Recent advances in hydraulic fracture mapping technologies have provided a wealth of information on fracture propagation in numerous geologic settings. Prior to such detailed measurements of actual fracture growth, fracture propagation was either assumed to be simple (single planar fracture) or the complexity was inferred based solely on fracturing pressure data. The nature or detail of this inferred fracture complexity and how it related to actual fracture growth (real fracture geometry) could not be determined. This resulted in significant uncertainty in fracture modeling, treatment designs, and many times, suboptimum field development. This paper illustrates the application of the various methods and techniques available to diagnose fracture complexity, including simple pressure diagnostics such as G-function pressure decline analysis and sophisticated microseismic and tiltmeter fracture mapping technologies. After identifying complexity in hydraulic fracture growth, this information must be integrated with fracture, reservoir, and geologic models to properly evaluate stimulation, completion, and develop options; however, without properly identifying the nature and detail of the fracture complexity, the solution can many times be wrong – resulting in economic loss.
This paper documents field observations of different mechanisms that result in fracture complexity and the corresponding physics that govern fracture growth in these reservoirs. These field observations of fracture complexity are supplemented by and related to results from mine-back and core-through experiments to better understand the relationship between fracture complexity, rock properties, and geology. Distinguishing between the various types of fracture complexity and properly modeling these complexities (in both reservoir and fracture models) can lead to significantly different treatment designs and field development strategies. The paper includes field case histories that document how the remediation of fracture complexity can lead to stimulation success, while in other cases it is the exploitation of fracture complexity that is the key to success.