Underground gas storage (UGS) wells have become the natonal strategy for natural gas storage and supply throughout China. PetroChina is building UGS facilities throughout the country, with planned construction extending from 2011 to 2015. The Chongqing gas storage well project in Central China is one of the constructed facilities. Because the life expectancy of gas storage wells is at least 50 years, long-term maintenance of well integrity is one of the major challenges faced during the construction and operations phases of UGS wells. The wells must bear the injection pressures, temperature changes, and frequent cycling of injection during production. With conventional cement, the pressure and temperature change during the injection and production phases can result in cement traction, compression, or microannulus failure. This leads to gas migration through the damaged cement sheath, which means the well will fail its mission as a UGS well.To maintain well integrity, a novel engineered flexible and expanding cement system has been introduced for UGS cementing in the Chongqing project, whereas past service companies have failed to deliver the fit-for-purpose solution. The optimized mechanical properties of this novel cement allow the cement to remain intact under extreme pressure and temperature changes.To prove the ability of the selected flexible and expanding cement to withstand the pressure change, logging was conducted at various times during the construction and after the casing pressure test cycle. The logs show excellent results.Since its implementation, the flexible and expanding cementing system has become the standard solution for China's UGS wells, in which long-term well integrity and sustained casing pressure are required. This paper discusses the challenges for cementing UGS wells, which case histories describe the successful implementation of the FEC solutions.

A single‐balanced mixer for operation in the microwave‐ and millimeter‐wave bands is presented. This monolithic microwave‐integrated circuit was implemented on AlGaAs/InGaAs/GaAs pseudomorphic high‐electron‐mobility transistor process with a chip size of 2.11 × 1.54 mm2. This mixer employs a planar Marchand balun and a low‐pass filter for isolating three ports corresponding to RF, LO, and IF ports. The best upconversion loss is 8 dB with an LO‐to‐RF isolation better than 30 dB. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2692–2694, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22884

This paper presents a compact X‐band, 9 W AlGaAs/InGaAs/GaAs PHEMT MMIC high power amplifier. This amplifier is designed to fully match a 50 Ω input and output impedance. Based on 0.35 μm gate‐length power PHEMT technology, a two‐stage power amplifier is fabricated on a 3‐mil thick wafer. While operating under 9 V DC bias condition, the characteristics of 17 dB small‐signal gain, an average of 9 W continuous‐wave output power, and 34% power added efficiency from 9.0 to 10.5 GHz can be achieved. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 257–261, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22102

Anisotropic wet etching of high resistivity silicon by TMAH for the fabrication of large area silicon radiation detectors is studied in this work. TMAH is widely applied in microelectronics and micromechanical fabrication etching low resistivity silicon, whereas the etching of high resistivity silicon was seldom studied by the industry. This work focused on the research of TMAH etching of high resistivity lager area silicon wafer aiming at its application in silicon radiation detector fabrication. We investigated the etching properties of TMAH of 4 inch (111) silicon wafers. Various parameters combinations were explored, such as TMAH solution concentration of 25wt%, 15wt% and 5wt%, and temperature of 95 °C, 90 °C and 85 °C. Etch rate, etch uniformity and silicon surface roughness were observed.

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