Abstract

Foamed fracturing fluids have been used in unconventional reservoirs to reduce the water use and minimize deleterious impact on water-sensitive formations. As part of a Department of Energy (DOE) sponsored program, we previously identified an optimal thermodynamic pathway to transform wellhead natural gas (NG) into pressurized NG suitable for use as the internal phase in a foamed fracturing fluid. This study now aims to extend that work by determining the impact of using NG foam fracturing fluids on hydraulic fracture geometry and on productivity from the unconventional reservoirs.

The current study is focused on investigating the impact of the NG-based foam of various foam qualities in hydraulic fracture geometries and their production through simulation models. Field data and laboratory based measurements for NG foam fluid properties are incorporated in the study. In addition, the transient response of the fluid flowback from foam based fluid is studied using numerical simulation. Comparative analysis is done with typical slickwater, linear gel, and crosslinked fluid application for hydraulic fracturing using 3D-complex hydraulic fracture models. 1D and 2D particle transport models have been used to verify the differences in proppant distribution in the hydraulic fractures.

Rapid wellbore clean-up, low formation damage, and effect of the relative permeability improvement are added advantages apart from reducing the water requirements for hydraulic fracturing. In addition to providing the logistical benefit of using wellsite liberated low pressure gas, NG foamed fracturing fluid has a dynamic fluid leak-off behavior and increased effective viscosity over the base fluid that allows pumping and transporting proppant at least 10% farther in the hydraulic fractures than linear gel. Slickwater displays poor proppant transport and hence poses inability to pump higher concentrations of sand. NG foam fracturing fluid on the other hand displays improved proppant transport and has been shown to create more complexity than slickwater in our simulations.

Use of NG foamed fracturing fluid has not been practiced widely yet. Application of NG Foamin field test and reaping the economic benefit from simplified logistics and improved production would enables operators to invest in creating a safer handling environment for wellsite application of NG foam.

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