R.D. Barree, Barree and Associates; M.K. Fisher, Pinnacle Technologies; R.A. Woodroof, ProTechnics a Core Laboratories Company
Hydraulic fracturing is key to the economic success of many oil and gas fields around the world and has improved production in low permeability reservoirs for more than 50 years. Successful stimulations are engineered to place the proper type and volume of slurry based on estimating the dimensions of the optimal fracture to be created in a specific wellbore. Several commonly used technologies are available which determine important fracture parameters such as fracture dimensions, fracture orientation, fracture conductivity and proppant placement effectiveness. Fracture models are today's most widely used tool to predict the optimal frac geometry based on conditional inputs such as closure stress, pore pressure, permeability, fluid saturation and numerous other mechanical and petrophysical properties of the reservoir. In many cases, these parameters are based on assumptions rather than hard data, and incorrect assumptions then lead to sub-optimal stimulation results.
Direct near-wellbore diagnostics such as radioactive tracers and temperature logging are often used to gather information about fracture height and proppant placement effectiveness, while direct far-field diagnostics such as tiltmapping and microseismic fracture mapping are used to determine hydraulic fracture dimensions and orientation.
Direct fracture diagnostics alone only tell the story of what happened after the fact on a given well, but they can also be used to build a calibrated fracture model which accurately predicts fracture growth in a reservoir. Depending upon the critical information needed for specific fracture stimulation, one or more diagnostic tools may be applied. These diagnostic tools will be discussed and compared in order to provide a reference of widely used diagnostic tools with strengths and limitations discussed along with examples of each in use in fracture optimization.