**9. Opportunities to improve fracture performance**

It is important to recognize that our intuition, our models, and our traditional interpretations of fracture performance are flawed, and can prevent us from recognizing opportunities to improve well productivity. While our industry has collected data demonstrating complexities (in reservoir description, in fluid flow regimes, in fracture geometry, in durability of proppant packs), the industry has been very slow to adapt designs to accommodate or capitalize on these realities.

More than a dozen specific recommendations have previously been discussed [19] to improve the productivity and profitability of fracturing treatments. However, a general theme is to continue experimenting and studying production from wells, with a healthy skepticism of model predictions and of historic rules of thumb regarding fracture design. Another common finding is that emphasis on improving the effectiveness and durability of treatments appears to be adding more value than blindly focusing on fracture length or treatment volume. There are a great number of field examples in which modest changes to fracturing designs resulted in very large changes to well productivity, convincingly demonstrating that our initial frac designs were insufficient to capture the full well potential. Figure 10 shows surprising increases in productivity were achieved by restimulating a modest perm oil reservoir and a tight gas reservoir with improved fracture designs more focused on the durability and conductivity of the fracturing treatments.

**Figure 10.** Experimentation with frac design often demonstrates the well potential is constrained by insufficient frac‐ ture designs [1, 20]

Similar production increases have been documented in hundreds of field studies in shales, carbonates, coals, and sandstones [1]. On one hand, it is frustrating to admit that after decades we have failed to optimize our fracturing treatments. On the other hand, it is great news that our fracs are not optimized. Reservoirs are often capable of tremendous increases in produc‐ tivity with improved fracture designs that accommodate and capitalize on our understanding of complexity.

### **Author details**

Vincent M. C.\*

design. There have been more than 140 published examples, and history-matching attempts have frequently indicated that fractures are not as effective or durable as previously

**•** Fields in which a carefully conducted field trial examines the role of a single variable in fracture design. For instance, when 150 wells are treated at 4 ppg and 150 offset wells are systematically selected to receive 6 ppg slurry, it is possible to achieve comparisons with compelling statistical significance. The difference in productivity is known to relate to the frac performance, and cannot be attributed to reservoir parameters. The evaluation of 200 published field examples [1] provides very credible evidence that fracs do not perform as most people anticipate, and that increased focus on fracture conductivity is merited.

**•** Wells that are connected by a propped fracture. As described previously, fractures can reach impressive lateral dimensions. It is not uncommon for fractures to intersect adjacent wellbores completed at the exact same depth or in the same formation subinterval. When this occurs, it provides a significant opportunity to investigate the initial and sustained continuity over time. In most cases, adjacent wells appear to lose hydraulic continuity over

**•** Infill drilling. In many tight reservoirs, we have successfully drilled wells within 200 feet of existing wells and encountered near-virgin reservoir pressures. In many shale reservoirs, infill wells are anticipated to recover nearly 80% of the reserves of adjacent parent wells drilled many years earlier, demonstrating that initial wells have not captured the available

**•** More sophisticated modeling and data analyses. While simple production data analyses yield non-unique solutions, several degrees of freedom can be removed with careful analyses of pressure-transient or rate-transient data. There have also been advances in interpretation of flow regimes from wells with complicated fracture networks. Even in the 400-nanoDarcy Barnett shale, production data do not indicate that the entire created

These efforts strongly indicate that additional focus on the conductivity, durability and

It is important to recognize that our intuition, our models, and our traditional interpretations of fracture performance are flawed, and can prevent us from recognizing opportunities to improve well productivity. While our industry has collected data demonstrating complexities (in reservoir description, in fluid flow regimes, in fracture geometry, in durability of proppant packs), the industry has been very slow to adapt designs to accommodate or capitalize on these

More than a dozen specific recommendations have previously been discussed [19] to improve the productivity and profitability of fracturing treatments. However, a general theme is to

*effectiveness* of the fracture is needed – not just a focus on created dimensions.

**9. Opportunities to improve fracture performance**

time, suggesting that the connecting fracture "collapses" or "heals".

anticipated [10, 20].

90 Effective and Sustainable Hydraulic Fracturing

reserves.

realities.

network remains highly effective.

Address all correspondence to: mike@fracwell.com

Fracwell Llc, Golden, Colorado, USA
