Unconventional technology for sealing and P&A of wells for prevention of global environmental disasters

Many, if not all of the oil and gas fields under development, have leaking wells. There are a lot of so-called abandoned, ownerless wells. Subsoil users, by one way or another, make efforts to eliminate leakage in such wells. At the same time there are no universal and reliable techniques. The problem of well leakage is seriously increasing when wells are decommissioned (plugged and abandoned, P&A), and even more so when the development of the field is finished. The techniques of plugging and abandonment do not guarantee the integrity of the abandoned wells for centuries. Obviously, then the abandoned field would become the object of a local ecological catastrophe. As the development of all oil and gas fields is completed, the Earth will enter the era of the Global Environmental Disasters. In this article authors propose innovative techniques and technical solutions for sealing procedures and plugging and abandonment operations on wells.

Preparation and performance evaluation of polyvinyl alcohol grafted polyacrylic acid for plugging

Well-leakage is a very difficult problem in the process of drilling at home and abroad. At present, it mainly relies on the cumulative effect of plugging slurry to implement plugging regardless of the number of times and costs. Commonly used plugging slurry and plugging technology are difficult to guarantee the success rate and scientific of plugging malignant leakage, which has an extremely bad impact on the development of the petroleum industry. In this study, With polyvinyl alcohol and acrylic acid as main agents, a plugging material of acrylic acid grafted polyvinyl alcohol was prepared, and the influence of the composition of the reaction system on the gel state of the system was studied. Through a series of singlefactor experiments, the best formula for preparing the plugging material was determined, polyvinyl alcohol and acrylic acid (specific gravity 1:3) + crosslinking agent (0.1wt%) + initiator (0.3wt%). The gel plugging agent using above formula to prepare has good gel strength and suitable gel time, and has a good application prospect in solving the problem of lost circulation.

Minimum gas injection of gas drilling while temperature and pressure coupling

Gas drilling technology not only has the advantages of avoiding well leakage, shale hydration expansion,reservoir pollution and other issues, but also can greatly improve the drilling speed 4 to 8 times, it is helpful to timely discover and effectively protect reservoir and improve recovery efficiency and single well production of oil and gas reservoir, especially has important significance for hard strata and dense reservoir exploration. However, there are some problems hindered the promotion of this technology, such as gas is hard to carries cuttings and gas hole blocking. One of the key technologies to solve these problems is the determination of gas volume. Most of today’s literature use formation temperature instead of annulus temperature to calculate minimum gas volume. Owing to gas’ PVT effect, temperature is dramatically influenced by pressure flow velocity, there will be big error if we use formation temperature instead of annulus temperature. Meanwhile, most of traditional minimum gas volume methods use top of the drill collar as key point. In this study, we found that on the top of the drill collar, the carrying kinetic energy of gas is not is not necessarily the minimum, and change of the key position is strongly influenced by wellbore structure and make-up of drill tool. Minimum gas volume determined by applying temperature - pressure coupling calculation is more close to site construction, under the given conditions, error of the minimum gas volume is about 0.4%.

Nanoprobing of Advanced Silicon-On-Insulator Transistors

As advanced silicon-on-insulator (SOI) technology becomes a more widespread technology offering, failure analysis approaches should be adapted to new device structures. We review two nanoprobing case studies of advanced SOI technology, detailing the electrical characterization of a compound gate-to-drain defect as well as the characterization of unexpected SOI source-to-well leakage.