Withstanding elevated temperatures in long cement sections
In an Eagle Ford Shale well in DeWitt County, Texas, an operator sought to mill nearly 6,000 ft of cement that remained in the horizontal section of the 5 1/2-in casing with a BHT of up to 346 degF. Milling this amount of cement using a standard positive displacement motor (PDM) and conventional mills at such an extreme temperature would not be possible on a single trip due to wear and degradation of mills and motors. In an offset well in which 2,000 ft of cement had to be milled out, the operator used conventional milling technology not suited for the environment and required four trips in the well at an average ROP of 25 ft/h to complete the operation.
Delivering fit-for-purpose intervention mill performance in extreme conditions
Schlumberger recommended a 4-in i-MILL TT mill powered by a 3 3/8-in Neyrfor TTT turbodrill to deliver a longer on-bottom time to complete the cement milling operation in one run.
Specifically designed for the removal of hard scales and cement, the i-MILL TT mill operates optimally with high-speed drive systems. Using the IDEAS integrated drillbit design platform, Schlumberger designed the mill to allow for force balance at the cutting structure, reducing lateral vibrations to deliver higher ROP and reduced mill wear and damage. The Neyrfor TTT turbodrill is a unique drive system with no elastomeric components, making it ideal for HT applications or interventions requiring extended milling times with conventional or nitrified fluids.