Challenges of Integrity Management of Pipelines and Erosion Control in Sand Producing Wells

Abstract

Abstract Sand production in oil and gas wells is becoming an increasing problem for operators due to sand settling, under-deposit corrosion, and/or erosion especially in sub-sea environment. The paper describes application of ultrasonic (UT) pipe wall thickness measurements and erosion calculations in assessing integrity management of pipelines in a subsea gas producing field. The subsea gas wells were completed with downhole sand control because of the unconsolidated nature of the reservoir sands. The gravel pack completions were designed to stop sand but allow some fines production to prevent plugging of the gravel packs and screens and hence loss of productivity. Some solids production was therefore expected over the life of the fields. After some time when additional gas wells were brought online, higher than expected sand production was observed. Thus, operators commissioned sand erosion studies and conducted UT wall thickness measurements in 2008 and two years later to measure wall thickness of the Pipeline End Manifold (PLEM) and associated spool pieces subsea. The results in the paper include a comparison of wall thickness measurements conducted in several key areas. The results indicate wall thickness measurements conducted in 2010 for most of the measurement locations were similar to 2008 results except for several regions where the UT measurements were questionable based on erosion calculations. One major observation from UT measurements is that most measured wall thicknesses were less than the nominal wall thickness by 0.5 to 1.0 mm including sections where no flow was going through (no erosion/ corrosion) indicating absolute values of UT measurements can not be trusted with confidence unless calibrated subsea. Finally, the paper describes how UT measurements, erosion calculations, production controls and operation philosophy can be combined to maintain asset integrity and to control erosion of pipelines.