**2. Complex flow regimes**

This paper will examine five limitations of hydraulic fractures and interpretation techni‐ ques, and describe the increases in well productivity that can be achieved when efforts are

**Keywords** Frac optimization, resolving non-unique solutions, proppant degradation, realistic

Early frac engineers certainly recognized that hydraulic fractures were complex features. Geologists, mining engineers, and prison chain gangs all assured us that rocks break in complex manners. But the math is hard, and we aren't capable of predicting nature's com‐ plexity. We cannot accurately calculate the pressure losses through a proppant pack with complex geometry, irregular aperture, and with several fluid phases flowing at high velocity. So our predecessors were forced to simplify the description. As a first-order approximation, they assumed that fracs were simple, vertical planes, with uniform width and predictable

Two subsequent generations of petroleum engineers have been introduced to simplified planar hydraulic fractures that have been distorted to fit on a textbook page, such as in Figure 1. Unfortunately, many engineers mistakenly envision fracs as wide, highly conductive channels instead of thin, narrow ribbons of proppant that extend deeply into the reservoir but are vulnerable in their hydraulic continuity. Fractures are commonly modeled to be symmetrical,

**Figure 1.** The proportions of fractures are often distorted and misrepresented in simplified models. This figure implic‐

made to address and compensate for these deficiencies.

**1. Introduction**

82 Effective and Sustainable Hydraulic Fracturing

hydraulic continuity.

conductivity, laminated reservoirs, complexity, restimulation

bi-wing planes that reliably contact the targeted hydrocarbons.

itly assumes the fracture grows symmetrically on either side of the wellbore.

Even if fractures were simple, wide features, with perfectly uniform proppant arrangements throughout the entirety of the fracture length and height, our industry would still overestimate the flow capacity of fractures by several orders of magnitude. Figure 2 shows the apparent flow capacity of proppant packs, measured in the laboratory.
