Subsea Leaks Cured with Pressure-Activated Sealant

Abstract

The paper describes the use of a pressure activated sealant technology to cure leaks in subsea wellbore equipment and control systems. The benefit of this technology is that use of an injectable pressure activated sealant to cure leaks provides a safe, cost-effective alternative to conventional well interventions. The paper outlines the capabilities of the pressure-activated sealants, the procedures used and the results of the sealant operations including case histories. Introduction As the industry moves into deeper waters, the capabilities of subsea wellbore equipment and control systems are severely tested. In spite of great advances in engineering, the complexity of the systems and the number of individual components in deepwater systems create numerous potential leak sites. Leaks can result in abnormal pressures in the wellbore equipment and control systems or releases of control fluids, oil, gas or other fluids. These leaks create issues of safety, environmental protection and cost. The costs of well interventions rise dramatically with depth. Over the life of a deepwater well, the costs and risks of conventional well operations can be prohibitive. In analyzing the long-term costs of subsea operations, the industry must investigate new intervention technologies to repair leaking subsea wellbore equipment and control systems in-situ without the need of mobilizing expensive and risky intervention operations. Common Subsea Failures Over the life of a subsea system, it is possible for a leak to occur in most of the components of a subsea well system. Connection leaks are found in umbilical lines, hydraulic lines, control systems, flow hubs, tubing, casing and similar components. Dynamic seal leaks are experienced in SCSSVs, actuators, valves control systems and similar components. Static seal leaks are seen in wellheads, packers, hangers and similar components. Downhole leak sources include tubing, casing, packers, sleeves and other components. During installation, damage to components can create a variety of leak sources. Sealant repairs have been performed on most of the above-listed components. Subsea Leaks-The Problems Analyzing and repairing leaking subsea systems is complicated by the remoteness of the equipment, the uniqueness of many of the subsea installations and the logistics of delivering a solution. Once installed, you can't put you hands on the hardware. The only means of analyzing leaks is through remote diagnostics - often limited to simply taking pressure readings. Further, many of the subsea systems have no service history, so there is no historical data to assist in diagnostics. Even if the problem is identified, the question is how do you deliver a solution? Do you use a rig, divers, ROV or some other method? What are the regulatory issues raised by the leak? As an engineer evaluates solutions to the problems created by leaks, a first step is an analysis of the problem followed by a review of the options. Traditionally, the solution has been a mechanical workover of the well including replacement of well components. Considerations include availability of a rig, service company availability and coordination, replacement equipment, the cost of all of these factors and the impact of lost production. Traditional Mechanical Repair Methods When repairing a subsea leak, traditional mechanical repair methods become much more complicated and expensive. Whereas repairs to platform equipment (such as a loose fitting) can be accomplished with a simple turn of a wrench, mechanical repair of a leak at a depth of 1,000 meters requires considering some very different repair options - including some very risky, complex and expensive options. The direct costs of any subsea repair operation can be in the millions of dollars. Beyond the direct costs of the mechanical repair options, an operator must take into consideration the risk-adjusted costs of the operations. The problems with most traditional mechanical repair options are as follows:The operation requires considerable engineering and scheduling preparations.The operation requires an expensive, complex multi-service vessel or rig.

Systematic Experimental Investigation on In-Situ Self-Adaptive Sealing Property of Composite Pressure-Activated Sealant for Curing Minor Tubular Leaks

“…The addition of rigid particles can cause the surface area to leak area ratio to increase by means of a bridging block in the leak path. As Rusch et al [20] have reported, for a pressure-activated sealant, the higher the surface area to leak area ratio, the more likely it is that the leak is sealed.…”