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SPE 53821 described a process for NORM/NOW (Naturally Occurring Radioactive Materials/Non-Hazardous Oilfield Waste) remediation that has benefits to industrial, regulatory and general public concerns. For the process to be successful the method must be adequately monitored. Both surface and downhole data must be monitored with a "cradle to the grave" mentality to ensure that the economic success of the process translates to practical safety and long-term containment. This paper describes the monitoring process, data analysis and equipment that was used at the CNO#2, NDW (NORM Disposal Well) site in Fourchon, Louisiana. The paper also discusses diagnostics that could not be applied for various reasons due to locale and well conditions. We will provide a description of the process to date and the "learning curve" of Phase 2 of the remediation project. Briefly, slurry waste injection is a process to inject slurry of 30-40% solids into a suitably characterized subsurface reservoir. In the case of NORM/NOW it merely means putting back the waste from where it came. The slurry is injected at 14-20bpm (barrels/minute) at 3900-4200 psia (BHP, bottomhole pressure) to 5000 feet. Typically, injection is initiated with clean water at or above fracture gradients. Injection is initiated as a step rate up to fracture pressure. Solid waste is then added to the process until the desired fluid properties are reached. The process is cyclic with 12-hour injection periods and 12-hour falloffs. The 12-hour cyclic process leads to a practical onsite operating scenario i.e. daylight operations with the same operating crew therefore minimising inconsistencies. Pressure data from both the injection and falloff periods are analyzed. The data acquisition covers a) continuous recording of surface and bottomhole pressures, b) cased hole injection logs, c) surface injection rate and density measurements, d)daily reporting of surface parameters and unusual parameter events, "incidents". The data analysis covers a) step-rate tests, b) injection and falloff tests, c) cased hole log analysis. The open hole log analysis was described in the previous paper and will be further refined here. Several "incidents' are presented to illustrate abnormalities with this kind of subsurface injection. |
