Single-trip multi-zone (STMZ) Frac-Pack completions can significantly reduce the time to complete wells with long productive intervals. This technique was used successfully in two Lower Tertiary completions in the deepwater Gulf of Mexico (GOM) Cascade/Chinook project in 2010 (26,000 ft TVD, 8900 ft water depth). With interval lengths exceeding 1,000 ft, reservoir pressures greater than 18,500 psi, and bottomhole temperatures higher than 250°F, these STMZ completions were the first of their kind. With a STMZ completion, all completion intervals in a well are perforated at once. Then all the lower completion hardware (screens, sleeves, packers, etc.) is assembled and run in the well and the packers are set. Through the manipulation of sliding sleeves, each interval is individually opened and frac-packed sequentially from the bottom interval to the top. Before moving to the next interval, the sleeves are closed and pressure tested, providing isolation between the wellbore and the reservoir. The steps are repeated until all the intervals are stimulated. The STMZ system saves a great deal of rig time over conventional stacked frac-pack systems by significantly reducing the number of trips in and out of the well with the work string. This paper discusses the challenges, planning, execution, and results of these STMZ completions with a focus on the downhole completion hardware. Also discussed are some planned modifications to the system that will reduce risk and improve performance in the future.
Multi-Zone Single Trip (MST) technology is used to perform sand-control treatments individually to multiple zones in a single trip. In Deepwater installations, Well Integrity, Operational Efficiency and Completion Excellence are critical success factors for overall project returns. Well integrity is accomplished by ensuring that completion components conform to the extreme downhole well conditions; that well control is present during each stage of the completion operations; and that zones are positively isolated during the high pressure frac-pack treatments. Also, well integrity needs to be maintained during the selective isolation string deployment and throughout the production life of the well. Operational efficiency is accomplished by establishing clear guidelines during the planning phase of the wells; ensuring the right personnel are involved at the right time; identifying and eliminating any possible operational risk; simplifying tool manipulations; establishing downhole tool diagnostics that enhance decision making; and finally, improving downhole tool visualization for operational clarity. Completion excellence is achieved by ensuring completion components are fit-for-purpose for the extreme high pressure and erosive environment with maximum flow areas for optimum production, built-in redundancy for flawless executions, and software modeling to simulate downhole conditions from installation through production phases. This paper is meant to show how these features were used in the most recent completion in the Cascade field and provide recommendations for similar operations while identifying areas of improvement for upcoming installations.
The paper is based on work performed during the design, implementation and operation of the Cascade and Chinook Field Development Project in ultra-deep water in the Gulf of Mexico. It describes the basis of design for the drilling and completion of the wells, new technology selection criteria, risk and cost mitigation plans applied during the well operations, ultra-high pressure perforating of an interval longer than 700 ft, application of the first Single-Trip Multi-Zone Frac Pack System (3 zones) in wells deeper than 27,000 ft MD, and the unique fracturing design approach used to deliver multiple fractures across 1200 ft of reservoir thickness. This case history paper will describe the pre-qualification work done with all critical systems and details of the well construction operations during the drilling and completion of the wells.The information provided will be useful for Operators to identify the technologies that are most suited for application in deep wells. It will also serve as a starting point for the design and construction of wells for other operators developing projects in the Lower Tertiary play, which is a key exploratory frontier in the U.S. Gulf of Mexico (USGoM). More than 12 discoveries have been made in the Lower Tertiary, with potential recoverable reserves of several billion barrels of oil.The results and conclusions presented in this paper are related to the feasibility and benefits of using new technology and prototype equipment in the Lower Tertiary environment. Field data from critical well operations will be included.The technical contributions of the work presented in this paper are as follows: pushing the technical limits of Single-Trip Multi-Zone frac-pack systems to depths over 27,000 ft using high (>30 bpm) fracture rates and high strength proppants; enhancing the knowledge gained from ultra-high pressure (>20,000 psi) tubing conveyed perforating systems; and presenting a well design criteria suitable for high drawdown (>12,000 psi) production operations.
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