Application of Mud Loss Control Techniques with High Strength Lost Circulation Materials on Well Shanan-3

The well Shanan-3 is a key exploratory well located at the No. Shanan-3 structural high in Shanan tectonic zone of the north sag in Tarim Basin. This well penetrated the Kumugeliemu Group of the Paleogene System in which multiple salt zones are developed. Above the salt zones there are multiple sandstones with low leak pressures (coefficient of leak pressure ≤ 1.4). To guarantee the safe drilling of the salt zones, the pressure-bearing capacity of these sandstones should be greatly enhanced. To control the mud losses in this hole section, a new mud loss control slurry was formulated with two core additives, one was a particle material with excellent detainability and the other, a compound lost circulation material which swells at hydration. The mud loss control slurry was optimized to make it adaptable to loss zones with different sizes of mud loss channels. Loss zones treated with the mud loss control slurry had pressure-bearing capacity of at least 15 MPa and resistance to the flow-back of the mud loss control slurry of at least 5 MPa. In field operations, mud loss control techniques of various kinds were used, the mud density was gradually increased from 1.4 g/cm³ to 1.75 g/cm³, and the pressure-bearing capacity was increased to 19 MPa, ensuring the smooth running of the casing string.