US20160194949A1 - Integrated well survey management and planning tool - Google Patents

Abstract

In one example, an integrated well survey management and planning tool is implemented by a computer system. The tool can receive a trajectory of a proposed well from a surface to a subterranean geological target to be reached by drilling the well, and a survey plan indicating the number, position and survey type of surveys to be performed on the well while drilling the well. The tool can apply multiple error models based on the survey type for drilling the well. Each error model defines a respective uncertainty in reaching the subterranean geological target by drilling the well along the received trajectory. The tool can display, in a user interface, the received trajectory of the well and an uncertainty indicator determined by applying the multiple error models. The uncertainty indicator represents a combination of respective uncertainties defined by the multiple error models and indicates an uncertainty in drilling the well on the received trajectory.

Description

TECHNICAL FIELD
• This disclosure relates to well survey management and planning.
BACKGROUND
• A well plan describes the well trajectory to be followed to take a well successfully from its surface position to the end of the well trajectory. Based on factors such as an expected use of a well (e.g., observation, production, injection, or multi-purpose well), parameters (e.g., production parameters, completion requirements, well dimensions, location), an expected life of the well, and conditions of the geological target (e.g., the subterranean reservoir) to be reached by the well, and other factors, the well plan outlines well objectives to be achieved during well drilling and well use. When drilling commences based on the well plan, the well can be periodically surveyed to obtain information describing the well being drilled and the obtained information interpreted, e.g., to compare a planned position and a determined position of the well. An operator can respond to deviations between the planned position and the determined position, e.g., by adjusting the drilling operations or by re-defining the well objectives (or both).
DESCRIPTION OF DRAWINGS
• FIG. 1 illustrates an example computer system to implement an integrated well survey management and planning tool.
• FIG. 2 is a flowchart of an example process to implement the integrated well survey management and planning tool during a planning stage.
• FIG. 3 illustrates an example user interface provided by the example computer system ofFIG. 1 in response to implementing the integrated well survey management and planning tool.
• FIG. 4 is a flowchart of an example process to implement the integrated well survey management and planning tool during an execution stage.
• FIG. 5 illustrates an example schematic of the example computer system ofFIG. 1.
• Like reference symbols in the various drawings indicate like elements.
DETAILED DESCRIPTION
• This disclosure describes an integrated well survey management and planning tool. The tool can be implemented as a comprehensive, interactive survey management computer software application that can enable better planning and evaluation of survey strategy. The tool can bring different aspects of survey management, e.g., outputs determined by different survey tools that need to be considered during planning and executing a well into a single interactive environment. By implementing the tool, results of some analysis and actual interference effects can be viewed during the planning stage and the execution stage, respectively.
• As described below, the tool can display multiple elements that affect well planning and surveying in a single interactive user interface on a display device. The interactive user interface can display the effect of a change in one parameter on other parameters, as applicable. Based on the outputs displayed in the user interface, an operator can adjust the choice of survey tools resulting in a well survey that achieves the well objectives, e.g., drill a well that reaches the intended geological target. In this manner, the tool can be implemented as an all-in-one interactive tool that can illustrate and optimize a survey for a well, platform, pad or field. For example, the tool can enable implementing as few surveys as necessary with survey tools that are as inexpensive as practicable. The tool can be implemented before or after commencing drilling operations (or both). Implementing the tool can enable operators to match the survey program with well objectives. The tool can be used to perform what-if analysis to determine the optimum length of non-magnetic material required in the BHA and to monitor the effects of variations in the earth magnetic field, due to solar storms for instance, on survey accuracy and allow for early determination if re-surveying is needed. Also the tool allows for the instantaneous verification that the correct earth magnetic model is being used and that the input variables are correct, the same applies for the declination correction being applied.FIG. 1 illustrates anexample computer system100 to implement the integrated well survey management and planning tool. In some implementations, the tool can be implemented as a computer software application including computer instructions stored on a computer-readable medium102 and executable by data processing apparatus104 (e.g., one or more computer processors). Thecomputer system100 can be connected to adisplay device106 and to one or more input devices108 (e.g., a mouse, a keyboard, a touchscreen, a stylus, an audio input device, or other input devices). In some implementations, thecomputer system100 can be a desktop computer, a laptop computer, a tablet computer, a smartphone, a personal digital assistant, a client computer of a server-client computer system, or other computer system.
• Thecomputer system100 can be connected to one or more well survey and planning computer systems (e.g., afirst computer system110a, asecond computer system110b, athird computer system110c) over one or more wired or wireless networks112 (e.g., a local area network, a wide area network, the Internet). Each well survey and planning computer system can execute a respective well survey and planning computer software application that receives survey information obtained from survey tools connected to each well survey and planning computer system. Thecomputer system100 can receive the survey information from the well survey and planning computer software applications over the one or more wired orwireless networks112. In some implementations, the one or more well survey and planning computer systems can be implemented as entities that are separate from thecomputer system100 that implements the integrated well survey management and planning tool. Alternatively, thecomputer system100 can implement the computer software applications implemented by each of the one or more well survey and planning computer systems.
• FIG. 2 is a flowchart of a process200 to implement the integrated well survey management and planning tool during a planning stage, i.e., before drilling commences. In some implementations, thecomputer system100 can implement the process200. At202, thecomputer system100 can receive multiple parameters. For example, the parameters can describe a location and a shape of a well and can be received, e.g., from a well operator. At206, thecomputer system100 can receive a survey plan indicating the number, position and survey type of surveys to be performed on the well while drilling the well.
• At204, thecomputer system100 can receive a trajectory of the well from a surface to a subterranean geological target to be reached by drilling the well. For example, an operator can provide the trajectory as an input to thecomputer system100. Alternatively, another computer system, which stores the trajectory, can provide the trajectory as an input to thecomputer system100. At208, thecomputer system100 can receive a selection of a survey tool from among multiple survey tools. A survey tool can be a physical type of surveying tool that can be carried into the well. For example, the tool can be carried into the well on a wire (e.g., a wireline, e-line, or other tool) or tubing. The survey tool can measure the location in three-dimensional space of the well. For example, either thecomputer system100 or one or more of the well survey and planning computer systems (or both) can be connected to the survey tool that surveys the well to be drilled along the received trajectory. In some implementations, thecomputer system100 can also receive the number, position and survey type of surveys to be performed on the well while drilling the well.
• At210, thecomputer system100 can apply multiple error models to the survey tool. An error model can be implemented as a computer software application as computer instructions stored on the computer-readable medium102 and executable by thedata processing apparatus104. Each error model can define a respective uncertainty in reaching the subterranean geological target by drilling the well along the received trajectory. Some error models can determine the respective uncertainty by accounting for influences of different error sources. In some implementations, thecomputer system100 can receive the error models, e.g., as inputs from an operator or from another computer system (or both). At212, thecomputer system100 can display, in a user interface114 (e.g., displayed in the display device106), the multiple parameters, the received trajectory of the well, an identifier identifying the survey tool and an uncertainty indicator determined by applying the one or more error models. The uncertainty indicator indicates an uncertainty in drilling the well on the received trajectory.
• The uncertainty indicator represents a combination of respective uncertainties defined by the multiple error models. In other words, the uncertainty indicator is an uncertainty of the well that represents a combination of uncertainties of each survey and spacing between the surveys. For example, each of multiple survey tools that are (or can be) implemented during a well survey is associated with a respective uncertainty. The uncertainty indicator described in this disclosure represents a combination of the multiple uncertainties associated with the multiple survey tools. Thecomputer system100 can determine the uncertainty indicator based, in part, on the locations of the survey tools. The uncertainty represented by the uncertainty indicator is more than the uncertainty in the accuracy of the tool itself. The uncertainty in the accuracy of the tool is determined by errors in the tool's ability to make measurements. In addition to the uncertainty of the tool, the uncertainty for the well represented by the uncertainty indicator represents an uncertainty in drilling the well along the target trajectory without being able to see the three-dimensional drilling space, i.e., without survey points and using measurements made by the survey tools during the previous survey. The uncertainty represented by the uncertainty indicator can increase as a time between successive surveys increases because the possible error builds. In some implementations, the uncertainty indicator can be determined based on the intended well trajectory and the survey tools that will be used (and the locations of the survey tools). The operator can then plan more or fewer survey points, different survey points, different survey tools (or combinations of them) based on a confidence (provided by the uncertainty indicator) that the well will hit the geological target.
• In this manner, thecomputer system100 can provide theuser interface114 as a comprehensive, interactive survey management module. The operator can use theuser interface114 to evaluate an effect of different numbers, positions and survey types of surveys that affect the uncertainty indicator. The operator can also use theuser interface114 to evaluate an effect of different error models and combinations of error models, measurement corrections (e.g., sag correction), drill string configuration (e.g., the NMDC), well configurations and factors including well location and drilling time of the year. For example, thecomputer system100 can provide each of the factors that affect the uncertainty indicator as a selectable option in theuser interface114. The operator can create combinations of selectable options (e.g., a combination of a first error model, a first correction, a first drill string configuration, a first location, a first drilling time, another combination of first and second error models, no correction, a second drill string configuration, the first location, a second drilling time, or other combinations) to determine the uncertainty indicator. In this manner, the operator can select/unselect available options and determine an effect on the uncertainty indicator. The operator can use the tool implemented by thecomputer system100 to determine a survey program (i.e., the number, position and survey types) that will enable the operator to drill a well that will reach the geological target.
• In the planning stage, thecomputer system100 can receive the multiple parameters, receive the trajectory of the well, receive the selection of the survey tool, apply the one or more error models and display the multiple well survey parameters before the well is drilled along the received trajectory. In an execution stage, thecomputer system100 can additionally receive actual drilling data and show the trajectory based on actual drilling data, as described below.
• FIG. 3 is an example of theuser interface114 provided by thecomputer system100 in response to executing the integrated well survey management and planning tool. Theuser interface114 includes multiple regions. In each region, thecomputer system100 displays either an input to or an output of the integrated well survey management and planning tool implemented by thecomputer system100. In some implementations, theuser interface114 includes aregion304 in which thecomputer system100 displays multiple parameters, e.g., a length of a non-magnetic drill collar (NMDC) to be positioned in the well, a sensor position in the NMDC at which a survey tool is to be positioned, and casing information describing at least one of a casing size, distance, or direction from the sensor position. Thecomputer system100 can receive the multiple parameters, which can also include a location and a shape of the well, either from an operator of thecomputer system100 or from one of the well survey and planning computer systems.
• Theuser interface114 includes aregion308 in which thecomputer system100 displays the trajectory of the well from the surface to the subterranean geological target based, in part, on the parameters. In theregion308, thecomputer system100 can also display the uncertainty indicator described above. In some implementations, thecomputer system100 can display the uncertainty indicator as including multiple ellipses, each occupying a different area. As described above, each ellipse represents a combination of uncertainties associated with different multiple survey tools. A change in an uncertainty associated with information obtained by one of the survey tools affects an uncertainty associated with information obtained by another of the survey tools. Each ellipse of the multiple ellipses accounts for the different uncertainties associated with the different survey tools. For example, an area occupied by each ellipse is a measure of uncertainty in drilling on the target trajectory at a respective depth that cannot be visualized by relying on survey points obtained from the survey tools during a previous survey. In addition, each ellipse is associated with a respective depth of the well from the surface to the subterranean geological target. Thecomputer system100 can display the multiple ellipses at multiple respective depths along the trajectory in theregion308 of theuser interface114.
• In some implementations, thecomputer system100 can determine a confidence level for each ellipse that represents a confidence that an actual trajectory of the drilled well will match the predicted trajectory. Thecomputer system100 can determine the confidence level for each ellipse based, in part, on uncertainties associated with the information obtained by the survey tools, as described above. Thecomputer system100 can additionally determine an uncertainty threshold at a respective depth that represents an acceptable deviation between the actual and predicted trajectories. The uncertainty threshold is a potential uncertainty that is so great that the target trajectory could possibly miss the geological target. Thecomputer system100 can also determine whether the possible actual trajectory will reach the geological target. Thecomputer system100 can determine that a first ellipse at a first depth does not satisfy an uncertainty threshold at that depth. In response, thecomputer system100 can display the first ellipse in theregion308 in a manner that is visually distinguishable from a second ellipse that satisfies the uncertainty threshold at a second depth. For example, thecomputer system100 can display ellipses that satisfy respective uncertainty thresholds in a color (e.g., green) and ellipses that do not satisfy the respective uncertainty thresholds in another color (e.g., red).
• In some implementations, multiple survey tools can be available and can be connected to (e.g., operated by) the well survey and planning computer systems. The operator of thecomputer system100 can select one or more survey tools, which can include, e.g., a single shock magnetic survey tool, a MWD magnetic survey tool with multi-shock type survey, or other survey tools. If the inaccuracies determined for the survey tools are higher than acceptable thresholds, then additional corrections can be applied. The corrections can include, e.g., SAG corrections to correct errors in the alignment of the survey tool, corrections to correct errors associated with the presence of magnetic components in the drill string, corrections due to earth's magnetic field based on geographic location (e.g., closer to the north or south poles), and other corrections.
• As described above, thecomputer system100 can receive a selection of one or more survey tools, e.g., from a user of thecomputer system100 or from one or more of the well survey and planning computer systems. In addition, thecomputer system100 can receive one or more error models to be applied to the selected survey tool through theuser interface114. For example, theuser interface114 can include aregion302 in which thecomputer system100 displays multiple error models including, e.g., at least one of an interpolation in-field referencing (IIFR) model, an in-field referencing (IFR) model, and a measurement while drilling (MWD) model. In this region, theuser interface114 can also include a correction applied to the readings, e.g., a sag correction. A user of thecomputer system100 can select one or more of the error models through theuser interface114. Thecomputer system100 can apply the selected one or more error models to the selected survey tool. In some implementations, thecomputer system100 can include an “Accuracy” field that specifies an acceptable deviation (e.g., 1-sigma, 2-sigma, 3-sigma) in theregion302. Thecomputer system100 can apply the selected one or more error models to the selected survey tool to determine that the errors fall within the deviation specified in the “Accuracy” field.
• In some implementations, the multiple parameters can include a geographic location at which the well is to be drilled and a drilling time, i.e., a time of the year when drilling operations are to be performed. A well survey and planning computer system can implement a geodetic model that can determine the earth's gravitational field and magnetic field strength at the location and at the drilling time. Theuser interface114 can include aregion306 in which thecomputer system100 displays an identifier identifying the geodetic model. Theuser interface114 can also include aregion312 in which thecomputer system100 can display the earth's gravitational field strength and magnetic field strength, and a dip angle of the magnetic field.
• In some implementations, the multiple parameters can include magnetics representing variations in the earth's magnetic field due to solar effects during the drilling time. Theuser interface114 can include aregion314 in which thecomputer system100 displays the magnetics during the drilling time. For example, one of the well survey and planning computer systems can determine and provide the magnetics to thecomputer system100 for display in theregion314. Thecomputer system100 can display a plot of the magnetics over a time that includes the drilling time in theregion314. Either thecomputer system100 or a well survey and planning computer system can compare the magnetics with a threshold magnetics for drilling the well. In some implementations, thecomputer system100 can display the magnetics at a particular time that satisfy the threshold magnetics to be visually distinguishable from magnetics at a different time that does not satisfy the threshold magnetics. For example, thecomputer system100 can display the magnetics that satisfy the threshold magnetics in a first color (e.g., green) and the magnetics that do not satisfy the threshold magnetics in a second, different color (e.g., red). Moreover, some of the survey tools measure orientation relative to the earth's magnetic field. Thecomputer system100 can account for the effect of the magnetics on the readings of the magnetic survey tools.
• Additional survey and planning information that thecomputer system100 can display in theuser interface114 can include an image of a SAG correction for the well (e.g., in a region318), an axial and cross-axial interference (e.g., in a region310) representing a disturbance in a magnetic field due to low magnetic permeability components in the well, and an output of the IFR/IIFR error models (e.g., in a region316). As described above, theuser interface114 is interactive. For example, when thecomputer system100 receives a change to an uncertainty defined by an error model (or any input to the integrated well survey management and planning tool) that results in a change to an uncertainty defined by another error model, thecomputer system100 can automatically and without user intervention update the uncertainty indicator (or any other aspect of the well plan or survey displayed in the user interface114). Thecomputer system100 can display the updated uncertainty indicator in theuser interface114. An operator of thecomputer system100 can make changes and see, e.g., in real time or near real time, an effect of the changes on the ellipse. In this manner, the operator can create different scenarios while designing the well survey plan.
• The techniques described above related to implementing the integrated well survey management and planning tool during the planning stage of well. After drilling has commenced, one or more survey tools can be implemented to monitor the drilling operation as described below with reference toFIG. 4. Thecomputer system100 can implement the integrated well survey management and planning tool to receive information determined by the one or more survey tools, and, in real time, update appropriate regions in theuser interface114. By doing so, the operator can compare the actual drilling information with the predicted drilling information, and make adjustments as necessary, e.g., to the drilling conditions, the survey tools, the error models (or combinations of them). In addition, the operator can visualize an effect of the actual drilled well on the ellipses. For example, if the as-drilled well lands at a center of a predicted ellipse, the subsequent ellipses over undrilled portions will not be as large as predicted.
• FIG. 4 is a flowchart of an example process to implement the integrated well survey management and planning tool during an execution stage. In some implementations, thecomputer system100 can implement the process400. At402, thecomputer system100 can receive survey data describing a well being drilled. For example, after the well drilling has commenced, a survey tool positioned at a location between the surface and the geological target to be reached by drilling the well can be implemented to obtain survey data that includes a trajectory of the well being drilled. The survey tool can be moved to different locations in the well. For example, after drilling for a certain period, drilling can be stopped and the survey tool, which can be near the drill bit, can be operated to take a survey. As described above, thecomputer system100 can receive a target trajectory along the well to be drilled to the geological target. At404, thecomputer system100 can determine an uncertainty indicator indicating an uncertainty in drilling the well on a target trajectory. For example, thecomputer system100 can determine the uncertainty indicator based at least in part on the survey data and the target trajectory. The uncertainty indicator can indicate an uncertainty (e.g., a confidence measure) in reaching the geological target by drilling the well along the target trajectory.
• At406, thecomputer system100 can display the uncertainty indicator in a user interface, e.g., in theuser interface114. As described above, in certain (but not all) instances, thecomputer system100 can have previously determined an uncertainty indicator for the well during a planning stage, i.e., before drilling commences. By implementing process400, thecomputer system100 can determine a revised uncertainty indicator for the well based, in part, on survey data that describe the well being drilled. The revised uncertainty indicator measured during the drilling stage, therefore, is an update to the uncertainty indicator determined during the planning stage. In some implementations, thecomputer system100 can receive at least a portion of a measured trajectory (i.e., the actual trajectory) of the well being drilled and compare the portion of the measured trajectory with the target trajectory determined during the planning stage. Thecomputer system100 can determine the revised uncertainty indicator based on the comparison. For example, upon determining that the as-drilled well lands at or near a center of an ellipse, then thecomputer system100 can determine that the uncertainty that the well will land in a subsequent ellipse in an undrilled portion is low. Consequently, thecomputer system100 can determine the revised ellipse to be smaller than a current ellipse. Alternatively, upon determining that the as-drilled well lands at or near a periphery of the ellipse, thecomputer system100 can determine the revised ellipse to be larger than or at least the same size as the current ellipse.
• The uncertainty indicator determined during the drilling stage, like the uncertainty indicator determined during the planning stage, can include multiple ellipses, each occupying a different area. Each ellipse is associated with a respective depth of the well from the surface to the subterranean geological target. One or more of the ellipses represents an uncertainty associated with a portion of the well that has not yet been drilled. Thecomputer system100 can display the multiple ellipses at multiple respective depths of the well in the user interface. In some implementations, thecomputer system100 can replace an ellipse at a depth determined during the planning stage with another ellipse at the depth determined during the drilling stage. In this manner, thecomputer system100 can replace one or more ellipses at respective one or more depths based on the survey data and the target trajectory. In some situations, thecomputer system100 can determine that an ellipse determined during the planning stage matches (e.g., occupies the same area as) an ellipse determined during the drilling stage. In such situations, thecomputer system100 may not replace the ellipse determined during the planning stage.
• In response to viewing ellipses associated with the revised uncertainty indicator, an operator may change aspects of a survey plan, e.g., to adjust the target trajectory from the as-drilled well and the plan such that the newly updated ellipses land at the geological target. At408, thecomputer system100 can receive a change to the survey plan that indicates the number, position and survey type of surveys to be performed on the well while drilling the well. As described above, the change can be responsive to the uncertainty indicated by the revised uncertainty indicator. For example, upon viewing the revised uncertainty indicator, an operator can determine to change the number, position, survey type, error models (or a combination) that was previously defined in the survey plan. The operator can, e.g., select a survey tool that the operator had not selected during the planning stage before drilling commenced. In some implementations, thecomputer system100 can display, in the user interface, multiple survey tools from among which the operator can make one or more selections.
• At410, thecomputer system100 can apply multiple error models based on the received change to the survey plan. Each error model defines a respective uncertainty in reaching the subterranean geological target by drilling the well. The uncertainty is based on a survey performed while the well is being drilled as well as the remaining target trajectory. The revised uncertainty indicator represents a combination of the respective uncertainties defined by the multiple error models. A change to an uncertainty defined by one of the error models can affect an uncertainty defined by another of the error models and the revised uncertainty indicator itself. At412, thecomputer system100 can determine such a change to the uncertainty indicator, and, at414 display the revised uncertainty indicator in theuser interface114.
• After the operator has adjusted the survey plan, well drilling can continue. Thecomputer system100 can continue to receive the survey data and determine the uncertainty indicator. For example, thecomputer system100 can receive the data in real time (or near real time) or concurrently with the well drilling (or both). Based on a change or changes to the uncertainty indicator (e.g., if the uncertainty indicator fails to satisfy an uncertainty threshold), the operator can provide changes to the survey plan resulting in thecomputer system100 revising the uncertainty indicator. In this manner, during the drilling stage, thecomputer system100 can be implemented as a tool that the operator can use to monitor and adjust drilling operations to reach the geological target by implementing as few and as inexpensive survey tools as practicable.
• FIG. 5 illustrates a schematic of theexample computer system100 ofFIG. 1. Theexample computer system100 can be located at or near one or more wells and/or at a remote location. Theexample computer system100 includes a data processing apparatus104 (e.g., one or more processors), a computer-readable medium102 (e.g., a memory), and input/output controllers170 communicably coupled by abus165. The computer-readable medium can include, for example, a random access memory (RAM), a storage device (e.g., a writable read-only memory (ROM) and/or others), a hard disk, and/or another type of storage medium. Thecomputer system100 can be preprogrammed and/or it can be programmed (and reprogrammed) by loading a program from another source (e.g., from a CD-ROM, from another computer device through a data network, and/or in another manner). The input/output controller170 is coupled to input/output devices (e.g., thedisplay device106,input devices108, and/or other input/output devices) and to anetwork112. The input/output devices receive and transmit data in analog or digital form over communication links such as a serial link, wireless link (e.g., infrared, radio frequency, and/or others), parallel link, and/or another type of link.
• Thenetwork112 can include any type of data communication network. For example, thenetwork112 can include a wireless and/or a wired network, a Local Area Network (LAN), a Wide Area Network (WAN), a private network, a public network (such as the Internet), a WiFi network, a network that includes a satellite link, and/or another type of data communication network.
• A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure.

Claims (19)

1. A computer-implemented well survey method comprising:

receiving a trajectory of a proposed well from a surface to a subterranean geological target to be reached by drilling the well;

receiving a survey plan indicating the number, position and survey type of surveys to be performed on the well while drilling the well;

displaying, in a user interface, a plurality of error models including at least one of an interpolation in-field referencing (IIFR) model, an in-field referencing (IFR) model, a measurement while drilling (MWD) model, or a sag correction model;

applying the plurality of error models based on the survey type for drilling the well, each error model defining a respective uncertainty in reaching the subterranean geological target by drilling the well along the received trajectory; and

displaying, in the user interface, the received trajectory of the well and an uncertainty indicator determined by applying the plurality of error models, the uncertainty indicator representing a combination of respective uncertainties defined by the plurality of error models, the uncertainty indicator indicating an uncertainty in drilling the well on the received trajectory.

2. The method ofclaim 1, wherein the uncertainty indicator includes a plurality of ellipses, each occupying a different area, each ellipse associated with a respective depth of the well from the surface to the subterranean geological target, the method further comprising displaying the plurality of ellipses at a plurality of respective depths in the user interface.

3. The method ofclaim 2, further comprising:

determining that a first ellipse does not satisfy an uncertainty threshold at a respective depth; and

displaying the first ellipse in the user interface in a manner that is visually distinguishable from a second ellipse that satisfies the uncertainty threshold at a respective depth.

4. The method ofclaim 1, further comprising receiving a selection of a survey tool from among a plurality of survey tools, the survey tool to be implemented to survey the well to be drilled along the received trajectory.

5. The method ofclaim 1, further comprising receiving the trajectory of the well, receiving the survey plan, and applying the plurality of error models before drilling the well along the received trajectory.

6. A computer-implemented well survey comprising:

receiving a trajectory of a proposed well from a surface to a subterranean geological target to be reached by drilling the well;

receiving a survey plan indicating the number, position and survey type of surveys to be performed on the well while drilling the well;

applying a plurality of error models based on the survey type for drilling the well, each error model defining a respective uncertainty in reaching the subterranean geological target by drilling the well along the received trajectory;

displaying, in a user interface, the received trajectory of the well and an uncertainty indicator determined by applying the plurality of error models, the uncertainty indicator representing a combination of respective uncertainties defined by the plurality of error models, the uncertainty indicator indicating an uncertainty in drilling the well on the received trajectory; and

receiving a plurality of parameters that describe a location and a shape of the well, wherein the plurality of parameters describing the well that are displayed in the user interface include a length of a non-magnetic drill collar (NMDC) to be positioned in the well, a sensor position in the NMDC at which a survey tool is to be positioned, and casing information describing at least one of a casing size, distance, or direction from the sensor position.

7. A computer-implemented well survey method comprising:

receiving a trajectory of a proposed well from a surface to a subterranean geological target to be reached by drilling the well;

receiving a survey plan indicating the number, position and survey type of surveys to be performed on the well while drilling the well;

applying a plurality of error models based on the survey type for drilling the well, each error model defining a respective uncertainty in reaching the subterranean geological target by drilling the well along the received trajectory;

displaying, in a user interface, the received trajectory of the well and an uncertainty indicator determined by applying the plurality of error models, the uncertainty indicator representing a combination of respective uncertainties defined by the plurality of error models, the uncertainty indicator indicating an uncertainty in drilling the well on the received trajectory;

receiving an earth's gravitational field and magnetic field strength at a geographic location at which the well is to be drilled at a drilling time determined based on a geodetic model used to determine the earth's gravitational field, and magnetic dipping; and

displaying, in the user interface, an identifier identifying the geodetic model, the earth's gravitational field strength and magnetic field strength, and a dip angle of the magnetic field.

8. The method ofclaim 7, further comprising receiving magnetics representing variations in the earth's magnetic field due to solar effects during the drilling time, the method further comprising displaying, in the user interface, the magnetics during the drilling time.

9. The method ofclaim 8, wherein displaying, in the user interface, the magnetics during the drilling time comprises:

displaying a plot of the magnetics over time that comprises the drilling time;

comparing the magnetics with a threshold magnetics for drilling the well;

displaying the magnetics that satisfy the threshold magnetics in a first color and the magnetics that do not satisfy the threshold magnetics in a second color that is different from the first color.

10. The method ofclaim 1, further comprising displaying, in the user interface, an image of a sag correction for the well.

11. The method ofclaim 1, further comprising displaying, in the user interface, axial and cross-axial interference representing a disturbance in a magnetic field due to low magnetic permeability components in the well.

12. The method ofclaim 1, further comprising:

receiving a change to an uncertainty defined by a first error model of the plurality of error models, the change resulting in a change to an uncertainty defined by a second error model of the plurality of error models;

in response to receiving the change, automatically and without user intervention:

updating the uncertainty indicator determined by applying the plurality of error models including the first error model and the second error model; and

displaying the updated uncertainty indicator in the user interface.

13. A non-transitory computer-readable medium storing instructions executable by data processing apparatus to perform operations comprising:

receiving a trajectory of a proposed well from a surface to a subterranean geological target to be reached by drilling the well;

receiving a survey plan indicating the number, position and survey type of surveys to be performed on the well while drilling the well;

displaying, in a user interface, a plurality of error models including at least one of an interpolation in-field referencing (IIFR) model, an in-field referencing (IFR) model, a measurement while drilling (MWD) model, or a sag correction model;

applying the plurality of error models based on the survey type for drilling the well, each error model defining a respective uncertainty in reaching the subterranean geological target by drilling the well along the received trajectory; and

displaying, in the user interface, the received trajectory of the well and an uncertainty indicator determined by applying the plurality of error models, the uncertainty indicator representing a combination of respective uncertainties defined by the plurality of error the uncertainty indicator indicating an uncertainty in drilling the well on the received trajectory.

14. The medium ofclaim 13, wherein the uncertainty indicator includes a plurality of ellipses, each occupying a different area, each ellipse associated with a respective depth of the well from the surface to the subterranean geological target, the operations further comprising displaying the plurality of ellipses at a plurality of respective depths in the user interface.

15. The medium ofclaim 14, the operations further comprising:

determining that a first ellipse does not satisfy an uncertainty threshold at a respective depth; and

displaying the first ellipse in the user interface in a color that is different from a color of a second ellipse that satisfies the uncertainty threshold at a respective depth.

16. The medium ofclaim 13, the operations further comprising receiving the trajectory of the well, receiving the survey plan, and applying the plurality of error models before drilling the well along the received trajectory.

17. A system comprising:

data processing apparatus; and

a computer-readable medium storing instructions executable by the data processing apparatus to perform operations comprising:

receiving a trajectory of a proposed well from a surface to a subterranean geological target to be reached by drilling the well;

receiving a survey plan indicating the number, position and survey type of surveys to be performed on the well while drilling the well;

displaying, in a user interface, a plurality of error models including at least one of an interpolation in-field referencing (IIFR) model, an in-field referencing (IFR) model, a measurement while drilling (MWD) model, or a sag correction model;

applying the plurality of error models based on the survey type for drilling the well, each error model defining a respective uncertainty in reaching the subterranean geological target by drilling the well along the received trajectory; and

displaying, in the user interface, the received trajectory of the well and an uncertainty indicator determined by applying the plurality of error models, the uncertainty indicator representing a combination of respective uncertainties defined by the plurality of error the uncertainty indicator indicating an uncertainty in drilling the well on the received trajectory.

18. A system comprising:

data processing apparatus; and

a computer-readable medium storing instructions executable by the data processing apparatus to perform operations comprising:

receiving a trajectory of a proposed well from a surface to a subterranean geological target to be reached by drilling the well;

receiving a survey plan indicating the number, position and survey type of surveys to be performed on the well while drilling the well;

applying a plurality of error models based on the survey type for drilling the well, each error model defining a respective uncertainty in reaching the subterranean geological target by drilling the well along the received trajectory;

displaying, in a user interface, the received trajectory of the well and an uncertainty indicator determined by applying the plurality of error models, the uncertainty indicator representing a combination of respective uncertainties defined by the plurality of error the uncertainty indicator indicating an uncertainty in drilling the well on the received trajectory;

receiving a geographic location at which the well is to be drilled, a drilling time, and magnetics representing variations in the earth's magnetic field due to solar effects during the drilling time;

receiving an earth's gravitational field and magnetic field strength at the geographic location at the drilling time determined based on a geodetic model used to determine the earth's gravitational field, and magnetic dipping; and

displaying, in the user interface, an identifier identifying the geodetic model, the earth's gravitational field strength and magnetic field strength, a dip angle of the magnetic field, and the magnetics during the drilling time.

19. A system comprising:

data processing apparatus; and

a computer-readable medium storing instructions executable by the data processing apparatus to perform operations comprising:

receiving a trajectory of a proposed well from a surface to a subterranean geological target to be reached by drilling the well;

receiving a survey plan indicating the number, position and survey type of surveys to be performed on the well while drilling the well;

applying a plurality of error models based on the survey type for drilling the well, each error model defining a respective uncertainty in reaching the subterranean geological target by drilling the well along the received trajectory;

displaying, in a user interface, the received trajectory of the well and an uncertainty indicator determined by applying the plurality of error models, the uncertainty indicator representing a combination of respective uncertainties defined by the plurality of error the uncertainty indicator indicating an uncertainty in drilling the well on the received trajectory; and

displaying, in the user interface, a plurality of parameters including a length of a non-magnetic drill collar (NMDC) to be positioned in the well, a sensor position in the NMDC at which a survey tool is to be positioned, and casing information describing at least one of a casing size, distance, or direction from the sensor position.

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