Research and development as well as field testing of re-frac candidate selection dates back to late 1990s and early 2000. Originally, re-frac (also called re-stimulation at the time) was routinely applied to gas storage wells to maintain deliverability and later to vertical production wells completed in tight gas formations. Completion and production of tens of thousands of shale wells that are characterized by high initial production followed by a sharp decline made it all but obvious that re-frac will become a prominent production strategy sooner rather than later.
The new commodity prices will make the application of re-fracturing in shale wells an attractive alternative to drilling new wells. Two facts make re-fracturing of the shale wells an attractive proposition:
only half of all hydraulic fracture stages end up being productive during the first round of completions,
the stages that have been successfully stimulated and have produced substantial amount of fluid, now have altered stress fields and therefor new fracs will penetrate new horizons.
Therefore, chances are that re-fracs will be accessing new and untapped reserves and will be just as effective as drilling new wells with better economics.
Once the decision is made that the re-frac is a viable production strategy, the question becomes, which wells should be re-frac-ed first? Operators must select from hundreds of potential candidate wells, those with the highest return on re-frac investment will be the best candidates. In such situations the operator is faced by two options:
use intuition or the traditional approaches,
learn from the data generate from completing the wells during the original completion in order to make the best decisions on re-frac candidates.
This paper presents a unique workflow for shale wells re-frac candidate selection based on advanced data-driven analytics. The workflow is presented in the form of a case study that includes hundreds of shale wells in Marcellus Shale. It is demonstrated that the data (well construction, well logs, completion and hydraulic fracturing practices along with production history) that is generated during the original development process can provide a treasure trove of information for making decisions during the re-frac stage of the field development.
