Abstract
A recent paper published data describing interactions between shale and commercial ceramic proppants. It reported that the diagenetic outgrowth materials formed were zeolites. The creation of these zeolites was reported to largely depend on the characteristics of the formation mineralogy and the fluid medium. It was further reported that when tested under dynamic conditions, these diagenetic-type reactions were not observed. The standard API crush test was used to indicate the percentage of fines generated.
This paper presents the results of extensive laboratory testing with sandstone and bauxite proppants at moderate reservoir temperatures and normal reservoir pH in which dramatic loss of proppant-pack permeability and proppant strength were observed. Zeolites were identified and responsible for much of the fines material created during the testing cycle. Zeolite deposits were also detected, even when bauxitic proppants were aged in the aqueous fluid medium alone. In both cases, the fluid medium was DI water, which is not a source of any metallic element. These results indicate that zeolite formation is also dependent on the chemistry of the proppant. Similar results have been reported for tests conducted under dynamic flow conditions. It is crucial to ensure that the true value of proppant strength degradation is determined; however, it is questionable that the API conductivity testing procedure is the best method.
This paper presents repeatable data generated from laboratory tests at reservoir temperatures, as well as at elevated temperatures, that indicate conditions under which zeolites are formed and the effect on proppant strength degradation using both single-grain crush-strength analysis and the API conductivity procedures. This data provides better information for the proper selection of proppant for given formation conditions.
