SpecialReport: Logging-While-Tripping The basic objective of all well stimulation is to get the best treatment compatible with cost. Why should the cost-to-information ratio consideration not govern the realm of fracture diagnostics, specifically the linked measurements of PCE and SDE? LWT provides a cost-effective alternative for acquiring high-quality data without many of the cost and operational barriers associated with deploying fiber optics or other fracture diagnostic techniques, but also can be used in combination with these diagnostic measurement tools. PCE originally was defined as a percentage of stimulated clusters over the total planned clusters per unit of measurement, mainly because of radioactive tracers being the primary diagnostic tool available at the birth of the unconventional developFIGURE 1A Neutron Count Rates Before and After Fracturing ment. Since the arrival of fiber optic sensing as a diagnostic tool for fracture monitoring, PCE has been redefined as the percentage of fracturing fluid entering a cluster with respect to the total amount of injected fluid per stage. Clusters that receive " full treatment " significantly outperform those that receive a small treatment or are screened out during stimulation. Stages and clusters with less effective treatment distribution have less effective productivity. PCE has been measured with a variety of technologies, including fiber optics distributed acoustic (DAS) and temperature (DTS) sensing, radioactive tracers, borehole imaging and production logging. While each of these technologies determines PCE through different measurements, they all strive to understand SDE for a given treatment stage. Recent fracturing trends have started to reverse the decade-long practice of reducing stage length and perforation cluster spacing in an effort to lower development costs. Aggressive limited-entry perforating designs have enabled successful extended stage length applications. SDE can decrease with an increase in the number of clusters treated per stage and a heel bias often exists when net entry pressure is variable. This decreased SDE translates into poor production performance. Near-Wellbore Region Lower PCE and poor SDE is driven by differences in the net entry pressure at each perforation cluster along a fracturing stage. Variability in net entry pressure is More Fluid Less Fluid FIGURE 1B Perforation Depths Plotted with Derived Frac Water Saturation (Individual Stage) SRV 12 ft 50 THE AMERICAN OIL & GAS REPORTER Neutron Count CH 100 Neutron Count OH STAGE 28 STAGE 29 100 400 400 10.8% 16.1% 9.4% 14.4% 15.8% 26.7% 7.1% STAGE 28 STAGE 27