A dynamic linear polymer was formed by the [2π + 2π] reversible cycloaddition reaction of a thymine-based monomer under topochemical conditions and was used in self-healing applications. The reversible polymerisation of the thymine monomer was confirmed by UV and GPC analysis. Irradiation at 302 nm resulted in polymerisation of the monomer, and irradiation with wavelengths lower than 240 nm resulted in depolymerisation and the production of oligomeric units. This leads to a reduction in the glass transition temperature, and promoted healing of surface scratches due to the increased chain mobility. The self-healing ability of scratched samples was assessed based on the visual disappearance of the damage. In addition, the mechanical properties of the polymer before and after healing were found to be similar. [a] Dr. M. Abdallh, Mr. P. He, Prof. M. T.

In this work, an elastic carbon composite, a new category of high-pressure/high-temperature (HPHT) seal material, was developed and its successful application in downhole valves is discussed to demonstrate how it could address sealing challenges in HTHP and sour wells exploration. As conventional oil and gas resources decline, exploration and production (E&P) activity increasingly involves operations in extreme HPHT conditions and corrosive sour environments (high in H2S and CO2), posing tremendous challenges on almost all aspects from drilling to completion and production. One of these challenges is developing reliable seals for various kinds of downhole valves, e.g., safety valves, chemical injection valves, pressure relief valves, etc., that must withstand HPHT and sour environments and must work under frequent impact and wear caused by operation or sands from downhole fluids. Under HT conditions (usually above 500° F), current valve seals made of plastic or rubber are no longer suitable, because the material loses its mechanical strength and becomes very soft. Therefore, these seal can easily extrude and fail under pressure. Metal-to-metal seals may perform better in HPHT conditions, but they have a very high failure rate due to low elasticity and high metallic hardness. To address this issue, an elastic carbon composite, a new category of HPHT seal material, was developed. Material tests show that this novel carbon composite material has excellent thermal stability up to 1,000° F and strong resistance to impact and wear. This paper discusses the material property of this novel elastic carbon composite. The application of the material in a chemical injection valve is also be provided as an example to show how this new composite addresses downhole seal challenges for valve applications. The novelty of this work is developing a new seal material that could enable downhole valve work at extreme HPHT conditions. Related knowledge and information of this work would benefit engineer in developing new technologies for various downhole valve tools.

As conventional oil and gas resources decline, interest in unexplored or underdeveloped areas has grown steadily in recent years. High-pressures and/or high-temperatures (HPHT) are the new normal when exploring these territories, posing tremendous challenges on almost all aspects from drilling to completion and production. One of these challenges is developing chemical injection systems with high integrity and reliability specifically for HPHT applications. The chemical injection systems provide precise wellbore chemistry management by pumping down chemicals via dedicated injection lines. Working principles of chemical injection systems for HPHT applications are not significantly different from those used under less-demanding well conditions; however, challenges remain due to harsh HPHT conditions that affect material and equipment performance. This paper presents the development and qualification of an HPHT chemical injection valve that is the key flow control device in a chemical injection system. The valve contains a pressure differential valve design that creates a "bubble-tight" seal between wellbore fluids and the surface, provides a constant flow rate, and eliminates valve cavitations. The valve was thoroughly tested at various temperatures, pressures and flow rates, and it withstood conditions representative of the most severe well environments. The design cycle was also shortened by integrating computational fluid dynamics (CFD) simulations into the design process and good agreement was achieved between the simulations and the experiments.

Downhole chemical injection (DHCI) systems provide precise wellbore production chemical management by pumping down chemicals via dedicated injection lines. Worldwide installation of DHCI systems has steadily increased as a large proportion of high-pressure, high-temperature (HPHT) wells are continuously drilled and completed in deepwater and ultra-deepwater fields. Ultra-low variable rate application in HPHT wells can help to control deposition of scales and enhance injection efficiency, which can lead to improved environmental protection, lower operating costs, high equipment reliability, and improved topside space usage. One of the most common failures in DHCI systems is the breakdown of check valves. This issue is significant. Stringent requirements exist for a continuous injection rate above a certain cracking pressure, preventing flow from the injection line to the wellbore at shut-in conditions and creating a zero-leak seal that prevents reverse flow from the wellbore to the injection line. To meet these requirements, a so-called "check valve" design is generally used, in which a pressure differential valve is put in series with a check valve. The pressure differential valve sets the cracking pressure and shut-in pressure of the system while the check valve prevents reverse flow from the wellbore. This paper is part of a series effort for developing chemical injection solutions for HPHT wells. Previous work summarizes development and qualification of a pressure differential valve at higher flow rates, while this paper presents qualification tests conducted to assess the performance of the pressure differential valve and check valve as a system for HPHT applications under extreme low flow rates. The qualification tests include initial material selection based on a sophisticated gas test, a liquid flow endurance test and a post inspection, followed by a second-round test. Test results indicate that a bubble-tight check valve can be qualified to 0.0016 gpm to 0.047gpm with a pressure rating greater than 10,000 psi and 350° F. The pressure differential valve and check valve can be used in different applications other than DHCI systems.