Patent Grant
11060397
The present disclosure relates generally to wellbore operations and more particularly to disposing a carrier downhole in a wellbore to evaluate an earth formation.
Hydrocarbon exploration and energy industries employ various systems and operations to accomplish activities including drilling, formation evaluation, stimulation, and production. Various measurement techniques may be employed to facilitate hydrocarbon exploration and production activities. A carrier can be disposed downhole in a wellbore to evaluate an earth formation. The formation evaluation can be useful for extracting hydrocarbons from the formation.
Embodiments of the invention described herein provide systems, methods, and computer program products for disposing a carrier downhole in a wellbore to evaluate an earth formation. In one embodiment, a method includes disposing a carrier in a borehole in an earth formation, the carrier comprising a logging assembly for performing a formation evaluation of the earth formation using a sensor in proximity to a borehole wall of the borehole, fluid being disposed at least partially between the sensor and the borehole wall. The method further includes estimating, by a processing device, an apparent dielectric loss angle of the fluid to determine a stand-off effect caused by the fluid using at least one of a logging with a closed pad technique, a logging in a cased-hole section technique, and a log-based estimation technique. The method further includes estimating, by the processing device, a formation dielectric loss angle. The method further includes determining, by the processing device, a formation resistance based at least in part on the formation dielectric loss angle. The method further includes adjusting the formation evaluation based at least in part on the estimated formation resistance that accounts for the stand-off effect caused by the fluid. The method further includes performing a wellbore operation based at least in part on the adjusted formation evaluation that accounts for the stand-off effect caused by the fluid.
In another embodiment, a system includes a carrier disposed in a borehole in an earth formation, the carrier comprising a logging assembly for performing a formation evaluation of the earth formation using a sensor in proximity to a borehole wall of the borehole, fluid being disposed at least partially between the sensor and the borehole wall. The system further includes a memory comprising computer readable instructions and a processing device for executing the computer readable instructions for performing a method, which includes estimating, by the processing device, an apparent dielectric loss angle of the fluid to determine a stand-off effect caused by the fluid using at least one of a logging with a closed pad technique, a logging in a cased-hole section technique, and a log-based estimation technique. The method further includes estimating, by the processing device, a formation dielectric loss angle. The method further includes determining, by the processing device, a formation resistance based at least in part on the formation dielectric loss angle. The method further includes adjusting the formation evaluation based at least in part on the estimated formation resistance that accounts for the stand-off effect caused by the fluid. The method further includes performing a wellbore operation based at least in part on the adjusted formation evaluation that accounts for the stand-off effect caused by the fluid.
Additional technical features and benefits are realized through the techniques of the present invention. Embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed subject matter. For a better understanding, refer to the detailed description and to the drawings.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages thereof, are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The diagrams depicted herein are illustrative. There can be many variations to the diagrams or the operations described therein without departing from the spirit of the invention. For instance, the actions can be performed in a differing order or actions can be added, deleted or modified. Also, the term “coupled” and variations thereof describes having a communications path between two elements and does not imply a direct connection between the elements with no intervening elements/connections between them. All of these variations are considered a part of the specification.
A detailed description of one or more embodiments of the disclosed system, apparatus, and method presented herein by way of exemplification and not limitation with reference to the figures. Disclosed are techniques for correction of mud stand-off effect on oil-based mud resistivity images for formation evaluation.
Apparatus for implementing the disclosure and features related to the disclosure is now discussed.
In the embodiment shown in
It may be desirable to perform formation resistivity imaging to identify bedding, fractures, faults, stratigraphic features, and borehole features, such as breakout and drilling-induced fractures. To accomplish the formation resistivity imaging, sensors in the tool 16 are used to collect data about a formation 26. The sensors include pads that are in contact (also referred to as “sensor-to-formation” contact) with a wall of the borehole 14. However, drilling fluid (“mud”) can come between the sensor pads and the formation, which affect resistivity measurement accuracy. This phenomenon is referred to as the “mud stand-off effect” and can cause resistivity measurements to be inaccurate.
According to the example of
In one embodiment, the tool 16 and/or the system 100 is configured for oil-based mud resistivity imaging of the formation 26 and/or another area of interest. The tool 16 includes one or more sensors that collect data, such as resistivity data, about the formation 26. Examples of such sensors can include density detectors and microresistivity electrode sensors. In an example, a sensor includes a transmission unit 28 and a reception unit 30. The sensor, having the transmission unit 28 and reception unit 30, can be disposed in a “pad” of the tool 16 such that the pad (and accordingly the sensor) is pressed firmly against the borehole wall in sensor-to-formation contact. The transmission unit 28 transmits signals into the formation 26, and the reception unit 30 receives return signals from the formation 26. Based on these return signals, the tool 16 generates an image (e.g., a resistivity image) of the wall of the borehole filled with oil-based mud (drilling fluid) and/or the formation 26. For example, features of the formation 26 can be evaluated by imaging formation fractures. Sensors are in sensor-to-formation contact with the borehole wall to improve the accuracy of data collected by the sensors. However, in cases where the oil-based mud come between the sensor/pad and the borehole wall (i.e., when “mud stand-off” occurs), the accuracy of data collected by the sensors, and thus the corresponding formation resistivity imaging, is reduced.
Images generated using the tool 16 can be analyzed to evaluate formation characteristics, such as identifying and characterizing natural and/or stimulated fractures (e.g., estimating strike, dip, and apparent aperture). This information is useful in evaluating formations, performing fracturing operations, and monitoring or evaluating other subterranean operations such as geothermal energy production. To improve the accuracy of formation evaluation performed by resistivity imaging, it is beneficial to correct for effects of oil-based mud standoff.
The data acquisition tool 16 is configured to monitor and/or collect data related to formation characteristics. The tool 16 may be deployed downhole via any suitable carrier and may be configured to operate in conjunction with other downhole or surface tools. In one embodiment, the tool 16 and/or other downhole components are in communication with one or more processing units or devices, such as a downhole electronics unit 32 and/or a surface processor such as the processing system 20. The processing devices are configured to perform functions including receiving, storing, transmitting and/or processing data from the tool 16, and providing control functionality to the system 100 to control the components thereof. The processing devices include any number of suitable components, such as processors, memory, communication devices and power sources. Communication can be achieved via any suitable configuration, such as acoustic, electrical or optical communication, wireless communication, and mud pulse telemetry.
It is understood that embodiments of the present invention are capable of being implemented in conjunction with any other suitable type of computing environment now known or later developed. For example,
Further depicted are an input/output (I/O) adapter 127 and a network adapter 126 coupled to system bus 133. I/O adapter 127 may be a small computer system interface (SCSI) adapter that communicates with a hard disk 123 and/or a tape storage drive 125 or any other similar component. I/O adapter 127, hard disk 123, and tape storage device 125 are collectively referred to herein as mass storage 134. Operating system 140 for execution on processing system 20 may be stored in mass storage 134. The network adapter 126 interconnects system bus 133 with an outside network 136 enabling processing system 20 to communicate with other such systems.
A display (e.g., a display monitor) 135 is connected to system bus 133 by display adaptor 132, which may include a graphics adapter to improve the performance of graphics intensive applications and a video controller. In one aspect of the present disclosure, adapters 126, 127, and/or 132 may be connected to one or more I/O busses that are connected to system bus 133 via an intermediate bus bridge (not shown). Suitable I/O buses for connecting peripheral devices such as hard disk controllers, network adapters, and graphics adapters typically include common protocols, such as the Peripheral Component Interconnect (PCI). Additional input/output devices are shown as connected to system bus 133 via user interface adapter 128 and display adapter 132. A keyboard 129, mouse 130, and speaker 131 may be interconnected to system bus 133 via user interface adapter 128, which may include, for example, a Super I/O chip integrating multiple device adapters into a single integrated circuit.
In some aspects of the present disclosure, processing system 20 includes a graphics processing unit 137. Graphics processing unit 137 is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display. In general, graphics processing unit 137 is very efficient at manipulating computer graphics and image processing, and has a highly parallel structure that makes it more effective than general-purpose CPUs for algorithms where processing of large blocks of data is done in parallel.
Thus, as configured herein, processing system 20 includes processing capability in the form of processors 121, storage capability including system memory (e.g., RAM 124), and mass storage 134, input means such as keyboard 129 and mouse 130, and output capability including speaker 131 and display 135. In some aspects of the present disclosure, a portion of system memory (e.g., RAM 124) and mass storage 134 collectively store an operating system to coordinate the functions of the components shown in processing system 20.
The teachings of the present disclosure may be used in a variety of well operations. These operations may involve using one or more treatment agents to treat a formation, the fluids resident in a formation, a wellbore, and/or equipment in the wellbore, such as production tubing. The treatment agents may be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Illustrative treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, anti-corrosion agents, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers etc. Illustrative well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc.
The present techniques provide for correcting for oil-based mud stand-off from oil-based mud resistivity images without the need to measure stand-offs between electrodes of the sensors and the wall of the borehole. Oil-based mud resistivity imaging tools can separately measure a real part and an imaginary part (magnitude and phase) of the impedance between the transmitting electrode and each receiving electrode (button) of the sensors of the tool 16. In ideal conditions, the oil-based mud is regarded as a perfect electrical insulator which only capacitively couples to high-frequency electromagnetic excitations, while the formation is simplified to a perfect electrical resistor. The equivalent circuit model for this simplified scenario is shown in
In particular,
In reality, oil-based mud does not act as a perfect insulator. In some cases, the electrical conductivity of typical oil-based mud is non-negligible, frequency dependent, and varies greatly depending on the oil/water ratio, downhole conditions, and chemical additives in the mud, for example. Meanwhile, the formation impedance is not entirely resistive. When the frequency is high and formation resistivity is high, the imaginary component in formation impedance due to formation dielectric permittivity becomes significant. In summary, both mud and formation impedances are complex values each having its own real and imaginary components. To compensate for the imperfect insulation of oil-based muds, it is desirable to account for mud stand-off by estimating the apparent dielectric loss of the mud.
is the complex impedance due to the mud stand-off and δma is the apparent dielectric loss angle of the mud,
δma=tan−1((Re(Zm))/Im(Zm)),
where Re(Zm) and Im(Zm) are the real and the imaginary components respectively of impedance measured by the tool 16 in homogeneous mud (with no formation present). Generally, δma is similar to, but may differ from, the actual dielectric loss angle of the mud, expressed as
where ω is angular frequency, σm is electrical conductivity, ε′m and is dielectric permittivity of the mud. This difference (between the apparent dielectric loss angle of the mud δma and the actual dielectric loss angle of the mud δm) is caused by the inhomogeneous electromagnetic field distribution across the electrodes of the sensor(s) of the tool 16, the fringing effect, and/or other current return paths specific to the imaging tool design of the tool 16.
In an ideal situation where oil-based mud is nonconductive, the apparent dielectric loss angle of the mud δma is approximately zero. Similar notation applies to formation impedance and the corresponding apparent formation dielectric loss angle δfa. The measured real-part impedance is the addition of real components of both
and
. If left untreated, the additional Re(Zm) in the final result not only leads to a general over-estimation of the formation resistivity but also causes the formation resistivity image to be stand-off dependent due to the fact that
is inversely proportional to stand-off to first order approximation. Because sensor stand-off is generally unknown, its effect cannot be easily corrected through regular techniques that involve estimating the magnitude of
. Image quality is therefore negatively influenced.
The present techniques improve resistivity imaging by correcting for oil-based mud stand-off from oil-based mud resistivity images. In particular, the present techniques estimate the apparent mud dielectric loss angle, which can be determined using one (or more) of three different techniques: a logging with a closed pad technique, a logging in a cased-hole section technique, and a log-based estimation technique.
The logging with a closed pad technique is now described and includes estimating the apparent dielectric loss angle δma when performing a logging operation within a borehole while pads connected to the logging assembly are in a closed position and thus are disengaged from the borehole wall. A wireline resistivity borehole imaging device (e.g., the tool 16) typically has a central mandrel and multiple pads (with sensor electrodes) connected to the mandrel through metallic arms and linkages that can be commanded to open up to allow the pads contact the borehole wall while logging.
When the diameter of the borehole 14 is relatively large, measurement of mud loss angle could be achieved through logging while the pads 402a, 402b are in a closed position, as shown in
The limitation of the logging with a closed pad technique is that the borehole has to be sufficiently large; otherwise, the formation affects the tool measurement even if the pad is in closed position.
The logging in a cased-hole section technique operates in smaller boreholes than the logging with a closed pad technique. In these smaller boreholes, measurements on mud properties are affected by formation properties that are generally unknown. In order to reduce the number of unknown formation properties, measurements can be obtained in a cased-hole section of the borehole 14 where the formation behind a highly conductive steel casing used to case the borehole is completely shielded by the casing and its influence on tool measurements is removed. If the casing inner diameter and the pad outer diameter are both known, forward modeling studies can be conducted and cross-plot charts can be created to estimate the apparent dielectric loss angle of the mud δma in homogeneous mud from the apparent dielectric loss angle of the mud δma inside the mud-filled casing.
The log-based estimation technique can be useful to estimate the apparent dielectric loss angle of the mud δma when the logging with a closed pad technique and the logging in a cased-hole technique are unavailable. The value for the apparent dielectric loss angle of the mud δma may be estimated using a minimum apparent dielectric loss angle of the overall measured impedance through a sufficiently large depth interval of the image log L, expressed as follows
In this example, it is assumed that the formation has a greater dielectric loss than the oil-based mud; therefore, the apparent dielectric loss angle of the overall measured impedance tends to be greater than or equal to the apparent dielectric loss angle of the mud δma depending on the stand-off. Effectively, this estimation uses the apparent dielectric loss angle of a measurement taken at the greatest stand-off value as the estimation of the apparent dielectric loss angle of the mud δma. The log-based estimation technique can also be used to verify the apparent dielectric loss angle of the mud δma determined using the logging with a closed pad technique and/or the logging in a cased-hole technique. This can provide confidence in the estimated apparent dielectric loss angle of the mud δma.
Once the apparent dielectric loss angle of the mud δma is estimated, the formation resistivity of the formation 26 can be determined by estimating the apparent formation dielectric loss angle δfa. The apparent formation dielectric loss angle δfa can be estimated through the true formation dielectric loss angle as follows:
where σf and ϵ′f are the conductivity and permittivity of the formation 26, respectively. The formation resistivity depends on whether δf is greater than a threshold value (e.g. 85 degrees) as described herein. It should be appreciated that the threshold can vary and can be greater than or less than the example of 85 degrees.
Estimation of the formation dielectric loss angle δf can be performed using the Complex Refractive Index Method (CRIM), which is a relation on complex dielectric permittivity of a formation given formation porosity, frequency, and complex dielectric permittivity of formation matrix and fluids. These parameters may be estimated based on prior knowledge or other logs acquired in the same well or locations with similar formation properties.
CRIM relates a complex permittivity of porous media to porosity φ filled by water, complex permittivity of water {dot over (ε)}w, and permittivity of matrix εm as follows:
{dot over (ε)}=[∅·√{square root over ({dot over (ε)}w)}+(1−∅)·√{square root over (εm)}]2
In the above expression {dot over (ε)}w={dot over (ε)}rw·ε0 and {dot over (ε)}rm={dot over (ε)}rm·ε0, where {dot over (ε)}rw represents a complex relative permittivity of water, {dot over (ε)}rm represents a complex relative permittivity of the mud, and ε0≈8.854 pF/m, which represents an absolute dielectric permittivity of free space. The impedance Ż (from
In this case, the loss angle in terms of impedance is 90 degrees.
The complex permittivity of water {dot over (ε)}w is a function of salinity, temperature, and frequency. The Meissner model can be used to estimate the range of temperature and salinity existing in oil wells according to one or more embodiments described herein. In the range of porosity, water salinity, temperature, frequency, and permittivity of matrix εm, loss angles below 85 degrees are possible when simultaneously the temperature is below 140 degrees Fahrenheit, salinity below 5 parts per thousand, and a frequency equal or above of 44 MHz or the porosity is much smaller than 1%, according to one or more embodiments described herein. Varying the porosity while maintaining fixed the rest of parameters, the loss angle remains constant.
The formation resistivity of the formation 26 depends on the value of the formation dielectric loss angle δf compared to a threshold. For example, If the formation dielectric loss angle δf is greater than a threshold value (e.g. 85 degrees), the formation resistance is:
Re(Zf)˜Re(Z)−Im(Z)*tan(δma).
However, if the formation dielectric loss angle δf is not greater than the threshold value (e.g. 85 degrees), the formation resistance is:
Re(Zf)˜Re(Z).
In some examples, if an estimation of the formation dielectric loss angle δf is not possible, both mathematical approximations can be applied on an entire log interval to generate two resistivity images. Either user-guided or computer-based selections can then be conducted on an interval-by-interval basis to produce a final resistivity image that represents the formation properties through a combination of the two resistivity images.
If formation conductivity is sufficiently high and frequency sufficiently low, the formation dielectric loss angle δf is considered greater than a threshold (e.g., 85 degrees). In such cases, the dielectric effect of formation is generally negligible (see
Re(Zf)˜Re(Z)˜Im(Z)*tan(δma).
It is apparent from
Zf*cos(δfa)*tan(δma).
However, since the formation dielectric loss angle δf is close to 90 degrees, this term is negligible.
In contrast, when formation resistivity is high and/or frequency is high, the formation dielectric effect is no longer negligible (see
Re(Zf)˜Re(Z).
Zm*sin(δma).
However, since Zm is small compared to Zf, this error term is negligible.
The present techniques provide advantages over existing techniques by estimating apparent dielectric loss angle of oil-based mud to determine a stand-off effect caused by the oil-based mud and further estimate a formation dielectric loss angle. From these two estimations, a formation resistance can be determined and used to adjust a formation evaluation. In other words, formation evaluations are improved by accounting for the stand-off effect caused by the oil-based mud. Wellbore operations can be more accurately performed as a result of improved formation evaluations accounting for the stand-off effect caused by the oil-based mud.
At block 901, the method 900 includes estimating an apparent dielectric loss angle δma of the oil-based mud (block 908) to determine a stand-off effect caused by the oil-based mud using at least one of a logging with a closed pad technique (block 902), a logging in a cased-hole section technique (block 904), and a log-based estimation technique (block 906). At block 912, a formation dielectric loss angle δf is determined using, for example, CRIM (block 914).
At decision block 910, the formation dielectric loss angle δf is compared to a threshold (e.g., 85 degrees). If the formation dielectric loss angle δf is greater than the threshold, the formation resistance is determined to be
Re(Zf)˜Re(Z)−Im(Z)*tan(δma),
where Re(Z) and Im(Z) are a real component and an imaginary component respectively of an impedance measured by the logging assembly in a borehole filled with oil-based mud in an earth formation, and δma is the apparent dielectric loss angle of the oil-based mud. However, if the formation dielectric loss angle δf is not greater than the threshold, the formation resistance is determined to be
Re(Zf)˜Re(Z),
where Re(Z) is a real component of an impedance measured by the logging assembly in a borehole filled with oil-based mud in an earth formation.
Additional processes also may be included, and it should be understood that the process depicted in
The components, modules, engines, etc. described regarding
The functionality of the processing system 1000 and its components are not described with reference to
At block 1102, a carrier (e.g., the borehole string 12) is disposed in a borehole (e.g., the borehole 14) in an earth formation (e.g., the formation 26). The carrier includes a logging assembly (e.g., the tool 16) for performing a formation evaluation, using the formation evaluation engine 1010, of the earth formation using a sensor in proximity to a borehole wall of the borehole. Oil-based mud is disposed at least partially between the sensor and the borehole wall.
At block 1104, the estimation engine 1012 estimates an apparent dielectric loss angle δma of the oil-based mud to determine a stand-off effect caused by the oil-based mud. The apparent dielectric loss angle δma is determined using at least one of a logging with a closed pad technique, a logging in a cased-hole section technique, and a log-based estimation technique. The logging with a closed pad technique includes estimating the apparent dielectric loss angle when performing a logging operation within the borehole while a pad connected to the logging assembly is in a closed position. The logging in a cased-hole section technique includes estimating an apparent dielectric loss angle in homogeneous mud from an apparent dielectric loss angle of oil-based mud inside a mud-filled casing of the borehole. The log-based estimation technique includes estimating the apparent dielectric loss angle of the oil-based mud based at least in part on a minimum apparent dielectric loss angle of an overall measured impedance through a depth interval of an image log.
At block 1106, the estimation engine 1012 estimates a formation dielectric loss angle δf. Such estimation can be performed using the complex refractive index model (CRIM). At block 1108, the formation resistance determining engine 1014 determines a formation resistance based at least in part on the formation dielectric loss angle.
At block 1110, the formation evaluation engine 1010 adjusts the formation based on the estimated formation resistance. This can include comparing the formation dielectric loss angle to a threshold (e.g., 85 degrees). When the formation dielectric loss angle is greater than the threshold, the formation resistance Re(Zf) is
Re(Zf)˜Re(Z)−Im(Z)*tan(δma),
where Re(Z) and Im(Z) are a real component and an imaginary component respectively of an impedance measured by the logging assembly in a borehole filled with oil-based mud in an earth formation, and δma is the apparent dielectric loss angle of the oil-based mud. However, when the formation dielectric loss angle is greater than the threshold, the formation resistance Re(Zf) is
Re(Zf)˜Re(Z),
where Re(Z) is a real component of an impedance measured by the logging assembly in a borehole filled with oil-based mud in an earth formation.
At block 1112, a wellbore operation can be performed based on the adjusted formation evaluation. This can include, for example, controlling a drill string by changing a property of the drill string to cause the drill to change trajectory with respect to the earth formation. Controlling the drill string can also include changing a weight on bit of a drill bit of the drill string, changing a rate of penetration of the drill bit, and the like.
Additional processes also may be included, and it should be understood that the process depicted in
Set forth below are some embodiments of the foregoing disclosure:
A method is provided, the method including: disposing a carrier in a borehole in an earth formation, the carrier comprising a logging assembly for performing a formation evaluation of the earth formation using a sensor in proximity to a borehole wall of the borehole, fluid being disposed at least partially between the sensor and the borehole wall; estimating, by a processing device, an apparent dielectric loss angle of the fluid to determine a stand-off effect caused by the fluid using at least one of a logging with a closed pad technique, a logging in a cased-hole section technique, and a log-based estimation technique; estimating, by the processing device, a formation dielectric loss angle; determining, by the processing device, a formation resistance based at least in part on the formation dielectric loss angle; adjusting the formation evaluation based at least in part on the estimated formation resistance that accounts for the stand-off effect caused by the fluid; and performing a wellbore operation based at least in part on the adjusted formation evaluation that accounts for the stand-off effect caused by the fluid.
The method of any prior embodiment, wherein the logging with a closed pad technique comprises estimating the apparent dielectric loss angle when performing a logging operation within the borehole while a pad connected to the logging assembly is in a closed position.
The method of any prior embodiment, wherein the logging in a cased-hole section technique comprises estimating an apparent dielectric loss angle in a homogeneous fluid from an apparent dielectric loss angle of fluid inside a fluid-filled casing of the borehole.
The method of any prior embodiment, wherein the log-based estimation technique comprises estimating the apparent dielectric loss angle of the fluid based at least in part on a minimum apparent dielectric loss angle of an overall measured impedance through a depth interval of an image log.
The method of any prior embodiment, wherein determining the formation resistance comprises comparing the formation dielectric loss angle to a threshold.
The method of any prior embodiment, wherein when the formation dielectric loss angle is greater than the threshold, the formation resistance is
Re(Zf)˜Re(Z)−Im(Z)*tan(δma),
where Re(Z) and Im(Z) are a real component and an imaginary component respectively of an impedance measured by the logging assembly in the borehole in the earth formation and being filled with an oil-based drilling fluid, and δma is the apparent dielectric loss angle of the fluid.
The method of any prior embodiment, wherein when the formation dielectric loss angle is less than the threshold, the formation resistance is
Re(Zf)˜Re(Z),
where Re(Z) is a real component of an impedance measured by the logging assembly in the borehole in the earth formation and being filled with an oil-based drilling fluid.
The method of any prior embodiment, wherein the apparent dielectric loss angle of the fluid is defined as:
where δma is the apparent dielectric loss angle of the fluid, Re(Zm) and Im(Zm) are a real component and an imaginary component respectively of impedance measured by the logging assembly in a homogeneous borehole fluid.
The method of any prior embodiment, wherein the formation dielectric loss angle is determined using a complex refractive index model.
A system is provided, the system including a carrier disposed in a borehole in an earth formation, the carrier comprising a logging assembly for performing a formation evaluation of the earth formation using a sensor in proximity to a borehole wall of the borehole, fluid being disposed at least partially between the sensor and the borehole wall; a memory comprising computer readable instructions; and a processing device for executing the computer readable instructions for performing a method including: estimating, by the processing device, an apparent dielectric loss angle of the fluid to determine a stand-off effect caused by the fluid using at least one of a logging with a closed pad technique, a logging in a cased-hole section technique, and a log-based estimation technique; estimating, by the processing device, a formation dielectric loss angle; determining, by the processing device, a formation resistance based at least in part on the formation dielectric loss angle; adjusting the formation evaluation based at least in part on the estimated formation resistance that accounts for the stand-off effect caused by the fluid; and performing a wellbore operation based at least in part on the adjusted formation evaluation that accounts for the stand-off effect caused by the fluid.
The system of any prior embodiment, wherein the logging with a closed pad technique comprises estimating the apparent dielectric loss angle when performing a logging operation within the borehole while a pad connected to the logging assembly is in a closed position.
The system of any prior embodiment, wherein the logging in a cased-hole section technique comprises estimating an apparent dielectric loss angle in a homogeneous fluid from an apparent dielectric loss angle of fluid inside a fluid-filled casing of the borehole.
The system of any prior embodiment, wherein the log-based estimation technique comprises estimating the apparent dielectric loss angle of the fluid based at least in part on a minimum apparent dielectric loss angle of an overall measured impedance through a depth interval of an image log.
The system of any prior embodiment, wherein when the formation dielectric loss angle is greater than a threshold, the formation resistance is
Re(Zf)˜Re(Z)−Im(Z)*tan(δma),
where Re(Z) and Im(Z) are a real component and an imaginary component respectively of an impedance measured by the logging assembly in the borehole in the earth formation and being filled with an oil-based drilling fluid, and δma is the apparent dielectric loss angle of the fluid.
The system of any prior embodiment, wherein when the formation dielectric loss angle is less than a threshold, the formation resistance is
Re(Zf)˜Re(Z),
where Re(Z) is a real component of an impedance measured by the logging assembly in the borehole in the earth formation and being filled with an oil-based drilling fluid.
Elements of the embodiments have been introduced with either the articles “a” or “an.” The articles are intended to mean that there are one or more of the elements. The terms “including” and “having” are intended to be inclusive such that there may be additional elements other than the elements listed. The conjunction “or” when used with a list of at least two terms is intended to mean any term or combination of terms. The term “coupled” relates to a first component being coupled to a second component either directly or indirectly via an intermediary component. The term “configured” relates to one or more structural limitations of a device that are required for the device to perform the function or operation for which the device is configured.
The flow diagrams depicted herein are just examples. There may be many variations to these diagrams or the steps (or operations) described therein without departing from the spirit of the invention. For instance, the steps may be performed in a differing order, or steps may be added, deleted or modified. All of these variations are considered a part of the claimed invention.
While one or more embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.
It will be recognized that the components or technologies may provide certain necessary or beneficial functionality or features. Accordingly, these functions and features as may be needed in support of the appended claims and variations thereof, are recognized as being inherently included as a part of the teachings herein and a part of the invention disclosed.
While the invention has been described with reference to exemplary embodiments, it will be understood that changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications will be appreciated to adapt a particular instrument, situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
This application claims the benefit of U.S. Provisional Application Ser. No. 62/686,974 filed Jun. 19, 2018, the entire disclosure of which is incorporated herein by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2313842 | Rigterink | Mar 1943 | A |
| 2332343 | Rigterink | Oct 1943 | A |
| 3315260 | Wesch | Apr 1967 | A |
| 4216449 | Kach | Aug 1980 | A |
| 4740265 | Bierlein | Apr 1988 | A |
| 8633701 | Itskovich et al. | Jan 2014 | B2 |
| 9513399 | Cheung et al. | Dec 2016 | B2 |
| 9671517 | Hayman | Jun 2017 | B2 |
| 20070046290 | Bespalov et al. | Mar 2007 | A1 |
| 20110199089 | Hayman | Aug 2011 | A1 |
| 20110199090 | Hayman | Aug 2011 | A1 |
| 20110241689 | Hayman | Oct 2011 | A1 |
| 20110241690 | Hayman | Oct 2011 | A1 |
| 20110309833 | Yang | Dec 2011 | A1 |
| 20120074946 | Forgang | Mar 2012 | A1 |
| 20130307546 | Li | Nov 2013 | A1 |
| 20140184229 | Bloemenkamp | Jul 2014 | A1 |
| 20140353719 | Kim | Dec 2014 | A1 |
| 20150008927 | Cheung | Jan 2015 | A1 |
| 20150355372 | Bloemenkamp | Dec 2015 | A1 |
| 20170227666 | Legendre et al. | Aug 2017 | A1 |
| Entry |
|---|
| Cametti et al.; “Complex Electrical Conductivity of Water-in-Oil Microemulsions”; The American Physical Society; Physical Review Letters; vol. 75, No. 3; Jul. 17, 1995; pp. 569-572. |
| International Search Report and Written Opinion Issued in International Application No. PCT/US2019/037054 dated Oct. 2, 2019; 10 Pages. |
| Jannin et al.; “Dielectric Properties of Nonaqueous Drilling Fluids from 1 MHz up to 20 GHz”; IEEE Transactions on Dielectrics and Electrical Insulation; vol. 21, No. 1; Feb. 2014; pp. 217-224. |
| Patil et al.; “Experimental Study of Electrical Properties of Oil-Based Mud in the Frequency Range from 1 to 100 MHz”; SPE Drilling & Completion; Sep. 2010; pp. 380-390. |
| Number | Date | Country | |
|---|---|---|---|
| 20190383131 A1 | Dec 2019 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62686974 | Jun 2018 | US |
