The determination of maximum injection pressures is an important component of planning and permitting for deep well disposal of liquid wastes. In the United States, safe injection pressures are defined as those that do not initiate or propagate fractures. The maximum injection pressures are often based on the closure pressure at the wellbore; however, higher pressures can sometimes be demonstrated to be safe. This was the case during the recent preparation of a nomigration petition and permit applications for deep well injection at the BP Chemicals Inc. Lima, Ohio, facilities. In this case, a substantial database existed, which included core mechanical properties, in situ stress tests and transient pressure tests on a specially drilled Stratigraphie test well, as well as about 20 years of injection flow and pressure history. These data were used to provide the required assurances to the regulatory agencies that injection over the closure pressure could be adequately defined. This analysis was complicated by the stress dependance of the injection formation permeability and the pluggage of the near wellbore region due to fines in the injection stream. This paper describes the database used and the analyses conducted to demonstrate that injection above closure pressure at BP Chemicals' facilities at Lima, Ohio, does not initiate or propagate fractures in the injection zone and that the injected fluids will be contained in the injection zone for at least 10,000 years.

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