Patent Application
20140202691
The present disclosure relates to systems, assemblies, and methods for conveying perforating and/or logging tools (hereinafter referred to as a “tool string”) in a wellbore where adverse conditions may be present to challenge downward movement of the tool string in the wellbore.
In oil and gas exploration it is important to obtain diagnostic evaluation logs of geological formations penetrated by a wellbore drilled for the purpose of extracting oil and gas products from a subterranean reservoir. Diagnostic evaluation well logs are generated by data obtained by diagnostic tools (referred to in the industry as logging tools) that are lowered into the wellbore and passed across geologic formations that may contain hydrocarbon substances. Examples of well logs and logging tools are known in the art. Examples of such diagnostic well logs include Neutron logs, Gamma Ray logs, Resistivity logs and Acoustic logs. Logging tools frequently are used for log data acquisition in a wellbore by logging in an upward (up hole) direction, from a bottom portion of the wellbore to an upper portion of the wellbore. The logging tools, therefore, need first be conveyed to the bottom portion of the wellbore. In many instances, wellbores can be highly deviated, or can include a substantially horizontal section. Such wellbores make downward movement of the logging tools in the wellbore difficult, as gravitational force becomes insufficient to convey the logging tools downhole.
The present disclosure relates to a method and system for correcting the downhole speed at which perforating and/or logging tools (hereinafter referred to as a “tool string”) are moving in a wellbore. The disclosed systems, assemblies, and methods can reduce risk of damage to the tool string and increase speed and reliability of moving the tool string into and out of wellbores. For example, certain wells can be drilled in a deviated manner or with a substantially horizontal section. In some conditions, the wells may be drilled through geologic formations that are subject to swelling or caving, or may have fluid pressures that make passage of the tool string unsuitable for common conveyance techniques. The present disclosure overcomes these difficulties and provides several technical advances.
The present disclosure relates generally to a system and method for correcting the speed of tool strings that are being lowered into or pulled out of a wellbore. The tool strings may be connected to the lower end of an electric wireline or slickline cable that is spooled off a truck located at the surface. As used herein the terms “cable” and “line” and “wireline” are used interchangeably and unless described with more specificity may include an electric wireline cable or a slickline cable.
In other implementations the tool string may be lowered into the wellbore via a drill pipe string, a coiled tubing string, and a conventional tubing string.
The subject method and system are used in some implementations in a cased wellbore or in other implementations are applicable in a partially cased wellbore. The tool string is adapted for use in highly deviated wellbores wherein it is a known practice to pump fluid from the surface behind a tool string to assist the tool in moving down the deviated wellbore.
General background of pump down tool technology is known in the art and is disclosed in pending application PCT/US/2010/44999. The automated pump-down system described in the afore referenced PCT patent application depends on sensor data to provide line tension and line speed. Typically, these readings would come from sensors and calculations done at the surface as prior art pump down operations do not include a tool string that has the capability to transmit this information from the tool string. Using surface data to describe events happening in the wellbore is not optimum due to the delay in the response of the sensors at the surface as well as the inaccuracies caused by the effect of wellbore conditions on the readings. Changes in tension at the cable head of the tool string and real tool string speed would not be instantaneously measured due to dampening effects of stretching of the wireline cable and different wellbore fluids. Accuracy of those measurements would also be affected by cable stretch, wellbore fluids, and well geometry.
If the pump pressure of the fluid behind the tool string is too great it may result in excessive downhole tension on the cable head that will result in breaking the cable or pulling the cable out from the cable head. It is desirable to control the pump pressure or line speed of the cable to keep the tension in the cable within safe parameters.
In some implementations, the down tool string of the present disclosure includes a device that measures the tension in the cable at the cable head and transmits that data as an analog signal to the surface via an electric wireline cable or other transmission means, and uses that data to control pumps and/or line speed.
Additionally, in some implementations the tool string of the present disclosure may include a device that calculates the speed of the downhole tool string at the cable head and transmits that data as an analog signal. (Examples of such devices include an accelerometer and/or a casing collar locator.)
Additionally, in some implementations a casing collar locator may be used to correct the downhole speed calculations.
In a first aspect, a method of correcting a downhole speed of a tool string moving in a wellbore includes inserting a tool string into a proximal upper end of the wellbore, said tool string includes a cable head connected at a first end to a cable, a casing collar locator, an accelerometer, and at least one downhole tool selected from the group consisting of a logging tool and a perforating tool, spooling out cable at the surface allowing the tool string to move into the wellbore, obtaining a downhole tool speed with an accelerometer and providing said data to a processor that calculates the downhole speed of the tool string based on the accelerometer data, moving the tool string past at least two casing collars and sending data to the processor including the depth of each of the collars and time that the casing collar locator passes each of the casing collars, calculating by the processor the average tool speed over the interval between collars, and comparing the downhole line speed as calculated by the processor using the data from the accelerometer to the average tool speed calculated by the processor based on the time and casing collar.
Various implementations can include some, all, or none of the following features. The method can also include determining by the processor that the average calculated downhole tool speed is less than or greater than the measured line speed, determining a correction factor, and determining a corrected downhole tool speed. The method can include determining by the processor that the casing collar is recorded at a measured depth where expected, determining a correction factor, and determining a corrected downhole tool speed. The method can include determining by the processor that the casing collar at calculated depth is shallower/deeper than expected, determining a correction factor, and determining a corrected downhole tool speed. The correction factor can be calculated using measured casing collar depth, time, and calculated casing collar depth. The correction factor can be determined in part using a calculation of a gravity coefficient given by the equation: gravity=pow(pow(AccX,2)+pow(AccY,2)+pow(AccZ,2), 0.5). The correction factor can be determined in part using a calculation of downhole tool given by the equation: speed=0.5*pow(gravity,2.0)*pow(intTime, 2.0).
In a second aspect, a method of correcting a downhole speed of a tool string moving in a wellbore includes inserting a tool string into a proximal upper end of the wellbore, said tool string including a cable head connected at a first end to a cable, a casing collar locator, and at least one downhole tool selected from the group consisting of a logging tool and a perforating tool, spooling out cable at the surface allowing the tool string to move into the wellbore, moving the tool string past at least two casing collars and sending data to a processor including the depth of each of the collars and time that the casing collar locator passes each of the casing collars; and calculating the average tool speed over the interval between collars.
Various implementations can include some, all, or none of the following features. The method can include determining that an average calculated downhole tool speed is less than or greater than measured line speed, determining a correction factor, and determining a corrected downhole tool speed. The method can include determining that a casing collar is recorded at a measured depth where expected, determining a correction factor, and determining a corrected downhole tool speed. The method can include determining that a casing collar at calculated depth is shallower/deeper than expected, determining a correction factor, and determining a corrected downhole tool speed. The correction factor can be calculated using measured casing collar depth, time, and calculated casing collar depth. The correction factor can be determined in part using a calculation of a gravity coefficient given by the equation: gravity=pow(pow(AccX,2)+pow(AccY,2)+pow(AccZ,2), 0.5). The correction factor can be determined in part using a calculation of downhole tool speed given by the equation: speed=0.5* pow(gravity,2.0)*pow(intTime, 2.0).
In a third aspect, a well logging system includes a tool string including a cable head connected at a first end to a cable, a casing collar locator, an accelerometer, at least one downhole tool selected from the group consisting of a logging tool and a perforating tool, and a processor adapted to receive data from the accelerometer and calculate a downhole tool speed, receive data from the casing collar locator including the depth of each of the collars and time when the casing collar locator passes at least two different casing collars, calculate the average downhole tool speed over the interval between collars, and compare the downhole tool speed as calculated by the processor using the data from the accelerometer to the average downhole tool speed calculated by the processor based on the time and casing collar location.
Various implementations can include some, all, or none of the following features. The system can also include determining that the average calculated downhole tool speed is less than or greater than measured line speed, determining a correction factor, and determining a corrected downhole tool speed. The system can include determining that the casing collar is recorded at a measured depth where expected, determining a correction factor, and determining a corrected downhole tool speed. The system can include determining that the casing collar at calculated depth is shallower/deeper than expected, determining a correction factor, and determining a corrected downhole tool speed. The correction factor can be calculated using measured casing collar depth, time, and calculated casing collar depth. The correction factor can be determined in part using a calculation of a gravity coefficient given by the equation: gravity=pow(pow(AccX,2)+pow(AccY,2)+pow(AccZ,2), 0.5). The correction factor can be determined in part using a calculation of downhole tool speed given by the equation: speed=0.5* pow(gravity,2.0)*pow(intTime, 2.0).
In a fourth aspect, a well logging system includes a tool string includes a cable head connected at a first end to a cable, a casing collar locator, at least one downhole tool selected form the group consisting of a logging tool and a perforating tool, and a processor adapted to receive data from the casing collar locator including the depth of each of the collars and time when the casing collar locator passes at least two different casing collars, and calculate the average downhole tool speed over the interval between collars.
Various implementations can include some, all, or none of the following features. The system can include determining that the average calculated downhole tool speed is less than or greater than measured line speed, determining a correction factor, and determining a corrected downhole tool speed. The system can include determining that the casing collar is recorded at a measured depth where expected, determining a correction factor, and determining a corrected downhole tool speed. The system can include determining that the casing collar at calculated depth is shallower/deeper than expected, determining a correction factor, and determining a corrected downhole tool speed. The correction factor can be calculated using measured casing collar depth, time, and calculated casing collar depth. The correction factor can be determined in part using a calculation of a gravity coefficient given by the equation: gravity=pow(pow(AccX,2)+pow(AccY,2)+pow(AccZ,2), 0.5). The correction factor can be determined in part using a calculation of downhole tool speed given by the equation: speed=0.5* pow(gravity,2.0)*pow(intTime, 2.0).
In the drawings and description that follow, like parts are typically marked throughout the specification and drawings with the same reference numerals. The drawing figures are not necessarily to scale. Certain features of the disclosure 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. The present disclosure is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the disclosure to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results.
In the following discussion and in the claims, the terms “including” and “comprising” are used in an inclusive fashion, and thus should be interpreted to mean “including, but not limited to.” Unless otherwise specified, any use of any form of the terms “connect,” “engage,” “couple,” “attach,” or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. Reference to up or down will be made for purposes of description with “up,” “upper,” “upwardly” or “upstream” meaning toward the surface of the well and with “down,” “lower,” “downwardly” or “downstream” meaning toward the terminal end of the well, regardless of the wellbore orientation. In addition, in the discussion and claims that follow, it may be sometimes stated that certain components or elements are in fluid communication. By this it is meant that the components are constructed and interrelated such that a fluid could be communicated between them, as via a passageway, tube, or conduit. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings.
Disclosed herein are systems and methods for automated monitoring and control of pump down operations. More specifically, the pump rate of a pump unit (or units), the line speed for a logging/perforating (L/P) unit, and the line tension for the L/P unit may be automatically monitored and controlled to enable efficient pump down operations. In at least some embodiments, pump down operations may be based on a predetermined line speed, a predetermined line tension and/or a predetermined pump rate. However, if any of these parameters change during pump down operations, the other parameters will be adjusted automatically. The techniques disclosed herein improve safety of pump down operations by eliminating the possibility of pumping the tools off the end of the wireline cable or other catastrophes.
As a specific example, if the monitored line tension surpasses a desired threshold, the line speed will be automatically reduced to maintain the desired line tension and the pump rate will be reduced in accordance with the amount of change in the line speed.
Thereafter, if the monitored line tension drops below the predetermined threshold, the line speed will be automatically increased (up to a desired line speed) and the pump rate will be increased in accordance with the line speed. Similarly, changes in the monitored pump rate during pump down operations may result in automated changes to the line tension and/or line speed of the L/P unit.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
The tool string 200 may be attached with a cable/wireline 111 via a cable head 211. In some implementations, the conveying process is conducted by pumping a fluid from the rig pump 122 into the upper proximal end of the casing string 112 (or 114) above the tool string 200 to assist, via fluid pressure on the tool string 200, movement of the tool string 200 down the wellbore 150. The pump pressure of the fluid above the tool string 200 is monitored, for example, by the truck 115, because the fluid pressure can change during the conveying process and exhibit patterns indicating events such as sticking of the tool string in the wellbore. As the tool string 200 is pumped (propelled) downwards by the fluid pressure that is pushing behind the tool string 200, the cable 111 is spooled out at the surface by the truck 115.
In some implementations the tool string will have sufficient weight that gravity will convey the tool string down the wellbore without the assistance of pump fluid pressure.
The tool string is securely connected with the cable 111 by cable head tool 211. As the tool string 200 is propelled down the bore of the drill string by the fluid pressure, the rate at which the cable 111 is spooled out maintains movement control of the tool string 200 at a desired speed.
In some implementations an accelerometer 221 may be included in the tool string 200 at various locations. One acceptable location is illustrated in
In
In
Referring to
At the surface there will be a load cell for determining the tension in the cable at the surface and a surface device to measure the line speed the cable is going into the well, as is well known in the art.
Referring to
As used herein with regard to speed calculations and speed adjustments and corrections factors, the term “measured depth” 412 is used to describe the depth of the casing collar determined using surface measurement of the amount of cable spooled out into the wellbore with or without line tension correction. The term “calculated depth” 413 is used to describe the depth of the casing collar determined using depth information calculated from accelerometers, line tension, and/or other sensors, and may include measured depth in the calculation. The term “expected depth” 416 is used to describe the depth of the casing collar determined based on correlation logs or other references, and is considered to be the true depth or actual known depth.
Referring to
The aforementioned measurements and calculations can be used to determine a course of action across several possible scenarios. In some examples, the calculated downhole tool speed is greater than measured line speed 420, the casing collar is recorded at a measured depth 412 shallower than expected 418, and the casing collar at a calculated depth 413 is found where expected 422. In such examples, the reaction is to do nothing 426, since the downhole calculation is determined to be correct.
In some examples, the calculated downhole tool speed is greater than measured line speed 420, the casing collar is recorded at a measured depth shallower than expected 418, and the casing collar at a calculated depth 413 is found where expected 422. In such examples, the reaction is to do nothing 426, since the downhole calculation is determined to be correct.
In some examples, the calculated downhole line speed is less than measured line speed 420, the casing collar is recorded at a measured depth deeper than expected 418, and the casing collar at calculated depth is found where expected 422. In such examples, the reaction is to do nothing 426, since the downhole calculation is determined to be correct.
In some examples, the average calculated downhole line speed is less than or greater than measured line speed 420, the casing collar is recorded at a measured depth 412 where expected, and the casing collar at calculated depth is shallower/deeper than expected 422. In such examples, the reaction is to do nothing 426, since the downhole calculation is determined to be correct.
In reference to the aforementioned scenario examples, if the downhole calculation is determined to be incorrect, then coefficients are recalculated 424 to calculate a new correction factor. The correction factor is calculated using measured casing collar depth 412, time, and calculated casing collar depth 413. Examples of equations that can be used to calculate the correction factor are given below:
Gravity=pow(pow(AccX,2)+pow(AccY,2)+pow(AccZ,2),0.5) Calculate gravity:
Speed=0.5*pow(Gravity,2.0)*pow(intTime,2.0) Calculate speed:
Time of measured casing collar depth−time of previous measured casing collar depth Calculate time difference (Delta time):
Measured casing collar depth−previous measured casing collar depth Measured casing length:
Calculated casing collar depth−previous calculated casing collar depth Calculated casing length:
Expected casing collar length−previous casing collar length Actual casing length:
Actual casing length/Delta time Actual speed(for use when measured speed is determined to be inaccurate):
Calculated casing length*measured speed/Actual casing length Actual speed (for use when measured speed is determined to be accurate):
(Actual speed/Calculated speed)−1 Correction factor (simplified):
Corrected speed=Speed*(1+correction factor) Corrected speed:
Simplified examples of correction factors and corrected speeds as determined using the equations above, are provided in the tables below:
In some implementations logging and/or perforating operations as described above and illustrated in
A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. Further, the method 400 may include fewer steps than those illustrated or more steps than those illustrated. In addition, the illustrated steps of the method 400 may be performed in the respective orders illustrated or in different orders than that illustrated. As a specific example, the method 400 may be performed simultaneously (e.g., substantially or otherwise). Other variations in the order of steps are also possible. Accordingly, other implementations are within the scope of the following claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US12/46867 | 7/16/2012 | WO | 00 | 1/29/2014 |
