Chemical Effect on Wellbore Instability of Nahr Umr Shale

Table 1

The drilling fluid properties of three horizontal wells of Nahr Umr Formation.

	Well no.
	N001H well-Hole 1	N001H well-Hole 2	N002H well	N006H well
Mud type	KCL-polymer	KCL-polymer	Salt saturated	BH-WEI
Density (g/cm^3)	1.25	1.25	1.28	1.28
Viscosity (s)	51	53	78	65
Plastic viscosity (cp)	26	27	41	39
Y.P (lb/100 ft^2)	24	26	31	29
Gel strength 10′′/10′ (lb/100 ft^2)	5/8	5/14	7/9	5/7
API filtrate (mL)	3.2	3.4	3.0	3
Mud cake (mm)	0.3	0.3	0.3	0.5
PH	9.5	9	9	8.5
Solid (%)	13	11	13	17
Sand (%)	0.3	0.3	0.2	0.3
Bentonite content (g/L)	27	26	38
Potassium (mg/L)			27000
Chloride (mg/L)			55000	11520
Ca^+ (mg/L)			200