A MORE COMPLETE MODEL FOR INJECTION WELL TESTING THAT INCLUDES THE EFFECTS OF SOLIDS DEPOSITION, TWO PHASE FLOW AND INJECTION INDUCED FRACTURES

Step‑rate injection well tests and production logging tools (PLT) are used to measure the injectivity, fracturing pressure and injection profile in an injection well. These measurements are significantly influenced by two‑phase flow, solids deposition and creation of any injection induced fracture in an injection well. The standard injection well test does not include two‑phase flow, solids deposition and injection induced fractures but rely only on single‑phase pressure transient equation with a constant skin. Applications A comprehensive injection well test simulator is developed that adds the effect of solids deposition and fracture growth to an approximate two‑phase pressure transient solution for more accurate interpretation of injection well tests. The presented model can be used for 1) low step‑rate injection tests under matrix injection to confirm the reservoir permeability, formation thickness, and initial skin; and 2) high step‑rate injection tests under fracturing conditions to predict the minimum horizontal stress, induced fracture lengths and injection profile expected during a water‑flood. Results, Observations, and Conclusions Since most injectors are fractured, it is shown through model results that injectivity tests are affected in a significant way by solids deposition and transience in the injection induced fracture lengths (ex. creation of an induced fracture or opening and closing of existing hydraulic fracture). A case study is presented where BHP and injectivity for an actual injection well is matched. Technical Contributions Standard injection well test can not model the dynamic skin created in an injection well due to solids deposition and fracture growth when injecting above the fracture gradient. For the first time a more complete injection well test model is developed based on Gringarten's infinite conductivity fracture model with two‑phase flow approximation for an injection well along with solids deposition and changing injection induced fracture lengths.