Most completion engineers use two-dimensional fracture models to design hydraulic fracture treatments. These engineers also use two-dimensional reservoir models to analyze post-fracture production and pressure buildup data. Normally, a completion engineer will concentrate only upon a single zone and will often design a well completion based upon the properties of that zone as computed from log data, core data, drilling data, or other information about the interval.
Once the interval has been evaluated, the completion engineer will pick the location of the perforations based upon the location of the net pay zone. Estimates of porosity, water saturation, and net pay thickness are used to determine where to shoot the perforations and to estimate the value of fracture height that will be input into the two-dimensional fracture design model.
By using a two-dimensional fracture design model, the completion engineer is dictating the fracture height and the fracture shape. If the engineer uses the wrong fracture height, then the calculated values of fracture length and width will also be wrong. Most of the time, an engineer tends to underestimate fracture height and, thus, overestimate fracture length.