In oil and gas reservoir exploitations, formation evaluations are undertaken to gain a better understanding of the reservoir and to optimize production. Formation evaluation typically relies on interpretation of near wellbore measurements carried out with logging tools. The logging tools are designed to estimate formation properties, such as porosity, water saturation, rock mechanical properties, permeability, and other formation properties at sequential positions along the wellbore. The formation properties enable preparation of a reservoir model using cells to discretise the reservoir and to apply numerical methods for calculation of production performance.
However, the number of cells that can be used in a reservoir simulation is limited so as to maintain reasonable computation times. Consequently, upscaling of the formation parameters is employed to allow practical models with a manageable number of cells. Various methods can be used for upscaling data from several centimeters to several tens of meters scale and for inferring properties away from the wellbore. However, such approaches introduce additional uncertainties that limit the usefulness of the formation evaluation.
In general, the present invention provides a system and methodology that facilitate formation evaluation. A logging tool is deployed to obtain formation related measurements. One or more mobile robots also are positioned in the subterranean environment at unique positions that facilitate the accumulation of data related to the formation. The data obtained from the logging tool and the one or more mobile robots is processed in a manner that enables deep formation evaluation.
Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:
In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.
The present invention relates to a system and methodology to facilitate subterranean formation evaluation, and the technique is useful in performing deep formation evaluations. According to one embodiment, a logging tool is conveyed downhole along a wellbore to measure parameters. However, the information obtained by the logging tool is supplemented by deploying at least one mobile robot into deeper regions of the formation. For example, one or more mobile robots may be deployed into side holes extending from the wellbore, and those robots are operated to obtain deep formation measurements. The measurements taken by both the logging tool and the mobile robot or robots are processed to better evaluate a given subterranean formation.
The technique effectively provides a solution enabling a deep formation evaluation that includes the use of measurements reflecting the properties of a larger volume of rock away from the wellbore. The approach alleviates errors in upscaling and provides a more representative reservoir description. According to one embodiment, the technique utilizes deep measurements, constrained by the near-wellbore data, to build a reservoir model on a more desirable scale. The actual scale may be determined by the resolution of the deep measurements provided by the mobile robots. In performing this type of constrained inversion, the near-wellbore data is honored, and extra information is provided via the deep measurements on, for example, the inter-well space. The upscaling is performed based on physics and measurements rather than solely on statistical averaging and/or interpolation. In some applications, this approach can be used to provide a model that more accurately reflects the true reservoir conditions, thus enabling a simulation that provides a better predictive capability for use in oilfield management.
In one embodiment, semi-autonomous or autonomous robots are conveyed downhole into a wellbore while attached to a main logging tool. The robots are deployed away from the main logging tool either further away in the wellbore and/or in side holes extending into the formation from the main borehole. The robots can later be retrieved by reattaching them to the main logging tool. In an alternate embodiment, the robots are deployed permanently in side holes extending from the wellbore to enable permanent monitoring of the formation in a variety of applications, including production monitoring applications, water encroachment detection applications, steam assisted gravity drainage applications, and other applications.
The robots are designed to carry sensors and may utilize one or more types of sensors. For example, each robot may comprise a sensor module having, for example, temperature sensors, pressure probes/sensors, gravimeters, acoustics sensors, e.g. hydrophones and 3C geophones, electrical resistivity sensors, and other types of sensors. Additionally, the robots may comprise electromagnetic, acoustic or other types of transmitters and receivers, e.g. triaxial induction coils, for formation evaluation that may be conducted in cooperation with other robots and/or the logging tool. For acoustic and electromagnetic sensors, both directional and omni-directional sources can be employed over a wide frequency band or, alternatively, by performing a transient measurement.
The arrangement of logging tool and one or more mobile robots also facilitates performance of various measurements by triggering sources/transmitters (e.g. electromagnetic sources, acoustics sources, pressure sources, or other sources) on the logging tool and reading resulting signals with a receiver/sensor package carried by one or more of the mobile robots. Similarly, measurements may be obtained by triggering sources on one or more of the mobile robots and reading resulting signals with a receiver/sensor package carried by the logging tool.
A number of measurement configurations can be employed according to the environment, well configuration, and desired results. For example, one configuration utilizes long-offset, single-well logging by the robots that are deployed further away from a transmitter of the logging tool along the wellbore. In another configuration, logging measurements are performed as the mobile robot shuttles along a side hole to enable a plurality of directional transmitter-receiver spacings for imaging the formation away from the side holes. According to another configuration, “cross-hole” measurements are performed between robots in the side holes and the logging tool in the wellbore. Similarly, cross-hole measurements can be performed between mobile robots in two or more side holes. Various combinations of these configurations also can be used to further improve an understanding of the reservoir. In one embodiment, miniaturized robots are deployed in different locations and utilize a wireless sensor network technology to communicate.
In the past, traditional logging measurements have been carried out using predesigned transmitter-receiver arrays with fixed spacings that are assumed to apply to all formation scenarios. However, the use of sensors deployed on one or more mobile robots enables selective spacing of transmitters and receivers along the wellbore and in the formation. As a result, an operator can optimally place the transmitters and receivers to, for example, maximize the sensitivity of the measurements to facilitate evaluation of formation properties. The mobile robots can be designed to provide data in real time and thus enable a real-time survey.
Referring generally to
The logging tool 24 is conveyed downhole by a suitable conveyance 32, such as a wireline or coiled tubing. Depending on the specific application, the logging tool 24 may comprise a variety of components for measuring parameters along wellbore 28. For example, the logging tool 24 may comprise an electromagnetic transmitter 34 and an electromagnetic receiver 36 for performing surveys of the subterranean formation 22. The logging tool 24 also may comprise other types of sensors and components, including acoustic sensor systems, pressure sensor systems, and other systems and components. In some applications, logging tool 24 comprises a locomotion module 38, such as a tractor, to facilitate movement of the logging tool along sections of wellbore 28, such as deviated wellbore section 30.
As illustrated, one or more mobile robots 26 are deployed at a desired distance from logging tool 24 to enable an enhanced evaluation of formation 22. For example, one mobile robot 26 is illustrated as deployed in wellbore 28 at a desired distance from logging tool 24. Alternatively or in addition, mobile robots 26 can be deployed in side holes 40 that extend deeper into formation 22 from wellbore 28. The positioning of mobile robots 26, along with their sensor modules, is selected for a given environment and application so as to substantially improve the collection of data and, ultimately, the deep formation evaluation.
In some applications, a plurality of mobile robots 26 may be permanently deployed in the reservoir/formation 22 at an early stage of oilfield development. In this particular embodiment, the mobile robots may be used to assist in geo-steering subsequent wells by illuminating the reservoir with pulsed electromagnetic and/or acoustic energy. The pulsed electromagnetic and/or acoustic energy enables determination by triangulation of the location of the drill bit while a development well is drilled into the formation.
The mobile robots 26 may comprise a memory and be operated in a memory mode in which data collected by the robot sensors is stored. At the end of a logging operation, for example, the mobile robots 26 can be actuated and returned to the logging tool 24 for retrieval to the surface and evaluation of the stored data via a processing system 42. Alternatively, the one or more mobile robots 26 may be directly linked with processing system 42 via one or more communication lines 44, which may be hardwired communication lines or wireless communication lines. For example, data may be sent from each mobile robot 26 to processing system 42 via acoustic or electromagnetic wireless telemetry through formation 22. By directly linking the mobile robots 26 with processing system 42, data can be provided in real time to facilitate monitoring of formation parameters and control of both mobile robots 26 and logging tool 24.
Data, e.g. control signals, also may be communicated from processing system 42 to each of the mobile robots 26 to control the function of individual robots. For example, the movement of individual mobile robots 26 may be controlled to, for example, change the position of specific robots in wellbore 28 and/or side holes 40. The control signals may be sent from processing system 42 to mobile robots 26 via the same types of wired and/or wireless telemetry techniques used to relay data from the robots to processing system 42. Similarly, data may be communicated between logging tool 24 and processing system 42 via hardwired or wireless communication lines 46. Logging tool 24 also can serve as a hub for communicating with the mobile robots 26 via a wireless (or wired) communication protocol that enables relaying of data to or from the surface in real time. The mobile robots 26 also can be designed to self organize as a wireless network system and to utilize various communication technologies that assist in tracking mobile robot position and in managing data gathering and communication.
The present technique is useful in horizontal wells to provide deeper reservoir description using, for example, cross-hole measurements and/or sensors spaced further apart than in conventional logging. However, the present technique also is applicable in vertical wells, such as the substantially vertical well illustrated in the embodiment of
In the example illustrated in
Each mobile robot 26 may be designed in a variety of configurations with many types of components used to assist navigation and measurements, depending on the environment, logging operation, parameters to be detected/monitored, and other desired goals of the system and methodology. Referring generally to
Also, in other applications a plurality of mobile robots 26 is designed and deployed to utilize sensor network technology, such as a wireless sensor network technology, to assist in keeping track of mobile robot location and to relay measured data and control commands sent via processing system 42. As illustrated schematically in
Referring again to
In a variety of applications, the mobile robot 26 is independently moved once separated from logging tool 24 via a locomotion module 58. The locomotion module 58 may comprise a tractor or other device operated in response to control signals sent from processing system 42. Power for locomotion module 58 may be provided by power module 52 to enable movement of robot 26 along wellbore 28 and/or side hole 40.
Each mobile robot also has a sensor module 60 that comprises a plurality of sensors 62 selected according to the well parameters that are to be detected and monitored for enhancing evaluation of the reservoir. Sensors 62 may comprise temperature sensors, pressure sensors, e.g. probes, gravimeters, acoustics sensors, e.g. hydrophones and 3C geophones, electrical resistivity sensors, and other types of sensors. In at least some applications, one or more of the mobile robots 26 also may comprise a device 64, such as a transmitter and/or receiver. By way of example, device 64 may comprise an electromagnetic transmitter and/or receiver, although the device 64 alternately may comprise acoustic, pressure, or other transmitters and/or receivers. In some applications, the electromagnetic device 64 may comprise triaxial induction coils designed to facilitate formation evaluation in cooperation with other robots and/or the logging tool 24.
Inclusion of electromagnetic, acoustic, pressure, or other devices 64 in one or more of the mobile robots 26 enables use of a wide variety of logging configurations with great flexibility and adjustability with respect to the distance between the transmitter and receiver. For example, one transmitter or receiver may be positioned on the logging tool 24 while the corresponding transmitter or receiver is positioned on one of the mobile robots 26. In the example illustrated in
In one example, logging tool electromagnetic transmitter 36 may be used in cooperation with a corresponding electromagnetic receiver 64 positioned on one of the mobile robots 26 or on a plurality of mobile robots 26. Similarly, the logging tool electromagnetic receiver 34 may be used in cooperation with a corresponding electromagnetic transmitter 64 positioned on one or more of the mobile robots 26 to optimize the data/information collected on formation 22. The information obtained is useful in constructing a reservoir model that more accurately reflects the true reservoir conditions and this enables a simulation with better predictive capability for use in oilfield management. In many applications, logging tool 24 is located in the wellbore during logging operations. However, one or more logging tools 24 also may be positioned at a surface location during a logging operation. If the logging tool or tools 24 are located at the surface and each tool comprises a transmitter/source, surface-to-wellbore measurements can be made while the mobile robot or robots 26 are moved along, for example, the side holes 40. Similarly, if the logging tool or tools 24 are located at the surface and each tool comprises a receiver, wellbore-to-surface measurements can be made while the mobile robots 26 are moved along the side holes 40 or along other subterranean features.
Another example of the flexibility afforded by a mobile robots 26 is illustrated in
The system 20 is useful in a variety of vertical and deviated wellbores and with many arrangements of side holes to provide an improved deep formation evaluation. The size and configuration of logging tool 24, as well as the components used to construct logging tool 24, can vary from one application to another according to factors, such as the environment and the parameters to be measured. With respect to the mobile robots 26, the number and arrangement of robots 26 may be adjusted as desired for a given logging operation. The robots may be deployed in the wellbore and/or in one or more side holes to obtain numerous measurements from a variety of configurations. Additionally, the size, structure, sensors, and other components in each mobile robot 26 may be selected according to the specific logging operation anticipated for a given formation. Deployment and retrieval of some or all of the mobile robots can be achieved independently or in combination with the logging tool.
Accordingly, although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Such modifications are intended to be included within the scope of this invention as defined in the claims.
This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 61/047,159, filed on Apr. 23, 2008, which is incorporated herein by reference.
Number | Date | Country | |
---|---|---|---|
61047159 | Apr 2008 | US |