A recently launched joint industry project (JIP) is working to improve petrophysical analysis methods to reduce the time and expense of characterizing tight sandstone gas reservoirs for exploration, appraisal, and production. The Petrophysics of Tight Gas Sandstones (PETGAS) III JIP, coordinated by the Industry Technology Facilitator (ITF) in partnership with Energie Beheer Nederland and Petroleum Development Oman, hopes its research findings will substantially enhance the industry’s ability to assess remote and stranded gas resources for economic viability.
Stranded gas by definition is gas that is undeliverable to the market for logistical or economic reasons. “Estimates of remote or stranded gas reserves range from 40% to 60% of the world’s proven gas reserves,” said Craig O’Brien, technology analyst at ITF.
The PETGAS research is being conducted by the University of Leeds (UK). Stage III, to run for 3 years, builds on the project’s earlier successful work on the petrophysical examination of tight gas sandstones.
A robust database of key petrophysical properties has been formed to enable rapid estimation of the properties of samples for which no petrophysical data are available, based on the samples’ microstructures. A specialist software, PETMiner, has been developed to visualize the petrophysical properties data.
Determining Economic Viability
“When producers are developing low-permeability objectives, the petrophysical properties largely determine whether gas fields are economically viable,” said University of Leeds Professor Quentin Fisher, the project’s principal researcher. “Current methods used in the industry are both expensive and time-consuming.”
“The research done over all stages of the project has been transformative in creating a workflow, database, and data-mining software, which allows operators to reduce the cost and time to estimate petrophysical properties in these tight sandstone prospects,” O’Brien said. “The work of the PETGAS JIP could in time play a key role in unlocking the significant potential of stranded gas resources in the southern North Sea and beyond.
“From a global context, the stakes are enormous. In regions where there is a drive to develop tight gas reservoirs, the margins for economic success are often finely balanced.”
A Set of Appraisal Tools
Over its stages, the PETGAS JIP has created a computerized reservoir consultant and a set of tools to help appraisal teams seek realistic petrophysical property analogs for reservoirs where laboratory measurements are not yet available.
These tools include:
- The PETMiner software, which can quickly process extremely large data volumes in different formats to create displays that can be analyzed to detect correlations between different sorts of data.
- Extensive rock testing data developed from cores provided by several ITF member companies, which include BG, Shell, and three European independents.
- State-of-the-art testing equipment, which includes a unique mercury injection tool that can measure capillary pressures at extremely high confining pressures (~650 MPa).
ITF and its JIP partners are developing a machine learning module to enable the software to recognize similarities in images, which can expedite the search for rock data likely to represent the reservoir in question. Often the goal is to identify a property that can be measured over a wide area, based on a well log. Exploration teams at the JIP sponsor companies are now able to integrate the project tools into their own reservoir characterization workflows.
PETGAS III is extending the JIP database by a further 15 core samples per sponsor and will continue extensive special core analysis test work on an additional seven samples per sponsor. The project remains open to late participants.