| Popis: |
Multiwell pilots are the final step of enhanced oil recovery (EOR) screening before the final investment decision. Data gathering is the primary purpose of any pilot, including data about the reservoir's response to the EOR method. A common technique for gathering data about spatial and temporal change in the reservoir resulting from injecting an EOR agent is time-lapse logging of an observation well positioned at some distance between the injectors and producers. Conventional observation wells are completed in cemented steel casing across the reservoir, and logged with nuclear measurements. However, fibre-reinforced plastic (FRP) casing is used instead of steel when a more sophisticated logging suite is required. For example, induction resistivity, crosswell resistivity, surface-to-borehole resistivity, and nuclear magnetic resonance are additional measurements that can be obtained if the casing material is nonconductive and nonmagnetic. It is important to establish that the annulus of any cemented well is hydraulically isolating. This is critical for an observation well in an EOR pilot to ensure that the well is not short-circuiting the flow of injected fluids via annular channels. Cement evaluation of steel-cased wells has been a routine service since the 1950s, with four generations of tools developed to refine this measurement. There is less experience of cement evaluation behind FRP casing. An acoustic-based method of cement evaluation has been demonstrated in one FRP casing size and thickness with laboratory experiments in a water tank without cement. The variation in FRP casing manufacture and casing wall thickness means the result from this experiment is not universal. A field procedure has been developed to extend this initial experiment to any FRP casing sample, and any cement recipe, and to measure both cemented and free FRP casing. These field experiments will determine for a specific FRP casing sample and cement whether the acoustic-based method of cement evaluation will provide a valid cement log. |
