Experimental Rock mechanics For Selecting an appropriate drilling fluid for drilling unstable formation in Noor field.

Major challenges encountered when drilling in the last hole in Noor field due Shale problems (sweeling, sloughing, washout, …) which are often caused by Incompatibilities of drilling fluids and shale, In Tanuma formations most of the drilling problems occur in the last hole because of the high concentration of shale about 85% (Ahmed K. Abbas,2018), This shows that selecting appropriate drilling mud is important when drilling through a shale formation. Compared with Non-inhibitive fluids, the inhibitive fluids have advantages such as resistance to Swelling, resistance to Collapse, being good to maintain the borehole stability. This paper describes an experimental technique to investigate five types of drilling fluids (fresh water bentonite, FCL mud, kcl-polymer, Nacl mud, and binary brine polymer mud) by immersion shale in drilling fluids for 1 and 30 days to select an appropriate drilling fluid. Compression and tensile testing are used to determine the quality of drilling fluids by establishing a relationship between the young modulus and a compression strength in addition to the shale swelling test. The result of these investigations gives an idea of the effects of various types of drilling fluids on shale.