Wang J.-H.,Tianjin University |
Qu Y.-D.,China Oilfield Services Ltd.
Shuili Xuebao/Journal of Hydraulic Engineering | Year: 2011
The unconsolidated undrained strength of saturated soft clay was studied by cyclic torsion and cyclic triaxial tests. The results show that the unconsolidated undrained cyclic strength depends on the static shear (deviatoric) stress acting on the soil element and is independent of the confining pressure for a specified number of cycles for failure. When static shear stress ratio acting on soil elements increases from 0.3 to 0.6, cyclic strength of the saturated soft clay also increases. It is found that the unconsolidated undrained cyclic strength satisfies the Mises failure criterion by analyzing the relationship between the cyclic shear strength and the cyclic compressive strength determined by cyclic torsion shear and cyclic triaxial tests respectively. It may conclude that the relationship describing unconsolidated undrained cyclic strength of saturated soft clay elements with general stress states can be determined by specified tests. Source
Guo W.-Y.,Mianyang Normal University |
Peng B.,China Oilfield Services Ltd.
Journal of Vinyl and Additive Technology | Year: 2012
Some starch-graft-polyacrylamide copolymers were prepared by the polymerization of corn starch with acrylamide in aqueous medium using a complex initiation system consisting of ceric ammonium sulphate and ammonium persulphate. The copolymers were applied to water-based drilling fluid as filtration control agents. Their grafting parameters such as percentage of grafting, grafting efficiency, and solution viscosity (η) were investigated by using elemental analyzer and rotational viscometer. The results showed that increases in initiator concentration and reaction temperature first favored and then impeded the grafting reaction. Grafting of acrylamide onto starch increased with the increase of monomer concentration. It also increased with increasing reaction time up to a certain degree and then leveled off. For the graft copolymers, a higher percentage of grafting and higher η were beneficial in decreasing the filtrate volume of water-based drilling fluid, even under an operating environments of 147°C and saturated salinity. A possible mechanism is proposed to interpret the improvement of fluid loss properties. © 2012 Society of Plastics Engineers. Source
Li Y.,China Oilfield Services Ltd.
Xinan Shiyou Daxue Xuebao/Journal of Southwest Petroleum University | Year: 2014
Towed streamer seismic acquisition is used in the traditional marine seismic exploration, and the signal-to-noise ratio of the collected data are greatly influenced by external environment. The influence of environment on seismic data can be reduced by changing the depth of the streamer. It's difficult to collect broad-seis data in China sea due to the limitations of seismic equipment. In order to break the limitation, a combined broad-seis survey of streamer and ocean bottom cable (OBC) was discussed in the article. There are four key techniques in survey design, including parameter argumentation, bin combined, feather angle and depth optimization. In parameter argumentation the method to compute line spaces through the most shallow purpose layer is discussed. For the space differences between towing and submarine cable detector, bin combined method was designed. In the situation of feather angle existence, we discussed the effect of horizontal change rate on limited wave point frequency and energy in data collection. In the end, we discussed the optimization of sinking depth of towing through depth changing test. Through analysis of these techniques, we have established the basic process of survey design of combined broad-seis acquisition of streamer and OBC. Source
Yu H.,China Oilfield Services Ltd.
Well Testing | Year: 2016
According to problems of condensates inflammable and explosive safety hazards when the condensates in testing production, measurement, storage and transportation, by application of the hermetically-sealed system, back-pressure control valve real-time monitoring automatic acquisition system, a better separated effect could be achieved to guarantee acquiring testing data accurately and safely. © 2016, The Editorial Department of Well Testing. All right reserved. Source
China National Offshore Oil Corporation and China Oilfield Services Ltd. | Date: 2013-11-20
A pushing and jam-releasing pup joint of a formation tester comprises a first jam-releasing arm (