A coupled wellbore-hydraulic fracture simulator for rigorous analysis of frac-pack applications

摘要

Frac pack stimulations have been used extensively to provide a combined treatment for well stimulation and sand control. It has been observed that treatment failure in such operations is often caused by a premature wellbore screen out. However, untillnow the design and evaluation of such treatments have been performed solely using fracture simulators that neglect the effect of the wellbore hardware (crossover ports, blank, screen, washpipe, etc.) on the treatment. In an effort to address this limitation, a wellbore simulator was coupled with a fracture simulator to provide the capabilities of predicting, and subsequently eliminating, such occurrences. The fracture simulator calculates the fracturing parameters such as proppant distribution in the fracture, fracture height, and two-dimensional fluid flow. These parameters provide the boundary conditions for the wellbore simulator. Additionally, the fracture simulator was enhanced to correctly simulate fluid leakoff and tip screen out designs in high permeability formations. The fluid and proppant flow around the screen is calculated ssing a pseudo three-dimensional wellbore simulator which provides a complete design and evaluation tool of frac pack treatment. The effects of a deviated wellbore, proppant bridging around the screen, proppant settling in the wellbore, and fluid flow through the screen are taken into account; in addition, the coupled simulator can model an induced wellbore screenout at the end of the treatment either due to a deliberate reduction of the injection rate or the shifting of the tool to the circulating position. This paper shows a field example using this coupled simulator to evaluate a frac pack treatment that was terminated due to a premature screen out. The calibration test is initially analyzed following which the frac pack treatment is simulated and compared with field measurements.