This paper presents the results, both of lab tests and field job, of the application of an innovative fluid, based on nanoemulsion technology, as cement spacer during a production optimization operation.
The exclusion of production levels in the well is a key operation during the cultivation of mature fields, especially at the occurrence of the arrival of formation water in wellbore; the usual practice is the exclusion through the displacement of a cement packer placed in front of the previous perforations, in order to be able to execute new ones above the water table: in the case reported, the cement packer was performed in an intra-packer zone performing an short-to-long string displacement with coiled tubing.
In addition to the cement slurry itself, during the execution of a cement packer are also involved other fluids, on all cement spacers: key performance of these fluids are related to wellbore cleaning and wettability modifications, especially in presence of Oil Base Mud used in drilling operations. In this case it was decided to use as cement spacer a specifically tuned nanoemulsion, the nanospacer, where the selected solvent and the high surface area led to a very high efficiency (with respect to commercial spacers) on OBM removal from the casing; furthermore, the selected surfactant mixture was able to efficiently reverse the wettability (with respect to commercially available spacers) increasing the cementing job efficiency.
This article reports the entire nanospacer selection process, based mainly on the comparison and compatibility lab tests with the commercial products and fluids involved, which then depends on the usage procedure in the field to increase its efficiency and effectiveness.
The conclusions reported at the end of this article show the final outcome of the work and the evidence of its success; it is therefore underlined how this technology can be properly applied in the context of the optimization of production and cement jobs, with the possible replacement/implementation of the existing technologies in use today.
Ensuring correct hydraulic isolation in the well, whether it is for primary cementation, a cement plug or partitioning of production levels, is not exclusively achievable through correct cement formulation and correct placement, but it is also necessary that the preparation and cleaning of the well are properly executed and with suitably formulated spacers.