Application of Downhole Well Integrity Technology in the Petroleum Industry, A Case Study in the Horizontal Wellbore

Wellbore integrity was a thorny issue in China since hundreds of thousands of wells needed to be repaired annually, leading to cost increase and production delay. This problem became more excruciating in the long horizontal wellbore considering the high risk of downhole tools stuck. So far casing damage in the horizontal wellbore was either chemically plugged or separated by bridge plug, posing huge threat to the reservoir and future operations. Solid expandable tubular was a rising star in the downhole workover programme, its application in the horizontal wellbore would further enrich our technical warehouse to enhance the wellbore integrity. In this paper, the challenges of horizontal wellbore workover operations were presented; the expandable technology was introduced and then innovated the adapt to the challenges, finally its field operation was described and relevant summaries of lessons were demonstrated. The results indicated that as the number of horizontal well increased dramatically, problems such as casing damage, sand plugging occurred more frequently, downhole tools usually needed additional force to forward in the horizontal part to finish well logging or other activities, casing integrity was necessary to prevent the stuck of downhole tools. Solid expandable tubular was a field proven technology, in order to overcome issues like tripping in process, expansion hurdles in the irregular well trajectory, the structure of solid expandable tubular was optimized radically. First the material of tubular was changed to achieve N80 steel grade after expansion, the OD of tubular was adjusted to maximize the annulus space between the casing and the tubular. Second the thread was restructured the further enhance its strength. Finally the rubber outside the tubular was innovated to prevent being worn out as much as possible during its friction with the horizontal wellbore. Field operation was carried out in west China, 18m length of expandable tubular was deliver into the end of 327m horizontal wellbore, expansion process was started and 41MPa expansion force was recorded. This paper served to enrich our capabilities to deal with workover operation in the horizontal wellbore, its content helped better understand the principle, procedure and potential of this enable technology.