Reducing the bottom-hole differential pressure by vortex and hydraulic jet methods

Reducing the bottom-hole differential pressure (BHDP) of a gas/oil well and so as to reduce the “chip hold-down effect” can significantly improve the rate of penetration (ROP). The fluid vortex and hydraulic jet methods are used to reduce the BHDP while the wellbore pressure is unchangeable to prevent wellbore instability. The depressurization theories of the two hydraulic pressure drawdown methods are studied. The structures, depressurization mechanism, depressurization capacity, and the current researches and developments of the hydraulic pressure drawdown tools, including the vortex tools and the jet hydraulic pressure drawdown tools (JHPDTs), are analyzed. Using field tests and flow field numerical calculation methods, the key factors which affect depressurization capacity of the vortex tools and the JHPDTs, and the design principles of the vortex bit and the jet pump bit are proposed. Different depressurization methods and structures are simulated, which shows the vortex and jet pump combination bit with 106 mm distance is preferable

Dichlorido[2-(3,5-dimethyl-1H-pyrazol-1-yl-κN 2)-1,10-phenanthroline-κ2 N,N′]cadmium(II)

The asymmetric unit of the title compound, [CdCl2(C17H14N4)], contains two independent mol­ecules in which the CdII ions are in distorted trigonal-bipyramidal CdN3Cl2 coordination environments. In the crystal structure, there is a π–π stacking inter­action involving a pyridine ring and a symmetry-related benzene ring, with a centroid–centroid distance of 3.5088 (19) Å

Poly[hexa-μ-acetato-bis­(dimethyl sulfoxide)­trimanganese(II)]

In the title complex, [Mn3(CH3CO2)6(C2H6SO)2]n, the MnII ions exhibit similar MnO6 octa­hedral coordination geometries but with different coordination environments. One type of MnII ion is surrounded by five acetate groups and a terminal dimethyl sulfoxide group, while the other lies on a twofold axis and is coordinated by six O atoms from three symmetry-related acetate ions. The acetate anions exhibit three independent bridging modes, which flexibly bridge the MnII ions along the c-axis direction, forming an infinite chain structure; the chains are further inter­connected through weak C—H⋯O and C—H⋯S hydrogen-bonding inter­actions

Numerical simulation on the impact dynamics of a novel rotation air hammer and experimental research

Novel rotation air hammer (NRAH) is a rock-breaking tool in the gas drilling. The rock-breaking ability of the NRAH is mainly from the collision between piston and drill bit in it. The collision makes the piston and the drill bit suffer from a high instantaneous impact stress, so that they are prone to failure. Thus, both of them are not only the most crucial parts of the NRAH, but also the easily damaged parts. So it is necessary to analyze the impact stress in them and optimize their structure to improve the security and reliability. First of all, we analyzed the working mechanism of the NRAH to understand motion and structure of the piston and the drill bit. Then we used the LS-DYNA program to analyze impact dynamics problem of the piston and the drill bit to obtain their stress change rule in the impact process. According to the structure optimization, the security coefficient of the piston and the drill bit has been obviously improved. Moreover, their energy conversion regulations were studied in the impact process of the NRAH and the last impacting velocity of the piston was computed, which can provide helpful for effective application of this tool in the field. Finally, based on the experimental study on the NRAH after the optimization, we found that its function had satisfied the design requirements as well as overall performance was improved