NO20131641A1 - MULTI-SEGMENT CRACKS - Google Patents

Abstract

A method may include identifying a discrete natural crack in a three-dimensional environment that includes a reservoir modeled by a three-dimensional grid model, which represents the discrete natural crack via a multi-segment model in a two-dimensional region within the three-dimensional grid model, which defines at least one fluid communication connection. the multi-segment model and the three-dimensional grid model defining boundary conditions for the multi-segment model, and solving the multi-segment model for the at least one connection, and the boundary conditions for providing values for fluid flow in the two-dimensional region.

Description

MULTISEGMENT CRACKS

BACKGROUND

[0001] Natural fractures can enable fluid storage, fluid flow, etc. Modeling natural fractures can facilitate understanding of fluid storage, flow, etc. Various methods described in this document concern the modeling of cracks.

SUMMARY

[0002] A method may include representing a discrete natural fracture with a multi-segment model in a two-dimensional region within a three-dimensional grid model, defining at least one connection for fluid communication between the multi-segment model and the three-dimensional grid model, which defines boundary conditions for the multi-segment model, and solving the multi-segment model given at least one connection and the boundary conditions, to provide values for fluid flow in the two-dimensional region. A system may include a processor to process information and memory to store modules, such as a reservoir module to model a reservoir in an underground three-dimensional environment via a three-dimensional grid model, a natural fracture module to model a natural fracture via a multi-segment model in a two-dimensional region, and a solution module for solving values of fluid flow in a fracture network based at least in part on modeling a natural fracture with a multi-segment model. Computer-readable storage media may include computer-executable instructions for instructing a computer system to grid a natural fracture region using multiple segments positioned with respect to a three-dimensional grid model, to solve a system of equations associated with the multiple segments to provide a solution, to introduce the solution as input to a system of equations associated with the three-dimensional grid model and solve the system of equations associated with the three-dimensional grid model.

[0003] This summary is provided to introduce a selection of terms which are further described below in the detailed description. This summary is not intended to identify key features or essential features of the subject matter for which a patent is sought, nor is it intended to be used as an aid in limiting the scope of the subject matter for which a patent is sought.

BRIEF DESCRIPTION OF THE FIGURES

[0004] Functions and advantages of the described implementations can be more easily understood by reference to the following description seen in connection with the accompanying figures.

[0005] Fig. 1 illustrates an example of a system that includes various components to model a geological environment;

[0006] Fig. 2 illustrates an example of a flowchart that includes a solver for solving a system of equations, and an example of a multi-segment well model;

[0007] Fig. 3 illustrates an example of a method for modeling cracks;

[0008] Fig. 4 illustrates an example of a method for modeling cracks in an environment;

[0009] Fig. 5 illustrates an example of a method for modeling cracks and wells in an environment;

[0010] Fig. 6 illustrates an example of a system, examples of modules, and an example of a crack network;

[0011] Fig. 7 illustrates an example of an environment that includes one or more natural cracks;

[0012] Fig. 8 illustrates examples of graphical user interfaces;

[0013] Fig. 9 illustrates an example of a method;

[0014] Fig. 10 illustrates an example of a solution scheme and an example of a method;

[0015] Fig. 11 illustrates an example of a solution scheme and an example of a method; and

[0016] Fig. 12 illustrates example components of a system and a network system.

DETAILED DESCRIPTION

[0017] The following description includes the best way currently known to practice the described implementations. This description should not be taken as limiting, it is only designed to describe the general principles of the implementations. The scope of the described implementations should be determined by reference to the issued patent claims.

[0018] Natural fractures may enable fluid storage, fluid flow, etc. As an example, a fluid reservoir may exist in an underground formation with natural fractures. Fluid can spread from the fluid reservoir into natural cracks that cross the fluid reservoir. In some cases, for a subterranean formation, more fluid may reside in natural fractures crossing a reservoir than in the reservoir itself (e.g., consider oil reserves in a large carbonate field).

[0019] As an example, a naturally fractured reservoir may include a rock matrix along with a set of natural fractures. In such an example, the rock matrix can be described by different properties (e.g. lithology properties, fluid properties, etc.). Natural cracks can include those formed due to stress, deformation, etc., for example due to forces associated with plate tectonic activity. Where multiple natural fractures have been cultivated in a formation they can form natural fracture networks which can, for example, contribute to storage (eg via porosity) and fluid flow (eg via permeability, transmissibility, etc.). When it comes to fluid production from such a reservoir, natural cracks can produce relatively fast fluid flow, and they can exist in different length scales from relatively small

(eg on the order of meters or less) to a scale that can be compared to one or more dimensions of the reservoir. For example, larger fractures can form "fracture corridors", which can, for example, be identified and mapped for a formation (eg, based on seismic data, seismic data interpretation, etc.).

[0020] With respect to natural fractures of shorter length (e.g. from a distribution of natural fractures), for example those below the resolution of a reservoir simulation can be simulated using a continuous approach (e.g. using one or more types of porosity model such as a dual porosity model). For larger natural fractures (eg, with a distribution of natural fractures), such as those having a dimension greater than a dimension of a reservoir model, such natural fractures can be modeled using fracture representations that can be mathematically linked to the reservoir model. For example, a workflow may include adding natural fracture representations to an existing model of a rock matrix coupled with a solution method to efficiently solve the resulting coupled sets of equations for modeling flow, etc. In such an example, the fracture representations may be dimensionless in a dimension of consideration of a dimension within the existing geological model. As an example, a workflow may include parameterizing one or more natural fracture representations without routing (eg, without modifying an existing geological model grid), the one or more fracture representations at a geological scale. Such an approach can reduce the preprocessing requirements for a geological model, while providing an opportunity to accurately represent the characteristics such as storage, flow, etc. of the one or more natural fractures.

[0021] As an example, natural cracks can be at least partially characterized by orientation and size (e.g. possibly in two dimensions with a dimensionless third dimension). As an example, a natural crack can be characterized in part by a length/width ratio, which can be greater than 100:1. Natural fissures can exist in clusters, for example, several hundred feet apart in a main direction (eg, orientation). Such natural fractures can improve permeability locally and can be favorable or unfavorable for methods to increase recovery. For example, natural cracks can relieve the pressure used by a hydraulic fracturing process in the borehole that is carried out to create artificial cracks. In such an example, fewer artificial cracks can be made, a smaller volume of artificial cracks can be made, etc. Furthermore, a mixed or hybrid network can be made that includes both artificial and natural cracks. As an example, where a natural fracture is "dry", fluid can flow from an artificial fracture into the natural fracture, which can be beneficial or detrimental, depending on the type of fluid flowing, location of the natural fracture, etc. As a for example, a hydraulic fracturing process can "reactivate" a natural fracture (or natural fractures). Where reactivation promotes flow of an undesired fluid (eg, water), the recovery of a desired fluid or fluids may be affected (eg, with respect to recovery, treatment, etc.). As an example, reactivating a natural fracture or fractures can be beneficial and improve the efficiency of a fracturing process.

[0022] As an example, modeling a natural fissure can improve decision making based on determinations of whether the natural fissure is favorable or unfavorable for one or more particular objectives. For example, if a natural fracture stores some amount of a desired fluid (e.g., a significant amount), modeling can improve decision-making as to where a producer well and an injection well can be placed to recover at least some of the desired fluid from the natural fracture (e.g. consider modeling flow due to applied pressure, breakthrough, recovery of desired fluid, etc.). As another example, if a natural fracture is substantially empty of a desired fluid, a recovery process may aim to avoid creating pathways that may cause flow of the desired fluid from another reservoir (e.g., a fluid reservoir, a filled crack etc.) to the natural crack. As yet another example, if a natural fracture stores an unwanted fluid, an extraction process for a desired fluid may aim to avoid the formation of pathways that could lead to mixing of the unwanted fluid with the desired fluid.

[0023] As an example, a natural fracture can be characterized with respect to a reservoir (eg with respect to an extraction process, eg hydraulic fracturing). As another example, a natural fracture may be characterized with respect to a chemical process such as acid treatment (eg, a process that includes introducing an acidic material into a natural fracture in a carbonate field to enlarge, widen, etc. the natural fracture ). Characterization of a natural crack may include a characteristic that is beneficial, detrimental, or neutral with respect to one or more objectives.

[0024] As an example, the permeability in a crack can be greater than in the material surrounding the crack. As mentioned, the cracks can be natural or artificial. An artificial fracture can be created by, for example, injecting fluid into a borehole to increase the pressure in the borehole beyond a level sufficient to cause fracturing of a surrounding formation or formations. In one such example, an artificial fracture is in fluid communication with the borehole. Thus, an artificial fracture can generally be considered to be part of a network that includes a borehole. In the case of chemical processes, such as acid treatment, such a process can be applied to a natural fracture or an artificial fracture (eg a hydraulic fracture). Acid treatment can be considered a stimulation operation where acid (e.g. hydrochloric acid) is injected into a formation (e.g. carbonate formation), so that the acid etches the fracture surfaces and forms conductive channels. As an example, hydrochloric acid can be introduced into a crack in a limestone formation to react with limestone to form calcium chloride, carbon dioxide and water. As another example, one can consider a dolomite formation where magnesium chloride is also formed. Acids other than hydrochloric acid can be used (e.g. hydrofluoric acid, etc.). As an example, a mixture of acids can be used.

[0025] In the case of pressure fracturing, the pressure to fracture a formation can be estimated in part based on a fracture gradient for the formation (eg, kPa/m or psi/ft). As an example, methods of creating the crack may involve combustion or explosion (eg, flammable gases, explosives, etc.). In the case of hydraulic fracturing, injected fluid (eg, water, other fluid, mixture of fluids, etc.) may be used to open and expand a fracture from a borehole, and may be used to transport a proppant through a fracture. A plugging agent may include sand, ceramic, or other particles that may keep the fractures open, at least to some extent, after a hydraulic fracturing treatment (eg, to preserve pathways for flow, whether, for example, from a wellbore to a reservoir or vice versa).

[0026] Artificial fractures can be oriented in any of a number of directions, which can be controlled at least to some extent (e.g., based on borehole direction, size, and location; based on pressure and pressure gradient with respect to time; based on injected material; based on the application of a proppant; based on existing load, etc.).

[0027] Hydraulic fracturing can be particularly useful for the production of natural gas, as well as for the production of so-called unconventional natural gas. A larger proportion of unconventional natural gas reserves worldwide can be categorized as undeveloped resources. Reasons for a lack of production from such reserves may include an industry focus on producing gas from conventional reserves and difficulties in producing gas from unconventional gas reserves. Unconventional gas reserves can be characterized by low permeability where gas has problems flowing into the wells without any kind of assistance. For example, one way to assist gas flow from an unconventional reservoir may involve hydraulic fracturing to increase the overall permeability of the reservoir.

[0028] Underground formations and related physical phenomena can be modeled using different methods. Such methods may involve routing, or other discretization, of one or more underground volumes that make up a formation. When a formation includes one or more fluids (eg, gas, liquid, or both), a modeling approach may also include formulation equations that incorporate physical phenomena such as pressure, saturation, and composition. As an example, an oil and gas field that extends through a volume measured in kilometers can be considered. A model of such a field may include many thousands of grid cells or grid points, where each cell or point has associated pressure, saturation and composition values, which may be unknown equations, for example possibly with respect to time. Given the initial values (e.g. the initial conditions) and the boundary values (e.g. the boundary conditions), an iterative solution method can be used in the model equations to determine the unknown equations at one or more points in time (e.g. steady state or transient).

[0029] As mentioned, a crack can be characterized according to an aspect ratio. As an example, a crack may include a length to width ratio greater than about 1000:1. As an example, a crack may include a width of the order of about one centimeter and a length of the order of about a hundred meters or more. With respect to modeling such a crack with grid cells or grid points, many such grid cells or grid points may be involved due to the extent of the crack. Consequently, the number of unknowns for a simulation can increase, which in turn can increase the demands on computing power.

[0030] As an example, a crack can be modeled using several connected segments. As an example, a segment can be defined as including features to characterize a natural crack. For example, a segment may be defined to include properties corresponding to a dual porosity model or "Darcy" model (eg for flow in a permeable medium driven by a pressure gradient). As an example, a reservoir (eg, a naturally fractured reservoir, a drusy carbonate reservoir, etc.) may be classified as a dual porosity reservoir (eg, a reservoir that includes high-permeability regions and low-permeability regions).

[0031] As an example, a fracture model can be defined using segments and associated equations for storage, flow, etc. for example to or from a reservoir. In such an example, a reservoir model may be defined using grid cells that include various geophysical features (eg, faults, horizons, etc.).

[0032] As an example, a segment to model part of a natural crack may be defined by a segment "pipe" and a node. As an example, sources, sinks, etc. can be "connected" to one or more segments that model a natural fracture. For example, consider a reservoir as a source or sinks in fluid communication with a natural fracture. As an example, a model of a natural fracture may include mathematical connections to one or more grid cells in a reservoir model. As an example, for modeling storage, flow, etc. in a fracture, a segment can be associated with equations to model multiphase fluid in a porous medium. For example, such equations may describe a Darcy flow model for each phase flow (eg, a Darcy flow model for phase pressure drop with multiple independent variables for each phase molar rate).

[0033] As mentioned, a reservoir model may include a three-dimensional grid (eg spatial grid) that can be iterated over time (eg temporal to provide a four-dimensional model). As an example, a reservoir can extend over hundreds of square kilometers and be several kilometers down in depth. The expansive nature of such a reservoir can draw in different types of physical phenomena. Such phenomena can exhibit macro-scale, micro-scale or a combination of macro- and micro-scale behaviour. Attempts to capture microscale phenomena via increased reservoir route density or more route densities can increase the demands on computing power and other resources. For example, increasing two-dimensional grid density by reducing the grid block spacing from 10 meters by 10 meters to 5 meters by 5 meters can significantly increase computing power requirements (e.g., a fourfold increase). Thus, some trade-offs may exist between modeling micro details and resource requirements.

[0034] Modeling cracks with grid blocks that approximate the crack geometry (eg, possibly less than about a couple of centimeters) can result in grid blocks that tend to be smaller in thickness than surrounding grid cells. In such an approach, size differences can lead to inaccuracies in the simulation, instabilities and small time steps. For example, a multi-segment approach to modeling cracks can be used without resorting to the introduction of grid blocks which can give rise to size inequality problems. As an example, a multi-segment approach to model one or more cracks may be followed by a grid approach, for example where the results of the multi-segment approach inform the grid approach. Such an example can augment a grid approach, for example by refining orientation, placement, etc. of a natural fracture using a multi-segment approach.

[0035] As an example, a method may include multi-segment modeling of fluid communication between: (i) one or more natural fractures and a reservoir; (ii) one or more natural cracks and one or more artificial cracks; (iii) one or more natural fractures and one or more boreholes; (iv) one or more artificial fractures and a reservoir; (v) one or more artificial fractures and one or more boreholes. In such an example, combinations can be modelled, so that a multi-segment model models indirect fluid communication between different types of units. For example, an artificial fracture can be modeled via a multi-segment model to be in fluid communication with a reservoir via a natural fracture. As noted, depending on the process implemented to create an artificial fracture, there may be inherent fluid communication with a borehole (eg via a borehole where pressure has been applied to create the artificial fracture).

[0036] As an example, a multi-segment model may include different types of segments. For example, a segment may be provided that may characterize conditions of the injection or production performance (eg, a segment associated with equations describing multiphase fluid flow entering or exiting a wellbore). As another example, a segment can be provided that can characterize multiphase fluid flow in a porous medium (eg, equations that can describe a Darcy flow model for each phase flow). As an example, a segment may be provided that may characterize a chemical process, a pressure process, etc. that may act on a formation (eg, acid treatment, fracturing, etc.).

[0037] As an example, a solution method may include solving a system of nonlinear equations for a multi-segment model that models one or more natural cracks. A solution for such a model can in turn be a component of a general nonlinear reservoir solution procedure. For example, a general reservoir solution procedure may employ a converged solution of a multi-segment model that models one or more natural fractures.

[0038] As an example, a multi-segment model may include discretizing and parameterizing one or more fracture corridors with respect to a reference system that may improve flexibility in manufacturing and computational efficiency for a field-wide fractured reservoir model. As an example, a multi-segment model can utilize the properties of a well model specification associated with a simulation framework. For example, the INTERSECT™ framework (Schlumberger Limited, Houston, Texas) includes a well model specification that specifies segments to create a multi-segment well model. In such an example, a "well" segment can be adapted to model a natural fracture, for example by providing one or more suitable boundary conditions. As an example, a boundary condition can be applied to a "well" segment that avoids a direct contact between that segment to the surface via a borehole so that the "well" segment can be used to model a natural fracture. Furthermore, a well model specification may include a type of segment to connect a well segment to a reservoir where this segment models a porous matrix instead of a channel (eg, a borehole). As an example, a natural fracture can be modeled using porous matrix segments (eg Darcy segments) with suitable boundary conditions (eg no direct flow to the surface, etc.).

[0039] As an example, a single natural fissure, multiple natural fissures (eg, possibly as a natural fissure corridor) can be represented as a two-dimensional "grid" or multi-segment network. In such an example, a 2D grid representing a natural crack can be described as multiple segments specified according to the equations of a porous medium (eg, Darcy segments).

[0040] As an example, a method may include solving equations for individual natural fractures in an interlaced manner relative to a reservoir model grid, which may provide a more robust solution than an approach that involves the natural fracture equations being solved simultaneously with the equations in the reservoir model grid.

[0041] As an example, a method may include placing one or more 2D grids with respect to a pre-existing grid (eg, a reservoir model grid). In such an example, a 2D grid that for example lacks a thickness (e.g. dimensionless in one dimension) can be inserted (e.g. mathematically) into an already existing grid along a grid line, or it can be inserted by using a process that includes grid cell splitting for pre-existing grid cells intersected by the 2D grid. Such a process may be less demanding than a process that aims to represent a natural crack with its thickness, which may involve introducing the grid cells into the already existing grid, where the introduced grid includes a dimension smaller than that of the already existing grid to the region where the grid is to be inserted.

[0042] As an example, a well model configured to model a natural fracture may be run with a boundary condition where the flow is zero, and this may connect a 2D grid for a multi-segment natural fracture to a reservoir grid.

[0043] As an example, a system may provide for the modeling of one or more fracture corridors using a multi-segment approach together with the use of a continuous dual porosity approach (eg for a subsurface region) to create a representative hybrid model, eg where large fracture corridors can be modeled explicitly using the multi-segment approach and an associated micro-fracture system can be represented by a dual (or multiple) porosity characterization model(s).

[0044] In terms of workflow, a reservoir engineer can start modeling a reservoir with some information about very large fracture details (eg, from seismic data, well testing, well logging, etc.); but the reservoir engineer may have little information and hence uncertainty about fractures or microfractures that are too small to be identified, which may have a significant influence on storage, flow, etc. Since a fracture system can affect long-term reservoir performance, in executing a work flow, the reservoir engineer may attempt to using multiple simulation models in an attempt to understand the impact of reservoir uncertainties and the variance in the characterization of the fracture system within the measurement tolerances of the production and recovery performance of the field.

[0045] As an example, given a system that includes modules for implementing a multi-segment model for one or more natural fractures, a reservoir engineer may perform a workflow that includes mapping natural fractures using available information to a map, and modeling natural cracks of the map using a multi-segment model. Further, the reservoir engineer may optionally perform a workflow that includes mapping one or more alternative natural fracture maps (eg, maps that may include possible alternative characteristics). For example, a workflow may include one or more of an uncracked base case, crack map, and the resulting crack representations, which can be fed into a simulator to enable simulation. In such an example where well performance is predicted and historical data exists, predicted well performance can be compared to the historical data.

[0046] If a mathematically stable uncracked base case exists in a reservoir grid model, a method can, as an example, include the introduction of 2D grids that represent natural cracks. In such an example, 2D grids can be introduced in series or parallel to vary the intensity and conductivity of the cracks. As such, such an approach can avoid re-routing the uncracked case of the base grid model and enable investigation of the effect of a given crack or crack set while having an assurance that the underlying base case remains stable. As an example, a multi-segment approach to natural fracture modeling can improve convenience, flexibility and resolution of the influence and sensitivity of fracture storage, flow, etc. on reservoir performance, recovery, etc. As an example, a multi-segment approach to natural fracture modeling can improve understanding of well placement, hydraulic fracturing, fluid injection, chemical treatment, etc. which can be linked to one or more objectives (e.g. production of a desired fluid).

[0047] Fig. 1 shows an example of a system 100 that includes different management components 110 to manage different aspects of a geological environment 150 (eg, an environment that includes a sediment pool, a reservoir 151, one or more fractures 153, etc. .). For example, the handling components 110 may allow direct or indirect control of sensing, drilling, injecting, pumping out, etc. with respect to the geological environment 150.1 in turn, additional information about the geological environment 150 may become available as feedback 160 (e.g. possibly as input to one or more of the handling components 110).

[0048] In the example in fig. 1, the handling components 110 include a seismic data component 112, another information component 114

(e.g. well/logging data), a processing component 116, a simulation component 120, an attribute component 130, an analysis/visualization component 142 and a workflow component 144.1 operation, seismic data and other information from components 112 and 114 can be fed into the simulation component 120.

[0049] In an example embodiment, the simulation component 120 may depend on the entities 122. The entities 122 may include earth entities or geological objects such as wells, surfaces, reservoirs, etc. In the system 100, the entities 122 may include virtual representations of actual physical entities such as is reconstructed for the purpose of simulation. The entities 122 may include entities based on data obtained via sensing, observation, etc. (eg, the seismic data 112 and other information 114). A unit can be characterized by one or more properties (eg a geometric column cell of a soil model can be characterized by a porosity property). Such properties may represent one or more measurements (e.g. acquired data), calculations, etc.

[0050] In an example design, the simulation component 120 may depend on a software framework, for example an object-based framework. In such a framework, the entities can include entities based on predefined classes to facilitate modeling and simulation. A commercially available example of an object-based framework is the MICROSOFT®.NET™ framework (Redmond, Washington), which provides a set of extensible object classes. In the NET™ framework, an object class encloses a module of reusable code and associated data structures. The object classes can be used to create object instances for use by a program, script, etc. For example, borehole classes can define objects to represent boreholes based on well data.

[0051] In the example in fig. 1, the simulation component 120 may process information to match one or more attributes specified by the attribute component 130 which may include a library of attributes. Such processing may occur prior to input to simulation component 120 (e.g. consider processing component 116). As an example, the simulation component 120 may perform operations on the input information based on one or more attributes specified by the attribute component 130. In an exemplary embodiment, the simulation component 120 may construct one or more models of the geological environment 150 that may be relied upon to simulate the behavior of the geological environment 150 (e.g. that respond to one or more actions, either natural or artificial). In the example in fig. 1, the analysis/visualization component 142 may enable interaction with a model or model-based results. As an example, output from the simulation component 120 may be fed into one or more other workflows as indicated by a workflow component 144 .

[0052] As an example, the simulation component 120 may include one or more functions of a simulator such as the ECLIPSE™ reservoir simulator (Schlumberger Limited, Houston Texas), the INTERSECT™ reservoir simulator (Schlumberger Limited, Houston, Texas), etc. As an example, a reservoir or reservoirs are simulated considering one or more enhanced recovery methods (e.g. consider a thermal process such as SAGD, etc.).

[0053] In an example embodiment, the management components 110 may include the functions of a commercially available simulation framework such as the "seismics for simulation" program PETREL® (Schlumberger Limited, Houston, Texas). The PETREL® frame has components that make it possible to optimize exploration and development operations. The PETREL® framework includes seismic-to-simulation software components that can output information for application in increasing reservoir performance, for example by improving the productivity of the resource team. Through the application of such a framework, different professionals (eg geophysicists, geologists and reservoir engineers) can develop a collaborative workflow and integrate operations to streamline processes. Such a framework can be considered an application, and can be considered a data-driven application (eg where data is entered for the purpose of simulating a geological environment).

[0054] In an example embodiment, various aspects of the handling components 110 may include add-ons or extensions that operate according to specifications in a framework environment. For example, a commercially available framework, marketed as the OCEAN® framework (Schlumberger Limited, Houston, Texas) allows plug-ins (or extensions) to be built into a PETREL® framework workflow. The OCEAN® framework environment utilizes

.NET® tools (Microsoft Corporation, Redmond, Washington) and offers stable and user-friendly interfaces for efficient development. In an example design, various components may be implemented as add-ons (or extensions) that conform to and operate according to specifications in a framework environment

(eg according to application programming interface (API) specifications, etc.).

[0055] Fig. 1 also shows an example of a framework 170 that includes a model simulation layer 180 together with a framework service layer 190, a framework core layer 195 and a module layer 175. The framework 170 may include the commercially available OCEAN® framework where the model simulation layer 180 is the commercially available model-focused software package PETREL®, which hosts the OCEAN® framework applications. In an example design, the PETREL® software can be considered a data-driven application. The PETREL® software can include a framework for model building and visualization. Such a model can include one or more grids.

[0056] The model simulation layer 180 can provide domain objects 182, act as a data source 184, provide rendering 186 and provide various user interfaces 188. Rendering 186 can provide a graphical environment where applications can display their data while the user interfaces 188 can provide the components of the user interface for a program a common expression.

[0057] In the example in Fig. 1, the domain objects 182 can include unit objects, property objects and possibly other objects. Property objects can be used to represent wells, surfaces, reservoirs, etc. geometrically, while property objects can be used to provide both property values, data versions and display parameters. For example, an entity object may represent a well where a property object provides log information as well as version information and display information (eg to display the well as part of a model).

[0058] In the example in fig. 1, data can be stored in one or more data sources (or data stores, generally physical data storage units), which can be in the same or different physical locations and accessible via one or more networks. The model simulation layer 180 can be configured to model projects. As such, a particular project can be saved where saved project information can include inputs, models, results and cases. When completing a modeling session, a user can thus save a project. At a later time, the project can be accessed and restored using the model simulation layer 180 which can recreate instances of the relevant domain objects.

[0059] In the example in Fig. 1, the geological environment 150 may be equipped with any of a number of sensors, detectors, activators, etc. For example, the equipment 152 may include communication circuits for receiving and transmitting information with respect to one or multiple networks 155. Such information may include information associated with downhole equipment 154, which may be equipment to obtain information, to assist in resource recovery, etc. Other equipment 156 may be located at a distance from a well site and include sensing circuits, detection circuits, radiation circuits or other circuits. Such equipment may include storage and communication circuits for storing and communicating data, instructions, etc.

[0060] As mentioned, the simulation component 120 in Fig. 1 may include one or more functions of a simulator such as the ECLIPSE™ reservoir simulator, the INTERSECT™ reservoir simulator, etc. Fig. 2 shows a flowchart 200 for an example of a process for simulating physical phenomena connected with an underground formation 210, which can for example be part of the geological environment 150 in flg. 1 or another geological environment. Fig. 2 also shows an example of a multi-segment well model 270 which can provide for the modeling of wells in the underground formation 210.

[0061] In the example in fig. 2, a grid block 220 provides for grid division of a surface, volume, etc. to represent the underground formation 210, while a model block 230 provides equations to model physical phenomena associated with the underground formation 210. The equations in the model block 230 can be discretized or on otherwise described with respect to one or more grids similar to that provided by the grid block 220 (eg, structured, unstructured, structured, and unstructured).

[0062] As an example, the equations can be solved to describe how values of dependent variables such as pressure (e.g. including capillary pressure, temperature, saturation, mole fraction (e.g. liquid mole fraction, vapor mole fraction, aqueous mole fraction, etc.), and mass rate (e.g. via mass conservation equations) may change with time. The equations may include various property-related terms, such as porosity, pore volume, viscosity, bulk density, gravitational density and permeability. As an example, the equations may be formulated in terms of molar flow (e.g. . to provide values that readily illustrate phenomena such as reaction conversion and stoichiometry).

[0063] As an example, reservoir simulation may include numerical solution of a system of equations describing the physics that determine a certain behavior of multicomponent, multiphase fluid flows in porous media in an underground reservoir. A system of equations can be formulated as coupled nonlinear partial differential equations (PDEs). Such PDEs can be discretized spatially and possibly temporally with respect to one or more grids. Systems of equations can be solved for unknowns using an iteration process. For example, iterations may occur for a series of time steps until a prescribed time is reached.

[0064] In the example in Fig. 2, a linearization block 240 provides for the linearization of a system of equations such as those provided by the model block 230. For example, linearization of a non-linear system of equations can occur by means of a Newton-Raphson method that involves forming of a Jacobi matrix of derivatives with respect to various unknowns. As an example, the underground formation 210 may be or is planned to be intersected by one or more wells. In such an example, a system of equations may include a reservoir part and a well part. With respect to the order of equations describing such parts, the introduction of the well part may affect one or more of order, matrix size, etc. compared to a system of equations for a reservoir without one or more wells. For example, a reservoir part may result in a diagonally structured Jacobi matrix (eg with some diagonal bandwidth), while a well part may result in the addition of boundaries to the diagonally structured Jacobi matrix.

[0065] For example, unknown values may include pressure values, "P", and saturation values, "S". For example, one or more grids may be imposed on an area of interest in a reservoir model to define a plurality of cells, each of which has one or more unknown properties associated therewith. Examples of unknown properties may include pressure, temperature, saturation, permeability, porosity, etc.

[0066] A solution block 250 can provide for solving a linear system of equations (eg a system of linear equations), for example for a specific time. As an example, a solver block 250 may implement one CPR method per CPR method block 260 (see, e.g., Wallis "Incomplete Gaussian Elimination for Preconditioning of Generalized Conjugate Gradient Acceleration", SPE Reservoir Simulation Symposium, Nov. 15-18, 1983, SPE 12265). In the example in fig. 2, the Solver block 250 may iterate in an attempt to reach one or more convergence criteria

(eg acceptable error). Where time is involved, time can be increased (eg via a time step) after convergence has been achieved for a prior time.

[0067] For example, a matrix can be arranged in a cell-by-cell layout where the cells have associated unknown factors. Such a matrix can include both zero cells and non-zero cells. The size or shape of a block can be determined by neighboring cells or other conditions. Furthermore, the properties of a numerical method may have an effect on one or more of block size, shape, etc. (eg order of the finite difference method, etc.).

[0068] Regarding the multi-segment well model 270, the nodes and segment pipes are shown for an example of a reservoir and a wellbore to model flow between the wellbore and the reservoir (eg, via grid cells that model the reservoir). As shown in the example in fig. 2, the multi-segment well model 270 may provide for the discretization of a well into a number of one-dimensional segments (eg, lines), where each of the segments includes a node and a segment pipe. In the multi-segment well model 270, a segment may include no connections to a reservoir grid cell or may include one or more connections to a reservoir grid cell. Such a model can, for example, model black three-phase oil, using mass conservation equations and a pressure drop equation associated with each well segment. As an example, well equations can be solved along with reservoir equations to provide pressure, flow rates (eg, mass flow rates, volume flow rates, velocities, etc.) and composition (eg, phase composition, etc.) in each segment.

[0069] As an example, the multi-segment well model 270 may be part of a well model specification of a frame such as the INTERSECT™ frame. As an example, such a well model specification can be adapted to model one or more natural fractures and possibly one or more artificial fractures. In such an example, one or more wells may be modeled in addition to one or more natural fractures, etc. For example, given a multi-segment representation of a natural fracture, a segment may be introduced that mathematically connects the natural fracture to a well. In such an example, a boundary condition or type of segment may exist to establish the mathematical connection, such as a Darcy segment of a porous natural fracture to a borehole segment of a well (eg, an open channel for fluid flow). In such a way, fluid communication can be modeled between a natural fracture and another unit in a multi-segment model. As an example, segments can be introduced to form a 2D grid for a fracture (eg where the 2D grid can be mathematically connected to a 3D grid used to model an underground formation). For example, the segments can form a plane that mathematically represents a crack for the purpose of modeling flow in the crack, from the crack and in the crack. In such an example, the flow may be for one or more fluids (eg, liquid, gas, injection fluid, production fluid, etc.). As mentioned, flow can be in the form of mass flow rate, volume flow rate, velocity, etc.

[0070] Fig. 3 shows an example of a method 300 which can be a workflow, for example for the performance of a reservoir engineer, etc. The method 300 includes an analysis block 310 to analyze the data and a decision block 320 to determine whether one or more cracks exists based at least in part on the data analysis. Where decision block 320 determines that no fractures exist, method 300 continues to a building block 330 to construct a model, which may be, for example, a reservoir model (eg, a model that includes a grid for modeling a three-dimensional underground region). In method 300, where decision block 320 determines that cracks exist, another decision block 340 determines whether at least some of the cracks exist as discrete cracks. For example, the decision block 340 may determine whether the data analysis of the analysis block 310 provides sufficient information regarding the existence of one or more discrete cracks that may be amenable to modeling using a multi-segment model. Where decision block 340 determines that no discrete cracks exist, method 300 continues to a building block 350 to construct a model that may include a continuous approach for modeling the existence of cracks (eg, small-scale cracks that cannot be considered "discrete" with respect to one or more of the criteria).

[0071] If decision block 340 determines that one or more discrete cracks exist, method 300 proceeds to a building block 360 to construct a discrete crack model. As shown in the example in fig. 3, the method 300 may include building a discrete crack model via a representation block 370 to represent one or more discrete cracks in 2D via segments and optionally represent at least one of the segments including one or more connections. Given a discrete fracture model, the method 300 may include a simulation block 380 to simulate flow in the one or more discrete fractures. In one such example, simulation of flow may include simulation of Darcy flow (eg, where one or more of the segments of a multi-segment model include equations describing Darcy flow).

[0072] For example, a simulation can simulate a state in a system. For example, a relatively stable state may exist in an underground formation where liquid is stored in one or more natural cracks in a reservoir. In such an example, a simulation can simulate a storage condition that provides information on whether or not liquid is stored in one or more natural cracks. As an example, such a simulation may not involve intermediate time steps to reach the steady state. As an example, given a steady-state solution, a well, artificial fracture, etc. can be introduced into a multi-segment model and a simulation model performed to model flow, for example from a well to a natural fracture, from an artificial fracture to a natural fracture, from a reservoir to a natural fracture, etc. As an example, a well can be a production well, an injector well or another type of well.

[0073] The method 300 is shown in fig. 3 in connection with various computer readable media (CRM) blocks 311, 321, 331, 341, 351, 361, 371 and 381. Such blocks generally include instructions suitable for execution by one or more processors (or processor cores) to instruct a computing device or a system to perform one or more actions. Although several different blocks are shown, a single medium may be configured with instructions to allow, at least in part, to perform various operations of the method 300. As an example, a computer-readable medium (CRM) may be a computer-readable storage medium.

[0074] Fig. 4 shows an example of a method 400 that includes an identification and representation block 410 for identifying and representing a natural fracture in a 2D region in a 3D environment with a reservoir, a definition block 420 for defining one or multiple connections for fluid communication between the 2D region and the reservoir in the 3D environment, a definition block 430 to define boundary conditions with respect to at least the 2D region (eg, consider a zero velocity condition for a natural fracture connected to a reservoir), a solver block 440 for solving the flow in the 2D region (eg, subject to the boundary conditions), and a solver block 450 for solving flow in the 3D environment based at least in part on a solution provided by the solver block 440 for flow in the 2D region .

[0075] As indicated in the example in fig. 4, a solution of the solution block 450 may inform an update block 412 to update one or more regions, an update block 422 to update one or more connections, and an update block 432 to update one or more boundary conditions. In such a manner, one or more loops may exist to investigate spatial variations, property variations, etc. As an example, one or more loops may refine a solution or solutions, for example, to more accurately model flow in a 3D environment that includes at least one 2D region, which may constitute a natural crack.

[0076] In the example in fig. 4, a 2D region can be a multi-segment region where several segments represent a natural crack. As an example, method 400 may include representing entities such as wells, artificial fractures, etc. In such an example, blocks 420 and 430 may provide appropriate connections and boundary conditions, respectively.

[0077] The method 400 is shown in fig. 4 in connection with various blocks on computer readable media (CRM) 411, 421, 431, 441 and 451. Such blocks generally include instructions suitable for execution by one or more processors (or processor cores) to instruct a computing device or system to execute one or multiple actions. Although different blocks are shown, a single medium may be configured with instructions to allow, at least in part, to perform various operations of the method 400. As an example, a computer-readable medium (CRM) may be a computer-readable storage medium.

[0078] As an example, a method may include identifying a discrete natural fracture in a three-dimensional environment that includes a reservoir, the underground formation, and the reservoir modeled by a three-dimensional grid model; representing the discrete natural crack via a multi-segment model in a two-dimensional region within the three-dimensional grid model; defining at least one connection for fluid communication between the multi-segment model and the three-dimensional grid model; define boundary conditions for the multi-segment model; and solving the multi-segment model for the at least one connection and the boundary conditions to provide values for fluid flow in the two-dimensional region. As an example, such a method may include solving the fluid flow for the three-dimensional grid model based at least in part on the values of fluid flow in the two-dimensional region.

[0079] As an example, a method may include defining at least one connection for fluid communication between a multi-segment model and a well, the well being modeled by another multi-segment model. Such a method may also include solving the multi-segment models to provide values for fluid flow in at least one two-dimensional region.

[0080] As an example, a method may include formulating a plan for creating an artificial fracture based at least in part on values for fluid flow in a two-dimensional region representing a natural fracture. As an example, a method may include representing an artificial crack via a multi-segment model in a two-dimensional region within a three-dimensional grid model and solving multiple multi-segment models to provide values for two-dimensional fluid flow regions.

[0081] As an example, a method may include defining at least one connection for fluid communication between a multi-segment model and a three-dimensional grid model by defining a connection for fluid communication between a discrete natural fracture and a reservoir. In such an example, the reservoir may include fluid and fluid flow values in a two-dimensional region, may represent flow of fluid from the reservoir to the discrete natural fracture, from the discrete natural fracture to the reservoir, or a combination of both.

[0082] As an example, a three-dimensional grid model may include at least some cracks in a three-dimensional environment using a continuous model. In such an example, other cracks can be considered discrete and modeled using one or more multi-segment models.

[0083] Fig. 5 shows an example of a method 500 which includes an identification block 510 for identifying one or more 2D regions in a 3D environment with one or more reservoirs, a model block 514 for modeling one or more wells in 3D -the environment with one or more reservoirs, a definition block 520 to define one or more connections of entities in the 3D environment (e.g., wells, fractures, reservoirs, etc.), a definition block 530 to define the boundary conditions in at least some of the entities in the 3D environment, and a solve block 540 to solve flow (eg, subject to the boundary conditions).

[0084] As an example, a 2D region may be a multi-segment region representing an existing crack (eg, natural or artificial or a hybrid thereof), a potential crack, etc. In terms of model block 514, the modeling may be for an existing well, an experimental well, a modification of an existing well, etc. As an example, a multi-segment model can include at least one natural fracture, and at least one well, either existing well, experimental well, etc.

[0085] In the example in fig. 5, the method 500 includes a determination block 550 for determining whether data exists in one or more existing wells. As an example, where the decision block 550 determines that such data exists, the method 500 may proceed to a history matching block 560 to perform history matching (eg, to compare a solution of the solution block 540 with data). Then, the method 500 may continue in a continuation block 570, which may continue to a loop action or other action. For example, if the decision block 550 determines that there is not enough data (eg, for history matching), the method 500 may proceed to the continuation block 570.

[0086] The method 500 is shown in fig. 5 in connection with various computer readable media (CRM) blocks 511, 515, 521, 531, 541, 551 and 561. Such blocks generally include instructions suitable for execution by one or more processors (or processor cores) to instruct a data processing device or to perform one or more actions. Although various blocks are shown, a single medium may be configured with instructions to allow, at least in part, the performance of various actions in method 500. As an example, a computer readable medium (CRM) may be a computer readable storage medium.

[0087] Fig. 6 shows an example of a system 600, examples of various modules 610 and an example of a crack network 680.1 the example in fig. 6, the system 600 includes one or more processors 602 operatively coupled to the memory 604. As an example, the memory 604 may store modules such as one or more of the modules 610, which may provide modeling storage, streaming, etc. in an underground environment. In the example in fig. 6, the modules 610 include a liquid reservoir module 612, a dry reservoir module 614, a module for existing wells 622, a module for experimental wells 624, a natural fracture module 642, an artificial fracture module 644 and one or more Solution modules 660.1 the example in fig. 6, the modules 610 may include instructions suitable for execution by one or more of the processors (eg, processor cores) to instruct a computing device or system to perform one or more actions. For example, the system 600 may be instructed by instructions from one or more of the modules 610.

[0088] As an example, a method may include implementing one or more of the module 610 to represent a network such as the crack network 680.1 example in fig. 6, the crack network includes 680 natural cracks and artificial cracks. As an example, the creation of a hydraulic fracture can be influenced by one or more natural fractures. For example, hydraulic fracture growth may proceed in a northeast-southwest direction reactivating natural fractures (dashed lines) that run in another direction or directions (see, e.g., arrows indicating possible hydraulic fracture propagation directions).

[0089] As an example, a method may include modeling natural fractures in an environment using a multi-segment model and solving the multi-segment model for storage, flow, etc., for example, with respect to a reservoir or reservoirs. In turn, a solution can be analyzed for potential artificial cracks. Such analysis may, for example, include positioning one or more wells to create one or more potential artificial fractures with respect to one or more natural fractures to generate a network that activates natural fractures as conduits for fluid flow. As an example, such an analysis may aim to avoid certain natural fissures and reactivate (eg exploit) other natural fissures. In such an example, delineation of natural fracture locations, features, etc. may occur using a multi-segment model, possibly in conjunction with a 3D grid model that models one or more reservoirs.

[0090] As an example, a model may include strain or one or more other factors that may relate to cracking. As an example, a natural multi-segment cracking model can be mathematically connected to a load model for a 3D environment. As an example, a model may include a chemical process (eg acid treatment). As an example, a natural multi-segment fracturing model can be mathematically coupled to a chemical reaction model for modeling a chemical process (eg, with respect to one or more fracturing properties). Where history matching is performed for fluid flow based at least in part on a solution for a natural multi-segment fracturing model, improvements to the natural multi-segment fracturing model may update one or more parameters associated with loading (eg, direction, etc.).

[0091] As an example, a system may include one or more processors for processing information, memory that is functionally coupled to the one or more processors, and modules that include instructions that can be stored in the memory and executed by at least one of the one or the several processors. Such modules may include a reservoir module for modeling a reservoir in a subsurface three-dimensional environment via a three-dimensional grid model, a natural fracture module for modeling a natural fracture via a multi-segment model in a two-dimensional region, a well module for modeling a well via a multi-segment model, and one or more solution modules for solving values of fluid flow in a fracture network based at least in part on modeling a natural fracture via a multi-segment model. As an example, a system may include an artificial crack module to model an artificial crack via a multi-segment model in a two-dimensional region. As an example, a system may include a solver module for solving values of fluid flow in a fracture network that includes at least one natural fracture and at least one artificial fracture.

[0092] As mentioned, boundary conditions can be defined (eg imposed) on one or more segments of a multi-segment model that models a natural fracture, natural fractures, etc. Fig. 7 shows an example of an environment 710 that includes various formations, a borehole and natural cracks. As indicated, the formations include fluid, such as oil, gas and/or water, which may define different zones. In terms of boundary conditions, a natural fracture may include a boundary condition between a natural fracture and another natural fracture, between a natural fracture and an oil-filled formation, between a natural fracture and a borehole, between a natural fracture and a gas-filled formation, between a natural fracture and a water-filled formation, etc. For example, a natural fracture may include multiple boundary conditions, for example, for both a borehole and a fluid-filled formation.

[0093] As an example, a formation may be considered fluid-filled or empty (eg, "dry"), depending on the type of fluid. For example, a gas-filled formation may be considered empty in the case of oil, where a goal is to produce oil. As indicated in the example environment 710 in Fig. 7, oil and water can coexist in a formation, and a strategy can be formulated to produce oil with minimal water content. As an example, such a strategy can be honed via the application of a multi-segment that models one or more natural fractures with respect to an environment (eg to avoid activation of a natural fracture that may lead to an increase in the water content of oil).

[0094] Fig. 8 shows an example of a graphical user interface (GUI) 810 that provides for the display of a grid 812, the wells 814 and 818 and the cracks 815 and an example of a GUI 830 that provides for the display of a grid 832, the wells 834 and 838, a crack 835 and a scale 836.

[0095] As for the graphical user interface (GUI) 810, it can also show the various units from another point of view, for example a floor plan in an x, y plane. The GUI 810 may include one or more data fields, for example for inputting parameters associated with the cracks 815. For example, a crack field depth may be specified along a depth dimension and a crack field orientation may be specified relative to a direction (e.g., possibly an angle) . As mentioned, natural cracks can occur as clusters or corridors, which can be oriented in a general direction (eg responding to previous stress, etc.). In the example in fig. 8, the GUI 810 may provide orientation of a field as a whole or individual cracks in a cluster or corridor.

[0096] In terms of the GUI 830, the natural crack 835 is represented as a 2D grid together with various values, which may be properties assigned to the 2D grid, solutions to a model for the 2D grid, etc. For example, the various the values implied by the scale 836 represent static properties (eg, permeability, etc.), dynamic values (eg, from a simulation, etc.). As an example, a GUI may present pressure values, saturation values (eg, percentage of a phase in a multiphase fluid system), porosity values, flow values, or other values associated with a Darcy or other model. Such values can be presented directly on a 2D grid. As an example, a GUI may include a graphical control that may be used to select one or more types of values and display such values (eg, using color, hatching, contours, etc.) with respect to a grid representing a crack. In such a way, a user can interact with the GUI to visualize values to determine a strategy, refine a strategy, update a model, etc. As an example, a visualization can be presented as a series of images with respect to time (e.g. e.g. a film), for example to illustrate flow, change in one or more properties, phase composition, etc. with respect to time.

[0097] As an example, the 2D grid may include 25 or more segments, which may be Darcy segments where each Darcy segment includes Darcy property values. In such an example, boundary conditions can be specified for at least some of the segments. For example, where the well 834 is connected to the crack 835, the segments along this boundary can include suitable boundary conditions. As another example, where well 838 connects to fracture 835, the segments along this boundary may include suitable boundary conditions.

[0098] As an example, well 834 may be specified to be a producing well while well 838 may be specified to be an injector well. In such an example, a multi-segment model may model fluid flow in the fracture 835 (e.g., the 2D grid) based on the conditions regarding injection of fluid via the injection well 838.1 such example, the fracture 835 may include boundary conditions that avoid movement of fluid to the surface (e.g. .eg one or more boundaries).

[0099] As an example, the natural fracture 835 may include one or more boundary conditions that mathematically couple it to a reservoir modeled by the 3D grid 832. As an example, where the well 838 is specified to be an injector well, it may inject a fluid, such as water causing movement of oil from an oil reservoir in fluid communication with the natural fracture 835 to flow to the well 834, which may be specified to be a producing well. In such an example, the 2D grid may be displayed in the GUI 830 to indicate the presence of a fluid, a fluid phase, fluid pressure, fluid flow, etc.

[00100] The GUIs 810 and 830 are shown in FIG. 8 in conjunction with various computer readable media (CRM) blocks 811 and 831. Such blocks generally include instructions suitable for execution by one or more processors (or processor cores) to instruct a computing device or system to perform one or more actions. Although various blocks are shown, a single medium may be configured with instructions to permit, at least in part, the performance of various actions associated with rendering the GUIs 810 and 830. As an example, a computer readable medium (CRM) may be a computer readable storage medium.

[00101] Fig. 9 shows an example of a method 900 which includes a model block 910 for modeling at least natural cracks, a generation block 920 for generating simulation results for at least the natural cracks, a model block 930 for modeling the artificial cracks at least partially built on the simulation results, a generation block 940 for generating simulation results for at least the artificial cracks and a planning block 950 for planning for or creating one or more artificial cracks based at least in part on the simulation results (e.g. for at least the natural cracks, for at least the artificial the cracks etc.).

[00102] The method 900 is shown in Fig. 9 in connection with various computer readable media (CRM) blocks 911, 921, 931, 941 and 951. Such blocks generally include instructions suitable for execution by one or more processors (or processor cores) to instruct a data processing device or a system to perform one or more actions. Although different blocks are shown, a single medium may be configured with instructions to allow, at least in part, the performance of various actions in method 900. As an example, a computer readable medium (CRM) may be a computer readable storage medium.

[00103] Fig. 10 shows an example of a solution diagram 1010 and an example of a method 1020. The solution diagram 1010 includes providing Solution Results for a fracture model 1018 to a reservoir model 1012.1 the example in fig. 10, the method 1020 revolves around the solution scheme 1010.1 a grid block 1030, the method 1020 lines up one or more crack regions (eg, to form one or more networks). For example, block 1030 may route one or more regions with multiple segments 1040, where each segment may be a Darcy (or fracture) segment 1046 or optionally another type of segment (eg, well segment 1042, a fracture well segment 1044, etc.).

[00104] As shown in the example in fig. 10, method 1020 includes a solve block 1050 for solving a system of equations for the crack regions. The equation system 1060 may include, for example, well equations 1062, fracture/well equations 1064, Darcy equations 1066, and fracture/formation equations 1068 (eg, connection equations). As an example, formulated equations for different phenomena in a crack system can be solved simultaneously until convergence. A solution to such a system of equations can by itself be used for field handling or other handling purposes.

[00105] In the example in fig. 10, the method 1020 includes an input block 1070 for inputting a solution to a fracture model into a comprehensive reservoir simulation (eg, according to the solution scheme 1010). The method 1020 also includes a solution block 1090 for solving the comprehensive reservoir simulation, for example as modeled using a three-dimensional grid.

[00106] The method 1020 also shows circuits or computer-readable media blocks 1035, 1055, 1075, and 1095, which may be physical components (e.g., actual circuits, storage devices, combinations thereof, etc.) configured to perform actions of their corresponding method blocks 1030 ,1050,1070 and 1090.

[00107] As an example, one or more computer-readable storage media may include computer-executable instructions for instructing a computer system to: grid one or more natural fracture regions with respect to a three-dimensional grid model of an underground formation comprising a reservoir, the one or more natural the crack regions represented via multiple segments; solving a system of equations associated with the multiple segments to provide a solution; introduce the solution as input to a system of equations associated with the three-dimensional grid model; and solve the system of equations associated with the three-dimensional grid model. In such an example, one or more computer-readable media may include computer-executable instructions for instructing a computer system to route the one or more natural fracture regions for individual natural fractures in a natural fracture corridor.

[00108] As an example, one or more computer-readable media may include computer-executable instructions for instructing a computer system to render representations of the natural fracture corridor on a screen. In such an example, the instructions may be included to instruct a computer system to render graphical controls to the screen for receiving commands to orient the natural fracture corridor with respect to the three-dimensionality of the subterranean formation.

[00109] Fig. 11 shows an example of a solution diagram 1100, and an example of a method 1110. The solution diagram 1100 includes providing a crack model that models one or more cracks 1106, such as one or more networks. The form 1100 provides for solving the fracture model and for inputting the result into a model that models a reservoir 1102.

[00110] In the examples in Fig. 11, a set of fracture equations can be solved together and independently of a set of reservoir grid cell equations for each non-linear iteration in a combined system of reservoir and fracture equations. From a reservoir grid solution point of view, such an approach has the effect of solving the reservoir system given a locally converged solution of at least one fracture system and possibly several fracture systems connected to a reservoir.

[00111] The method 1110 includes a delivery block 1114 that supplies reservoir equations and a delivery block 1118 that supplies fracture equations. A solution block 1122 includes (a) solving the equations followed by (b) solving the reservoir equations. An example approach to performing various actions in block 1122 is presented with respect to blocks 1126 through 1142. Next, method 1110 provides a solution for a time "T" using an output block 1146.

[00112] In the example in fig. 11, the solver block 1122 may implement braided loops that converge solutions to various equations. An outer loop converges a solution to the reservoir equations via a decision block 1142, an inner loop converges a solution to the equations for fractures via a decision block 1134, and an innermost loop converges a solution to the equations for a particular fracture system via a decision block 1130. Accordingly, the blocks 1126 to 1142 begin with initialization of fracture equations per block 1126 (eg, optionally based on output from a reservoir model simulator), followed by converging solutions for each individual fracture system and then converging the solutions globally for multiple fracture systems. After convergence of the fracture systems, an update block 1138 may update unknown reservoir equation factors (eg, independent variables). A simulator can solve the reservoir equations using a method that iterates values of unknowns until convergence. Once converged, the result can be output per output block 1146. Such a result aims to include a global solution for a reservoir with associated fracture systems.

[00113] Fig. 11 also shows various computer readable media (CRM) blocks 1116, 1120, 1124, 1125 and 1148, which correspond to method blocks 1114, 1118, 1122 and 1146, respectively. While blocks are displayed individually, a single computer-readable medium may include instructions of blocks 1116, 1120, 1124, 1125, and 1148.

[00114] Fig. 12 shows components of an example of a computer system 1200 and an example of a network system 1210. The system 1200 includes one or more processors 1202, memory and/or storage components 1204, one or more input and/or output devices 1206 and a bus 1208.1 example design, instructions may be stored in one or more computer-readable media (eg, memory/storage components 1204). Such instructions may be read by one or more processors (eg, processor(s) 1202) via a communication bus (eg, bus 1208), which may be wired or wireless. The one or more processors may execute such instructions to implement (in whole or in part) one or more attributes (eg, as part of a method). A user can view output from and interact with a process using an I/O device (eg, device 1206). In an example embodiment, a computer-readable medium may be a storage component, such as a physical memory storage device, such as a chip, a chip-in-a-pack, a memory card, etc.

(eg a computer-readable storage medium).

[00115] In an example design, the components may be distributed, for example, in the network system 1210. The network system 1210 includes the components 1222-1, 1222-2, 1222-3,...1222-N. For example, the components 1222-1 may include the processor(s) 1202, while the component(s) 1222-3 may include memory accessible to the processor(s) 1202. Further, the component(s) 1202-2 may include an I/O device for presentation, and possibly interaction with a procedure. The network may be or include the Internet, an intranet, a cellular network, a satellite network, etc.

[00116] Although only a few examples of designs have been described in detail above, those skilled in the art will readily understand that it is possible to make many modifications to the examples of designs. Accordingly, all such modifications are intended to be included within the scope of this disclosure, as defined in the following claims. In the claims, the means plus function clauses are intended to cover the structures described in this document that perform the stated function, and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw cannot be structurally equivalent because a nail has a cylindrical surface with which to fasten pieces of wood together, while a screw has a helical surface, in the context of fastening pieces of wood a nail and a screw can be equivalent structures. It is the express intention of applicant not to invoke 35 USC § 112, section 6 for limitations on any of the claims herein, except where the claim expressly uses the words "means for" together with an associated function.

Claims (20)

What is required is: 1. Method comprising: identifying a discrete natural fracture in a three-dimensional environment comprising a reservoir, the underground formation and the reservoir modeled by a three-dimensional grid model, and representing the discrete natural fracture with a multi-segment model in a two-dimensional region within the three-dimensional grid model; defining at least one connection for fluid communication between the multi-segment model and the three-dimensional grid model; define boundary conditions for the multi-segment model; and solving the multi-segment model for at least one connection and the boundary conditions to provide values for fluid flow in the two-dimensional region. 2. The method according to claim 1, comprising solving the three-dimensional grid model for fluid flow based at least in part on the values for the fluid flow in the two-dimensional region. 3. The method according to claim 1, where the multi-segment model comprises segments which each comprise a node and a segment pipe. 4. The method according to claim 1, wherein the multi-segment model comprises segments comprising associated equations to model fluid flow according to Darcy's law. 5. The method according to claim 1, where the values for liquid flow comprise values for multiphase liquid flow. 6. The method according to claim 1, comprising defining at least one connection for fluid communication between the multi-segment model and a well, where the well is modeled by a multi-segment model. 7. The method according to claim 6, comprising solving the multi-segment models to provide values for the fluid flow in at least the two-dimensional region. 8. The method according to claim 1, comprising formulating a plan to create an artificial crack based at least in part on the values of the fluid flow in the two-dimensional region. 9. The method according to claim 1, comprising representing an artificial crack with a multi-segment model in a two-dimensional region within the three-dimensional grid model and solving the multi-segment models to provide values for fluid flow in the two-dimensional regions. 10. The method according to claim 1, wherein the definition of at least one connection for fluid communication between the multi-segment model and the three-dimensional grid model comprises defining a connection for fluid communication between the discrete natural fracture and the reservoir. 11. The method according to claim 10, wherein the reservoir comprises liquid and wherein the values for the liquid flow in the two-dimensional region represent a flow of liquid from the reservoir to the discrete natural fracture. 12. The method according to claim 10, wherein the reservoir comprises fluid and wherein the values for fluid flow in the two-dimensional region represent a flow of fluid from the discrete natural fracture to the reservoir. 13. The method according to claim 1, wherein the three-dimensional grid model includes at least some cracks in the three-dimensional environment by means of a continuous model. 14. System comprising: one or more processors for processing information; memory functionally coupled to the one or more processors; and modules comprising instructions stored in memory and executable by at least one of the one or more processors, the modules comprising: a reservoir module for modeling a reservoir in a subsurface three-dimensional environment with a three-dimensional grid model, a natural fracture module for modeling a natural fracture with a multi-segment model in a two-dimensional region, a well module for modeling a well with a multi-segment model, and one or more solution modules for solving values for fluid flow in a fracture network at least partially based on modeling a natural fracture with a multi-segment model. 15. The system according to claim 14, comprising an artificial crack module for modeling an artificial crack with a multi-segment model in a two-dimensional region. 16. The system according to claim 15, where the one or more solution modules are used to solve values for fluid flow in a crack network comprising at least one natural crack and at least one artificial crack. 17. One or more computer-readable storage media comprising computer-executable instructions for instructing a computer system to: grid one or more natural fracture regions for a three-dimensional grid model of an underground formation comprising a reservoir, one or more natural fracture regions represented by multiple segments; solving a system of equations associated with the multiple segments to provide a solution; feed the solution as input to a system of equations associated with the three-dimensional grid model; and solve the system of equations associated with the three-dimensional grid model. 18. The one or more computer-readable media of claim 17, further comprising computer-executable instructions for instructing a computer system to route the one or more natural fracture regions for individual natural fractures in a natural fracture corridor. 19. The one or more computer-readable media of claim 18, further comprising computer-executable instructions for instructing a computer system to render representations of the natural fracture corridor on a screen. 20. The one or more computer-readable media of claim 19, further comprising computer-executable instructions for instructing a computer system to render graphic controls to the display to receive commands that can be used to orient the natural fracture corridor with respect to the three-dimensional model thereof underground formation.