Agile petrophysical analysis

Time is money in the oil and gas business. Graeme Eastwood discusses the secret to agile petrophysical analysis and the drivers behind them.

“When petrophysics and rock physics are combined in an integrated workflow they can be performed in a tightly integrated loop improving the consistency, veracity and utility of the results”
-Graeme Eastwood

Informed decisions in exploration and production begin with a good understanding of the subsurface. Placing the next well, how to maximize production or the best approach to secondary recovery - decisions improve when supported by petrophysical evaluation. Time is a rare luxury in these decisions and, regardless of complexity, the analysis must be completed rapidly to be useful. Agility describes the combination of balance, co-ordination, speed and reflexes that enables quick completion of a task and timely course corrections along the way. These agile characteristics apply well to petrophysical analysis, enabling quick evaluations that adapt to each situation.

Integrated petrophysics and rock physics

The cornerstone of agile petrophysical analysis is the ability to perform rock physics modeling within a petrophysical framework. This integration provides balance and can discover, and correct, such issues as borehole and invasion effects, unknown mineral mix and properties, thin and laminated beds, missing logs or gaps, and 4D time-lapse effects. When petrophysics and rock physics are combined in an integrated workflow they can be performed in a tightly integrated loop improving the consistency, veracity, and utility of the results. This enables rapid shifting between petrophysics and rock physics and holds parameters, zones and equations constant between the two disciplines. Integration reduces uncertainty in corrections and increases efficiency. Improved accuracy and data trustworthiness make precise reservoir management viable.

Collaborative analysis

For the best results, agile petrophyscial analysis should be collaborative in all phases. Multiple petrophysicists and geoscientists should be able to work together on the petroelastic model in a multi-user environment. The analysis becomes a co-ordinated effort that both speeds the analysis and improves the results by allowing real-time assessments, experimentation, idea sharing and joint decision-making. High quality logplots, crossplots, maps and other presentation tools also support collaboration and fast, informed decision making. These tools make it easy to share results, and coordinate next steps, whether during peer review or management presentation.

Fast, lierative modeling

Petrophysical analysis is not a one-time task that proceeds in only one direction to an end result. It is a multi-directional process that encompasses multiple disciplines and requires iteration as more information becomes available or new reservoir properties emerge. The petroelastic model must also incorporate additional field data as new wells are drilled. Details from these wells could challenge the fundamental model and must be incorporated at that level. This process may involve hundreds of wells and many geoscientists who must conclude the analysis quickly to be effective in decision-making. The best models are those that bring in new data and incorporate it rapidly without prejudice.

Adaptation to new demands

Quick reflexes are as necessary in the oil business as they are in nature. Geoscientists continually improve and modify their methods for best results in each analysis. What works well in West Texas may not work well in the Middle East. Adaptive petrophysical tools must rapidly add new capabilities as they are needed and allow geoscientists to work with data suitable to each situation.

In PowerLog, for example, two new modules added through agile development can now be used to analyse laminated sand-shale and other bedding sequences, providing interactive overlay graphs for analysis. Once these inputs are used to correct resistivity for anisotropy then saturation of the sand beds is computed and thin, laminated pay can be seen more clearly. The other module lets users easily and interactively pick, save, recall, edit and share dips from borehole image logs.

Agile petrophysical analysis provides significant benefit to geoscientists and the decisions they support. It is a process designed for speed but able to make quick adjustments as needed, provide cross-discipline balance and co-ordinate for best decision-making. In these times of increasing geologic complexity, challenging plays and economic pressure, agile petrophysical analysis is just what the industry needs.

BIO

Graeme Eastwood is Middle East Regional Manager for Fugro-Jason, a leading provider of reservoir characterisation products and services. He joined the company in 2003 as Business Manager for Southeast Asia and moved to the Middle East in 2007. Eastwood has 17 years' experience in the industry, including previous positions within Schlumberger.