This work aims to determine the material qualification of 13Cr-L80 casing for sour conditions which is of great importance to check the sulfide stress cracking susceptibility, confirm the range of applicable conditions and recommend anti-corrosion materials. First, the casing material was tested to judge whether its properties were normal. Secondly, the testing matrix was defined to determine actual casing exposure conditions. Thirdly, slow strain rate testing was used to screen the conditions. Fourthly, thirty-day tests of uniaxial tensile specimens were conducted to check for SSC susceptibility. The casing material satisfied API 5CT standards and could be used for slow strain rate testing and sulfide stress cracking testing. The testing matrix is intended to distinguish the combined effect of temperatures (41, 75, 140 °F), chloride levels (1000, 13 000 mg × L−1), pH (3.5, 5.5) and partial pressures of H2S (3.5 psi) in shut-in and flowing conditions. The slow strain rate testing showed a reduction of signs of embrittlement with increased temperature, suggesting that the mechanism is supported by sulfide stress cracking. The 13Cr-L80 passed field-specific qualification tests for sulfide stress cracking resistance in sour wells at maximum H2S partial pressures of 3.5 psi in the casing-tubing annulus. The API 5CT 13Cr-L80 casing application is in compliance with ISO15156/NACE MR0175 standards as long as the aggressiveness of the field conditions does not go beyond the envelope conditions tested (3.5 psi of H2S, pH 3.5, temperature of 41 or 75 °F).
This paper presents the evolution of completion sand control designs for the Peng Lai field in Bohai Bay, offshore China. A range of sand control designs from open hole gravel packs to open hole standalone screens to cased hole high rate water packs and cased hole frac-packs have been tried over time. Evaluation of these various designs indicates that single-trip multi-zone cased hole frac-pack designs provide the most effective method for developing the thick, low net-to-gross, unconsolidated sandstone reservoirs in this waterflood field. The paper describes the completion design and evaluation process used in the field and shows how field challenges led to innovative frac-pack downhole equipment designs. This paper highlights completion practices and results from a range of well types used to develop the large Peng Lai field, offshore China. Development challenges and productivity and reliability results for alternative completion designs are discussed on the basis of field performance. The resulting preferred design, consisting of cased hole frac-packs using large-bore and small-bore single-trip multi-zone equipment are then discussed in further detail with emphasis on development of an innovative, fit-for-purpose, small-bore design. The installation challenges, solutions and successes experienced during the design and installation process and the actual performance and benefits of the new system are also discussed in this paper. Over the course of Peng Lai field development, a range of alternative completion sand control designs have been tried and evaluated. Cased hole frac-packs provide the most effective completion method for the thick, low net-to-gross, sandstone reservoirs. To enable effective completions in sidetracked wells, a 7" single-trip multi-zone frac pack tool has been developed. This small-bore system has been used to complete 13 wells with 67 zones in the field to date, saving over 43 rig days and $8MM. This paper presents reliability and productivity comparisons for a range of alternative completion sand control designs in a single, large field environment. A new 7" single-trip, fit-for-purpose design has been developed for the field and successfully implemented in multiple well campaigns. Installation time data and cost savings are provided.
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