A case study is presented involving Noble Energy Mississippi Canyon Deepwater (DW) Gulf of Mexico frac packs performed over the last 5-years. This paper describes the role that proppant tracers and gravel pack (GP) logs played in improving operations, ensuring a complete annular pack, evaluating frac pack (FP) efficiency, and providing data for decision making as well as identification of best practices.
Eight (8) DW completions involving thirteen (13) FP treatments and an associated seventeen (17) GP logs have been performed over the last 5-years in water depths ranging from 4,000 to 7,000-ft and reservoir intervals between 15,000 and 27,000-ft with pore pressures between 10.5 and 14.1-ppg.
Proppant tracers and GP logs were utilized to confirm GP integrity, assist in reservoir performance evaluation, help guide start-up procedures, and serve as reference information for creating best practices in the operator's FP designs. The proppant tracers were injected into the proppant slurries from the start of proppant addition until screen-out. In most cases, washpipe-deployed spectral gamma ray and gamma density logging tools were then pulled across the completion interval as the washpipe was pulled out of the hole to record the frac coverage and annular pack quality. In cases in which a re-log or re-frac was performed, the logging tools were deployed via slickline.
Seventeen (17) logs were evaluated and categorized in this paper to demonstrate the benefits gained. Some cases are limited to observations only (within the limits of the gamma ray tools, without final understanding of the why or how). However, on two (2) occasions, the logs identified that the gravel pack tools had failed and/or that there was no annular pack achieved. Both zones were re-stimulated and re-logged which confirmed annular GP integrity. Both wells are currently producing without compromise to productivity, flux limit or any detrimental sand control issues. If the logs had not been run and evaluated, both wells likely would have failed, losing either the lower or both the lower and upper intervals. On two (2) other occasions, voids were identified in the gravel packed intervals. In the first instance, the log was re-run after the upper completion (10-days later), and the pack had settled, eliminating the void. This information saved the operator from an unnecessary wellbore intervention ($10 MM+), allowing the ramp of the well to maximum design rate without otherwise imposed constraints. It also provided the confidence to move ahead on the subsequent instance where a void was identified.
The results and the learnings presented in this paper can assist others in the industry when similar challenges are faced. Deepwater completions must be productive and reliable. Proppant tracing and gravel pack logging can assist the operator in real-time operational decision making, production start-up procedures, and future completion design modifications, to ensure that maximum benefit is realized from the sand control treatment. This is another useful tool that every completion program needs in order to ensure success and avoid preventable failures.
