Refracs have historically been difficult to design, complex to execute, and results largely unpredictable. Under normal circumstances initial completion designs have many unknown variables, including reservoir quality along the multistage lateral, as well as the far field reservoir quality.
When it comes to refracturing multistage horizontal wells a few newer challenges emerge, including reservoir depletion and the operation’s complexity of multiple liner stages. As for any production case study, the proof is "in the pudding," or with any technology or procedure, proof is in a production case study. For simplicity of evaluation, we have compiled all the recompletes and refractures in North Dakota. We shall evaluate the data behind the statistical refrac designs, some of the production results, and learn whatever industry can for the success and risk of refracturing wells.
Selecting informational inputs for refrac design basis may be difficult due to lack of availability. Parameters may be unavailable or unknown, to a larger extent than for the initial completion. Choosing which parameters to optimize may greatly affect incremental production results. Understanding refrac economics specifically related to production and EUR prior to re-fracing may help in de-risking projects. One of the goals of this paper is to also de-risk the theories of refracturing by documenting the statistics, successes, and failures. At the time of writing this paper, multistage fractured horizontal wells were started 20 years ago. Original completions had 20+ years of production predicted before abandonment, and many wells had been refractured instead of abandoned. The protection of primary or parent wells from fracture driven interactions (FDI) when infill or child wells are drilled and fractured have also resulted in libraries of refracs in many formations. It has been recently understood that refracturing the parent wells has aided in lowering the loss of production on the infill or child wells by reducing the pressure depletion prior to fracturing the newer pad wells. Finally, the ESG aspect and reduction of our impact on the environment by refracturing is seen in many ways, a few of which are:
• Recycling wells instead of abandoning them and getting production from new wells only
○ Saves the environmental impact of installing new pipelines
○ Limits the number of vertical wellbores surface and production casings and their seals to fresh-water aquifers and the atmosphere
• Fracturing a second time has less of a carbon footprint than drilling and fracturing a new well including duplicate operations like tie-ins and pipelines
• Increasing the recovery per well so that we need to drill fewer total wells per year, extending our energy independence for decades
A very large amount of data for North Dakota has been gathered and reviewed. The focus of this paper is on the refracs and recompletions, the operational methods, the risks, and the production results.