Midsection supervisor holding clipboard


RESOLVE has been developed as a master controller to communicate and control the link between Reservoir Simulators, Process Simulators, other third party software, as well as client proprietary tools and the IPM suite.

RESOLVE: Features - Main

  • Application to connect and run integrated models comprising of an unlimited number of applications
  • Hyper-threaded
    • Strong parallelisation of solver algorithm wherever this is possible
    • Makes use of local (multi-processor) and network (remote machine) resources
  • Any topography of connected system is allowed
    • No fixed concept of upstream or downstream
  • Entirely open architecture
    • User connections can be developed (many examples of this)
    • The application as a whole can be controlled from an external controller
    • In addition to our optimisers, users can use their own external optimiser (see below)
  • Models can be run predicatively or at a snapshot in time

RESOLVE: Reservoir Coupling

  • Petroleum Experts-developed algorithm for improved coupling stability
  • Non-iterative - good performance
    • default scheme does not use Newton coupling (although available as an option)
    • iteration between reservoirs and GAP is possible, but is rarely required with the default algorithm
  • Tested extensively on fields throughout the world
  • Adaptive time-stepping also available

RESOLVE: Surface Network Implementation

  • Resolve is set up to take full advantage of the features of Petroleum Experts 'GAP' software
    • optimisation
    • connection to material balance (MBAL)
    • production AND injection systems in a single license
    • distribution of network models and parallel optimisations over a network


  • Thermodynamic consistency between applications in an integrated model is ensured Black-oil models can be mixed with fully compositional models

RESOLVE: Event/well management

  • Comprehensive event / well management scheme
    • entirely open-ended
  • Any variable of any application in an integrated system can be interrogated to perform (if ... then ... action) directives
    • An action does not have to apply to the application in which the event took place
  • Actions can be complex
    • e.g. well ranking based on an associated variable (e.g. water cut, potential, revenue calculation)
    • e.g. switching from HP to LP separation while simultaneously changing compressor curves
  • This is all available through a simple user interface
    • Very complex management can be performed through a VBA script, hence the management is completely open ended
  • Schedules embedded in the client applications will be honoured in a Resolve run

RESOLVE: Optimisation

  • Two levels of optimisation
    • Non-linear optimisation in GAP
    • Successive linear optimisation in RESOLVE
  • Optimisation problems can be distributed over ALL applications in an integrated model
    • RESOLVE determines most efficient iteration scheme to calculate derivatives
    • Tested extensively on real-field cases

RESOLVE: version control

  • Tight integration with Petroleum Experts ModelCatalogue
  • RESOLVE models can be checked in and out
    • All associated models from the client applications are also checked in and out

RESOLVE: link to Excel

  • Dynamic linking (drag and drop) to Microsoft Excel for:
    • Calculation
    • Reporting
    • Stream splitting / manipulation


  • All application 'instances' can be added to the framework through a simple 'drag-and-drop' interface
  • Wizards are available for common tasks, e.g.
    • Voidage replacement
    • Configuration tasks
  • Run-time data from client applications (e.g. diagnostics) is channelled through the RESOLVE GUI

RESOLVE: Reporting

  • Comprehensive and dynamic
    • Results appear dynamically during the run, allowing instant access to the results and improved trouble-shooting
    • Optimisation and loop iteration results are stored separately at every timestep
    • Any variable of any client application can be added to the 'standard' variables always displayed by RESOLVE.

The structure of RESOLVE makes it very straight forward to link - through a DLL - a particular engineering tool. RESOLVE uses OpenServer, which means a user can write own link to RESOLVE as well as use the standard ones.

Link to third party software:

  • Process Simulators
    • UniSim - Honeywell
    • Hysys - Aspentech
    • Pro II - Schneider Electric
  • Reservoir Simulators
    • Eclipse 100 - Schlumberger Black Oil reservoir simulator
    • Eclipse 300 - Schlumberger Compositional reservoir simulator
    • IMEX - CMG Black Oil reservoir simulator
    • GEM - CMG Compositional reservoir simulator
    • Pumaflow - IFP reservoir simulator
    • VIP - Halliburton reservoir simulator
    • Tempest - Roxar
    • tNavigator - Rock Flow Dynamics
  • Tables/Statistical Tools
    • EXCEL
    • Crystal Ball - Oracle
    • @Risk - Palisade
  • Dynamic Multiphase Simulators
    • LedaFlow -Kongsberg
  • Proprietary to clients
    • PSim - ConocoPhillips reservoir simulator
    • MoReS - Shell reservoir simulator
    • GigaPowers - Saudi Aramco reservoir simulator
    • Chears - Chevron reservoir simulator


RESOLVE has been extensively tested on many fields all over the world, and its fast calculations (e.g. tight gas, shale oil/gas etc…) have been proven time and again for field development and Economic analysis. NPV, IRR and other Economic analysis can be easily used to drive a simulation and make decisions on operational strategy.

Global Optimisation

There is no “one solution fits all” optimiser algorithm that exists which can be universally applied to the upstream oil and gas system (because the problem is defined as a Mixed Integer Non-Convex Non-Linear Optimisation Problem). RESOLVE contains an SLP and Routing optimiser, combining this with the NLP optimiser in GAP allow for potentially a three tiered optimisation, where the user must formulate a way in which to make all of these search algorithms interact, to find the global maxima. As such RESOLVE has multiple levels of sophistication in the way it combines it’s multi tiered optimisation problems, using linear, non linear and integer algorithms together to address the complexity of interaction that exist within the upstream system. All of which can be triggered and controlled dynamically from Visual Workflows.

Data Objects

A number of unique and efficient computational functionalities are abundant across the IPM suite: this is what makes the IPM tools industry leading in terms of the diversity of analysis that can be performed in a single suite of applications. It is these capabilities/functionalities that have been isolated and exposed for the user as Data Objects: in this way all of the features are no longer native to the application in which they originated, rather they are available for a user to expose to any logic or workflow as needed. In addition to all the IPM calculations, there are also many other functions that are included. The list is continuously expanding, and today include data objects related to PVT, Data Stores, Maths Libraries, Wells, Tight Reservoirs, SAGD Processes, Multi-Well Allocation, Smart Well (ICD) Analysis, Probabilistic tools and Transient calculations.

Flow Assurance

Flow assurance studies centre around the detection of specific phenomena that are a function of the fluid PVT or the pipeline hydraulics (e.g. Slugging, Liquid loading, Wax formation, Hydrate formation, etc.). The underlying applications detect the phenomena, whilst the controlling logic in RESOLVE provides the mitigation action that is in line with field strategy. Transient hydraulic/Thermal simulations are usually done in isolation of steady state models, using rates, pressure and PVT that may not represent the dynamically changing nature of the field. In RESOLVE, qualifying criteria can be setup in Visual Workflows, and these would then trigger the transient simulation (LedaFlow®) using consistent pressure, rates, PVT and field specific data (i.e. well/pipe deviation). Having performed the transient analysis, the steady state analysis would continue. This ensures that steady state and transient calculations are done according to where they are most useful and coupling of the two methods allows for formidable workflows to be constructed. Currently RESOLVE has the driver to link to the transient simulator LedaFlow®.

Transient & Steady State Model

The concept of Integration was pioneered by Petroleum Experts in 1990 and it involves the elimination of artificial boundary conditions that would otherwise have existed if engineers study each individual element of a field in isolation. The same concept is expanded in RESOLVE as a vendor neutral system, by enabling the link between any application (from any vendor) that describes a part of the system to other software in a dynamic and fully integrated fashion. Reservoir simulators can therefore be connected to well models, surface facilities, process, re-injection and any other element that the user requires as part of their formulation. As part of this process, PVT handling, physical models of correcting IPRs, a variety of coupling schemes and other means that ensure that these connections are not only mechanically simple, but physically robust and efficient were invented by Petex and are available to the users as part of the unique collection of features of RESOLVE. Integration is the starting point of formulating robust solutions to petroleum engineering challenges and this is the base level of the capabilities of RESOLVE and the starting point of using the other features available.

Integration of Sub-Surface and Surface Models

RESOLVE has proprietary algorithms to perform the physically consistent coupling between reservoir simulators to well, network and process models (referred to as IPR Scaling). Commonly used techniques in the industry, such as the iterative Newton coupling, are computationally expensive, inflexible and restrictive. The Petex IPR scaling method allows for multiple simulation models from multiple vendors to be part of the model, being connected to a surface network that can include multiple levels of optimisation. Adaptive time-stepping allows the granularity in calculations when events occur in the field to be captured. The result is that mass and pressure balance exist across the system, irrespective of the underlying simulators, using fundamentally different physical principles at their core. Currently the following simulators can form part of a RESOLVE model: Eclipse (E100, E300), IMEX, GEM, PUMAFLOW, PSIM, NEXUS, VIP, tNavigator and TEMPEST (with more currently under development). In addition, many clients have created connections that are proprietary to their companies and the tools that they use internally.


Complex facilities, compression trains, and heat exchange processes (among others) ready the fluid for export are best captured in process simulators. In reality these systems are directly connected to the upstream system and any change in the feed composition and conditions will have a direct impact on the performance of the process. As such, RESOLVE allows the full downstream response, to be captured over time by the integration of these models with the upstream process systems including UniSim, HySys and ProII. As thermodynamic consistency is key to ensuring these dynamic connections happen in a physically consistent manner, RESOLVE includes unique Lumping/Delumping algorithms that allow the orchestration of PVT transfers between applications. Black Oil models can be delumped to fully compositional descriptions and vice versa, so that the PVT requirements of each engineering application are satisfied.

Resolve Integrated Model

RESOLVE is a platform designed for the engineer to express the engineering ideas and formulate solutions as integrated engineering studies in a vendor neutral environment. The software, commercialized in 2002 as a strategic advancement in the concept of Integrated Production Modelling (IPM), moved the development of models from the Petex domain to a vendor neutral platform. From the outset of IPM the intention was to expand the capabilities of the tool in such a way that engineers would be able to express their ideas in an easy to use platform that would require no coding at all. Today, RESOLVE encompasses many unique capabilities listed in this document, including nested optimisation, visual workflows, advanced PVT handling, data objects etc. Each of these items encompasses decades of research and petroleum engineering experience. This ensures that solutions are formulated easily and include the optimum level of physical interactions between each element of the system.

Scenario & Probabilistic Studies

Within RESOLVE the Scenario Management capability allows multiple realisations of field strategies or underlying model setup to be run in parallel or on separate nodes using the clustering/hyper threading capabilities built into the tool. There is often a degree of uncertainty in the field information and the operating strategies. For instance reservoir volumes, or well deliverability are assessed on a P10, P50 and P90 basis, and there are many field development scenarios that satisfy the design criteria. The response of the integrated system will change depending upon which assumptions are considered, and these can all be assessed using a combination of the Scenario Manager and the relevant Data Objects (Sensitivity Tools, the Case Manager and links to CrystalBall™ and @Risc™ among others).

Clustering & Hyperthreading

For efficient processing and faster calculations times hyper threading and clustering capabilities are part of RESOLVE. In the former the parallelisation of solver algorithms have been implemented, and the use of local (multi core processing) or network (remote machines) computing clusters is available. In the latter context the PXCluster (Petroleum Experts clustering) has been designed to distribute computations over multiple computational nodes.

Visual Workflows

Petex’s Visual Workflows are a natural evolution of the Event driven scheduling functionality (existed in RESOLVE for over a decade now), which allow engineers to seamlessly create controlling logic that drives the development and management of the field without entering a single line of code. Logic can be implemented (using Visual Workflows) to control the simulation, and perform additional calculations to assess the likelihood of certain events (e.g. hydrate formation), and even propose mitigation actions (e.g. chemical dosing of MEG to the pipelines). All of this can be automated in a workflow to be dynamically assessed at each timestep.