Stable Dispersion of Coal Fines during Hydraulic Fracturing Flowback in Coal Seam Gas Reservoirs An Experimental Study

TL;DR

This study investigates how additives like SDBS and ethanol can stabilize coal fines in hydraulic fracturing fluids, reducing fines aggregation and retention, thereby improving the reliability of coal seam gas extraction.

Contribution

It provides experimental evidence that trace amounts of SDBS significantly enhance coal fines dispersion stability under various conditions, a novel approach for improving hydraulic fracturing fluids in CSG reservoirs.

Findings

SDBS at 0.001 wt% drastically improves dispersion stability.

Lower fines retention with SDBS confirmed by fractal analysis.

Additives effectively reduce fines aggregation across tested pH and salinity ranges.

Abstract

In subterranean coal seam gas CSG reservoirs, massive amounts of small-sized coal fines are released during the production and development stages, especially during hydraulic fracturing stimulation. These coal fines inevitably cause mechanical pump failure and permeability damage due to aggregation and subsequent pore throat blockage. This aggregation behavior is thus of key importance in CSG production and needs to be minimized. Consequently, such coal fines dispersions need to be stabilized, which can be achieved by the formulation of improved fracturing fluids. Here, we thus systematically investigated the effectiveness of two additives; ethanol, 0.5 wt percent and SDBS, 0.001 and 0.01 wt percent, on dispersion stability for a wide range of conditions: pH 6 to 11, salinity of 0.1 to 0.6 M NaCl brine. Technically, the coal suspension flowed through a glass bead proppant pack, and fines retention was measured. We found that even trace amounts of sodium dodecylbenzene sulfonate SDBS i.e. 0.001 wt per cent drastically improved dispersion stability and reduced fines retention. The retention was further quantified by fractal dimensional analysis, which showed lower values for suspensions containing SDBS. This research advances current CSG applications and thus contributes to improved energy security.