Abstract: In some aspects, techniques and systems for modeling fluid flow are described. Pressure gradient values for respective nodes of a one-dimensional flow model are computed. The nodes represent locations of fluid flow along a flow path, and the pressure gradient values are computed based on an approximation of the flow velocity at a point on the flow path. A pressure drop between two opposite ends of the flow path is calculated based on the pressure gradient values. An improved approximation of the flow velocity for the point on the flow path is calculated based on a difference between the calculated pressure drop and a pressure drop boundary condition.

Abstract: In one example of determining fracturing rheological behavior of fracturing fluids, a reference viscosity and fluid properties of a fracturing fluid are received. A fracturing rheological behavior of the fracturing fluid is modeled using a fluid model that models the fracturing rheological behavior of Newtonian and non-Newtonian fluids based, in part, on the received reference viscosity and the received fluid properties of the fracturing fluid. The fracturing rheological behavior of the fracturing fluid is provided. If a fracturing fluid is a mixture of two or more fracturing fluids, then a rheological behavior of the mixture is modeled based on a mixing rheological model. The fracturing rheological behavior of the mixture is then modeled based on the rheological behavior modeled by the mixing rheological model.

Abstract: Determining flow through a fracture junction in a complex fracture network. A flow of a fracturing fluid through a fracture junction of a complex fracture network is modeled using a fluid flow model that models flow based, in part, on mass balance and momentum balance. The fracture junction includes a first outlet to flow a first portion of the fracturing fluid and a second outlet to flow a second portion of the fracturing fluid. A ratio of a first volumetric flow rate of the first portion and a second volumetric flow rate of the second portion, and the pressure drop across the junction are determined in response to modeling the flow of the fracturing fluid through the fracture junction according to the fluid flow model. The determined ratio of flow rates and/or the determined pressure drop is provided.

Abstract: In some aspects, techniques and systems for modeling fluid flow are described. A flow model represents intersecting flow paths for well system fluid. The flow paths intersect at a flow path intersection. A band matrix and an intersection table are generated based on the flow model. The band matrix represents fluid flow within the respective flow paths, and the intersection table represents fluid flow between the flow paths at the flow path intersection. The flow model can be operated using the band matrix and the intersection table, for example, to calculate fluid flow variables at various locations along the flow paths.

Abstract: In one example of determining fracturing rheological behavior of fracturing fluids, a reference viscosity and fluid properties of a fracturing fluid are received. A fracturing rheological behavior of the fracturing fluid is modeled using a fluid model that models the fracturing rheological behavior of Newtonian and non-Newtonian fluids based, in part, on the received reference viscosity and the received fluid properties of the fracturing fluid. The fracturing rheological behavior of the fracturing fluid is provided. If a fracturing fluid is a mixture of two or more fracturing fluids, then a rheological behavior of the mixture is modeled based on a mixing rheological model. The fracturing rheological behavior of the mixture is then modeled based on the rheological behavior modeled by the mixing rheological model.

Abstract: In some aspects, techniques and systems for modeling fluid flow are described. A flow model represents intersecting flow paths for well system fluid. The flow paths intersect at a flow path intersection. A band matrix and an intersection table are generated based on the flow model. The band matrix represents fluid flow within the respective flow paths, and the intersection table represents fluid flow between the flow paths at the flow path intersection. The flow model can be operated using the band matrix and the intersection table, for example, to calculate fluid flow variables at various locations along the flow paths.

Abstract: Determining flow through a fracture junction in a complex fracture network. A flow of a fracturing fluid through a fracture junction of a complex fracture network is modeled using a fluid flow model that models flow based, in part, on mass balance and momentum balance. The fracture junction includes a first outlet to flow a first portion of the fracturing fluid and a second outlet to flow a second portion of the fracturing fluid. A ratio of a first volumetric flow rate of the first portion and a second volumetric flow rate of the second portion, and the pressure drop across the junction are determined in response to modeling the flow of the fracturing fluid through the fracture junction according to the fluid flow model. The determined ratio of flow rates and/or the determined pressure drop is provided.

Abstract: In some aspects, techniques and systems for modeling fluid flow are described. Pressure gradient values for respective nodes of a one-dimensional flow model are computed. The nodes represent locations of fluid flow along a flow path, and the pressure gradient values are computed based on an approximation of the flow velocity at a point on the flow path. A pressure drop between two opposite ends of the flow path is calculated based on the pressure gradient values. An improved approximation of the flow velocity for the point on the flow path is calculated based on a difference between the calculated pressure drop and a pressure drop boundary condition.