No abstract

,~ study was made of t he creep behavior in tensio n at 300 0 700 0 900 0 and 1 200 0 F of initi, !I y annealed high-purity nickeL Discontinuous flow was dbsel' v~d in ~ach of' the three stages of creep, and . it was affected by ~e mperatu~'e, s train rate, and prior-strain hi stor y. Th e phenomenon of s tram aglllg was especially promlll ent at 300 0 F as manifested by t he attainment of an appreciable creep life in specimens stressed in excess of the te ns ile streno-th at this temperatur~. The experimentall'esults are analyzed in terms of t he past and prese~ t theories of deformat IOn of metals. Stralll hardenlllg, recovery, and t he initiation , propagation , and types of fractures obtamed dunng creep are further evaluated by means of true-stress-truestrain and hardness data obtained at room temperature and by metallographic examination of the fractured specimens.

Short-time tensile tests were m ade at temperatures ranging from 75 0 to 1,700 0 F on high-purity nickel, copper, a 70-percent-nickel-30-percent-copper alloy, and a 70-percenteopper-3 0-percent-nickel alloy. The high-purity component metals and the two alloys were investigated in the initial conditions, as annealed for a uniform grain size, a nd as colddrawn 40-percent reduction in area. The results were affected m a rkedly by variations in the nickel content, temperature, and degree of cold-working. However, the effects of colddrawing at room temperature were obliterated at temp eratures above that of recrystallization.The effects of cold-drawing the 30 % -Ni-70 % -Cu a lloy differe nt amounts a nd of variatio ns in g rain size of the copper on the ten sile properties are evaluated. R es uHs on the tensil e properties of the same annealed materials at low temperat u res are included for completeness.

There is a very large number of wells worldwide that leak or have sustained casing pressure (SCP). In Central Europe and the Middle East there are hundreds of wells with reports of trapped pressure that cannot be bled off. In the US and Canada there are thousands of wells leaking to surface, which may or may not be discharged to the atmosphere. Furthermore, 25% of all wells in the Gulf of Mexico have measurable sustained casing pressure. Additionally, remedial work fixing issues relating to cement failure has been estimated to be more than $50M a year in the US alone. Throughout the lifecycle of a well, planned cycle or operational changes can contribute to unknown damage to the cement sheath integrity that is hard to identify or locate, including the generation of a microannulus. Within flow paths, hydrocarbons can either migrate to surface, or become trapped below the wellhead leading to pressure build-up. Typical events occur during cementing, while perforating or stimulating, throughout the subsequent production, and even after abandonment. These can easily create this loss of cement integrity. This paper describes a novel isolation system that is activated only when a cement integrity problem occurs. The system will automatically and rapidly form a complete hydraulic barrier by swelling in the presence of hydrocarbon flow. Once activated, it will seal the damaged zone, and will even be able to be activated again, should further damage occur again during production or abandonment. The system has properties equivalent to conventional cement systems, and requires no modifications to standard surface equipment. High pressure static and dynamic laboratory tests highlight the ability of the system to rapidly shut off gas flows within 30 minutes. Field tests have also highlighted the robustness of the system, with a number of wells currently using the system remaining leak-free. Introduction The number of wells worldwide that leak or have sustained casing pressure (SCP) is an astonishingly high percentage, and as the demand for natural gas is increasing, the situation is likely only to get worse. In the United States, for example, demand will continue to grow during the next two decades, and has been estimated to reach a level as high as 35 quadrillion Btu (quads) by the year 2020.1 Correspondingly, a high number of new wells will need to be constructed to cater for this demand. If there is no change in current well construction techniques and materials, the incidence of leaks or of SCP is likely to track the well construction rate at a similar pace. Techniques for locating and exploiting natural gas have made huge advances since the early days of 1821 when the first natural gas well in the United States was drilled. However, m any of today's wells are still at risk, despite modern advances in well construction processes and materials. Failure to isolate sources of hydrocarbon either early in the well construction process or long after production begins has resulted in abnormally pressured casing strings and leaks of gas into zones that would otherwise not be gas-bearing. Abnormal pressure at the surface may often be easy to detect, although the source or root cause may be difficult to determine. Even when attempting "industry best practices" some annular pressure problems still occur. The quality of field practices may exacerbate tubing and casing leaks. The interdependencies of various well-construction processes is critical to building successful gas and oil wells for the future.2 This paper describes a new novel concept for zonal isolation based on a new material called self-healing cement (SHC). This concept does not preclude good cementing practices, but will enhance the chance of success where perceived long term pressure risk is anticipated. The objective of SHC is to provide long-term zonal isolation with a material that has self-repairing properties within the set cement. For example, this material enables automatic repair when a microannulus, internal cement crack or other flow path is created, and thus prevents flow of formation fluids through potential leak paths along the annulus. The concept focuses on long-term durability of the cement sheath material in oil and gas wells, and thus cement sheath repair without the need for well intervention.

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.