PanMesh - Numerical Well Test Analysis Software

Quick Links to Information Below

• PanMesh Overview
• Typical Applications for PanMesh
• Key Technical Features of PanMesh
• The Challenge for Well Testing

• PanMesh Technology Overview
• Benefits of PanMesh
• PanMesh Simulation
• PanMesh 3.0 Released

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• EPS Software Brochure
• EPS Products At-A-Glance

PanMesh Overview

Many analytical models have been developed, and are still being developed, to describe different well and reservoir configurations. However, approximations or simplifying assumptions have to be made in order to make the mathematics manageable, and there is a limit to the complexity that can be achieved analytically.

PanMesh uses numerical simulation which envelopes all existing analytical solutions and has potentially unlimited flexibility. The reservoir and completion are discretised into a number of blocks or elements, and the flow and pressure equations are solved across each of these. Almost any geometry can be represented, encompassing multiple layers, irregular boundaries, multiple completions, and so on. Numerical simulation provides the opportunity to model real completions and complex geology in three dimensions.

Its revolutionary patented mesh generation technology has encapsulated all the power of full 3-D numerical simulation in an easy to use software tool. PanMesh makes numerical simulation accessible to the well test analyst without requiring simulation expertise.

The use of a numerical simulator enables the well test analyst to reach beyond the capabilities of analytical simulation in terms of complexity of reservoir structure and completion design. PanMesh’s color visualization facility tracks the pressure as it propagates through the reservoir, enabling the analyst to see how changes in the model structure correlate with changes in the pressure derivative.

Typical Applications for PanMesh

PanMesh can be used to simulate bottomhole flowing pressures for history matching to a well test data set, or to design a well test. Flowing pressures can also be generated at any point in the reservoir for interference test simulation. Because PanMesh is a 3-D simulator, this includes vertical interference tests.

Because it is fully integrated into PanSystem, PanMesh fulfils the same basic simulation objectives as the quick and advanced simulators available in PanSystem in terms of model validation and test design, and occupies a similar place in the workflow.

Additionally, the use of a numerical simulator enables the well test analyst to reach beyond the limits of analytical simulation in terms of complexity of reservoir structure and completion design.

PanMesh’s color visualization facility offers a deeper understanding of the nature of the transient response. By tracking the pressure as it propagates through the reservoir, it enables the analyst to see how changes in the model structure correlate with changes in the pressure derivative.

Key Technical Features of PanMesh

The PanMesh graphical interface has been designed to make setting up the model a simple task, and the whole simulation process, from start to finish, retains many of the benefits of analytical methods in terms of workflow and speed.

• Single Well Finite Element Simulator
• 3-dimensional
  • Fast automatic meshing with local refinement around wellbore, economical meshing algorithm aims to provide an accurate solution that will incur a minimum simulation time
  • PanMesh uses a patented complex 3-D mapped mesh generation technology, using a 20-node brick format with quadratic interpolation
  • Fast solver provides solutions in seconds to minutes, depending on model complexity
  • Generates real-time and pressure response for any well test flow schedule
  • Pressure response at any selected point in the reservoir can also be generated
  • ‘Pressure at a point’ capability allows horizontal and vertical interference tests to be modeled
  • Can be used to history match an existing well test or to design a future test
  • History file stores the entire simulation (pressure vs. time at all nodes) for future replay
  • Batch mode for multiple runs and sensitivity studies
• Reservoir Complexity
  • Geometry
    • Can be drawn over a reservoir map outline if available
    • Template option for preset reservoir forms
  • 3-dimensional permeability
  • Multiple layers (with/without vertical communication), multiple regions within each layer
  • Independently dipping layers, varying layer thicknesses via tilted surfaces or stepped sub-layers
  • Different rock and fluid properties per region
  • Irregularly-shaped internal fault structures
  • Partially sealing faults/fissures
  • Irregularly shaped outer boundary
  • 3-D graphical display of the reservoir structure
  • No-flow and constant pressure upper/lower and outer boundaries
  • Multiphase flow using multiphase pseudo-pressure, and/or different fluid properties per region with static interfaces
• Well and Completion
  • Vertical, slant, or horizontal well, with defined azimuth
  • Up to six open intervals
• Visualization
  • Color contouring allows advance of pressure disturbance to be tracked with time through the reservoir, on any selected plane
  • Simultaneous display of pressure derivative shows correlation between derivative ‘events’ and reservoir features encountered by the leading edge of the color contours
  • Radius of investigation iso-pressure surface display
  • ‘Save views’ option stores selected visualization
  • Flow plane feature shows orientation and relative magnitude of flow on any plane, while stream tube option displays flow path into the well from any selected point
  • Percentage flowrates per open interval (for a nominal constant total rate)
  • Pore volume per layer, total bulk reservoir volume

The Challenge for Well Testing

• Geological models are getting more detailed and need to be validated
• Wells are becoming more complex
• Staff have little time in which to assimilate all the information available
• Conventional well test analysis is nearing its limits…

...whilst there are less people able to concentrate effort on understanding it.

The Solution is PanMesh

• Integrates the different disciplines:
  • complex geological models
  • real life well completions
• Enables teams to really understand how a well test is behaving - without being specialists
• Low Costs:
  • As quick as the conventional approach
  • Integrated with PanSystem - easy to use

PanMesh Technology Overview

PanMesh is an add-on to PanSystem, eP’s market leading well test analysis software. PanMesh uses finite element numerical modeling to simulate well tests involving typical modern "real world" complexity. In particular, we have designed it so it can handle a wide range of well testing questions facing the petroleum engineer:

• Is my geological model correct?
• What impact is the well completion having on the well test and on well performance, and how do I assess it?

The combination of PanSystem with PanMesh allows well data to be transformed into information and then into real knowledge about the reservoir. The value obtained from a well test is magnified as a result.

PanMesh is a Windows program developed to run with PanSystem to address the need to extend the capabilities of traditional analytical well testing techniques. Based on finite element technology the program can be used to calculate the pressure response for reservoirs and wells in a wide variety of cases not covered by analytical models. The objective of the program is to accurately model the more complex well testing cases analytical techniques fail to address while at the same time retaining the efficiency of the traditional approach. The software uses automatic mesh generation, exports its results as type curves back to PanSystem.

Work Flow

Finite Element Technology

Finite element modeling is a widely accepted technique for engineering design and modeling For well testing the approach offers some specific benefits. The method deals naturally with layered, non-homogeneous geological strata and the twenty – noded iso parametric brick used to generate the mesh conforms accurately to all external boundaries and internal interfaces. The solver technology used in PanMesh is very fast and the simple set up procedure makes the complete process very efficient.

Geometry

Modern drilling and completion techniques can produce wells with a wide range of geometries. On setting up the data model in PanSystem different layers and an altered zone around the well can be defined to model skin factors and the deviation of the well can be set to any value. The well can be completed partially to model those reservoirs not fully perforated. Regions can be defined throughout the reservoir with varying properties such as permeability. A number of templates are provided which assists users in building a model to match their reservoir from a starting approximation.

Visualization

The data transferred from PanSystem are used to define, rapidly and automatically, the finite element mesh from the wellbore to the outer boundary. This mesh can be viewed in PanMesh as a solid model or as a wire frame and can be rotated and viewed in section or plan. The mesh can be set as Coarse, Medium, Fine or Superfine so if the pressure response shows some noise or instability on the coarse setting, the meshing algorithm can be run again on a finer setting. When the user is satisfied with the mesh, the simulation is started and as it proceeds the log-log plot of the draw down equivalent response is created while the pressure distribution in the reservoir is displayed in color contouring in a separate window. The initial color transition is set to occur at a Pd=.1 following the conventional definition of depth of investigation. At the end of the simulation the user can run through the simulation from start to finish viewing the pressure transient as it moves through the reservoir. This can be done in plan or section and the final display of the end-point represents the semi steady state pressure and flow distribution around the well. The pressure transient response display can be stored for playback later allowing useful comparison between different model characteristics.

The data generated is then transferred to PanSystem for completion of the analysis.

Accuracy

The accuracy of PanMesh has been validated by detailed comparison of the simulation results with a wide range of analytical reservoir and boundary models. The default settings for the mesh, the simulation time and other parameters have been selected to ensure the user needs make only minimal changes to achieve satisfactory results.

Development

The release of the second major upgrade to PanMesh provides a new platform for the delivery of well test analysis technology. User experience is already proving that the application is capable of addressing a wide range of the industry’s requirements. As with all eP software, continued investment will ensure that the software continues to evolve to meet users needs.

Conclusion

PanMesh delivers the benefits of accurate numerical well test analysis while retaining the ease of use and flexibility of traditional well testing packages. Its wide applicability means that there are few oil and gas field developments that would not benefit from its use.

Benefits of PanMesh

PanMesh represents a significant step forward in the ability of engineers to reflect real geological structures and well completions in their well test analyses.

PanMesh allows the user to import a map of the reservoir, draw up boundaries, which reflect true geological characteristics and orient the well in any direction and at any deviation through the reservoir. The software then automatically generates a finite element mesh from the inner boundary at the well out to the limits of the reservoir. This finite element mesh then is used to generate the pressure response against time throughout the reservoir which is displayed as a sequence of colored maps or sections as well as the traditional pressure and derivative plot display.

The benefits that this program brings are:

• The reservoir model reflects accurately the shape of the geological structure tested.
• The well completion and orientation is accurately modeled.
• Reservoir anisotropy can be incorporated into the model.
• Multiple layers and regions can be specified reflecting real geological complexity.
• Constant pressure and no-flow boundaries can be specified in the model.
• The ease of use and speed of workflow of traditional analysis methods are retained.
• Visualization of the pressure transient moving through the reservoir provides much clearer insight to pressure response features.

Following its second major release, this software is fundamentally changing the way well testing is performed and is rapidly being adopted by the industry.

PanMesh Simulation

PanMesh 3.0 Released

Version 3, the most significant new release of this leading well test analysis software for a number of years, is now available and will be shipped to all maintained clients in January. It is up to 30 times faster, and includes a number of key enhancements.

Key new capabilities are:

• PanMesh solver speed has been increased by up to a factor of 30 on some examples.
• A batch run capability has been provided to allow multiple model sensitivities to be run at the same time.
• Faults in the PanMesh model are now allowed to intersect.
• It is possible to print a Pd-Td plot from PanMesh.
• PanMesh reporting capabilities have been significantly improved.