Annular fluid or gas migration, resulting in surface hydrocarbon leaks or sustained casing pressure (SCP), is a problem operators face worldwide. With energy demands escalating, it becomes increasingly important to maintain production from existing wells and bring new wells on line without delay. Internal company policies regarding health, safety and environment, along with increased government scrutiny of the petroleum industry, can require wells to be shut-in if leaks or SCP are present. Estimates of the number of leaking wells have varied widely as reporting standards have evolved over time and from country-to-country. In Western Canada, however, there are detailed reports of over 18,000 wells having Surface Casing Vent Flow (SCVF) that in some cases requires them to be shut in and production suspended. From spud-in to abandonment, an oil well is subjected to numerous, repeated events that could compromise zonal isolation. Resulting damage, in the form of cracks in the isolation material or the creation of a microannulus, can allow hydrocarbons to flow to surface or become trapped below the wellhead. This paper will describe a novel zonal isolation material that responds to a loss of hydraulic isolation. If hydrocarbon flows occur within or around the primary cement sheath, the material will seal these flows and re-establish well integrity. The system, which has slurry properties comparable to standard oilfield cements, is designed to be pumped as part of any primary cementing operation on wells drilled with water or oil-based drilling fluids. This material was used in well construction operations for wells drilled in Eastern Alberta, and can be applied to reduce the incidents of SCVF in this area. This ability of this system to eliminate hydrocarbon flows has been confirmed with high-pressure laboratory testing, and it has been successfully field tested in Western Alberta. Introduction As worldwide demand for petroleum continues to increase, operators face the challenges not only of finding new reserves of oil and gas, but also of maximizing the productivity and longevity of the wells that are drilled into existing reservoirs. According to the International Energy Agency (Oil Market Report 2007; Press Release 2006), worldwide petroleum demand is expected to increase by 13.9 million BOPD, from the current level of 85.9 million BOPD to 99.5 million BOPD, over the next seven years. By contrast, production has increased by only 6.7 million BOPD over the last seven years (Short-Term Energy Outlook 2007). If the industry is to keep pace with this demand, operators will have to look at ways to maximize returns from individual wells, in addition to improving overall reservoir recovery. Great advances have been made in cementing practices over the years. These advances include improvements in fluid displacement modeling as well as the development of slurries with improved chemical and rheological properties. These advances have gone a long way towards improving hydraulic isolation, but they do not address damage to the cement sheath that may occur days, months or years after the cement has set. This potential for loss of hydraulic isolation during or after a well's productive life represents a weak link in hydraulic isolation. A damaged cement sheath can allow the migration of hydrocarbons, which can reach the wellhead in the form of sustained casing pressure (SCP) or surface casing vent flows (SCVF), potentially requiring a well to be shut-in, repaired or abandoned prior to the end of its productive life.