With over 300 trillion cubic feet of recoverable gas and a formation pressure that exceeds 9,000 psi, "Vaca Muerta" (located in Argentina) is the second-largest shale gas reservoir in the world.

To increase production efficiency and reduce production costs, oil and gas companies have developed their well's trajectory from vertical to horizontal, increasing over time the lateral length to over 9,800 ft. and bringing greater completion challenges. The most common method of completions is "Plug and Perf". Consequently, the use of coiled tubing (CT) requires a thorough understanding of the friction coefficient (CoF) between the CT string and the completion and the different forces exerted in the string. This understanding has become vital to predict the feasibility of reaching the bottom of the well, because the plugs must be milled out and the well cleaned out after the stimulation treatment and during its producing stage.

This document demonstrates, through two case studies, the existence of sticking effects, caused by the differential pressures between the wellbore and the formation, in a particular perforation cluster of high-pressure horizontal wells targeting the "Vaca Muerta" formation.

Because these are high-pressure horizontal wells, with all the perforation clusters targeting the same formation, and they are affected by the same hydrostatic pressure, it might have led to a misunderstanding of the CT CoF and/or stuck pipe situation.

This document will also describe a successful set of maneuvers that are designed to overcome these differential pressure-like stuck pipe situations, once diagnosed.

To understand these effects, two operations where the CT string experienced differential pressure-like sticking will be described. The first, from a clean-out operation during the earliest stages of flowback and the second, from a plug milling operation, both performed in high-pressure horizontal wells.

Correctly identifying this effect is key for preventing HSE risks, well-control situations and cost increases for the services and operator companies.

You can access this article if you purchase or spend a download.