Injection water quality is a primary factor affecting the ease with which water can be injected into a reservoir and the overall success of a waterflood operation. Proper water quality can also keep waterflood maintenance costs low by reducing the amount of remedial work normally required on injection wells. Most injection systems if properly designed minimize oil carryover and solids content. Water conditioning prevents scale deposition, reduces solids, and allows recovery of carryover oil, resulting in minimum injection pressures. The type of water conditioning process necessary is determined by equipment evaluation and water analyses (including compatibility predictions and membrane filter testing).
Equipment evaluations, such as retention time studies that determine vessel residence time, describe the current mechanical operation of the system. Water analyses and compatibility studies predict the probability of scaling, corrosion, and solids formation occurring within the system. Membrane filter tests are performed to determine the type and amount of suspended solids contained in the water. From these tests, proper water conditioning techniques are implemented. All data should be gathered throughout the system to detect changes occurring between the water source(s) and the injection wells. Changes in such factors as pressure, temperature, and dissolved solids influence problem development.
Graphic representation of data, such as oil concentration (ppm) versus time (days) of a particular vessel's influent and effluent, assists in setting and meeting objectives for injection water quality. Special analyses, such as core flow tests and filtration studies, also define cost-effective solutions to problems.