Determination of reservoir boundaries

Abstract

A system for steering a drilling assembly includes a processor configured to receive a material property profile of a subterranean region, the material property profile including one or more layers. The material property profile is generated from at least one material property data value measured within a depth interval of a borehole. The processor is configured to define a first reservoir boundary location associated with the depth interval from at least one first material property value associated with a first layer and being less than a predefined threshold material property value and at least one second material property value associated with a second layer, the second material property value being greater than the predefined threshold material property value. The processor is configured to determine a reservoir thickness, and define an optimum borehole location associated with the depth interval based on the reservoir thickness or a second reservoir boundary location.

Description

65RNV-510772-WO-2JNT1044PCTDETERMINATION OF RESERVOIR BOUNDARIESCROSS REFERENCE TO RELATED APPLICATIONSThis application claims the benefit of U.S. Application No. 63 / 733,270, filed on December 12, 2024, which is incorporated herein by reference in its entirety.BACKGROUND

[0001] Various operations are performed by the energy industry to evaluate earth formations and produce hydrocarbons. Such operations include drilling, stimulation and production. Various types of sensor devices and logging tools are utilized by the energy industry in order to evaluate earth formations and reservoirs, for purposes such as exploration, formation evaluation, stimulation and production.

[0002] Some measurement data can be used to evaluate the architecture of subsurface formations. For example, digital models of earth formations can be constructed using data ranging from seismic measurements, nuclear measurements, and core or cuttings data. In addition, data and / or images acquired from measurement devices such as resistivity and gamma tools can provide information used to construct formation models.SUMMARY

[0003] An embodiment of a system for steering a drilling assembly through a subterranean region includes a processor configured to receive a material property profile of the subterranean region, the material property profile including one or more layers. The material property profile specifies, for each layer of the one or more layers, a layer material property and location information with respect to a location of each layer, and the material property profile is generated from at least one material property data value measured within a depth interval of a borehole in the subterranean region by a measurement tool in the borehole. The processor is configured to define a first reservoir boundary location associated with the depth interval from at least one first material property value associated with a first layer of the one or more layers, the first material property value being less than a predefined threshold material property value and at least one second material property value associated with a second layer of the one or more layers, the second material property value being greater than the predefined threshold material property value. The processor is also configured to determine a reservoir thickness associated with the depth interval or a second reservoir boundary location65RNV-510772-WO-2JNT1044PCT associated with the depth interval, and define an optimum borehole location associated with the depth interval based on the reservoir thickness or the second reservoir boundary location. The system is configured to steer with a steering device the drilling assembly to reduce a difference between an actual borehole location and the optimum borehole location.

[0004] An embodiment of a method of steering a drilling assembly through a subterranean region includes receiving a material property profile of the subterranean region, the material property profile including one or more layers. The material property profile specifies, for each layer of the one or more layers, a layer material property and location information with respect to a location of each layer, the material property profile generated from at least one material property data value measured within a depth interval of a borehole in the subterranean region by a measurement tool in the borehole. The method also includes defining a first reservoir boundary location associated with the depth interval from at least one first material property value associated with a first layer of the one or more layers, the first material property value being less than a predefined threshold material property value and at least one second material property value associated with a second layer of the one or more layers, the second material property value being greater than the predefined threshold material property value. The method further includes determining a reservoir thickness associated with the depth interval or a second reservoir boundary location associated with the depth interval, defining an optimum borehole location associated with the depth interval based on the reservoir thickness or the second reservoir boundary location, and steering the drilling assembly to reduce a difference between an actual borehole location and the optimum borehole location.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

[0006] Figure 1 depicts an embodiment of a downhole system that includes a measurement apparatus, device or tool configured to perform measurements of a subterranean region and / or borehole;

[0007] Figure 2 is a flow diagram depicting an embodiment of a method of analyzing a subterranean region, the method including identification of reservoir boundaries;

[0008] Figure 3 depicts an example of a section of a model of a subterranean region around a borehole, the section including a material property profile for which an upper reservoir boundary and a lower reservoir boundary of a reservoir are identified;65RNV-510772-WO-2JNT1044PCT

[0009] Figure 4 depicts another model section similar to the model section of Figure 3, the model section including a material property profile for which no reservoir boundary is identified;

[0010] Figure 5 depicts another model section similar to the model section of Figure 3, the model section including a material property profile for which an upper reservoir boundary is identified;

[0011] Figure 6 depicts another model section similar to the model section of the model section of Figure 3, the model section including a material property profile for which a lower reservoir boundary is identified;

[0012] Figure 7 is a view of a model along a borehole path, including various model sections corresponding to those shown in Figures 3 - 6 and including examples of optimum borehole locations calculated using the method of Figure 2;

[0013] Figure 8 is a view of another model along a borehole path;

[0014] Figure 9 depicts another view of the model of Figure 8, and an example of a model generated by inversion of resistivity data:|0015 | Figure 10 depicts another view of the model of Figure 9, and shows examples of identified boundary locations;

[0016] Figure 11 depicts a portion of the model of Figure 9, and shows examples of identified boundary locations and optimum borehole locations;

[0017] Figure 12 depicts a portion of the model of Figure 9, and shows examples of identified boundary locations and optimum borehole locations; and

[0018] Figure 13 depicts a portion of the model of Figure 9 and shows examples of identified boundary locations and optimum borehole locations.DETAILED DESCRIPTION

[0019] Figure 1 illustrates an embodiment of a downhole system 10 including a borehole string 12 disposed in a borehole 14 that penetrates a subterranean region. The subterranean region may include a formation 16. The downhole system 10 is configured to perform one or more downhole operations, such as drilling, measurement, data acquisition, and / or system analysis.

[0020] In an embodiment, the downhole system 10 includes devices or systems for in- situ measurement of characteristics of the formation 16, the borehole string 12 and / or the borehole 14. For example, the downhole system 10 includes a measurement apparatus such65RNV-510772-WO-2JNT1044PCT as a measurement tool 18 configured to perform resistivity and / or other electromagnetic measurements, gamma ray measurements, nuclear magnetic resonance (NMR) measurements, and / or other types of measurements. In this embodiment, the measurement tool 18 is part of a logging-while-drilling (LWD) sub or assembly, but is not so limited.

[0021] The measurement tool 18 includes a tool body 20, such as a mandrel, pipe segment or other elongated structure. The tool body 20 may be part of a rotating component, such as a LWD or drilling sub connected to a drilling assembly 23, which includes a drill bit 22, and may include other components, such as a drilling motor 25 and / or a steering system 27. The tool body 20 may have a fluid conduit or inner bore (not shown) for allowing flow of drilling mud, formation fluids and / or for other fluids 29 through the tool body 20.

[0022] In an example, the measurement tool 18 includes at least one transmitting antenna 24 for emitting electromagnetic signals into the formation 16, and at least one receiving antenna 26 for detecting signals resulting from a response of the formation 16 to the electromagnetic signals. In case of more than one transmitting antenna 24 and / or more than one receiving antenna 26, the at least two transmitting antenna 24 and / or the at least two receiving antenna 26 may be located at various distances.

[0023] Detected signals may be transmitted to an electronics module 30, where detected signals from the receiving antenna 26 may be amplified and processed. Amplified signals may be processed (e.g., by a processor 32) at the electronics module 30 close to or within measurement tool 18 or provided to additional electronics and a processing device (e.g., a surface processor 34 and / or a processing device at a remote location). The electronics module 30 and / or processing device may include a processor 32 (such as a processor 38) and a storage device (such as a storage device 40).

[0024] The downhole system 10 may include or be connected to one or more processors. For example, the downhole system 10 includes a downhole processor 32 and / or the surface processor 34. The surface processor 34 is part of, or attached to surface equipment 36 (e.g., a drilling rig). The one or more processors may also be a remote processor (e.g., in a data center or workstation). The surface processor 34, in an embodiment, includes the processor 38 and the data storage device 40 (or a computer-readable medium) for storing data, models and / or computer programs or software.

[0025] The borehole string 12 may be equipped with transmission equipment to communicate with surface components, such as the surface processor 34. Such transmission equipment may take any desired form, and different transmission media and methods may be65RNV-510772-WO-2JNT1044PCT used, such as wired, fiber optic, and / or wireless transmission methods (e.g., mud pulse telemetry, electromagnetic telemetry, acoustic telemetry, etc.).

[0026] Embodiments described herein are not limited to the specific configuration shown in Figure 1, as the embodiments may be applicable to various downhole systems. For example, measurement tools and methods described herein may be used with wireline systems and / or production systems.

[0027] A processing device, such as the surface processor 34, the downhole processor 32, and / or a remote processor, acquires a model of a subterranean region that may include a hydrocarbon reservoir. The model may be generated (at least in part) based on inversion of downhole measurements, such as a measurement of a material property (e.g., a property of the formation 16). For example, the model may be based on one or more of resistivity, azimuthal resistivity, gamma, azimuthal gamma, nuclear, azimuthal nuclear, acoustic, azimuthal acoustic, nuclear magnetic resonance (NMR) measurements, or any other measurements known in the art, performed by a measurement device (e.g., the measurement tool 18).

[0028] The processing device employs logic or an algorithm to detect a boundary of the reservoir. A “boundary” refers to a location of a transition between subterranean regions having different material properties. Such properties may include geological, lithological, mineralogical, and / or petrophysical properties, such as porosity levels, grain sizes, mineral content or composition, fluid content (e.g., water content, hydrocarbon content, gas content, etc.), and others. For example, a boundary may correspond to the transition between hydrocarbon-bearing rock and non-hydrocarbon-bearing rock.

[0029] Boundary identification may be used as part of updating or enhancing a geological or structural model. Boundary identification as described herein may be used to control directional parameters that are used for borehole placement (e.g., to steer drilling assembly 23 through formation 16), for example, by means of an updated or enhanced geological / structural model, such as by steering the drilling assembly 23 to position the borehole 14 within the formation 16 (e.g., within a desired formation layer such as a reservoir or between desired layer boundaries or reservoir boundaries) and follow an optimal path within the formation 16.

[0030] Figure 2 shows aspects of an embodiment of a method 50 of analyzing downhole measurement data to generate, update, or enhance a model of the subterranean region. For example, one meaning of model enhancement in this context includes the improvement of the model resolution (e.g., the discretization of the model). In an embodiment,65RNV-510772-WO-2JNT1044PCT the downhole measurement data is analyzed to generate, update, or enhance the model derived by performing an inversion process on the downhole measurement data (e.g., resistivity logging data). Aspects of the method 50 are discussed in conjunction with a downhole operation using the downhole system 10 of Figure 1 including drilling assembly 23. However, embodiments are not so limited, as the method 50 can be used in various systems and contexts related to subterranean regions such as for wireline measurements, measurements on completion strings, etc.

[0031] The method 50 includes a plurality of steps represented by blocks 51 -57. All of the steps may be performed in the order described, but the method is not so limited. For example, two or more of the steps may be performed in a different order or at least partially at the same time, or the method may include fewer or more than steps 51 - 57.

[0032] At block 51, measurement data is acquired by using the measurement tool 18 at one or more locations in the borehole 14, for example to generate a borehole log. The measurement data may comprise one or more measurement data values at each borehole location (e.g., depth or depth interval). In an embodiment, the measurement data relates to resistivity, conductivity, or permittivity (dielectric constant) measurements (generally referred to as “resistivity measurements” within this disclosure) performed using the measurement tool 18 at various locations along the borehole 14. In an embodiment, measurement data at each borehole location may include resistivity data acquired from electromagnetic signals that may be transmitted with various frequencies by one or more transmission sources (e.g., one or more transmitting antennas 24) and / or received by one or more receivers (e.g., one or more receiving antennas 26) at various distances from the transmission source of the electromagnetic signals. In an embodiment, the measurement data includes azimuthal resistivity measurements.

[0033] At block 52, an algorithm is executed on the measurement data to generate a model section of the subterranean region at the location where the measurement data is acquired. The model section includes a modelled material property profile.

[0034] A modelled material property profile in the context of this disclosure includes one or more material property values (e.g., from the formation 16) as a function of the distance from borehole 14 in a selected direction. Those skilled in the art will appreciate that thicknesses or distances may be defined in various directions, such as, but not limited to, directions parallel or anti-parallel to the direction of gravity (i.e., vertical thickness, vertical distance), directions perpendicular to a formation layer or formation boundary (i.e., stratigraphic thickness, stratigraphic distance), directions along an object (e.g., distance or thickness along a borehole),65RNV-510772-WO-2JNT1044PCT and / or directions perpendicular to the object relative to which the thickness or distance is measured (such as perpendicular to the borehole from which the distance is measured). All of these meanings of the term “thickness” or “distance” are included within the context of this disclosure.

[0035] In an embodiment, the algorithm executed at block 52 includes an inversion (e.g., a numeric inversion). The execution of the algorithm may include using one or more measurement data values from the measurement data to generate, update, or enhance certain model parameters, such as model material properties and / or model geometrical parameters (e.g., locations, such as distance from the borehole, of a boundary or boundaries, borehole location, reservoir location, and the like).

[0036] Notably, the number of measurement data values per borehole location and the number of determined material property profiles per borehole location may not be equal. Typically, the number of measurement data values per borehole location is greater than the number of determined material property profiles. For example, if measurement data values are acquired from a first electromagnetic signal and a second electromagnetic signal with a first and second frequency, respectively, and are acquired at a first distance and a second distance from the transmission source of the signals, this may lead up to four resistivity measurement data values at each borehole location corresponding to the four possible combinations of two operating frequencies with two distances. A single resistivity profile with one or more layer boundaries may be determined, for example, using less than four resistivity values.

[0037] The inversion process utilizes the measurement data acquired, which can include logging data (e.g., measurement data values in the form of curves and / or images, frequently referred to as borehole logs, such as curves A - D in Figure 9) acquired by a measurement tool 18 located in a drilling assembly 23, elsewhere in borehole string 12, or at one or more other locations along borehole 14. Such data can be acquired as measurementwhile-drilling (MWD) or logging-while-drilling (LWD) data, or acquired after borehole 14 has been drilled, e.g., as wireline logs.

[0038] Generally, an inversion process includes generating an initial estimate or initial model or model section comprising one or more modelled material property profiles. Synthetic measurement data is calculated using the initial material property profile and is compared to the acquired measurement data, and then the initial material property profile is iteratively adjusted to result in an updated material property profile by which updated synthetic measurement data is calculated until synthetic measurement data and acquired measurement65RNV-510772-WO-2JNT1044PCT data match reasonably well (for example, until the difference between synthetic and acquired measurement data is below a predefined threshold value). As noted above, the number of measurement data values per borehole location may not be equal to (e.g., may be greater than) the number of determined material property profiles per borehole location.

[0039] At block 53, parameters related to boundary determination are selected or predefined (boundary determination parameter). The selected / predefined boundary determination parameters, in an embodiment, include a material property threshold (material property minimum and / or maximum), a defined reservoir thickness or defined reservoir boundary distance, and a predefined minimum reservoir thickness and / or predefined minimum reservoir boundary distance. A minimum reservoir thickness or minimum reservoir boundary distance may be used in cases where two layer boundaries are identified, and a defined reservoir thickness or a defined reservoir boundary distance may be used in cases where one layer boundary is identified (see below).

[0040] The boundary determination parameters may also include an “optimum placement” parameter, which is indicative of an optimum or preferred location of a borehole relative to one or more boundaries. The optimum placement may be defined as a distance from a boundary, for example to place the borehole in a location predicted to improve or maximize production from the reservoir.

[0041] For example, the optimum location may be selected to centralize the borehole within a reservoir; the location may thus be a vertical or stratigraphic distance from a boundary that is about 50% of an estimated thickness (e.g., if one boundary is identified) or a calculated distance (e.g., if two boundaries are identified). The optimum location may be any desired distance from a boundary.

[0042] At block 54, model material property data values in the material property profile are inspected and compared to the material property minimum and / or maximum. In an embodiment, the material property profile is iteratively evaluated by reading the material property successively at each layer of the material property profile. A boundary is selected at a location where the model material property changes from a first value that is less than the material property minimum or maximum to a second value that is greater than the material property minimum or maximum, or vice versa.

[0043] The identified profile layers where the model material property values continuously remain above or below the material property threshold (i.e., above the material property minimum or below the material property maximum) are identified as a model65RNV-510772-WO-2JNT1044PCT reservoir. The thickness of the reservoir at a respective location of the borehole may be estimated based on other information (e.g., previous model versions, geological data, offset well data, etc.).

[0044] At block 55, if two model reservoir boundaries are selected, the processor calculates a distance between the model reservoir boundaries (i.e. the reservoir thickness), and determines whether the calculated reservoir thickness is greater than the minimum reservoir thickness. If so, the processor identifies the layer boundaries as reservoir boundaries, such as a lower reservoir boundary and / or an upper reservoir boundary, and associates the distance between the reservoir boundaries as the thickness of the reservoir.

[0045] At block 56, a desired or optimum borehole location is determined based on the location of the upper reservoir boundary and / or lower reservoir boundary. The optimum borehole location may be selected based on a reservoir thickness determined from the model, or may be selected based on a distance from a boundary or an estimated thickness (e.g., if only one boundary is determined). As noted above, the number of determined material property profiles per borehole location may be less than the number of measurement data values per borehole location. In a case where only one material property profile per borehole location is used, this will then lead to only one optimum borehole location per borehole location even though more than one material property data value per borehole location are used to calculate said optimum borehole location.

[0046] At block 57, various actions can be performed based on the one or more identified reservoir boundaries and / or the optimum borehole location. Examples of actions include generating and presenting a model along the borehole 14 that includes the identified reservoir boundary or reservoir boundaries, and may include optimum borehole locations (see below). Other actions include adjusting, based on the identified reservoir boundaries and / or the optimum borehole location, operational parameters such as borehole trajectory, drilling assembly inclination, drilling assembly azimuth, weight-on-bit (WOB), torque-on-bit (TOB), rate of penetration (ROP), rotational velocity (rpm), steering direction of the drilling assembly 23, steering force of the drilling assembly 23, and time parameters. Operational parameters may be adjusted by an operator or by an automatic steering system based on the model along the borehole 14.

[0047] Other actions can include using the model along the borehole 14 in various simulations and other models, and using the model along the borehole 14 to plan or design energy industry operations. Those skilled in the art will appreciate that the methods described65RNV-510772-WO-2JNT1044PCT herein are suited in particular for automated systems. Such automated systems may be constructed in a way that one or more steps (e.g., steps as shown in described with respect to Figure 2) will be executed automatically, for example without any human interaction. At least portions of one or more of the steps may be executed downhole, which requires less communication from downhole to surface and / or vice versa and, thus, helps to save telemetry rate. Thus, the analysis can be done much more often, for example at the same rate as the acquisition of measurements, such as the measurements by measurement tool 18, or at a fraction of the sampling rate (e.g., at a rate that is half the sampling rate, a third of the sampling rate, etc.). One or more of the actions may be executed in real-time, e.g., while the operation (e.g., drilling operation) is ongoing.

[0048] Embodiments described herein present numerous technical effects and advantages. For example, the embodiments provide for improved analysis and estimation of earth formation properties, and improved positioning of boreholes within reservoirs.

[0049] The embodiments provide a method that can be effectively used to optimally position a borehole along or within a reservoir, including cases where the reservoir becomes thinner or thickens along the borehole 14. For example, well placement is determined relative to reservoir thickness, as opposed to absolute distance, providing for better placement especially in reservoir with variable thickness along the borehole. In addition, as the method is applied to results of an algorithm (e.g., the algorithm executed at block 52 in Figure 2), the method may be independent from the method used to generate material property profiles of the subterranean region. In particular, the method may be independent from the type of inversion workflow used. Accordingly, there is no need to customize any inversion workflow or any other workflow to generate a material property profile of the subterranean region.

[0050] Figures 3-6 depict examples of a material property model section 60 derived from downhole measured material property data. Each section of the material property model section 60 includes at least one material property profile 62 (horizontal axis) showing material property data values as a function of distance from the borehole (vertical axis). Figures 3 - 6 also depict the location 75 of the actual borehole (i.e., the location 75 where the distance to the borehole is zero and below of which the distance to the borehole may be negative). Material property model sections 60 may represent a region around a respective location (e.g., measured depth or measured depth interval, true vertical depth or true vertical depth interval) of a borehole (e.g., borehole 14). The term of “depth” may refer to various types of depth that are65RNV-510772-WO-2JNT1044PCT known in the art, such as measured depth (i.e., borehole length or distance along the borehole), true vertical depth, true stratigraphic depth, etc.

[0051] The material property profile 62 represents one or more material property values at one or more model section layers 64. The material property profiles 62 terminate at a defined distance 67a, 67b from the actual borehole location 75. The distances 67a, 67b at which the material property profiles terminate may be related to (e.g., may correspond to) the depth of detection or the depth of investigation of the measurement.

[0052] Depth of detection in this context may refer to a distance from the borehole from where a boundary could be detected by a measurement signal that is higher than the noise level of the measurement by a predefined factor (e.g., two times or three times higher). Depth of investigation in this context may refer to a distance from the borehole up to which a predefined percentage of the measurement signal is created (e.g., 50% or 90%). Depth of detection / investigation may depend on the measurement type, the measurement tools used, and may be different for different material property profiles and therefore the defined distances 67a, 67b at which the material property profiles terminate may be different in the directions above and below the location 75 of the actual borehole.

[0053] The material property profile 62 is inspected iteratively, i.e., the material property data values of each model section layer 64 are analyzed successively. As shown, each model layer 64 may be defined by steps or changes in the material property profile 62. In this example, the model section layers 64 are defined by step changes in the material property profile at distances 69. Each material property data value is compared to the material property threshold (which in this case is a material property minimum), indicated by a vertical line 66.

[0054] Figure 3 shows a material property model section 60, from which both an upper reservoir boundary 68 and a lower reservoir boundary 70 of a reservoir 65 are identified (“Case #1”). As shown, the material property profile 62 crosses the vertical line 66 indicating the material property threshold which in this case is a material property minimum (i.e., transitions from a value that is less than the material property minimum to a value that is greater than the material property minimum) at selected reservoir boundaries 68 and 70.

[0055] As shown, the material property values between the selected reservoir boundaries 68 and 70 continuously remain above the material property minimum. The distance between the selected boundaries 68 and 70 is compared to the predefined minimum reservoir thickness (which is one of the selected / predefined boundary determination parameters). If the distance between the selected boundaries 68 and 70 is greater than the predefined minimum65RNV-510772-WO-2JNT1044PCT reservoir thickness, the selected reservoir boundary 68 is identified as a top or upper reservoir boundary, and the selected reservoir boundary 70 is identified as a base or lower reservoir boundary 70.

[0056] For example, the predefined minimum reservoir thickness is 2 meters and the calculated reservoir boundary distance is 3 meters. Accordingly, as the calculated reservoir boundary distance is greater than the predefined minimum reservoir thickness, the processor extracts and outputs boundary location and / or reservoir thickness information (e.g., location such as distance of upper reservoir boundary 68 and / or lower reservoir boundary 70, and / or boundary distance I reservoir thickness).

[0057] An optimum borehole location 72 may be selected to be at a distance from the upper reservoir boundary 68 and / or the lower reservoir boundary 70, or may be related to the boundary distance or reservoir thickness. For example, the optimum borehole location 72 may be selected or predefined to be at a relative distance from the upper reservoir boundary 68 that is about 45% of the reservoir thickness (e.g., in the vertical direction). As another example, the optimum borehole location 72 may be selected or predefined to be at an absolute distance of about 1.35 meters from the upper reservoir boundary 68. Such relative or absolute predefined distances for the optimum borehole location 72 may belong to the boundary determination parameters that were predefined or selected as described above.

[0058] Figure 4 shows an example of a section of the material property model section 60, where no reservoir boundary 68, 70 is identified (“Case #2’’). As shown, the material property profile 62 remains below the material property minimum indicated by the vertical line 66. Accordingly, no reservoir boundary information is identified.

[0059] Figures 5 and 6 show examples in which only one reservoir boundary is identified (“Case #3”, “Case #4”). In the example of Figure 5 (“Case #3”), a reservoir boundary 74 is selected. The material property below the selected reservoir boundary 74 remains greater than the material property minimum indicated by the vertical line 66, but does not again cross the vertical line 66 indicating the material property minimum. In this case, the selected reservoir boundary 74 is identified as an upper reservoir boundary 74. The location of the upper reservoir boundary, along with a predefined / selected reservoir thickness 63 a is output. Notably, the predefined / selected reservoir thickness 63a extends beyond the maximum distance 67b from the borehole (in a direction below the borehole) where the material property model section 60 is terminated (e.g.. at a distance from the actual borehole location 75 that is greater than the depth of detection or depth of investigation of the measurement for this material65RNV-510772-WO-2JNT1044PCT profile 62). Hence, a lower reservoir boundary 76 for the reservoir 65 is identified at a distance from the borehole that is greater than the distance where model section 60 is terminated (e.g., greater than the depth of detection or depth of investigation of the measurement for this material profile 62).

[0060] Because in the cases of Figures 5 and 6 only one reservoir boundary is identified, the optimum borehole location 72 at this material property model section 60 is based on the defined reservoir thickness (see, for example, block 53 in Figure 2). For example, the optimum borehole location 72 may be at a relative distance from the upper reservoir boundary 74 or the lower reservoir boundary 76, such as a percentage of the defined reservoir thickness, (for example, equal to about 50% of the defined reservoir thickness).

[0061] In the example of Figure 6 (“Case #4”), the lower reservoir boundary 76 is identified from the material property profile 62. The material property above the selected layer boundary 76 remains greater than the material property minimum indicated by vertical line 66, but does not again become less than the material property minimum indicated by vertical line 66. In this case, the selected reservoir boundary 76 is identified as a lower reservoir boundary 76, and a location of the lower reservoir boundary 76 and the defined reservoir thickness is output. Notably, the predefined / selected reservoir thickness 63b extends beyond the distance 67a from the borehole (in a direction above the borehole) where material property model section 60 is terminated (e.g., at a distance from the actual borehole location 75 that is greater than the depth of detection or depth of investigation of the measurement for this material profile 62). Hence, an upper reservoir boundary 74 of reservoir 65 is identified at a distance from the borehole that is greater than the distance 67a or 67b where material property model section 60 is terminated (e.g., greater than the depth of detection or depth of investigation of the measurement for the material profile 62). The optimum borehole location 72 in this example is at a distance from the lower reservoir boundary (selected reservoir boundary 76) that is equal to about 45% of the defined reservoir thickness. The optimum borehole location 72 may be located at a distance from the actual borehole 75 that is greater than the depth of detection and / or depth of investigation.

[0062] Figure 7 is a view of a model of the subterranean region around a borehole path 80. The model includes a variety of material property sections 60 similar to those shown in Figures 3 - 6, which are illustrated in Figure 7 as vertical lines or stripes. Each vertical line or stripe in Figure 7 corresponds to one material property section 60 as shown in Figures 3 - 6. In this example, the material property is resistivity and the depth scale of the material property65RNV-510772-WO-2JNT1044PCT profiles corresponding to Figures 3 - 6 is true vertical depth. In contrast to Figures 3 - 6, in Figure 7 the material property is shown color-coded or shaded, where lower data values are indicated by darker shade and higher data values are indicated by lighter shade. The width of the single lines or stripes in Figure 7 may be related to the sampling rate of the measurements and / or the distance of borehole locations where the measurements were taken that were used by the algorithm to generate resistivity profiles as discussed with respect to Figures 2 and 3 - 6. For example, the width of the single lines or stripes in Figure 7 may correspond to the distance of borehole locations or multiples of the distance of borehole locations where the measurements were taken that were used to generate the resistivity profiles. Figure 7 shows the material property above and below a borehole path 80 (in a vertical direction). Optimal borehole locations 72 relative to the borehole path are selected at various sections as described above.

[0063] Although the various model views show resistivity values and boundaries in a vertical plane, embodiments are not so limited, as the boundaries may be detected in a horizontal or deviated plane. Thus, designators of “upper” and “lower” are not intended to limit the orientation of the boundaries. For example, boundaries may be identified along a horizontal or deviated direction perpendicular to a stratigraphic layer, perpendicular to the borehole, or any other direction.

[0064] Figure 8 depicts a synthetic example of a subterranean region 90. The subterranean region 90 includes a reservoir 92 shown by various regions, base rock 94 shown by several regions and overburden rock 96 shown by other regions. A borehole path 98 runs horizontally through the subterranean region 90.

[0065] Figures 9-12 depict an example of a model 100 generated based on an inversion of synthetic resistivity measurement data (curves A - D indicating four different resistivity measurements at each borehole location), and examples of boundary identifications performed as described herein. In this example, the model 100 is generated using multi-component inversion modeling (e.g., multicomponent-while-drilling inversion, also known as MCWD inversion) of the synthetic resistivity measurement data.

[0066] The model 100 is generated based on synthetic measurement data, including synthetic resistivity measurement data 102. The synthetic resistivity measurement data 102 includes synthetic resistivity measurement data from various resistivity measurements (e.g., curves A - D for 2 MHz and 400 kHz operating frequency derived from signal attenuation and signal phase difference). Since the subterranean region 90 is a synthetic example, the synthetic65RNV-510772-WO-2JNT1044PCT measurement data is calculated and Figures 8 - 13 are used to demonstrate how the method disclosed herein works. From the synthetic measurement data 102, model sections corresponding to material property model sections 60 described with respect to Figures 3 - 6 were created and are depicted in Figures 9 - 13 as shaded or color-coded model sections (an example of which is indicated by label 93). For the sake of clarity, only one of the model sections is labelled in Figure 9 but those skilled in the art will understand that the complete illustration of model 100 is built up by a stack of model sections 93.

[0067] As shown in Figure 9, inversion quality results 106 are provided, which indicate the inversion quality of each section (e.g., based on the level of match or mismatch between measured data 102 and data that is calculated by using model 100). The inversion quality results 106 are color coded or shaded, where lighter portions 108 indicate high quality and darker portions 110 indicate low quality. The inversion quality results 106 can be used to exclude or weight one or more model sections 93. For example, model sections with an inversion quality value above or below a predefined inversion quality threshold value may be ignored or excluded from model 100 and may be replaced by, interpolated between, or extrapolated from one more model sections 93 with an inversion quality value that is respectively lower or higher than the predefined inversion quality threshold value. For example, model sections 93 with an inversion quality value above or below a predefined inversion quality threshold value may be replaced by, interpolated between, or extrapolated from one or more neighboring model sections 93 (for example, adjacent model sections) with an inversion quality value that is respectively lower or higher than the predefined inversion quality threshold value.

[0068] Figure 10 shows reservoir boundaries identified by analyzing the model 100 according to the method 50. Upper reservoir boundary markers 112 indicate the location of an upper reservoir boundary of the reservoir 92, and lower reservoir boundary markers 114 indicate the location of a lower reservoir boundary of the reservoir 92.

[0069] Figures 11 and 12 show a portion of the model 100 and the subterranean region 90, in which both upper and lower reservoir boundaries were identified. Figure 11 shows an example in which the optimum borehole location was selected to be equidistant from the upper and lower reservoir boundaries indicated by upper and lower reservoir boundary location markers 112 and 114. The optimum borehole locations at various sections are represented by optimum borehole location markers 116. In contrast, Figure 12 shows an example in which65RNV-510772-WO-2JNT1044PCT the optimum borehole location was selected to be at a distance from the upper reservoir boundary corresponding to 25% of the reservoir thickness.

[0070] In the example of Figure 12, a depth of detection curve 120 indicates the depth of detection associated with resistivity measurements performed along the borehole path 98. Data collected (i.e., acquired, received, measured, or calculated) that refers to a distance from the borehole that is beyond the depth of detection indicated by the depth of detection curve 120 may be ignored or excluded from boundary identification as described herein. In another embodiment, collected data that refers to a distance from the borehole that is beyond the depth of investigation may be ignored or excluded from boundary identification as described herein. In addition, data collected in sections having a low inversion quality (e.g., at measured depths that align with darker portions 110) is excluded or replaced, for example, by neighboring material property profiles or by extrapolations from or interpolations between neighboring material property profiles with higher inversion quality.

[0071] In another embodiment, data related to layer boundary locations (e.g., reservoir boundary locations), borehole location (e.g., optimum borehole location) may be smoothed along the borehole path 98. For example, data related to layer boundary locations (e.g., reservoir boundary locations), borehole location (e.g., optimum borehole location) may be corrected using smoothing algorithms such as regression by means of a mathematical function, such as but not limited to an exponential function, a polynomial function, a spline function, or by using a running average (e.g., a running average over a predefined interval of the borehole path 98 or a running average over a predefined number of data values).

[0072] Figure 13 depicts portions of the subterranean region 90 and the model 100, and shows examples of optimum borehole locations calculated when only one boundary is identified. In this example, optimum borehole location points (markers 116) are selected based on an absolute distance from an upper reservoir boundary or lower reservoir boundary, or a percentage of an estimated reservoir thickness.

[0073] Set forth below are some embodiments of the foregoing disclosure:

[0074] Embodiment 1: A system for steering a drilling assembly through a subterranean region, the system comprising: a processor configured to receive a material property profile of the subterranean region, the material property profile including one or more layers, the material property profile specifying, for each layer of the one or more layers, a layer material property and location information with respect to a location of each layer, the material property profile generated from at least one material property data value measured within a65RNV-510772-WO-2JNT1044PCT depth interval of a borehole in the subterranean region by a measurement tool in the borehole, the processor configured to perform: defining a first reservoir boundary location associated with the depth interval from at least one first material property value associated with a first layer of the one or more layers, the first material property value being less than a predefined threshold material property value and at least one second material property value associated with a second layer of the one or more layers, the second material property value being greater than the predefined threshold material property value: determining a reservoir thickness associated with the depth interval or a second reservoir boundary location associated with the depth interval; and defining an optimum borehole location associated with the depth interval based on the reservoir thickness or the second reservoir boundary location, wherein the system is configured to steer with a steering device the drilling assembly to reduce a difference between an actual borehole location and the optimum borehole location.

[0075] Embodiment 2: The system of any prior embodiment, wherein: the material property profile is a first material property profile, the depth interval is a first depth interval, and the at least one material property data value includes the at least one first material property data value, and the processor is further configured to receive a second material property profile generated from at least one second material property data value measured within a second depth interval; and the optimum borehole location is a first optimum borehole location and the processor is further configured to define a second optimum borehole location associated with the second depth interval.

[0076] Embodiment 3 : The system of any prior embodiment, wherein the first optimum borehole location is corrected by the second optimum borehole location.

[0077] Embodiment 4: The system of any prior embodiment, wherein the processor is configured to define the optimum borehole location without human interaction.

[0078] Embodiment 5: The system of any prior embodiment, wherein at least a portion of the processor is in the borehole while defining the optimum borehole location.

[0079] Embodiment 6: The system of any prior embodiment, wherein the processor is further configured to determine the reservoir thickness or the second reservoir boundary location based on a predefined minimum reservoir thickness.

[0080] Embodiment 7: The system of any prior embodiment, wherein the processor is configured to define a depth of investigation or a depth of detection for the measurement of the at least one material property data value and the material property profile is temrinated based on the defined depth of detection or the defined depth of investigation.65RNV-510772-WO-2JNT1044PCT

[0081] Embodiment 8: The system of any prior embodiment, wherein at least one of a distance between the first reservoir boundary location and the borehole, a distance between the second reservoir boundary location and the borehole, or a sum of the reservoir thickness and the distance between the first reservoir boundary location and the borehole is greater than at least one of the defined depth of detection and the defined depth of investigation.

[0082] Embodiment 9: The system of any prior embodiment, wherein: the depth interval is a first depth interval and the defined depth of investigation is a first defined depth of investigation associated with the first depth interval and the defined depth of detection is a first defined depth of detection associated with the first depth interval, and the processor is further configured to define a second depth of investigation associated with a second depth interval of the borehole or a second depth of detection associated with the second depth interval of the borehole; and the first defined depth of investigation is different than the second defined depth of investigation or the first defined depth of detection is different than the second defined depth of detection.

[0083] Embodiment 10: The system of any prior embodiment, wherein the material property profile is generated by an inversion having an inversion quality associated with the depth interval and the processor is further configured to define the optimum borehole location by using the inversion quality.

[0084] Embodiment 11 : A method of steering a drilling assembly through a subterranean region, the method comprising: receiving a material property profile of the subterranean region, the material property profile including one or more layers, the material property profile specifying, for each layer of the one or more layers, a layer material property and location information with respect to a location of each layer, the material property profile generated from at least one material property data value measured within a depth interval of a borehole in the subterranean region by a measurement tool in the borehole; defining a first reservoir boundary location associated with the depth interval from at least one first material property value associated with a first layer of the one or more layers, the first material property value being less than a predefined threshold material property value and at least one second material property value associated with a second layer of the one or more layers, the second material property value being greater than the predefined threshold material property value; determining a reservoir thickness associated with the depth interval or a second reservoir boundary location associated with the depth interval; defining an optimum borehole location associated with the depth interval based on the reservoir thickness or the second reservoir65RNV-510772-WO-2JNT1044PCT boundary location; and steering the drilling assembly to reduce a difference between an actual borehole location and the optimum borehole location.

[0085] Embodiment 12: The method of any prior embodiment, wherein the material property profile is a first material property profile, the depth interval is a first depth interval, the at least one material property data value includes the at least one first material property data value, the optimum borehole location is a first optimum borehole location, and the method further comprises: receiving a second material property profile generated from at least one second material property data value measured within a second depth interval; and defining a second optimum borehole location associated with the second depth interval.

[0086] Embodiment 13: The method of any prior embodiment, wherein the first optimum borehole location is corrected by the second optimum borehole location.

[0087] Embodiment 14: The method of any prior embodiment, wherein defining the optimum borehole location is executed without human interaction.

[0088] Embodiment 15: The method of any prior embodiment, wherein the optimum borehole location is defined by a processor in the borehole.|0089| Embodiment 16: The method of any prior embodiment, further comprising determining the reservoir thickness or the second reservoir boundary location based on a predefined minimum reservoir thickness.

[0090] Embodiment 17: The method of any prior embodiment, further comprising defining a depth of investigation or a depth of detection for the measurement of the at least one material property data value, wherein the material property profile is terminated based on the defined depth of detection or the defined depth of investigation.

[0091] Embodiment 18: The method of any prior embodiment, wherein at least one of a distance between the first reservoir boundary location and the borehole, a distance between the second reservoir boundary location and the borehole, or a sum of the reservoir thickness and the distance between the first reservoir boundary location and the borehole is greater than at least one of the defined depth of detection and the defined depth of investigation.

[0092] Embodiment 19: The method of any prior embodiment, wherein: the depth interval is a first depth interval and the defined depth of investigation is a first defined depth of investigation associated with the first depth interval and the defined depth of detection is a first defined depth of detection associated with the first depth interval, and the method further comprises defining a second depth of investigation associated with a second depth interval of the borehole or a second depth of detection associated with the second depth interval of the65RNV-510772-WO-2JNT1044PCT borehole; and the first defined depth of investigation is different than the second defined depth of investigation or the first defined depth of detection is different than the second defined depth of detection.

[0093] Embodiment 20: The method of any prior embodiment, wherein the material property profile is generated by an inversion having an inversion quality associated with the depth interval, and the optimum borehole location is defined based on the inversion quality.

[0094] One or more aspects of the embodiments described herein can be included in an article of manufacture (e.g., one or more computer program products) having, for instance, computer usable media. The media has therein, for instance, computer readable instructions, program code means or logic (e.g., code, commands, rules, etc.) to provide and facilitate the capabilities of the present invention. The article of manufacture can be included as a part of a computer system or provided separately. These instructions may provide for equipment operation, control, data collection and analysis and other functions deemed relevant by a system designer, owner, user or other such personnel, in addition to the functions described in this disclosure.|0095| In support of the teachings herein, various analyses and / or analytical components may be used, including digital and / or analog systems. The system may have components such as a processor, storage media, memory, input, output, communications link (wired, wireless, pulsed mud, optical or other), user interfaces, software programs, signal processors (digital or analog) and other such components (such as resistors, capacitors, inductors and others) to provide for operation and analyses of the apparatus and methods disclosed herein in any of several manners well-appreciated in the art. The term “processors” may include one or more individual processing units like microcontrollers for example. The processing units may be located at different locations. For example, one processing unit may be located within the borehole and the other processing unit may be at the earth’s surface or one processing unit may be located in a first downhole tool and the other processing unit may be in a second downhole tool at a distance from the first downhole tool. In such cases, the various processing units may still be called collectively a processor.

[0096] One skilled in the art will recognize that the various 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.65RNV-510772-WO-2JNT1044PCT

[0097] The use of the terms “a” and “an” and “the” and similar terms in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should be noted that the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier “about" used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity).

[0098] 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.

[0099] While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, the invention is 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 claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited.

Claims

65RNV-510772-WO-2JNT1044PCTCLAIMSWhat is claimed is:

1. A system for steering a drilling assembly through a subterranean region (16), the system characterized by: a processor (32,34) configured to receive a material property profile (62) of the subterranean region (16), the material property profile (62) including one or more layers (64), the material property profile (62) specifying, for each layer (64) of the one or more layers, a layer material property and location information with respect to a location of each layer (64), the material property profile (62) generated from at least one material property data value measured within a depth interval of a borehole (14) in the subterranean region (16) by a measurement tool (18) in the borehole (14), the processor (32,34) configured to perform: defining a first reservoir boundary location associated with the depth interval from at least one first material property value associated with a first layer (64) of the one or more layers (64), the first material property value being less than a predefined threshold material property value and at least one second material property value associated with a second layer (64) of the one or more layers (64), the second material property value being greater than the predefined threshold material property value; determining a reservoir thickness associated with the depth interval or a second reservoir boundary location associated with the depth interval; and defining an optimum borehole location associated with the depth interval based on the reservoir thickness or the second reservoir boundary location, wherein the system is configured to steer with a steering device (27) the drilling assembly to reduce a difference between an actual borehole location and the optimum borehole location.

2. The system of claim 1, wherein: the material property profile (62) is a first material property profile (62), the depth interval is a first depth interval, and the at least one material property data value includes the at least one first material property data value, and the processor (32,34) is further configured to receive a second material property profile (62) generated from at least one second material property data value measured within a second depth interval; and the optimum borehole location is a first optimum borehole location and the processor (32,34) is further configured to define a second optimum borehole location associated with the second depth interval.65RNV-510772-WO-2JNT1044PCT3. The system of claim 2, wherein the first optimum borehole location is corrected by the second optimum borehole location.

4. The system of claim 1 , wherein the processor (32,34) is configured to define the optimum borehole location without human interaction.

5. The system of claim 4, wherein at least a portion of the processor (32,34) is in the borehole while defining the optimum borehole location.

6. The system of claim 1, wherein the processor (32,34) is further configured to determine the reservoir thickness or the second reservoir boundary location based on a predefined minimum reservoir thickness.

7. The system of claim 1, wherein the processor (32,34) is configured to define a depth of investigation or a depth of detection for the measurement of the at least one material property data value and the material property profile (62) is terminated based on the defined depth of detection or the defined depth of investigation.

8. The system of claim 7, wherein at least one of a distance between the first reservoir boundary location and the borehole (14), a distance between the second reservoir boundary location and the borehole (14), or a sum of the reservoir thickness and the distance between the first reservoir boundary location and the borehole (14) is greater than at least one of the defined depth of detection and the defined depth of investigation.

9. The system of claim 7, wherein: the depth interval is a first depth interval and the defined depth of investigation is a first defined depth of investigation associated with the first depth interval and the defined depth of detection is a first defined depth of detection associated with the first depth interval, and the processor (32,34) is further configured to define a second depth of investigation associated with a second depth interval of the borehole (14) or a second depth of detection associated with the second depth interval of the borehole (14); and the first defined depth of investigation is different than the second defined depth of investigation or the first defined depth of detection is different than the second defined depth of detection.

10. The system of claim 1, wherein the material property profile (62) is generated by an inversion having an inversion quality associated with the depth interval and the processor (32,34) is further configured to define the optimum borehole location by using the inversion quality.65RNV-510772-WO-2JNT1044PCT11. A method of steering a drilling assembly through a subterranean region (16), the method characterized by: receiving a material property profile (62) of the subterranean region (16), the material property profile (62) including one or more layers (64), the material property profile (62) specifying, for each layer (64) of the one or more layers (64), a layer material property and location information with respect to a location of each layer (64), the material property profile (62) generated from at least one material property data value measured within a depth interval of a borehole (14) in the subterranean region (16) by a measurement tool (18) in the borehole (14); defining a first reservoir boundary location associated with the depth interval from at least one first material property value associated with a first layer (64) of the one or more layers (64), the first material property value being less than a predefined threshold material property value and at least one second material property value associated with a second layer (64) of the one or more layers (64), the second material property value being greater than the predefined threshold material property value; determining a reservoir thickness associated with the depth interval or a second reservoir boundary location associated with the depth interval; defining an optimum borehole location associated with the depth interval based on the reservoir thickness or the second reservoir boundary location; and steering the drilling assembly to reduce a difference between an actual borehole location and the optimum borehole location.

12. The method of claim 11, wherein the material property profile (62) is a first material property profile (62), the depth interval is a first depth interval, the at least one material property data value includes the at least one first material property data value, the optimum borehole location is a first optimum borehole location, and the method further comprises: receiving a second material property profile (62) generated from at least one second material property data value measured within a second depth interval; and defining a second optimum borehole location associated with the second depth interval.

13. The method of claim 12, wherein the first optimum borehole location is corrected by the second optimum borehole location.

14. The method of claim 11 , further comprising defining a depth of investigation or a depth of detection for the measurement of the at least one material property data value,65RNV-510772-WO-2JNT1044PCT wherein the material property profile (62) is terminated based on the defined depth of detection or the defined depth of investigation.

15. The method of claim 17, wherein at least one of a distance between the first reservoir boundary location and the borehole (14), a distance between the second reservoir boundary location and the borehole (14), or a sum of the reservoir thickness and the distance between the first reservoir boundary location and the borehole (14) is greater than at least one of the defined depth of detection and the defined depth of investigation, and wherein: the depth interval is a first depth interval and the defined depth of investigation is a first defined depth of investigation associated with the first depth interval and the defined depth of detection is a first defined depth of detection associated with the first depth interval, and the method further comprises defining a second depth of investigation associated with a second depth interval of the borehole (14) or a second depth of detection associated with the second depth interval of the borehole (14); and the first defined depth of investigation is different than the second defined depth of investigation or the first defined depth of detection is different than the second defined depth of detection.

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