure that is slow, non-uniform, or otherwise inconsistent may produce a pressure profile that has more peaks, and more peaks in the first and second derivatives. At block <NUM>, the start time <NUM> is identified as the time at which the first and second derivatives <NUM>, <NUM> separate enough from each other before the reference time and within the observed ambient pressure. The start time is identified by finding a difference of the first derivative and the second derivative that meets a threshold difference (e.g., <NUM>) occurring before the reference time and within the ambient pressure. At block <NUM>, the discard time is identified as a separation of the first derivative and second derivative in association with the peak or trough pressure. The discard time may also be the time at which the pressure pulse reaches the end of the flowline <NUM>, and thus, the discard time may also be calculated using the acoustic velocity of the reflected pressure waves and the length of the flowline <NUM> under inspection.

Upon identification of the start and end times of the pressure pulse, the computer system <NUM> may conduct a quality check of the pressure pulse. At block <NUM>, the computer system <NUM> may determine the velocity of the valve closure, which may be used to determine whether the velocity of the valve closure is sufficient to generate a pressure pulse along enough of the flowline. The velocity of the valve closure may also indicate whether the valve properly sealed. The computer system <NUM> may also use a max valve closure time (end time minus start time), which may be set as <NUM> to <NUM> seconds, to determine whether the valve closed adequately to generate a pressure pulse. If the pressure pulse does not satisfy the quality check at block <NUM>, the flowline inspection may be repeated at block <NUM> or flagged for review by the analyst.

The computer system <NUM> may also provide ratings for the valve closure to indicate whether valve closure is reliable for further analysis, needs review, or needs to be repeated. Green conditions, which indicate reliable results, may meet the following criteria: one peak of the first derivative during valve closure; one peak of the second derivative during valve closure, a pressure peak or trough is identifiable at the end of pressure profile with an associated separation of the first and second derivatives, the valve closure time is within the max closure time. Yellow conditions, which indicate that the results may need to be reviewed by an analyst, have one or more of the following conditions: two first derivative peaks during valve closure time, two second derivative peaks during valve closure, no pressure peak or trough is identifiable at the end of the pressure profile with associated separation of first and second derivatives, and the valve closure time is equal to the max closure time. Red conditions, which indicate that the recorded pressure profile may need to be rejected and the flowline inspection method may need to be repeated, have one or more of the following conditions: three or more first derivative peaks during valve closure, three or more second derivative peaks during valve closure timeframe, no pressure peak or trough is identifiable at the end of the pressure profile with associated separation of first and second derivatives, and the valve closure time exceeds the max closure time.

At block <NUM>, the computer system <NUM> uses the reference time and the pressure profile to identify a tubular parameter characterizing the flowline <NUM>. The tubular parameter may include any one or combination of an inflow into the tubular, a flowline collapse of the flowline, an effective diameter of the flowline, a deposit in the flowline, a leakage in the flowline, and a failure of the flowline. The computer system <NUM> also may determine the location of the tubular parameter along the flowline <NUM>.

The flowline inspection method of <FIG> may also apply to inlet pressure profiles where the pressure sensor <NUM> is positioned downstream from the valve <NUM>. For examples, <FIG> and <FIG>show graph views of a pressure profile <NUM> generated from a valve closure of an inlet according to one or more embodiments. <FIG> is the zoomed-in view of the imitation of the pressure pulse. The inlet pressure profile produce a pressure drop rather than the pressure rise depicted in <FIG>. The first derivative curve <NUM> demonstrates that the reference time <NUM> may be identified as the local minima rather than the local maxima of <FIG>, and a similar adjustment in the flowline inspection method may be applied to identifying the local minima for the end time.

<FIG> and <FIG> show graphs of zoomed-in views of other example pressure profiles <NUM>, <NUM> that benefit from the automated flowline inspection method <NUM>, in accordance with one or more embodiments. <FIG> shows a pressure profile <NUM> which exhibits multiple peaks along the curves for the first and second derivatives <NUM>, <NUM>. Without the automated approach of identifying the parameters of the pressure profile described herein using the computer system <NUM>, the pressure profile depicted in <FIG> is prone to misinterpretation. For example, the wrong peak for the reference time or end time may be identified among the multiple peaks. The computer system <NUM> may identify the reference time <NUM>, the start time <NUM>, and the end time <NUM> as being located along the first and second derivatives <NUM>, <NUM> based on the automated identification method described with respect to <FIG>. In certain embodiments, however, a leveled time <NUM> may be used to determine a true end time <NUM>. For example, the true end time <NUM> is determined as the last peak of the first derivative <NUM> before the leveled time <NUM>. Thus, the automated identification method described herein provides an accurate and efficient technique of identifying the pressure pulse parameters for complex pressure profiles with multiple peaks in the curves for the first and second derivatives.

<FIG> also depicts a pressure profile <NUM> with a high potential for misinterpretation without the automated inspection method described herein. The pressure change initiated near <NUM> seconds can be misinterpreted as a faulty valve closure, which leads to the next pressure change closer to <NUM> seconds being misinterpreted as the valve closure for purposes of determining the parameters of the pressure pulse. The automated inspection method described herein, however, identifies the pressure change initiated near <NUM> seconds as the valve closure because there is a greater pressure change closer to the ambient pressure level. The pressure fluctuations observed near <NUM> seconds were verified to be deposits in the flowline.

This discussion is directed to various embodiments of the present disclosure. The drawing figures are not necessarily to scale. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness.

Certain terms are used throughout the description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function, unless specifically stated. In the discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to. " Also, the term "couple" or "couples" is intended to mean either an indirect or direct connection. In addition, the terms "axial" and "axially" generally mean along or parallel to a central axis (e.g., central axis of a body or a port), while the terms "radial" and "radially" generally mean perpendicular to the central axis. The use of "top," "bottom," "above," "below," and variations of these terms is made for convenience, but does not require any particular orientation of the components.

Reference throughout this specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure. Thus, appearances of the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

Claim 1:
A method of inspecting a flowline, comprising:
recording a pressure profile using a sensor connected to a flowline;
generating a pressure pulse in the flowline by closing a valve connected to the flowline;
characterized by:
calculating a first derivative and a second derivative of the pressure profile; and
determining one or more parameters of the pressure pulse based on the first derivative and the second derivative of the pressure profile, wherein the one or more parameters comprise any one or combination of a start time of the valve closure, an end time of the valve closure, and a discard time associated with the pressure pulse that represents the time at which the pressure pulse reaches the end of the flowline or at which the pressure pulse has attenuated to a degree that the sensor can no longer adequately record the pressure value over a background level of a signal present within the flowline, the method further comprising identifying a reference time by finding a peak value of the first derivative following a change in pressure that exceeds a threshold value;
and:
identifying the start time by finding a difference of the first derivative and the second derivative that meets a threshold value occurring before the reference time;
identifying the end time by finding a peak of the second derivative occurring after the reference time; and
identifying the discard time by finding an additional difference of the first derivative and the second derivative that meets an additional threshold hold value occurring after the reference time.