Microwave heating effects on formation damages in tight gas sands

In tight gas sand reservoir, formation damages cause severe reduction of gas production rate. In this study, the microwave heating method is used to heat tight sandstones and investigates how microwave heating influences the petrographic and petrophysical properties of these samples by using various experimental techniques and numerical simulation. It is demonstrated that removing formation damage and enhancing reservoir quality with microwave heating is feasible in the near wellbore region

The role of peripheral input and its contribution to phantom limb pain

Following amputation, nearly all amputees report non-painful phantom phenomena and many of them suffer from chronic phantom limb pain (PLP) and residual limb pain (RLP). The etiology of PLP remains elusive and there is an ongoing debate on the role of peripheral and central mechanisms. Few studies have examined the entire somatosensory pathway from the truncated nerves to the cortex in amputees with PLP compared to those without PLP. The relationship between afferent input, somatosensory responses and the change in PLP remains unclear. The present thesis aimed at identifying whether peripheral afferent input can induce PLP and how it interacts with somatosensory processing and postamputation pain. Transcutaneous electrical nerve stimulation was applied on the truncated median nerve, the skin of the residual limb and the contralateral homologous nerve in twenty-two traumatic upper-limb amputees (12 with and 10 without PLP). Using somatosensory event-related potentials, the ascending volley was monitored through the brachial plexus, the spinal cord, the brainstem and the thalamus to the primary somatosensory cortex. There were no significant differences in the electrical potentials generated by the stimulation from the truncated nerve or the skin of the residual limb in amputees with and without PLP. Peripheral input could evoke PLP in amputees with chronic PLP (7/12), but not in amputees without a history of PLP (0/10). In addition, peripherally induced potentials through the spinal-subcortical segment were significantly positively associated with evoked RLP, but not PLP. Peripheral input can enhance PLP but seems insufficient to cause it. These findings indicate the multifactorial complexity of PLP and also suggest different mechanisms for PLP and RLP

Least Squares Based Iterative Algorithm for the Coupled Sylvester Matrix Equations

By analyzing the eigenvalues of the related matrices, the convergence analysis of the least squares based iteration is given for solving the coupled Sylvester equations AX+YB=C and DX+YE=F in this paper. The analysis shows that the optimal convergence factor of this iterative algorithm is 1. In addition, the proposed iterative algorithm can solve the generalized Sylvester equation AXB+CXD=F. The analysis demonstrates that if the matrix equation has a unique solution then the least squares based iterative solution converges to the exact solution for any initial values. A numerical example illustrates the effectiveness of the proposed algorithm

Research and Field Application of Top Screen Cementing Technology with the Salvaging Type Plug-Drilling-Free Tool

Top screen pipe cementing technology of casing in horizontal well has been one of the main completion, especially for developing reservoirs with bottom and edge water and heavy oil reservoirs. Main drawbacks of screen top cementing completion technology in horizontal wells are casing wear in the process of drilling plug and burrs in the inner surface after drilling plug which are obstacles of well intervention. The salvaging type Non-plug-drilling tool eliminates the disadvantages of plug-drilling. By optimizing tool structure, improving technology, the reliability of salvaging type plug-drilling-free tool has been increased. More than 133 wells in 2012 had adopted the salvaging type plug-drilling-free tool with high reliability in Pai 601 Block of Xinjiang with 100% success rate.  Key words: Horizontal well; The salvaging type plug-drilling-free technology; Completion; Top screen cementing technology; Field applicatio