This disclosure relates generally to antennas, such as those used in the well-logging applications, and related systems and methods.
Resistivity logging tools are used to measure the resistivities of earth formations surrounding a borehole, such as in a hydrocarbon (e.g., oil, natural gas, etc.) well. One approach for performing resistivity measurements is by lowering a wireline-conveyed logging device into a wellbore after the wellbore is drilled. Another approach is to make such measurements while the well is being drilled, which is referred to as logging-while-drilling (LWD) or measurement-while-drilling (MWD). LWD or MWD techniques may allow corrective actions to be taken during the drilling processes if desired. For example, wellbore information if available in real time may be used to make adjustments to mud weights to prevent formation damage and to improve well stability. In addition, real time formation log data may be used to direct a drill bit to the desired direction (i.e., geosteering).
Generally speaking, there are two types of LWD tools for measuring formation resistivity, namely lateral tools and induction or propagation tools. Each of these tools relies on an electromagnetic (EM) measurement principle. A lateral tool may use one or more antennas or electrodes to inject low-frequency transverse magnetic fields into the formations to determine borehole and formation responses by measuring the current flow through the formations to the receivers. Lateral resistivity tools are generally responsive to azimuthal variations in formation resistivities around the borehole.
Propagation-type tools emit high-frequency electric fields into the formation to determine borehole and formation responses by measuring voltages induced in the receivers or by measuring difference responses between a pair of receivers or between the transmitter and the receiver. For example, for a propagation tool, incoming signal phases and amplitudes may be measured at each of several receivers with respect to the phases and amplitudes of the signals used to drive the transmitter. Induction-type transmitters generate magnetic fields that induce currents to flow in the formations. These currents generate secondary magnetic fields that are measured as induced voltages in receiver antennas disposed at a distance from the transmitter antenna.
This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
A wellbore apparatus is provided herein which may include first and second tubular members joined together in end-to-end relation, the first tubular member having a reduced outer diameter end portion. The wellbore apparatus may further include a removable modular antenna assembly including a cylindrical dielectric housing removably positioned on the reduced outer diameter end portion of the first tubular member, at least one antenna coil carried by the cylindrical dielectric housing, and a first electrical connector coupled to the at least one antenna coil. The wellbore apparatus may also include resistivity processing circuitry coupled to the first electrical connector to determine an electrical resistivity of a wellbore based upon the at least one antenna coil.
A related method for making a wellbore apparatus may include providing first and second tubular members to be joined together in end-to-end relation, with the first tubular member including a reduced outer diameter end portion, and removably positioning a cylindrical dielectric housing of a removable modular antenna assembly on the reduced outer diameter end portion of the first tubular member. The removable modular antenna assembly may include at least one antenna coil carried by the cylindrical dielectric housing, and a first electrical connector coupled to the at least one antenna coil. The method may also include coupling the first electrical connector to resistivity processing circuitry, and joining the first and second tubular members together in end-to-end relation with the removable modular antenna assembly carried by the reduced outer diameter end portion of the first tubular member.
The present description is made with reference to the accompanying drawings, in which example embodiments are shown. However, many different embodiments may be used, and thus the description should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. Like numbers refer to like elements throughout, and prime notation is used to indicate similar elements in different embodiments.
Referring initially to
Referring more particularly to
The removable modular antenna assembly 40 further illustratively includes one or more antenna coils 46 carried by the cylindrical dielectric housing 41, and a first electrical connector 47 coupled to the antenna coil(s). A second electrical connector 48 is carried by the first tubular member 43 and coupled with resistivity processing circuitry 49. The second electrical connector 48 mates with the first electrical connector 47 to thereby provide an electrical connection between the antenna coil 46 and the resistivity processing circuitry 49, which determines an electrical resistivity of a wellbore based upon the antenna coil. The resistivity processing circuitry illustratively includes a controller and a transmitter and/or receiver 51 coupled thereto. As noted above, multiple antenna assemblies 40 may be spaced apart along the drill string 31 to transmit and receive signals to and from the geological formation 35. As such, the controller 50 may interface with multiple transmitters and receivers for respective antenna assemblies 40. Transmitters and receivers may also be coupled to multiple antenna assemblies 40 (i.e., shared), and a given antenna assembly may be used to alternate between transmitting and receiving in some embodiments.
The controller 50 may be carried on the drill string 31 in the tool section behind the drill bit 33 in an electronic chassis. The controller 50 may collect resistivity measurement data and store it for later retrieval (such as when the drill string 31 is removed from the borehole 32), or it may communicate the resistivity measurement data up to a well logging control center outside of the well via telemetry or a wired connection. The controller 50 may first process the measured values to make resistivity determinations, or it may collect raw measurement data for later processing.
In the example illustrated in
In the illustrated example, the reduced outer diameter end portion 42 of the first tubular member 43 defines a shoulder 52 with adjacent portions of the first tubular member, and the second electrical connector 48 is carried by the shoulder as shown. An electrical connection is achieved upon sliding the antenna assembly 40 into place on the reduced outer diameter portion 42, which will engage the first electrical connector 47 into the second electrical connector 48. In the present example, the reduced outer diameter end portion 45 of the second tubular member 44 may then be inserted in the cylindrical dielectric housing 41 and coupled with the reduced outer diameter end portion 42 of the first tubular member 43 (e.g., they may be threadably coupled together). However, in other embodiments where the second tubular member 44 does not have the reduced outer diameter portion 45, the antenna assembly will slide onto the first tubular member 43, and the second tubular member is coupled to the reduced diameter portion 42 of the first tubular member. For example, the inner surface of the second tubular member 44 may have threads for engaging corresponding threads on the reduced outer diameter portion 42 of the first tubular member 43, or they may be coupled by other suitable connectors.
It should also be noted that more than one antenna assembly 40 may be positioned between the first tubular member 43 and the second tubular member 44 in the present embodiment, as well as the other embodiments discussed below. That is, one or more antenna assemblies 40 may be positioned on the reduced diameter portion 42 of the first tubular member 43, and if the second tubular member 44 also includes the reduced outer diameter portion 45, then one or more antenna assemblies may be positioned there as well.
In the present example, the first electrical connector 47 comprises a body portion 53 that is integrally formed or molded with the dielectric housing 41 (although it may be separately installed in some embodiments) and includes at least one electrode 54 carried by the body portion. Furthermore, a sealing ring(s) 55 is also associated with the removable modular antenna assembly. In the present example, the sealing ring 55 is carried by the body portion 54 to seal out water, mud, dirt, or other materials that could compromise the electrical connection to the resistivity processing circuitry 49. In some embodiments, a set screw or other locking device may also be used to securely couple the first and second connectors 47, 48 together, if desired.
A related method for making a wellbore apparatus is now described with reference to the flow diagram 60 of
Turning now to
In accordance with another example embodiment shown in
Turning now to
It will be appreciated that the above-described removable modular antenna assemblies may be installed and uninstalled on a downhole tubular (such as a housing or collar), removed, or replaced as desired. This may allow antennas to be readily replaced in the field when worn or damaged, rather than having to remove large drill collars or other tubular sections and send them offsite for service or re-fitting of permanent embedded antennas, for example. Additionally, the removable antenna assemblies allow pressure balancing, thus reducing size variation with pressure. In some embodiments, the antenna coil 46 may be mounted on a ceramic or polymer core, and then molded in a fluid resistant polymer or elastomer (e.g., rubber). Example dielectric material may include PEEK, SPS or other thermoplastic or thermoset, for example.
Many modifications and other embodiments will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that various modifications and embodiments are intended to be included within the scope of the appended claims.