**4.3 Selection for re-fracturing**

Many wells are drilled with outdated completion designs; for that, they aren't efficiently producing the reservoir formations. These wells are specifically targeted when engaging re-fracturing because it is an economical practice to mitigate the flow rate decline and maximize reservoir deliverability [44].

The process of choosing which well to re-fracture is known as "candidate selection" [45], and the following are criteria which are often considered [46]:


**Figure 4.**

*(left) a hydraulic fracturing stimulation created a fracture network (right) after re-fracturing, and additional complex fracture network has developed (Allison & Parker 2014 [38]).*

The selection methodology must be customized to fit the particular needs of a given field where substantial incremental reserves can be added if the correct candidate selection process is followed [47].

#### **4.4 Evaluation of re-fracturing**

After re-fracturing, a well may experience increase in production due to new fractures or extension of existing fracture networks. The success of re-fracturing can be determined by empirical parameters such as production rate 30 days before and following re-fracturing, EUR ratio based on DCA [48].

Computer programs can simulate re-fracturing scenarios at a considerable degree of accuracy despite the fact that all predictive methods lack robustness that accounts for the original production depletion and the conditions after re-fracturing. However, as technology advances, well performed computer models are able to generate trustworthy forecasts that allow decision-makers to confidently evaluate the economic success or failure of re-fracturing.
