Two wells have been designed and completed using a combination of monitoring, isolation and injection control equipment to provide an understanding of injection behavior in extended-reach laterals and possible matrix bypass events (MBE) in the Nikaitchug field in Northern Alaska. These lower completion designs also provided a means to evenly distribute injection along the length of the lateral section as well as a means of mitigation and control of water if necessary.
In order to facilitate direct injection, a specifically formulated breaker system was developed to provide a delay to allow spotting in the openhole horizontal prior to running the liner and lower completion injection control assemblies. The ability to place the breaker system after drilling the horizontal mitigated risk associated with temporary flowback when inflow control devices were installed. Both post intervention and flow back were not desired.
The breaker system was formulated to provide a delay and allow the liner and injection control assembly to be installed before degradation of the residual filtercake caused uncontrollable losses thus allowing the completion phase to proceed as planned. The filtercake was deposited by a reversible invert reservoir drill-in fluid system used to drill the horizontal sections. The breaker system was unique in that it was blended as an invert emulsion and consisting of an oil continuous phase and an aqueous discontinuous phase that included a glycol acid precursor. An oil-based system was desired to reduce friction thus facilitating the installation of the lower completion hardware for these extended-reach wells.
This paper discusses the upfront assessment process, the reversible invert drill-in fluid system, the chemistry and subsequent optimization of the breaker system to achieve the drilling and completion objectives. In addition, the actual field results and lessons learned will be discussed.