Waste water disposal wells have a set of unique challenges that accompany their respective stimulation treatments. Those challenges are mainly attributed to the sub optimal quality of the disposed water compared to typical injection water.
A waste water disposal well has abruptly lost the ability to inject water. The subject well has been repeatedly stimulated in recent years. A full system QA/QC of the disposed water at the disposal wells has shown satisfactory results and compliances with environmental standards of water quality except for this well that ceased to inject. Well-A flowed back dead oil and exhibited an exceptionally high shut in wellhead pressures compared to offset injectors. To further identify the extent of oil inside the wellbore, a custom tailored gradient survey was conducted with multiple pressure points across the well interval. The gradient survey revealed accumulated oil columns in the upper part of the wellbore that was the main reason for the high wellhead pressure and contributed to the cease of injection.
Moreover, the disposed water has tested incompatible with normal Treatment Approachs that were successfully used in the same field. Different stimulation approaches have been considered to restore and enhance those two disposal wells injectivites. The contemplated treatment designs were plain acid treatment, acid in diesel treatment, chemical diversion, emulsion breaking surfactants, organic solvents, and mechanical diversion.
This paper presents the analytical diagnostic tools used to identify and comprehend the challenges associated with the disposal well in question and investigate probable causes for loss of injectivity using the inflow performance relation (IPR) and the out flow performance relation (OPR). Moreover, based on the findings of the IPR/OPR investigation, the paper would illustrate the best treatment to restore the injectivity of the well and delineate the decision making processes that have led to the successful flow back and stimulation treatment of the two waste water disposal wells using organic solvents and plain acid. Rigorous assessments of chemical treatment elements, treatment deployment methods, and stimulation techniques will all be thoroughly presented in this paper.