Page 51: of Offshore Engineer Magazine (Jan/Feb 2014)

50 52

Pipelines to the existing Ashdod Onshore Terminal The time consuming process increased when comparing baseline data to future (AOT) for gas sales into the Israel Natural the risk of delays that could drain battery inspection results and integrity measures

Gas Line (INGL). life and cause a failed run. To account for such as engineering assessments and

Weatherford’s Pipeline and Specialty the time and unforeseen delays, a two- determining growth rates. For deepwater

Services (P&SS) group was contracted hour window was built into the sched- subsea lines, where normal onshore non- to provide the pipeline pre-commission- ule. This resulted in a 12-hour delayed destructive examination (NDE) validation ing and inspection, including tieback activation from the time the tool was practices are cost prohibitive, accuracy is pipelines, monoethylene glycol (MEG) inserted into the PLR on board the vessel. key to managing costs. pipelines, infeld fowlines, gas and The delay was programed into the system Compared to magnetic fux leakage condensate injection pipelines, Tamar and the inspection was successfully con- (MFL) tools, ultrasonic technology yields sales gas export pipeline and utility pipe- ducted. better sizing accuracy in determining lines. Integrating these services through wall loss and pipe wall thickness. This

Ultrasonic inspection a single contractor was key to reducing is because ultrasonic pulse echo physics logistical and scheduling constraints for Non-destructive ultrasound testing has are a more direct measurement of wall overall project success. been used for in-line inspection since loss. But in some cases, MFL is a better

The Tamar project’s challenges and the 1980s. The technology measures wall solution because it can be more forgiv- solutions involved subsea fooding, thickness based on ultrasound compres- ing of dirt, debris, rough internal pipe testing and MEG injection; dewatering, sion waves directed into the pipe wall. surfaces, and waxy liquids. This neces-

MEG conditioning and nitrogen purging; Ultrasonic transducers positioned 90° to sitates a comprehensive pre-inspection and base-line inspection of the system’s the pipe wall use an impulse-echo mode assessment prior to selection of the 16-in. tieback. The inspection was suc- to transmit an acoustic wave and receive appropriate technology. cessfully conducted using Weatherford’s return echoes. The echoes represent

Accuracy is important latest generation of highly accurate the locations of the internal and exter-

UTWM tools. nal pipe wall, and other metallurgical Accurate measurement of wall thick-

Pre-commissioning operations anomalies such as laminations. ness directly infuences the calculation were successfully conducted using A UTWM baseline inspection identi- of a corrosion feature failure pressure.

Weatherford’s Denizen subsea pre-com- fes and classifes non-injurious signals MFL tools do not typically measure wall missioning system. Flooding, cleaning, such as mid-wall laminations and other thickness but instead infer it from several and gauging the twin 147km x 16in. mill-related anomalies; a baseline cor- sources, including API pipe specifcation, pipelines were completed from a vessel rosion survey provides wall loss sizing pipeline construction data, and/or esti- at the shallow end of the 240m to 1700m data. Greater accuracy is important mated variations in the magnetic feld. water depth run. when assessing anomalies, assigning This provides only a relative assessment

In-line inspection surveys were con- risk, and prioritizing maintenance and due to pipeline data inaccuracies, or

A topside pipeline ducted during the fooding operations. expenses. Accurate anomaly classifca- diffcultly in obtaining data because of launcher receiver at Tamar enhances deepwater

A caliper tool was pumped to verify min- tion and sizing is particularly valuable asset ownership transfers, unavailable

Photo coutesy of Weatherford imum bore, followed by a UTMW tool for data, or unrecorded pipeline reroutes and the wall thickness baseline survey. After modifcations. pre-commissioning the inspection, dewatering operations Inferred measurements also do not were conducted for all 5 km of the Tamar consider wall thickness tolerances from in-feld and tieback pipelines. the pipe mill. As a result, an MFL cor-

Tight scheduling constraints for the rosion wall loss depth measurement commissioning technology to mechani- subsea launch presented a challenge depends on a relative measurement of cally displace and introduce pipeline for the 16in. UTWM in-line inspec- the pipe wall, which decreases the siz- fuids. tions. Normally, there would ing accuracy beyond the normal in-line have been suffcient battery inspection (ILI) tool sizing tolerance,

Deepwater challenge life to run the inspection tool. because in addition to toler-

The long-distance, deepwater Tamar However, in this case, the ances associated with tool pipeline project for Noble Energy is a time needed for a subsea anomaly sizing, there are also subsea gas production and transporta- launch required a delayed tolerances associated with the tion system that connects the deepwater activation. actual pipe spool wall thick- gas feld in the Mediterranean Sea to The ILI tool frst ness from the mill. an offshore receiving and processing had to be inserted into Acceptable tolerances platform linked to the existing Mari-B the pipeline launcher from the mill can be as high

Platform. receiver (PLR) onboard as ± 10% for pipe wall thick-

Gas in the Tamar feld comes from fve the vessel. A vessel crane nesses between 5 mm and high fow rate subsea wells produced moved the launcher with 15 mm in welded pipeline. through separate infeld fowlines to a the ILI tool to the pipeline Tolerances for pipe walls subsea manifold. Dual subsea pipelines end manifold (PLEM) and greater than or equal to 15 mm transport production from the subsea a hydraulic lock secured the manifold approximately 149km to the pipeline end termination (PLET) to

A skid mounted remote logger

Tamar Offshore Receiving and Processing the pipeline. An ROV was used to turn

Photo courtesy of Weatherford

Platform. The processed gas is delivered the subsea valves and launch the pig. oedigital.com January 2014 | OE 53 052-OE0114_Pipelines1_Tamar.indd 53 12/19/13 6:28 PM