Shenzi 16-Inch Oil Export SCR CVA Verification
Authors: Qiu Weiyong , Song Ruxin , Stanton Paul N. , Casadaban Rene , Stark Mike 
Published: July 2009

In 2006 Enterprise developed a 16-inch oil export system from Shenzi field located in Green Canyon Block 653 in the Gulf of Mexico, approximately 120 nautical miles offshore in approximately 4,375 ft of water depth. The oil export system is attached to the Shenzi TLP host facility. The 16-inch oil export SCR system is subject to the CVA (Certified Verification Agent) verification required by MMS (Minerals Management Service) 30 CFR Part 250 [Ref. 1]. NTL No. 2007-G14 [Ref. 2] was issued pursuant to 30 CFR 250.103 to provide clarification and guidance for pipeline riser design, fabrication, and installation under the platform verification program specified in 30 CFR 250.909 through 918. This paper summarizes the 16-inch oil export SCR CVA verification procedure.

This paper presents a systematic SCR CVA verification procedure. The CVA verification procedure includes SCR CVA verification preparation, and verification of SCR design, fabrication, and installation. The verification procedure and table formats developed are unique and applicable to other types of pipeline risers in the Gulf of Mexico.

Introduction

The Shenzi field is located in the deepwater central Gulf of Mexico approximately 120 miles from the Louisiana coast. The field comprises Green Canyon Blocks 609, 610, 653, and 654. Water depth at the site is approximately 4,300 ft. Figure 1 presents the Shenzi Field layout [Ref. 3].

The Shenzi Oil Export Pipeline and SCR will transport crude oil from BHP Billiton's Tension Leg Platform (TLP) in Green Canyon Block 653 in approximately 4500 fsw to the Ship Shoal 332B Platform in approximately 435 fsw. Figure 2 presents an artist's rendering of the Shenzi TLP [Ref. 3].

30 CFR Part 250 was published in the Federal Register on July 19, 2005. The rule became effective on August 18, 2005. 30 CFR 250.909 through 250.918 applies to new pipeline risers attached to the floating platforms in the Gulf of Mexico. The rule defines the CVA nomination, CVA's primary responsibilities, CVA's primary duties during the design phase, CVA's primary duties during the fabrication phase, and the CVA's primary duties during the installation phase. The detailed engineering design of Shenzi 16-inch oil export SCR started at the beginning of 2006. So it was one of the earliest SCRs subjected to the CVA program.

This paper presents a systematic SCR CVA verification procedure developed during Shenzi 16-inch oil export SCR CVA verification project. The verification procedure includes SCR CVA verification preparation, SCR design CVA verification, SCR fabrication CVA verification, and SCR installation CVA verification. The verification procedure and table formats developed are unique and applicable to other types of pipeline risers in the Gulf of Mexico.

SCR Design Data

SCR Data

The API 5L X-65 steel grade has been selected for the oil export SCR. Table 1 summarizes the oil export SCR data, pipe wall thickness tolerances, corrosion allowance, SCR coating data, and VIV suppression device data.

Internal Fluid, Design Pressure and Temperature

Design pressure and temperature are 3,540 psig and 140 ?F. For normal operating condition, the pressure and temperature are 3,220 psig and 120 ?F. For hurricane shut-down condition, the pressure and temperature are 3,540 psig and 120 ?F. The oil density is 54.0 pcf and the pressure reference elevation is 200 ft above mean sea level for all conditions.