Analyzing Crack Data to Develop a Cost Efficient Quality Assurance Program Optimized for Inspecting Drill Pipe Cracked Due to Exposure to H2S in West Texas Delaware Basin
Authors: Gokhale Samit , Brown Dexter 
Published: October 2020

Most drilling rigs in the West Texas Delaware Basin (WTX) are supplied with 5" 19.50# S-135 grade drill pipe. Exposure of this pipe to hydrogen sulfide (H2S) creates potential of cracking from hydrogen stress cracking (HSC). Such cracked pipes often exhibit longitudinal cracks with crack origination at OD or ID depending on local stress concentrators. This poses a unique challenge as traditionally used drill pipe inspections specificed in API RP 7G-2 (2015) (referred to as API) and DS-1 Volume 3 (2012) (referred to as DS-1) are designed for transverse flaws like fatigue cracks and thus do not provide a cost-effective standardized inspection program specifically designed for drill pipe cracked from HSC. Infrastructure in WTX further complicates the issue as full-length ultrasonic units (FLUT) used for inspecting longitudinal flaws (typically used for landing strings for deep water operations) are not cost effective for onshore drilling operations and not readily available in WTX. This lack of coverage in used drill pipe inspections for HSC was identified as a contributing factor to drill pipe failures that were experienced after H2S exposure events.

To remedy this problem, a drill pipe inspection program designed for cracks from exposure to H2S was developed. A trial program was undertaken, wherein various inspection technologies with specific coverage and procedures were executed on pipe exposed to H2S. Initially, the pipe was inspected and re-inspected using multiple technologies to document effectiveness of specific inspection methods. The crack morphology including location, orientation and size was cataloged to understand characteristics of H2S induced cracks and determine effectiveness of an inspection method in detecting specific crack types. Crack data collected across numerous inspections was analyzed to determine trends on crack occurrence and morphology. This analysis aided in development of an optimized inspection program that was effective and cost efficient. To address various exposure levels and pipe conditions, three inspection categories with increasing coverage and criticality were designed. Implementation of this optimized inspection program has aided in detecting over 100 cracked drill pipe joints and prevented twist off incidents. The cracks detected with this H2S specific inspection program would have gone undetected using traditional (DS-1 and API) used drill-pipe inspection categories.

This paper details various inspection methods and the modified inspection coverage and procedures implemented. The H2S induced drill pipe crack data and analyzed trends on crack occurrence and morphology collected over the testing program are included. The paper presents the inspection program designed for detecting cracks induced in drill pipe from H2S exposure. Also included is discussion on three separate inspection categories with increasing criticality to address various exposure levels and pipe conditions.