The Significance of Post-Injection Pressure in Well Treatments

The behaviour of wellhead pressure immediately following the injection of liquids or slurries used in well completion and workover treatments can often indicate the success of the operation. Because the rate of wellhead pressure build-down after injection is related to the transmissibility of the exposed formation to the treating fluid, an interpretation of the success or failure of the fluid to communicate with the reservoir is possible. Treatments designed to plug-up or clean-out formation flow channels can both be evaluated. Several examples are given· which illustrate how immediate estimates of treatment effectiveness and well quality can be made. Such early appreciation can speed completion and workover operations. The importance of improved data collection is stressed and a minor change in fracturing job procedure is suggested. Reference is made to additional knowledge that may be gained by quantitative analysis of post-injection pressures.