Gasmod Development History
In the Beginning
Gasmod was developed by PHH Engineering Ltd. in 1978 to assist in performing gas reservoir studies. It was built as a 3D finite difference reservoir simulator and formulated in terms of pseudo pressure to yield improved accuracy relative to the alternative pressure (potential) formulation. Gasmod provided the foundation for the multi-purpose Gcomp reservoir simulator, which was developed in 1979-1980 in response to some large North African reservoir studies.
In order to allow forecasting to the plant gate, a simplistic surface network was added in the early 1980’s. This network model was based on a sequential network solution, whereby there is only one path from a well to the plant. It was not structured to allow for the flow splitting that would arise from line looping or multiple processing plants (demands or sales points). This was a serious limitation.
In 1985, PHH Engineering Software Ltd. developed a model for the real-time transient simulation of a batched pipeline network. The simultaneous solution of the network proved very stable and computationally efficient. The steady state solution from this model was subsequently incorporated into Gasmod in the early 1990’s, when it was ultimately required for consulting projects.
The stability of the simultaneous solution was continually tested by projects of increasing complexity. The very successful model of the Stratton field in 1995, with its low and high pressure gathering systems and tight reservoir, convinced PHH that the algorithms were solid and the solution was quite scalable. PHH felt comfortable committing to fixed price (shallow gas) projects involving thousands of wells. Encana had a defined need for Gasmod with their Suffield project which had more than 7,000 wells penetrating up to 3 reservoir zones and 7 interconnected processing plants. They had previously contracted a software company to develop a simulator to model the project, which ended up being unstable and was subsequently abandoned.
The Suffield project which used well groupings to reduce the number of well nodes to about 2,000, was very successful and many additional Encana projects followed. Encana’s support allowed PHH to continually upgrade the model with capabilities such as storage reservoirs, a faster LEQ solver, multi-phase network, multi-component network, etc. The successes also resulted in additional clients and a multitude of additional large scale shallow gas projects and gas storage projects. The largest project was the Hatton Bigstick field for Apache. For some infill drilling forecasts, the project had 7,000 wells penetrating three reservoir zones that were described with 1,000,000 grid blocks. A list of substantial, non-confidential projects simulated with Gasmod is included below. Due to the turmoil in the industry, the listed owner/operator may not be the current owner of the property.
The early Gasmod software used file based input and pre and post processors to streamline input and interpret output. In order to make it more user-friendly for clients, the development of a GUI linked to a database started in early 2000. In order to simplify software maintenance, the engine would provide a file of the data provided by the GUI in the same format used by the DOS version of the simulator. This allowed a DOS simulation to easily duplicate a Windows simulation. In addition, the capability to populate a data base from a DOS input file was developed. A major effort was undertaken to make the database responsive for large projects that had many years of history. Ultimately, a proprietary database was implemented.
Shallow Gas to Shale
The shale/tight gas revolution was disastrous for shallow gas and Coal Bed Methane projects. Therefore, the focus of Gasmod development changed to pipeline integrity management and the efficient solution of shale/tight gas projects. The primary interest was in reducing the cost (staff-time) of setting up reliable models and providing suitable displays of model results. Gasmod is currently being used by 3rd party consultants to assess the risk of pipeline failure due to internal corrosion. These consultants have assessed more than 10,000 pipe licenses across Western Canada in less than 3 years using the model. In order to get the proper flows through pipe licenses, the models were constructed based on ‘as-built’ pipeline systems. Gasmod’s inherent stability for complex networks made it possible to perform this work very cost effectively.
Part of the VMG Family
Since being acquired by VMG in late 2015, the latest developments in Gasmod consist of incorporating energy balance, calculations using the VMGThermo property package for the fluid properties. The solution of the energy balance allows for the addition of line heaters (chillers) to the network and the prediction of flowing temperatures and hydrate formation temperatures throughout the system.
Gasmod has a proven history as established software and VMG is eager to continue its development and success. There are many capabilities being implemented that, in the future, will allow users to model their fields from reservoir through plant product and make the forecasts and predictions needed to conduct their business and maximize value.
Historical and Current Gasmod Clients and Projects
Peter H. Holst, P.Eng., VMG Calgary
Gordon Slemko, P.Eng., VMG Calgary
Please contact your local VMG office for more information.