Summary

Foam fracturing fluids provide a means to reduce water consumption by replacing most of the water used in a fracturing job by industrial gases as N2 or CO2. Foams also have the potential to provide increased well productivity, based on improved proppant placement, faster fluid cleanup and reduced reservoir damage. We have built a new experimental apparatus to measure the transport of proppant by foams under high pressure (2000–3000psi) and developed a computational fluid dynamics (CFD) model to enable extension of the results to real fracture geometries. Our laboratory results show that proppant transport by water is dominated by bed transport, whereas transport by foams is primarily in suspension. Both simple foams (without thickener added) and thickened foams transport proppant substantially further than water.

Introduction

Oil and gas sources that rely on hydraulic fracturing have remained active even in the face of dramatically lower prices. This is further evidence, if it were needed, of the tremendous economic significance of fracturing technology. Nevertheless, improvements in the productivity of fractured wells, and management of their environmental impact, are both urgently needed in order to continue to meet stringent cost per barrel (or per cubic foot) requirements. The current rigorous market is the right time to implement technological improvements that can lead to higher production per well.

In parallel with productivity improvement, it is necessary to manage the overall "footprint" per well, i.e. the consumption of resources, most notably water and proppant. Progress in these areas also reduces truck traffic to and from the wellsite. These advances are win-win solutions, reducing producer cost and environmental impact in a single move.

The idea of using foam fracturing fluids to reduce water consumption and disposal requirements, by replacing most of the water used in a fracturing job by N2 or CO2, is not new. However, foam fluid implementation is generally limited to underpressured or highly water-sensitive reservoirs. This is largely attributable to logistical issues in N2 and CO2 supply, lack of availability of pumping equipment and capable crews, and perceived higher cost. In this article we will briefly discuss how foam fracturing can reduce total fluid consumption, i.e. not simply replacing water by N2 or CO2, then introduce our new laboratory apparatus designed measure the transport of proppant by various fracturing fluids, and finally review our initial results comparing foams with water. These results support the proposal that foam fracturing fluids can provide improved proppant placement and therefore improve well productivity, as well as reduced water consumption.

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