Petrophysical workflows help maintain consistency between projects and interpreters. This is a major challenge for many companies in the oil and gas sector. Due to the interpretative nature of subsurface evaluations there are several choices that petrophysicists and geologists are confronted with, and these choices can collectively lead to interpretations that are vastly different over the duration of the project, even when both use the same data in their interpretations. The consequences of highly variable interpretations include:
- Poor capital allocation decisions. Inconsistent interpretations between workers in different plays or areas can lead management to wrongly believe that one area is better than another resulting in over-weighted capital allocation towards areas with lower reservoir quality. This is especially a problem in new areas with little to no production history and can be exacerbated by the aggressiveness in which interpreters are willing to push their own projects.
- Over/under-confidence in a company’s acreage base. Teams within companies are often split along the lines of development teams in charge of a company’s existing acreage and exploration/new ventures teams that are charged with finding acreage outside a company’s existing assets. Differences in interpretations between these teams can lead company’s to either believe that they either need to acquire new assets or shun new opportunities in favor of their own.
- Costly experimentation in a search to improve results. Companies are always seeking to improve their results, especially when competitors have superior results. However, with a poor or inconsistent evaluation of different areas within a play it is easy for management to believe that differences in results are driven by differences in drilling and completion techniques instead of differences in the underlying reservoir quality, which can lead them to fund costly one-off experiments in search of a silver bullet that doesn’t exist.
If you’ve been in the industry for a few years or more, then it’s likely that you’ve seen at least one of these first hand. If these problems go unchecked hundreds of millions in value can be destroyed while competitors thrive. These problems can be alleviated by using consistent petrophysical workflows.
When analyzing where inconsistencies begin to arise there are two areas for scrutiny:
- When interpretations move from one technical domain to another, such as from geology to engineering.
- When interpretations move from one scale to another. For example, when there is a transition from a facies-based core analysis to a regional facies analysis based on well logs.
There are many of these transitions, and when they overlap with one another there should be emphasis placed on making sure that work done translates across smoothly and in-line with the previous worker’s interpretations.
Within many company’s standard workflow there are many areas where difficult handoffs may occur, which is compounded by the iterative nature of the work and the timing of when different subsurface disciplines may be involved.
The handoff from petrophysicist to geoscientist is one that is difficult because it often involves a move from being quantitative to highly-qualitative, from a single-well focus to a multi-well focus, and from a specialist domain to a generalist domain. As interpretations are advanced through different stage gates and concepts advance to management for spending decisions inconsistencies can balloon if thorough feedback cycles and cross-checks are not regularly performed.
One of the most effective tools for battling such inconsistencies is the implementation of robust workflows.
Workflows provide a method for enforcing consistency in both the approach and in making interpretive decisions for staff. A rigorous implementation of a workflow can help managers ensure that a majority of the interpretations they are presented can be trusted. Implementing workflows is especially important at certain key moments in the interpretation, such as when G&G staff look to propagate out interpretations across a play.
Below, I present a basic petrophysical workflow that G&G staff can implement in almost any mapping package.
The workflow above is divided into two parts – replicating the key well analysis and propagating the interpretation through a play area.
In replicating the key well analysis the interpreter needs to understand what methods they can propagate through a play area. For example, if a sonic porosity model was used in the key well analysis, and very few wells have a sonic log across the area of interest, an alternative method such as a density porosity model may be required. During this phase it is also likely that the petrophysical methods will need to be simplified as many of the methods available in specialist petrophysical software may not be available within mapping packages. Ideally, petrophysical staff should be involved in this phase to prevent errors from being introduced.
Once the key well’s interpretation has been matched using appropriate methods, the interpretation can be propagated throughout the project. However, without the right tools, the resultant interpretation will be too generic. This is why Danomics Petrophysics uses parameter mapping as a method to provide every well with its own custom interpretation. Once the interpretation has been propagated throughout a play, it is important to pull in additional key wells, and do comparisons of new key wells to interpretations derived from the initial key well. If the match is still adequate then the analysis can be considered ready for use in the decision making process. If the match is inadequate, more iterations and alternative methods will be required.
By integrating a robust workflow companies can ensure that interpretations from different areas, plays, and interpreters can be treated as apples-to-apples and that the best answers are the ones rising to the top. This is crucial when making capital allocation decisions.
To enact these workflows staff need access to the right toolkits, such as Danomics’ petrophysical platform, which offers a number of workflow controls that can help ensure accuracy and consistency.