As oil fields approach maturity, unwanted water production often starts negatively affecting oil recovery. Under these circumstances, operators may extend the well's useful life by plugging and abandoning (P&A) underperforming intervals and perforating a new formation. In Ecuador, this workflow is traditionally completed with wireline or tubing-conveyed perforating. An alternative method using enhanced coiled tubing (CT) is presented here; it enables a rigless and efficient workflow that leverages real-time downhole data for on-the-fly optimization.
The new workflow relies on CT-conveyed technologies without requiring any additional conveyance methods. CT delivered four different services to initiate the abandonment by anchoring a 7-in. cast-iron bridge plug, complete the abandonment with a low-viscosity cement plug, simulate wellbore dynamics during nitrogen pumping to generate the required underbalance conditions for perforating, and perforate with a 40-ft ballistic payload of 4 1/2-in. guns.
Coupled with real-time downhole telemetry, the enhanced CT workflow provided critical downhole conditions, including fluid levels, accurate depth placement and control, bridge plug setting confirmation, underbalance conditions, perforating head activation and detonation, and post-perforation inflow monitoring.
Compared with traditional methods, the workflow with enhanced CT introduces several benefits toward completing P&A of old intervals and perforation of new ones. These benefits include enabling a rigless workover, eliminating the need and cost of a workover rig, reducing operational duration by 13%, and potentially reducing asset footprint and field crews by 95% and 70%, respectively. Elimination of a workover rig reduces environmental impact and the number of personnel on location (i.e., risk). The workflow also extends both reach and efficiency of the service in horizontal wells, enables underbalanced perforation, and delivers actionable real-time downhole data. These data elevate traditional P&A workflows and create a step change in efficiency. First, they allow tracking key downhole parameters that help guarantee a reliable operation of each of the tools and services. Second, they shed insights as to the actual downhole conditions throughout the intervention to enable the operator and the field crews to make on-the-fly decisions to deliver a safe and optimal service. Those decisions may include fine-tuning the prescribed treatment or extending the scope of the intervention by leveraging the CT's pump-through capabilities to maximize well performance and meet, or exceed, the operator's objectives.
The innovative combination of real-time telemetry with abandonment and perforating technologies proved a step change in operational efficiency and range, fueled by the quantity and quality of data recoded during the operation. This case study also marks the first documented perforation with 4 1/2-in. guns with fiber optic real-time downhole telemetry. Furthermore, the integrated, rigless solution provides operators with an opportunity to extend their workover activity pipeline and free up their workover fleet for other activities.
