TRACTOR-CONVEYED ULTRASONIC SCANNING TOOL IN HORIZONTAL CASED HOLES: A CASE STUDY PRESENTING A SOLUTION FOR EVALUATION ZONAL ISOLATION IN UNCONVENTIONAL WELLS

摘要

Horizontal well drilling is one of the primary technologies unlocking the potential that unconventional reservoirs have provided the industry. However, the advantage of added reservoir exposure is trumped by the difficulty for intervention. Logging operations in shale wells are particularly difficult, due to complex well profiles typically including high dogleg severity and resulting in conveyance and centralization issues, even in horizontal intervals. Many regulatory agencies now require cement bond logs as evidence for proper zonal isolation in these types of wells. Traditionally, wire line-conveyed logging has been hampered by the inability to access high-angle and horizontal portions of the wellbore and as such, has only been able to quantify cement bond conditions in vertical and low-angle well intervals. The following case study describes the use of a novel centralization method combined with tractor-conveyance to successfully acquire cement integrity data in horizontal wells. Two successful logging jobs were performed in Marcellus shale (Washington County, PA) wells for Rice Energy, a local operator seeking to verify improved zonal isolation during the multi-stage fracturing process of the horizontal intervals. The available mono-conductor string (ultrasonic scanning tool, cement bond log tool) operated seamlessly when run with a third-party logging tractor, while complying with operational requirements for pressure control. The inclusion of various concentric centralizer assemblies aided in maintaining ideal centralization and reducing conveyance-related friction to ensure log quality. The client was not only able to acquire zonal isolation data, but was also very satisfied with log quality that could positively identify cement integrity in both horizontal sections. The use of conventional equipment with an “out-of-the-box” approach solved one of the most complicated challenges with horizontal well intervention.