Patent Publication Number: US-11397279-B2

Title: Comparison of wells using a dissimilarity matrix

Description:
FIELD 
     The present disclosure relates generally to the field of comparing wells using a dissimilarity matrix. 
     BACKGROUND 
     Correlation of different wells using well logs and/or well cores may provide insights on whether and/or how different segments of the wells are linked together. Lithostratigraphic correlations of wells may result in erroneous representations of the spatial distributions of rock properties and/or internal structure of a reservoir. 
     SUMMARY 
     This disclosure relates to comparing wells. First well information, second well information, first well marker information, second well marker information, and/or other information may be obtained. The first well information may define subsurface configuration of a first well. The first well information may include a first set of values that define the subsurface configuration at a first set of positions within the first well. The second well information may define the subsurface configuration of a second well. The second well information may include a second set of values that define the subsurface configuration at a second set of positions within the second well. The first well marker information may define a first set of marker positions within the first well. The second well marker information may define a second set of marker positions within the second well. 
     A dissimilarity matrix for the first well and the second well may be generated. A dimension of the dissimilarity matrix may be defined by a first number of positions within the first set of positions and a second number of positions within the second set of positions. Element values of the dissimilarity matrix may be determined based on comparison of the subsurface configuration of the first well at corresponding positions within the first well and the subsurface configuration of the second well at corresponding positions within second first well, and/or other information. A gated dissimilarity matrix may be generated from the dissimilarity matrix based on the first set of marker positions within the first well, the second set of marker positions within the second well, and/or other information. The element values of the dissimilarity matrix corresponding to the first set of marker positions and not corresponding to the second set of marker positions within the second well may be changed relative to other element values in the gated dissimilarity matrix. Correlation between one or more marker positions within the first well and one or more marker positions within the second well may be determined based on the gated dissimilarity matrix and/or other information. 
     A system that compares wells may include one or more electronic storage, one or more processors and/or other components. The electronic storage may store well information, information relating to well, information relating to subsurface configuration of well, information relating to positions within well, well-marker information, information relating to marker positions within well, information relating to dissimilarity matrix, information relating to gated dissimilarity matrix, information relating to correlation between wells, information relating to correlation between marker positions within wells, and/or other information. 
     The processor(s) may be configured by machine-readable instructions. Executing the machine-readable instructions may cause the processor(s) to facilitate comparing wells. The machine-readable instructions may include one or more computer program components. The computer program components may include one or more of a well information component, a well marker information component, a dissimilarity matrix component, a gated dissimilarity matrix component, a correlation component, and/or other computer program components. 
     The well information component may be configured to obtain well information for multiple wells. The well information for a well may define subsurface configuration of the well. The well information for a well may include a set of values that define the subsurface configuration of the well at a set of positions within the well. For example, the well information component may be configured to obtain first well information, second well information, and/or other well information. The first well information may define subsurface configuration of a first well. The first well information may include a set of values that define the subsurface configuration of the first well at a set of positions within the first well. The second well information may define subsurface configuration of a second well. The second well information may include a set of values that define the subsurface configuration of the second well at a set of positions within the second well. 
     In some implementations, at least one of the first well and the second well may be a natural well. In some implementations, at least one of the first well and the second well may be a virtual well. 
     The well marker information component may be configured to obtain well marker information for multiple wells. The well marker information for a well may define a set of marker positions within the well. For example, the well marker information component may be configured to obtain first well marker information, second well marker information, and/or other well marker information. The first well marker information may define a set of marker positions within the first well. The second well marker information may define a set of marker positions within the second well. 
     The dissimilarity matrix component may be configured to generate a dissimilarity matrix for multiple wells. For example, the matrix component may be configured to generate a dissimilarity matrix for the first well and the second well. A dimension of the dissimilarity matrix may be defined by a number of positions within the set of positions within the first well and a number of positions within the set of positions within the second well. Element values of the dissimilarity matrix may be determined based on comparison of the subsurface configuration of the first well at corresponding positions within the first well and the subsurface configuration of the second well at corresponding positions within second first well, and/or other information. 
     In some implementations, the element values of the dissimilarity matrix may be determined based on the comparison to be greater than or equal to zero. Greater element values may reflect greater dissimilarity between the subsurface configuration of the wells at corresponding position within the wells. 
     The gated dissimilarity matrix component may be configured to generate a gated dissimilarity matrix from a dissimilarity matrix. The gated dissimilarity matrix may be generated based on the set of marker positions within different wells, and/or other information. For example, the gated dissimilarity matrix for the first well and the second well may be generated based on the set of marker positions within the first well, the set of marker positions within the second well, and/or other information. The element values of the dissimilarity matrix corresponding to the set of marker positions within one well (e.g., the first well) and not corresponding to the set of marker positions within the other well (e.g., the second well) may be changed relative to other element values in the gated dissimilarity matrix. 
     The correlation component may be configured to determine correlation between different wells based on the gated dissimilarity matrix and/or other information. The correlation determined between different wells may include correlation between marker positions within the different wells. For example, the correlation component may be configured to determine correlation between the first well and the second well based on the gated dissimilarity matrix for the first well and the second well, and/or other information. The correlation component may be configured to determine correlation between one or more marker positions within the first well and one or more marker positions within the second well based on the gated dissimilarity matrix for the first well and the second well, and/or other information. 
     In some implementations, determination of the correlation between the marker position(s) within the first well and the marker position(s) within the second well based on the gated dissimilarity matrix may include generation of a path within the gated dissimilarity matrix. The path may be generated based on a directed walk within the gated dissimilarity matrix and/or other information. The element values corresponding to the set of marker positions within one well (e.g., the first well) and not corresponding to the set of marker positions within the other well (e.g., the second well) may be changed relative to the other element values to obstruct traversal of the path through corresponding elements of the gated dissimilarity matrix. 
     In some implementations, the path may include a minimum-cost path. In some implementations, the path may represent a scenario of correlation between positions within the different wells. For example, the path may represent a scenario of correlation between position within first well and positions within the second well. 
     In some implementations, the element values corresponding to the set of marker positions within one well (e.g., the first well) and not corresponding to the set of marker positions within the other well (e.g., the second well) may be changed relative to the other element values by increasing the element values to infinity. In some implementations, the element values corresponding to the set of marker positions within one well (e.g., the first well) and corresponding to the set of marker positions within the other well (e.g., the second well) may be preserved to allow traversal of the path. 
     In some implementations, the element values corresponding to the set of marker positions within one well (e.g., the first well) and not corresponding to the set of marker positions within the other well (e.g., the second well) may be indirectly changed relative to other element values by changing the other element values. 
     These and other objects, features, and characteristics of the system and/or method disclosed herein, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. As used in the specification and in the claims, the singular form of “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example system that compares wells. 
         FIG. 2  illustrates an example method for comparing wells. 
         FIGS. 3A-3D  illustrate example segments of two wells. 
         FIG. 4  illustrates example marker positions within two wells. 
         FIG. 5  illustrates an example dissimilarity matrix for a pair of wells. 
         FIG. 6  illustrates an example gated dissimilarity matrix for a pair of wells. 
         FIG. 7  illustrates an example representation of a gated dissimilarity matrix for a pair of wells. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to comparing wells. Well information may define subsurface configuration of different wells. Marker information defining marker positions within the wells may be obtained. A dissimilarity matrix for the wells may generated, with the element values of the dissimilarity matrix determined based on comparison of corresponding subsurface configuration of the wells. A gated dissimilarity matrix may be generated from the dissimilarity matrix based on the marker positions within the wells. The elements values of the gated dissimilarity matrix corresponding to one set of marker positions and not corresponding to the other set of marker positions may be changed. Correlation between the wells may be determined based on the gated dissimilarity matrix such that correlation exists between a marker position in one well and a marker position in another well. 
     The methods and systems of the present disclosure may be implemented by and/or in a computing system, such as a system  10  shown in  FIG. 1 . The system  10  may include one or more of a processor  11 , an interface  12  (e.g., bus, wireless interface), an electronic storage  13 , and/or other components. First well information, second well information, first well marker information, second well marker information, and/or other information may be obtained by the processor  11 . The first well information may define subsurface configuration of a first well. The first well information may include a first set of values that define the subsurface configuration at a first set of positions within the first well. The second well information may define the subsurface configuration of a second well. The second well information may include a second set of values that define the subsurface configuration at a second set of positions within the second well. The first well marker information may define a first set of marker positions within the first well. The second well marker information may define a second set of marker positions within the second well. 
     A dissimilarity matrix for the first well and the second well may be generated by the processor  11 . A dimension of the dissimilarity matrix may be defined by a first number of positions within the first set of positions and a second number of positions within the second set of positions. Element values of the dissimilarity matrix may be determined by the processor  11  based on comparison of the subsurface configuration of the first well at corresponding positions within the first well and the subsurface configuration of the second well at corresponding positions within second first well, and/or other information. A gated dissimilarity matrix may be generated by the processor  11  from the dissimilarity matrix based on the first set of marker positions within the first well, the second set of marker positions within the second well, and/or other information. The element values of the dissimilarity matrix corresponding to the first set of marker positions and not corresponding to the second set of marker positions within the second well may be changed relative to other element values in the gated dissimilarity matrix. Correlation between one or more marker positions within the first well and one or more marker positions within the second well may be determined by the processor  11  based on the gated dissimilarity matrix and/or other information. 
     A well may refer to a hole or a tunnel in the ground. A well may be drilled in the ground for exploration and/or recovery of natural resources in the ground. For example, a well may be drilled in the ground to aid in extraction of petrochemical fluid (e.g., oil, gas, petroleum, fossil fuel). A well may be drilled in one or more directions. For example, a well may include a vertical well, a horizontal well, a deviated well, and/or other type of well. 
     A well may expose and/or run through different types of materials (e.g., sedimentary rocks) in the ground. The materials in the ground may be grouped into related packages. For example, rocks in the ground may be grouped into packages of rocks that are bounded by chronostratigraphic surface and/or sequence stratigraphic boundaries. Rocks may be related based on their depositions by the same flow and/or sediment transport event. Because the flow and the associated sediment transport are highly correlated spatially, the spatial distribution and spatial variabilities of the sedimentary rocks that are produced by the flow and sediment transport may be predicted. 
     Geologic analysis and/or reservoir characterization workflow may include determining correlations between segments of different wells. A segment of a well may refer to a part of the well (e.g., a vertical part of the well). A segment of a well may include and/or be defined by one or more materials within a part of the well (e.g., sedimentary rock within a part of the well). A segment of a well may include and/or be defined by one or more materials surrounding a part of the well (e.g., sedimentary rock surrounding a part of the well). A correlation between segments of wells may refer to connection, correspondence, and/or relationship between a segment of one well to a segment of another well. A segment of one well correlated to a segment of another well may indicate that the two segments were deposited at the same time (chronostratigraphically) and/or have similar/related characteristics. 
     Correlation of wells may be determined lithostratigraphically. Lithostratigraphic correlation of wells may include correlation of wells based solely on their physical and/or petrographic features. Lithostratigraphic correlation of wells may include correlation of wells that maximize cross correlations between pairs of log signals. That is, lithostratigraphic correlation may correlate wells by looking for similar patterns in the pairs of log signals. For example, segments of different wells may be linked together based on similarity of geo-patterns within the segments. However, such correlation of well segments may erroneously represent spatial distributions of rock properties and/or reservoir internal heterogeneity. 
     For example,  FIGS. 3A-3D  illustrate example segments of a well A  310  and a well B  320  drilled into ground  302 . The segments of the well A  310  and the well B  320  may include division of the well A  310  and the well B  320  into related packages. The well A  310  may include segments  312 ,  314 ,  316 ,  318 , and the well B  320  may include segments  322 ,  324 ,  326 ,  328 . As shown in  FIG. 3B , lithostratigraphic correlation of segments of wells A  310  and well B  320  may result in linking of the segment  312  to the segment  322 , linking of the segment  314  to the segment  324 , linking of the segment  316  to the segment  326 , and the linking of the segment  318  to the segment  328 . Such linking of well segments may result in a railway track style of correlation where the rock packages in the well A  310  is linked to similar rock packages in the well B  320 , which may imply that the linked well segments are connected. 
     Such representation of spatial distributions of rock properties and/or reservoir internal heterogeneity may not be correct. For example,  FIGS. 3C and 3D  illustrate alternative spatial distributions of rock properties and/or reservoir internal heterogeneity between the well A  310  and the well B  320 . In  FIG. 3C , the well A  310  and the well B  320  may be drilled into the ground with similar properties/characteristics (e.g., delta lobes of a delta plain). However, the well A  310  and the well B  320  may be physically separated (e.g., separated by fringing parts of the delta lobes) and the segments  312 ,  314 ,  316 ,  318  of the well A  310  may not be connected to the segments  322 ,  324 ,  326 ,  328  of the well B  320 . In  FIG. 3D , the well A  310  and the well B  320  may be drilled into the ground with deposited layers being slanted with respect to the ground  302 . The segment  312  of the well A  310  may correlate to the segment  328  of the well B  320  (rather than the segment  322 ). The segments  322 ,  324 ,  326  of the well B  310  may not correlate to any segments of the well A  310 . The segments  314 ,  316 ,  318  of the well A  310  may or may not correlate to segments of the well B  320  below the segment  328 . 
     An important advancement in geological studies is the development of chrono- and sequence stratigraphy. Chrono- and sequence stratigraphy recognizes that sediment rocks are deposited sequentially, one layer after the other over time. Application of chrono- and sequence stratigraphy may enable prediction of rock properties from known locations, such as at locations of wells, to unknown locations such as locations between wells and/or away from wells. In contrast with the litho-stratigraphy where the grouping of rocks is based on similar rock properties, chrono- and sequence stratigraphy enables characterization of the rocks by grouping them into generically related packages. Because the rocks within the chrono- and sequence stratigraphy are generically related, within each package, the property distributions and their spatial variations are closely related to the associated depositional processes. These depositional processes are mostly spatially continuous and may be predicted. By identifying and linking the generically related packages, a chrono- and sequence stratigraphic framework may be obtained. The framework may then be used for making predictions of related geologic properties away from the wells, as well as for building reservoir models by filling the properties in the volumes defined by the layers given by the framework. 
     Referring back to  FIG. 1 , the electronic storage  13  may be configured to include electronic storage medium that electronically stores information. The electronic storage  13  may store software algorithms, information determined by the processor  11 , information received remotely, and/or other information that enables the system  10  to function properly. For example, the electronic storage  13  may store well information, information relating to well, information relating to subsurface configuration of well, information relating to positions within well, well-marker information, information relating to marker positions within well, information relating to dissimilarity matrix, information relating to gated dissimilarity matrix, information relating to correlation between wells, information relating to correlation between marker positions within wells, and/or other information. 
     The processor  11  may be configured to provide information processing capabilities in the system  10 . As such, the processor  11  may comprise one or more of a digital processor, an analog processor, a digital circuit designed to process information, a central processing unit, a graphics processing unit, a microcontroller, an analog circuit designed to process information, a state machine, and/or other mechanisms for electronically processing information. The processor  11  may be configured to execute one or more machine-readable instructions  100  to facilitate comparing wells. The machine-readable instructions  100  may include one or more computer program components. The machine-readable instructions  100  may include one or more of a well information component  102 , a well marker information component  104 , a dissimilarity matrix component  106 , a gated dissimilarity matrix component  108 , a correlation component  110 , and/or other computer program components. 
     The well information component  102  may be configured to obtain well information for multiple wells. Obtaining well information may include one or more of accessing, acquiring, analyzing, determining, examining, identifying, loading, locating, opening, receiving, retrieving, reviewing, selecting, storing, utilizing, and/or otherwise obtaining the well information. The well information component  102  may obtain well information from one or more locations. For example, the well information component  102  may obtain well information from a storage location, such as the electronic storage  13 , electronic storage of a device accessible via a network, and/or other locations. The well information component  102  may obtain well information from one or more hardware components (e.g., a computing device, a component of a computing device) and/or one or more software components (e.g., software running on a computing device). Well information may be stored within a single file or multiple files. 
     The well information for a well may define subsurface configuration of the well. Subsurface configuration of a well may refer to attribute, quality, and/or characteristics of the well. Subsurface configuration of a well may refer to type, property, and/or physical arrangement of materials (e.g., subsurface elements) within the well and/or surrounding the well. Subsurface configuration of the well may be defined as a function of spatial location (e.g., vertical spatial location, lateral spatial location). 
     The well information for a well may include a set of values that define the subsurface configuration of the well at a set of positions within the well. A set of values may include one or more values, and a set of positions within a well may include one or more positions within the well. A position within a well may refer to a spatial location within a well. A position within a well may be defined in terms of vertical spatial location (e.g., depth) and/or lateral spatial location (e.g., x-y location). 
     For example, the well information component  102  may be configured to obtain first well information, second well information, and/or other well information. The first well information may define subsurface configuration of a first well. The first well information may include a set of values that define the subsurface configuration of the first well at a set of positions within the first well. The second well information may define subsurface configuration of a second well. The second well information may include a set of values that define the subsurface configuration of the second well at a set of positions within the second well. 
     The well information may define subsurface configuration of a well by including information that describes, delineates, identifies, is associated with, quantifies, reflects, sets forth, and/or otherwise defines one or more of content, quality, attribute, feature, and/or other aspects of the subsurface configuration of the well. For example, the well information may define subsurface configuration of a well by including information that makes up the content of the well and/or information that is used to identify/determine the content of the wells. For instance, the well information may include one or more well logs (of natural well, of virtual well), information determined/extracted from one or more well logs (e.g., of natural well, or virtual well), information determined/extracted from one or more well cores (e.g., of natural well, or virtual well), and/or other information. For example, the well information may provide information on one or more properties of a well, such as rock types, layers, grain sizes, porosity, and/or permeability of the well at different positions within the well. 
     In some implementations, at least one of the multiple wells (e.g., the first well and the second well) may be a natural well. For example, the first well or the second well may be a natural well. As another example, both the first well and the second well may be natural wells. A natural well may refer to a physical well. A natural well may refer to a well that exists or existed in the real world. For example, a natural well may refer to a well that is drilled in the real world. Well information for a natural well may include information extracted from the natural well. For example, well information for a natural well may include a series of values extracted from the well log and/or the core data of the well. Well information for a natural well may have N w  data values, and the j th  value may be represented as w[j], j∈[1, . . . , Nw]. 
     In some implementations, at least one of the multiple wells (e.g., the first well and the second well) may be a virtual well. For example, the first well or the second well may be a virtual well. As another example, both the first well and the second well may be virtual wells. A virtual well may refer to a synthetic well and/or a digital well. A virtual well may refer to a well that exists or existed in a virtual world. For example, a virtual well may refer to a well that is generated using one or more computer models. A virtual well may refer to a well that is generated in one or more computer simulations. Well information for a virtual well may include information extracted from the virtual well. For example, well information for a virtual well may include a series of values extracted at a lateral spatial location in a computer-generated representation of a subsurface region. Well information for a virtual well may have N a  data values, and the i th  value may be represented as a[i], i∈[1, . . . , Na]. 
     A computer-generated representation of a subsurface region (subsurface representation) may be representative of the depositional environment of wells (e.g., wells to be compared). A subsurface representation may include geologically plausible arrangement of rock obtained from a modeling process (e.g., stratigraphic forward modeling process). A subsurface representation may provide simulated subsurface configuration at different locations within a simulated subsurface region (e.g., provide simulated well log values at locations in a three-dimensional (x-y-z) coordinate system). 
     A subsurface representation may be generated using one or more subsurface models. A subsurface model may refer to a computer model (e.g., program, tool, script, function, process, algorithm) that generates subsurface representations. A subsurface model may simulate subsurface configuration within a region underneath the surface (subsurface region). Examples of subsurface configuration simulated by a subsurface model may include types of subsurface materials, characteristics of subsurface materials, compositions of subsurface materials, arrangements/configurations of subsurface materials, physics of subsurface materials, and/or other subsurface configuration. 
     An example of a subsurface model is a computational stratigraphy model. A computational stratigraphy model may refer to a computer model that simulates depositional and/or stratigraphic processes on a grain size scale while honoring physics-based flow dynamics. A computational stratigraphy model may simulate rock properties, such as velocity and density, based on rock-physics equations and assumptions. Input to a computational stratigraphy model may include information relating to a subsurface region to be simulated. For example, input to a computational stratigraphy model may include paleo basin floor topography, paleo flow and sediment inputs to the basin, and/or other information relating to the basin. In some implementations, input to a computational stratigraphy model may include one or more paleo geologic controls, such as climate changes, sea level changes, tectonics and other allocyclic controls. Output of a computational stratigraphy model may include one or more subsurface representations. A subsurface representation generated by a computational stratigraphy model may be referred to as a computational stratigraphy model representation. 
     A computational stratigraphy model may include a forward stratigraphic model. A forward stratigraphic model may be an event-based model, a process mimicking model, a reduced physics based model, and/or a fully physics based model (e.g., fully based on physics of flow and sediment transport). A forward stratigraphic model may simulate one or more sedimentary processes that recreate the way stratigraphic successions develop and/or are preserved. The forward stratigraphic model may be used to numerically reproduce the physical processes that eroded, transported, deposited and/or modified the sediments over variable time periods. In a forward modelling approach, data may not be used as the anchor points for facies interpolation or extrapolation. Rather, data may be used to test and validate the results of the simulation. Stratigraphic forward modelling may be an iterative approach, where input parameters have to be modified until the results are validated by actual data. Usage of other subsurface models and other subsurface representations are contemplated. 
     The well marker information component  104  may be configured to obtain well marker information for multiple wells. Obtaining well marker information may include one or more of accessing, acquiring, analyzing, determining, examining, identifying, loading, locating, opening, receiving, retrieving, reviewing, selecting, storing, utilizing, and/or otherwise obtaining the well marker information. The well marker information component  104  may obtain well marker information from one or more locations. For example, the well marker information component  104  may obtain well marker information from a storage location, such as the electronic storage  13 , electronic storage of a device accessible via a network, and/or other locations. The well marker information component  104  may obtain well marker information from one or more hardware components (e.g., a computing device, a component of a computing device) and/or one or more software components (e.g., software running on a computing device). Well marker information may be stored within a single file or multiple files. 
     The well marker information for a well may define a set of marker positions within the well. A set of marker positions may include one or more marker positions. A marker position may refer to a position within a well (natural well, virtual well) that has been selected for comparison. A marker position may refer to a position within a well (natural well, virtual well) that has been selected for comparison to other marker positions within another well. A marker position within a well may be selected based on the subsurface configuration of the well at the corresponding position. For example, a marker position within a well may be selected based on certain rock types, layers, grain sizes, porosity, and/or permeability of the well at the corresponding position. As another example, a marker position within a well may be selected based on subsurface properties, geometry, and/or other sedimentary process information available within a subsurface representation. For instance, a marker position within a well may correspond to an important geologic boundary within the well and/or other features of interest, such as erosion, within the well. 
     In some implementations, a marker position within a well may be selected based on interpretation of well logs and/or analysis of seismic data. In some implementations, a marker position within a well may be selected based on interpretation and/or analysis of the corresponding subsurface configuration. For instance, a marker position may be selected based on the corresponding position (e.g., small interval) within the well including a certain number of surfaces. Other selection of marker positions are contemplated. 
     The well marker information for a well may define a set of marker positions within the well by including information that describes, delineates, identifies, is associated with, quantifies, reflects, sets forth, and/or otherwise defines the set of marker positions within the well. For example, the well marker information may one or more marker positions within a well by including information that specifies/identifies the marker position(s) and/or information that is used to identify/determine the marker position(s). For example, for a natural well, the well marker information may include a subset of the positions corresponding to data values of the natural well (included within well information). The subset  ⊆[1, . . . , Nw] may define the indices of the well information data values and may correspond to the marker positions within the natural well. As another example, for a virtual well, the well marker information may include a subset of the positions corresponding to data values of the virtual well (included within well information). The subset  ⊆[1, . . . , Na] may define the indices of the well information data values and may correspond to the marker positions within the virtual well. 
     For example, the well marker information component  104  may be configured to obtain first well marker information, second well marker information, and/or other well marker information. The first well marker information may define a set of marker positions within the first well. The second well marker information may define a set of marker positions within the second well.  FIG. 4  illustrates example marker positions within two wells. The well marker information for a well A  410  may define marker positions  412 ,  414 ,  416  within the well A  410 , and the well marker information for a well B  420  may define marker positions  422 ,  424 ,  416  within the well B  420 . The marker positions  412 ,  414 ,  416  may correspond to positions (e.g., area, volume, segment, interval) that has been selected within the well A  410  for comparison to the marker positions  422 ,  424  within the well B  420 , and vice versa. 
     The dissimilarity matrix component  106  may be configured to generate a dissimilarity matrix for multiple wells. A dissimilarity matrix may be generated for a pair of wells (e.g., for two natural wells, for two virtual wells, for a natural well and a virtual well). For example, the matrix component  106  may be configured to generate a dissimilarity matrix for the first well and the second well. A dissimilarity matrix may include an array of values (e.g., numbers, symbols, expressions). The values may correspond to different positions within the pair of well, and the values may characterize the extent of dissimilarity in the subsurface configuration of the corresponding positions within the pair of wells. 
     The dimension of the dissimilarity matrix may be characterized by a number of rows, a number of columns, and/or dimensional characteristics of the dissimilarity matrix. A dissimilarity matrix may be defined as a two-dimensional matrix. The dimension of a dissimilarity matrix may determine the number of elements within the dissimilarity matrix. 
     The dimension of the dissimilarity matrix may be defined by the number of positions within the individual sets of positions within the pair of wells. For example, the dimension of the dissimilarity matrix for the first well and the second well may be defined by the number of positions within the sets of positions within the first well and the number of positions within the set of positions within the second well. 
       FIG. 5  illustrates an example dissimilarity matrix for a well A  510  and a well B  520 . Well information for the well A  510  may define the subsurface configuration of the well A  510  at a set of positions (N A  set) within the well A  510 . The N A  set may include A number of positions. Well information for the well B  520  may define the subsurface configuration of the well B  520  at a set of positions (N B  set) within the well B  520 . The N B  set may include B number of positions. A dissimilarity matrix D AB    500  may be generated for the well A  510  and the well B  520 . The dimension of the dissimilarity matrix D AB    500  may include a row number of A and a column number of B. 
     Element values of the dissimilarity matrix may be determined based on comparison of the subsurface configuration of the wells at corresponding positions within the wells, and/or other information. Element values may refer to values of elements within the cells of the dissimilarity matrix. For example, element values of the dissimilarity matrix for the first well and the second well may be determined based on comparison of the subsurface configuration of the first well at corresponding positions within the first well and the subsurface configuration of the second well at corresponding positions within second first well, and/or other information. The element values of the dissimilarity matrix may be calculated by comparing the data values of the different wells at the corresponding positions within the different wells. The element values of the dissimilarity matrix may enable comparison of subsurface configuration similarity between different positions within the wells. 
     In some implementations, a function of two data values a and w of the pair of wells, d(a,w), may return a dissimilarity measure reflecting the extent of dissimilarity between the corresponding positions. The element values of the dissimilarity matrix D Na×Nw  may be defined such that the ith row and jth column are defined as D[i,j]=d(a[i],w[j]). 
     For example, the element values of the dissimilarity matrix may be determined based on quantity and/or quality of matching between the subsurface configuration of the wells at the corresponding positions. For instance, lithological comparison (e.g., using pattern recognition techniques, pattern matching techniques, lithostratigraphic analysis techniques, etc.) may be performed between the subsurface configuration of wells at corresponding positions to determine to what extent the subsurface configuration of a well at a particular position matches the subsurface configuration of a different well at a particular position. 
     In some implementations, the element values of the dissimilarity matrix may be determined based on the comparison of the subsurface configuration of the wells to be greater than or equal to zero. Greater element values may reflect greater dissimilarity between the subsurface configuration of the wells at corresponding position within the wells. 
     The gated dissimilarity matrix component  108  may be configured to generate a gated dissimilarity matrix from a dissimilarity matrix. For example, the gated dissimilarity matrix component  108  may be configured to generate a gated dissimilarity matrix for the first well and the second well from the dissimilarity matrix for the first well and the second well. A gated dissimilarity matrix may include an array of values. The dimension of the gated dissimilarity matrix may be the same as the dimension of the dissimilarity matrix. For example,  FIG. 6  illustrates an example gated dissimilarity matrix G AB    600  for the well A  510  and the well B  520 . The gated dissimilarity matrix G AB    600  may be generated from the dissimilarity matrix D AB    500 . 
     A gated dissimilarity matrix may be generated based on the set of marker positions within different wells, and/or other information. For example, the gated dissimilarity matrix for the first well and the second well may be generated based on the set of marker positions within the first well, the set of marker positions within the second well, and/or other information. The element values of the gated dissimilarity matrix may be determined based on the element values of the dissimilarity matrix. One or more element values of the gated dissimilarity matrix may be same as the corresponding element value(s) of the dissimilarity matrix. One or more element values of the gated dissimilarity matrix may be changed from the corresponding element value(s) of the dissimilarity matrix. 
     For example, the element values of the dissimilarity matrix corresponding to the set of marker positions within one well (e.g., the first well) and not corresponding to the set of marker positions within the other well (e.g., the second well) may be changed relative to other element values in the gated dissimilarity matrix. The element values may be directly changed relative to other elements values by changing the element values. The element values may be indirectly changed relative to other elements values by changing the other element values. The element values may be changed relative to other element values in the gated dissimilarity matrix to control how correlation between the wells are determined. The element values may be changed relative to other element values in the gated dissimilarity matrix to ensure that a marker position in one well is correlated to a marker position in the other well. Thus, the gated dissimilarity matrix may be generated to require correlation between the wells to be determined such that marker positions in one well are correlated to marker positions in the other well. 
     In some implementations, the element values corresponding to the set of marker positions within one well (e.g., the first well) and not corresponding to the set of marker positions within the other well (e.g., the second well) may be changed relative to the other element values by increasing the element values to infinity. The other element values of the gated dissimilarity matrix may be the same as the dissimilarity matrix. Such element value determination for the gated dissimilarity matrix may be represented as G[i,j]=D[i,j] ∀i∉ Ωj∈ , ∞ otherwise. The element values corresponding to the set of marker positions within one well (e.g., the first well) and not corresponding to the set of marker positions within the other well (e.g., the second well) may be changed to prevent traversal of a path for determining correlation between the wells. On the other hand, the element values corresponding to the sets of marker positions within both wells (corresponding to the set of marker positions within one well (e.g., the first well) and corresponding to the set of marker positions within the other well (e.g., the second well)) may be preserved to allow traversal of the path for determining correlation between the wells. 
     For example, referring to  FIG. 6 , gated dissimilarity matrix G AB    600  may include cells corresponding to different pairs of positions within the wells well A  510  and the well B  520 . The cells G 1,2  and G A, 2  may correspond to marker positions within only one of the well A  510  and the well B  520 . The cell G 2,2  may correspond to a marker position within both of the well A  510  and the well B  520 . The element value of the cell G 2,2  may be the same as the element value of the cell D 2,2 . The element values of the cells G 1,2  and G A, 2  may be set to infinity. Such change in and/or setting of the element values may prevent the path for determining correlation between the well A  510  and the well B  520  from traversing through the cells G 1,2  and G A, 2 , while allowing traversal of the path through the cell G 2,2  when traversing across the second column. 
     In some implementations, the element values corresponding to the set of marker positions within one well (e.g., the first well) and not corresponding to the set of marker positions within the other well (e.g., the second well) may be indirectly changed relative to other element values by changing the other element values. For example, the element values corresponding to the sets of marker positions within both wells may be changed to require certain traversal of the path for determining correlation between the wells. For example, referring to  FIG. 6 , the element value of the cell G 2,2  may be changed to require the path for determining correlation between the well A  510  and the well B  520  to travel through the cell G 2,2  when traversing across the second column. 
     The correlation component  110  may be configured to determine correlation between different wells based on the gated dissimilarity matrix and/or other information. The element values of the gated dissimilarity matrix may be used to determine the correlation between the wells. The correlation between the different wells may be determined deterministically and/or probabilistically based on the element values of the gated dissimilarity matrix. 
     The correlation determined between different wells may include correlation between marker positions within the different wells. For example, the correlation component  110  may be configured to determine correlation between the first well and the second well based on the gated dissimilarity matrix for the first well and the second well, and/or other information. The correlation component  110  may be configured to determine correlation between one or more marker positions within the first well and one or more marker positions within the second well based on the gated dissimilarity matrix for the first well and the second well, and/or other information. That is, correlation may be determined based on the gated dissimilarity matrix so that a marker position within the first well is correlation with a marker position within the second well. 
     In some implementations, determination of the correlation between the marker position(s) within the first well and the marker position(s) within the second well based on the gated dissimilarity matrix may include generation of one or more paths within the gated dissimilarity matrix. A path may be generated based on a directed walk within the gated dissimilarity matrix and/or other information. A path may represent a scenario of correlation between positions within the different wells. For example, a path may represent a scenario of correlation between position within first well and positions within the second well. In some implementations, a path may include a minimum-cost path. The minimum-cost path may be determined based on a dynamic warping algorithm. For example, the following dynamic time warping algorithm (DTW) and cost function (C p ) may be used to determine the minimum-cost path: 
     
       
         
           
             
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     The element values of the gated dissimilarity matrix may limit and/or restrict how the path may traverse across the gated dissimilarity matrix. For example,  FIG. 7  illustrates an example representation  700  of a gated dissimilarity matrix for a pair of wells. The representation  700  may include columns  712 ,  714 ,  716 ,  718  corresponding to marker positions within one well and rows  722 ,  724 ,  726 ,  728  corresponding to marker position within the other well. The one or more values of the representation  700  along the columns  712 ,  714 ,  716 ,  718  may be changed to prevent and/or allow traversal of the path. For example, the element values corresponding to the set of marker positions within one well (e.g., the first well) and not corresponding to the set of marker positions within the other well (e.g., the second well) may be changed relative to the other element values to obstruct traversal of the path through corresponding elements of the gated dissimilarity matrix. 
     For example, for a minimum-cost path, the values of the representation  700  along the columns  712 ,  714 ,  716 ,  718  that do not cross with the rows  722 ,  724 ,  726 ,  728  may be changed to infinity, thereby preventing transversal of the minimum-cost path through those points. The values of the representation  700  along the columns  712 ,  714 ,  716 ,  718  that crosses with the rows  722 ,  724 ,  726 ,  728  may be preserved, thereby allowing traversal of the path through those points. The points not allowing traversal of path may be shown as dark lines in the representation  700 . The dark lines correspond to walls that block the traversal of the path. The points allowing traversal of path may be shown as open circles  730  in the representation  700 . The open circles  730  may correspond to gates through which the path may traveling in determining correlation between the different wells. Thus, correlation determined between the two wells may include linkage between marker positions in one well and marker positions in the other well. In some implementation, use of a sub-sequence dynamic warping algorithm may result in up to | |−| |+1 sub-segment similarity measures and detailed correlations. Other changes in element values and other types of paths are contemplated. 
     Implementations of the disclosure may be made in hardware, firmware, software, or any suitable combination thereof. Aspects of the disclosure may be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a tangible computer-readable storage medium may include read-only memory, random access memory, magnetic disk storage media, optical storage media, flash memory devices, and others, and a machine-readable transmission media may include forms of propagated signals, such as carrier waves, infrared signals, digital signals, and others. Firmware, software, routines, or instructions may be described herein in terms of specific exemplary aspects and implementations of the disclosure, and performing certain actions. 
     In some implementations, some or all of the functionalities attributed herein to the system  10  may be provided by external resources not included in the system  10 . External resources may include hosts/sources of information, computing, and/or processing and/or other providers of information, computing, and/or processing outside of the system  10 . 
     Although the processor  11  and the electronic storage  13  are shown to be connected to the interface  12  in  FIG. 1 , any communication medium may be used to facilitate interaction between any components of the system  10 . One or more components of the system  10  may communicate with each other through hard-wired communication, wireless communication, or both. For example, one or more components of the system  10  may communicate with each other through a network. For example, the processor  11  may wirelessly communicate with the electronic storage  13 . By way of non-limiting example, wireless communication may include one or more of radio communication, Bluetooth communication, Wi-Fi communication, cellular communication, infrared communication, or other wireless communication. Other types of communications are contemplated by the present disclosure. 
     Although the processor  11  is shown in  FIG. 1  as a single entity, this is for illustrative purposes only. In some implementations, the processor  11  may comprise a plurality of processing units. These processing units may be physically located within the same device, or the processor  11  may represent processing functionality of a plurality of devices operating in coordination. The processor  11  may be separate from and/or be part of one or more components of the system  10 . The processor  11  may be configured to execute one or more components by software; hardware; firmware; some combination of software, hardware, and/or firmware; and/or other mechanisms for configuring processing capabilities on the processor  11 . 
     It should be appreciated that although computer program components are illustrated in  FIG. 1  as being co-located within a single processing unit, one or more of computer program components may be located remotely from the other computer program components. While computer program components are described as performing or being configured to perform operations, computer program components may comprise instructions which may program processor  11  and/or system  10  to perform the operation. 
     While computer program components are described herein as being implemented via processor  11  through machine-readable instructions  100 , this is merely for ease of reference and is not meant to be limiting. In some implementations, one or more functions of computer program components described herein may be implemented via hardware (e.g., dedicated chip, field-programmable gate array) rather than software. One or more functions of computer program components described herein may be software-implemented, hardware-implemented, or software and hardware-implemented 
     The description of the functionality provided by the different computer program components described herein is for illustrative purposes, and is not intended to be limiting, as any of computer program components may provide more or less functionality than is described. For example, one or more of computer program components may be eliminated, and some or all of its functionality may be provided by other computer program components. As another example, processor  11  may be configured to execute one or more additional computer program components that may perform some or all of the functionality attributed to one or more of computer program components described herein. 
     The electronic storage media of the electronic storage  13  may be provided integrally (i.e., substantially non-removable) with one or more components of the system  10  and/or as removable storage that is connectable to one or more components of the system  10  via, for example, a port (e.g., a USB port, a Firewire port, etc.) or a drive (e.g., a disk drive, etc.). The electronic storage  13  may include one or more of optically readable storage media (e.g., optical disks, etc.), magnetically readable storage media (e.g., magnetic tape, magnetic hard drive, floppy drive, etc.), electrical charge-based storage media (e.g., EPROM, EEPROM, RAM, etc.), solid-state storage media (e.g., flash drive, etc.), and/or other electronically readable storage media. The electronic storage  13  may be a separate component within the system  10 , or the electronic storage  13  may be provided integrally with one or more other components of the system  10  (e.g., the processor  11 ). Although the electronic storage  13  is shown in  FIG. 1  as a single entity, this is for illustrative purposes only. In some implementations, the electronic storage  13  may comprise a plurality of storage units. These storage units may be physically located within the same device, or the electronic storage  13  may represent storage functionality of a plurality of devices operating in coordination. 
       FIG. 2  illustrates method  200  for comparing wells. The operations of method  200  presented below are intended to be illustrative. In some implementations, method  200  may be accomplished with one or more additional operations not described, and/or without one or more of the operations discussed. In some implementations, two or more of the operations may occur substantially simultaneously. 
     In some implementations, method  200  may be implemented in one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, a central processing unit, a graphics processing unit, a microcontroller, an analog circuit designed to process information, a state machine, and/or other mechanisms for electronically processing information). The one or more processing devices may include one or more devices executing some or all of the operations of method  200  in response to instructions stored electronically on one or more electronic storage media. The one or more processing devices may include one or more devices configured through hardware, firmware, and/or software to be specifically designed for execution of one or more of the operations of method  200 . 
     Referring to  FIG. 2  and method  200 , at operation  202 , first well information, second well information, and/or other information may be obtained. The first well information may define subsurface configuration of a first well. The first well information may include a first set of values that define the subsurface configuration at a first set of positions within the first well. The second well information may define the subsurface configuration of a second well. The second well information may include a second set of values that define the subsurface configuration at a second set of positions within the second well. In some implementation, operation  202  may be performed by a processor component the same as or similar to the well information component  102  (Shown in  FIG. 1  and described herein). 
     At operation  204 , first well marker information, second well marker information, and/or other information may be obtained. The first well marker information may define a first set of marker positions within the first well. The second well marker information may define a second set of marker positions within the second well. In some implementation, operation  204  may be performed by a processor component the same as or similar to the well marker information component  104  (Shown in  FIG. 1  and described herein). 
     At operation  206 , a dissimilarity matrix for the first well and the second well may be generated. A dimension of the dissimilarity matrix may be defined by a first number of positions within the first set of positions and a second number of positions within the second set of positions. Element values of the dissimilarity matrix may be determined based on comparison of the subsurface configuration of the first well at corresponding positions within the first well and the subsurface configuration of the second well at corresponding positions within second first well, and/or other information. In some implementation, operation  206  may be performed by a processor component the same as or similar to the dissimilarity matrix component  106  (Shown in  FIG. 1  and described herein). 
     At operation  208 , a gated dissimilarity matrix may be generated from the dissimilarity matrix based on the first set of marker positions within the first well, the second set of marker positions within the second well, and/or other information. The element values of the dissimilarity matrix corresponding to the first set of marker positions and not corresponding to the second set of marker positions within the second well may be changed relative to other element values in the gated dissimilarity matrix. In some implementation, operation  208  may be performed by a processor component the same as or similar to the gated dissimilarity matrix component  108  (Shown in  FIG. 1  and described herein). 
     At operation  210 , correlation between one or more marker positions within the first well and one or more marker positions within the second well may be determined based on the gated dissimilarity matrix and/or other information. In some implementation, operation  210  may be performed by a processor component the same as or similar to the correlation component  110  (Shown in  FIG. 1  and described herein). 
     Although the system(s) and/or method(s) of this disclosure have been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred implementations, it is to be understood that such detail is solely for that purpose and that the disclosure is not limited to the disclosed implementations, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present disclosure contemplates that, to the extent possible, one or more features of any implementation can be combined with one or more features of any other implementation.