Well Testing by Deduction

Showing how Solution Seeker successfully use a deduction test methodology to achieve high-quality well tests.

Traditionally, well tests are performed by routing individual wells through a test separator, allowing engineers to isolate a single well’s behaviour. However, for various reasons, a test separator might not always be available. This can be due to tie-ins, physical restrictions or other constraints in the production setup.

One option to the traditional test separator is a deduction test. In this test engineers try to single out a well’s production by looking at the difference in total production when shutting down one well at the time. As production is temporarily reduced, it’s critical that these tests are conducted as efficiently as possible while still obtaining high-quality results.

Deduction testing

Normally, several wells are producing into the same production separator. Thus, we can measure the total production from all of the wells, but do not know the contribution from each individual well. The trick is to close one well and now measure how much less the wells are producing. This drop in production is equal to the now closed in well's contribution. Note that this process can be complicated in practice as closing one well will affect the production of the other wells and tuning is typically required to ensure that the other wells are producing under similar circumstances as before closing the well.

Solution - an application that aids the engineer in all the phases of testing
To make deduction tests run as efficiently as possible while still producing solid results, we have developed a proprietary deduction test application. There are four main processes the application assists with before, during, and after testing.

Before testing is initialized it is important to determine a stable time interval with low uncertainty in the rate metrics as a benchmark for the test. The application automatically picks out stable periods using our proprietary data-mining framework Squashy.

Once the test has started and the well in question is shut-in, the application helps the production engineers to monitor the remaining wells that are still producing. The objective is that the remaining wells are producing under conditions that resemble the state before the well was shut-in. This is to make sure that we can make a fair comparison, and isolate out the effect of only the well that is being tested.

When the test period has stabilized and the producing wells are close to their original state, the application analyses the uncertainties of the test parameters. Once the uncertainties are within acceptable thresholds, the engineers are notified so that they can end the test with high-quality results.

Finally, all historical tests are stored and structured in a well test database that gives an easy accessible overview of tests. The application will also detect all historical tests and stores them in the same database. For convenience, the results can be exported to common file formats.

Outcome - more efficient testing and less deferment
Within the use case of deduction testing our partners have experienced several benefits with our solution.

One of the greatest benefits of having live data available is the ability to become condition-based in everything we do, including deduction testing. One of the key value drivers of this application is the facilitation and enabling of the engineers to run shorter tests based on knowledge of the uncertainty in the test results. Instead of running fixed-length tests, our partners are now able to finish the test when they have an acceptable result, which can be hours earlier than what they used as a fixed length earlier.

The uncertainty measures in themselves are also valuable, since they act as a live quality measure. This makes it possible to factor in the uncertainty and quality when comparing the results over time, to see how the wells are evolving. Further, the application allows the production engineer to customize what measurements they want to look at, and is an efficient workflow tool that gathers all the important information in one place.