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"Sequential Fully Implicit Well Model for Reservoir Simulation" in Patent Application Approval Process

May 27, 2014



By a News Reporter-Staff News Editor at Information Technology Newsweekly -- A patent application by the inventor H., Dogru Ali (Dhahran, SA), filed on September 30, 2013, was made available online on May 15, 2014, according to news reporting originating from Washington, D.C., by VerticalNews correspondents.

This patent application is assigned to Saudi Arabian Oil Company.

The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates to computerized simulation of hydrocarbon reservoirs in the earth, and in particular to simulation of flow profiles along wells in a reservoir.

"Well models have played an important role in numerical reservoir simulation. Well models have been used to calculate oil, water and gas production rates from wells in an oil and gas reservoirs. If the well production rate is known, they are used to calculate the flow profile along the perforated interval of the well. With the increasing capabilities for measuring flow rates along the perforated intervals of a well, a proper numerical well model is necessary to compute the correct flow profile to match the measurements in a reservoir simulator.

"It is well known that simple well models such as explicit or semi implicit models could be adequate if all reservoir layers communicated vertically for any vertical wells in a reservoir simulator. For these models, well production rate is allocated to the perforations in proportion to the layer productivity indices (or total mobility). Therefore, the calculations are simple and computationally inexpensive. The structure of the resulting coefficient matrix for the reservoir unknowns remains unchanged. Specifically, the coefficient matrix maintains a regular sparse structure. Therefore, any such sparse matrix solver could be used to solve the linear system for the grid block pressures and saturations for every time step for the entire reservoir simulation model.

"However, for highly heterogeneous reservoirs with some vertically non-communicating layers, the above-mentioned well models cannot produce the correct physical solution. Instead, they produce incorrect flow profiles and in some occasions causes simulator convergence problems.

"With the increasing sophistication of reservoir models, the number of vertical layers has come to be in the order of hundreds to represent reservoir heterogeneity. Fully implicit, fully coupled well models with simultaneous solution of reservoir and well equations have been necessary to correctly simulate the flow profiles along the well and also necessary for the numerical stability of the reservoir simulation. In order to solve the fully coupled system, generally well equations are eliminated first. This creates an unstructured coefficient matrix for the reservoir unknowns to be solved. Solutions of this type of matrices require specialized solvers with specialized preconditioners. For wells with many completions and many wells in a simulation model, this method has become computationally expensive in terms of processor time."

In addition to the background information obtained for this patent application, VerticalNews journalists also obtained the inventor's summary information for this patent application: "Briefly, the present provides a new and improved computer implemented method of solving well equations together with reservoir equations in a reservoir simulation model having formation layers having vertical fluid flow and flow barrier layers with no vertical fluid flow. The computer implemented method forms a reduced well model system for the wells in a reservoir simulation model by assembling as a single vertical flow layer the flow layers having vertical flow between the vertical flow barriers in the reservoir model in the vicinity of the wells only. For a production rate specified well, the method then solves the reduced well model system by matrix computation (using a direct sparse matrix solver) for the bottom hole pressure of the well and reservoir unknowns for the grid blocks where well is going through (reduced well model system). This method is repeated for all the wells in a reservoir simulator. Next, the method then solves the full reservoir simulation model by treating each well as having the determined bottom hole pressure, thereby determines completion rates for the layers of the well for the full reservoir model, and determines total rate for the well from the determined completion rates for the layers of the well. The method then forms a record of the determined completion rates for the layers and the determined total rate for the well.

"The present invention provides a new and improved data processing system for forming a well model for reservoir simulation of well in a subsurface reservoir from a reservoir model having formation layers having vertical fluid flow and flow barrier layers with no vertical fluid flow. The data processing system includes a processor which performs the steps of solving by matrix computation the reduced well model system model for the bottom hole pressure of the well and reservoir unknowns around the well and solving the full reservoir model by treating the well as having the determined bottom hole pressure. The processor also determines completion rates for the layers of the well for the full reservoir model and determines total rate for the well from the determined completion rates for the layers of the well. The data processing system also includes a memory forming a record the determined completion rates for the layers and the determined total rate for the well.

"The present invention further provides a new and improved data storage device having stored in a computer readable medium computer operable instructions for causing a data processor in forming a well model for reservoir simulation of well in a subsurface reservoir from a reservoir model having formation layers having vertical fluid flow and flow barrier layers with no vertical fluid flow to perform steps of solving by matrix computation the reduced well model system model for the bottom hole pressure of the well and reservoir unknowns and solving the full reservoir model by treating the well as having the determined bottom hole pressure. The instructions stored in the data storage device also include instructions causing the data processor to determine completion rates for the layers of the well for the full reservoir model, determine the total rate for the well from the determined completion rates for the layers of the well, and form a record the determined completion rates for the layers and the determined total rate for the well.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIGS. 1A and 1B are schematic diagrams for a well model in a reservoir simulator of multiple subsurface formation layers above and below a flow barrier in a reservoir being formed into single layers according to the present invention.

"FIGS. 2A and 2B are schematic diagrams for a well model in a reservoir simulator of multiple subsurface formation layers above and below several vertically spaced flow barriers in a reservoir being formed into single layers according to the present invention.

"FIG. 3 is a schematic diagram of a well model for simulation based on an explicit model methodology illustrated in radial geometry.

"FIG. 4 is a schematic diagram of a well model for simulation based on a fully implicit, fully coupled model methodology.

"FIG. 5 is a schematic diagram of a well model for reservoir simulation with a comparison of flow profiles obtained from the models of FIGS. 3 and 4.

"FIG. 6 is a schematic diagram of a finite difference grid system for the well models of FIGS. 3 and 4.

"FIGS. 7A and 7B are schematic diagrams illustrating the well model reservoir layers for an unmodified conventional well layer model and a well layer model according to the present invention, respectively.

"FIGS. 8A and 8B are schematic diagrams of flow profiles illustrating comparisons between the models of FIGS. 7A and 7B, respectively.

"FIG. 9 is a schematic diagram of a well layer model having two fracture layers in radial coordinates.

"FIG. 10 is a functional block diagram or flow chart of data processing steps for a method and system for a fully implicit fully coupled well model with simultaneous numerical solution for reservoir simulation.

"FIG. 11 is a functional block diagram or flow chart of data processing steps for a method and system for a sequential fully implicit well model for reservoir simulation according to the present invention.

"FIG. 12 is a schematic diagram of a linear system of equations with a tridiagonal coefficient matrix for an explicit well model for a one dimensional reservoir simulator with a vertical well

"FIG. 13 is a schematic diagram of a linear system of equations with a tridiagonal coefficient matrix for a fully implicit well model for a one dimensional reservoir simulator with a vertical well

"FIG. 14 is a schematic diagram of a linear system of equations with a tridiagonal coefficient matrix for a constant bottom hole pressure well model for a one dimensional reservoir simulator with a vertical well for processing according to the present invention.

"FIG. 15 is a functional block diagram or flow chart of steps illustrating the analytical methodology for reservoir simulation according to the present invention.

"FIG. 16 is a schematic diagram of a computer network for a sequential fully implicit well model for reservoir simulation according to the present invention."

URL and more information on this patent application, see: H., Dogru Ali. Sequential Fully Implicit Well Model for Reservoir Simulation. Filed September 30, 2013 and posted May 15, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=1025&p=21&f=G&l=50&d=PG01&S1=20140508.PD.&OS=PD/20140508&RS=PD/20140508

Keywords for this news article include: Information Technology, Saudi Arabian Oil Company, Information and Data Storage, Information and Data Processing.

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Source: Information Technology Newsweekly


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