Chemical Effect on Wellbore Instability of Nahr Umr Shale

Table 6

Experimental results of shale UCS after immersing in drilling fluid.

Drilling fluid type	Organic salt	KCL-polymer	Gel-polymer
UCS without immersing (MPa)	48.62	51.09	47.22
UCS with immersing of 24 h (MPa)	40.16	44.8	44.8
UCS with immersing of 48 h (MPa)	37.81	41.41	43.02
UCS with immersing of 72 h (MPa)	35.64	39.82	41.69
UCS with immersing of 96 h (MPa)	34.96	39	40.33