Abstract
A common cause of failure with Surface-Controlled Sub-Surface Safety Valves (SC-SSSV) is a defect in the downhole hydraulic line, which controls the valve from surface. Such a failure (Control-Line (CL) leaking or plugged) generates production losses and requires the intervention of a costly workover rig – usually not immediately available. A large number of wells have been closed in due to CL problems.
This paper presents a pilot test of a "control-line free" Wireline-Retrievable (WR) SC-SSSV concept, which replaced a conventional Subsurface Safety Valve and maintained the well producing under surface controlled conditions without the need for a work over or wellhead modifications.
A Wire line retrievable, flapper type self-equalizing Safety Valve has been interfaced with an HPU (Hydraulic Power Unit) and downhole electronics, which are operated by an electromagnetic signal transmitted from surface through the formation and using the conductivity of the tubing. The surface emitter continuously sends a signal (low frequency) to the SC-SSSV. As the system is designed to be fail-safe, the normally-closed valve remains open while receiving the signal and closes as soon as the signal is lost. This control line free SC-SSSV can be set in any landing nipple profile. It has been installed by normal wire line operation in active onshore oil producing well for three months using a standard SC-SSSV lock mandrel.
25 periodic functional tests consisting of closing the valve and bleeding down the tubing pressure to confirm the integrity of the well pressure containment below the closed valve were performed for validation.
The primary application is to secure wells with a damaged CL or wells completed without any SC-SSSV. It provides an immediate cost-effective solution – allowing production to resume with a surface-controllable safety barrier while avoiding or postponing an expensive work over.
The pilot test has been successfully carried out over the 90 day period in a harsh environment onshore well usually equipped with SC-SSSV. The wellhead was fitted with two sensors: one pressure transducer on the flow line and one temperature probe connected to the surface emitter (for fire hazard detection) to act as temporary ESD for this test. Adjustable thresholds were set to switch off the surface emitter and shut-in the well in the event of any anomalies. Two unplanned events occurred during the 90 days pilot test: a temperature probe breakdown and a surface antenna disconnection. In both cases, the EM-signal was interrupted and the SC-SSSV closed and secured the well.
Temporary solutions, such as the normally-open velocity or ambient valves, can be considered according to current safety policy but lacks ability to be connected to an emergency shut down system. The Electromagnetic "control line free" SC-SSSV provides an effective and reliable surface controlled solution in the event of control line failure, or lack of hydraulic control system, on a standard SC-SSSV installation tied in to an existing emergency shut down system.
This breakthrough wireline product has proven to be easy to install and offers new possibilities for managing in a safe and effective manners the unexpected failures of hydraulic SC-SSSV.
