What Do the Surface Pressures Tell Us During Shale-Fracturing Operations?

摘要

The industry has relied on three primary measurements during fracturing operations: surface pressure, surface flow rate, and surface proppant concentration. The downhole environment is challenging for instrumentation. What can the surface pressure indicate? What does the surface pressure not indicate? Often, the pressure measurement is miles away from the event. This long distance often obscures the transient pressure signature, the surface pressure measurement as a function of time. These obscurations are caused by the speed of sound in the carrier fluid, the compressibility of the pipe in the completion, and other factors. A transient finite difference model of a horizontal multiple interval completion for an induced fracture shale reservoir was developed to investigate the pressure transient signatures of different events during the fracturing operation. Model results will be shown for different types of events, such as sleeve shifting, fracture initiation, opening a sleeve into a zone with an existing fracture, fracturing a zone with high leakoff, etc. Certain types of events have distinct pressure signatures. Other events can have similar pressure signatures. Some events can have no surface pressure signature at all. The model results will be compared with field data. While the focus of the results is on horizontal multiple interval shale completions, the results can also provide insight into other types of fracturing operations and will aid in the interpretation of pressure signatures.