Laboratory and Mathematical Modelling of Fines Production from CSG Interburden Rocks

Abstract

Twelve clastic core samples from the Walloon Coal Measures, Surat Basin were tested for disintegration in artificially produced fluids varying in ionic strength. XRD data confirm the presence of smectite (water sensitive clay) in the samples. Flow-through rock disintegration experiments demonstrate that the higher the concentration of smectite and soluble plagioclase is, the quicker rock disintegrates in artificial low ionic strength fluid. Pre-soaking of rocks with high ionic strength fluid reduces rock disintegration rate in low ionic strength fluids. This is explained by very strong clay-clay and clay-sand attraction forces, evidenced through zeta-potential measurements, which inhibit rock degradation. For the studied samples it is clear that rock disintegration rate is proportional to fluid velocity. Experimental rock disintegration data are fitted by a power erosion model with two adjusted parameters: fluid ionic strength and Reynolds number. The experimental results satisfactorily agree with theoretical data. Rock disintegration rates are calculated as released particle volume per thickness of interburden layer per day at a fixed Reynolds number and low ionic strength. The laboratory work suggests that keeping wells under strong ionic fluid during shut-in times and a reduction of water production rate will preserve rock integrity for a longer period of time.

Response and Mechanism of Coal Fine Production to Differential Fluid Action in the Baode Block, Ordos Basin

“…(1) the low rank coal in the Powder River Basin has extremely high reservoir permeability and shallow coal seam burial depth, often achieving high production without fracturing and other stimulation means, which significantly reduces the occurrence of coal fine production [13] and (2) the solid particles produced by low-rank coalbed methane wells (such as in the Surat Basin) are mainly inorganic minerals from sandstone and mudstone interlayers in coal measures, which is due to the thin interbedding of coal seams and sandstones in this basin, the low diagenesis of sandstones, and the easy disintegration into coal fine under the action of water sensitivity, acid sensitivity, etc. [14,15]. However, the physical properties and solid particle production of low-medium rank coal reservoirs in China are different from those in foreign countries, and the permeability is very low.…”

A novel approach for using silica nanoparticles in a proppant pack to fixate coal fines

“…Bituminous coal fines have been shown to cause a 35% decline in permeability when subjected to water flow (Guo et al 2016) and a 24.4% decline in conductivity when subjected to only 2% of coal fines flow into the proppant pack (Zou et al 2014). Thus, coal fines can block the proppant pack and cause a decline in fracture conductivity (Bai et al 2017), resulting in reduced production and failure of production equipment (Marcinew and Hinkel 1990;Badalyan et al 2016). Several authors have studied coal fines suspension thus far, but have largely performed experiments in DI or distilled water (Zou et al 2014), while hydraulic fracturing fluid is usually saline (nearly 0.6 M) to be geo-chemically compatible with reservoir formations fluid (Guo et al 2015;Patel et al 2016;Shi et al 2018).…”