3-1/2 " stage collar 一、Application 3-1/2”Drilling stage cementing tool is a special equipment which divided the cementing job for twice. It’s mainly used for the following condition. 1. A large amount of cement 2. The stratum cannot bear too much fluid column pressure 3. Seal off special horizon 4. Prevent air channeling after cementing 5. The temperature difference is too big between interval isolation ,cement slurry performance is not easy to adjust. 二、Structure 3-1/2 ˝(Ф88.9)stage cementing tool is mainly composed by two stage collar(body)、 Flexible plug、flexible plug seat(bump pressure seat)、gravity type open plug and closing plug. 三、Performance feature 1.The open plug seat and closing plug sleeve with left-hand to connect the threads, in case of rotating when drilling the open plug seat 2.Special organization prevent closing seat…