Paper: Working Pressure Upgrading of Wellhead Equipment For Stimulation Work

One of the most common problems encountered in designing a stimulation treatment is a low working pressure rating of surface equipment. Quite often, tubular goods are capable of much higher working pressures than the wellhead equipment, and the primary limit of pressure and injection rate is above ground. Breakdown and "Ball Out" treatments are often restricted by low working pressure ratings when the maximum allowable pressure at the pump is less than the pressure required to inject fluid into new or fluid-damaged perforations. Even though high pressures may be required for only a few minutes, it is vital to successful completion of a well that each perforation or zone be opened. Pressure limitations can be especially critical since the fracture area developed and proppant transport are direct functions of injection rate. When the pressure limiting component of a well system is above ground it can usually be "upgraded" safely and reliably by one of these methods: 1. Isolating the wellhead from treating pressure 2. Substitution of a "Treating Tree" for the production Christmas tree 3. Special landing joints or "Top Out Joints" for working through blow out preventers or wellhead assemblies where conventional trees have not been installed. Each of these methods has its strong and weak points and warrants detailed examination.