SpecialReport: Seismic Acquisition & Reservoir Modeling FIGURE 2 Imaged Volume Depth Slices Centered on Frac Stage During Three Minutes of Pump Time 30 Minutes (Left) And 70 Minutes (Right) after Starting Pumping for that location). A synthetic signal was imposed in the traces at each location and imaged using the depth imaging method. The signal for each location focused the voxel in the depth volume for the source of that impulse. Multiple impulses were inserted in the trace panel for each location, but all impulses occurred within the same time window of the trace data and were integrated across that time window. There was no signal in the trace at the upper left corner of the depth slice. At the upper right location, there was one impulse in the data. The middle location had three impulses and the lower left location had 10 impulses. The location with only one impulse is much weaker than the image at the location with 10 impulses. Accordingly, the depth volume accurately mapped the locations of the impulses and showed that the integration process combined all of the impulses at a single location to build the signal and suppress the noise. Figure 2 illustrates the episodic nature of the fracturing process. Both images show a depth slice at the well depth of FIGURE 3 Induced Fractures by Time of Activation During Treatment Early in Stage Activation Time 104 THE AMERICAN OIL & GAS REPORTER Late in Stage the imaged volume centered on the location of one stage of a multistage horizontal well. The left-hand image shows the integration of signals from this stage over three minutes of pump time at 30 minutes after pumping started. The right-hand image shows the integration of signals from the same stage location for three minutes of pump time at 70 minutes after pumping started. As can be seen, the same fracture is activated at two times during pumping. The amplitude of the first activation is clearly much larger than the amplitude in the second activation of the same fracture. During the process of computing and integrating the depth volumes of seismic signals, a record is kept of the clock time at which each voxel is activated. The clock time of fracture activation is called fracture propagation (FP) and provides the time sequence of fracture opening. This allows fracture formation to be tracked over time through the volume and adds detailed knowledge of the fracture opening process that can be used in treatment design. Figure 3 shows the total induced fracture system for the entire pumping time for the same frac stage shown in Figure 2. The colors show the first time of activation for each part of the fracture, from early to late stage pumping (the earliest times are at the frac stage location along the well). The first time of activation goes to the left early in the pumping process and then progresses systematically to the right during the remaining pumping time. The activation to the left happens in a very short time interval, while the