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Li Y.,China University of Petroleum - Beijing | Li Y.,China National Petroleum Corporation | Su W.,Great Wall Drilling Company | Wang Z.,Dagang Oilfield Company | And 3 more authors.
Shiyou Xuebao/Acta Petrolei Sinica

Compared with main layers in Daqing oilfield, the class II oil layer is characterized by severe interlayer heterogeneity that makes features of its polymer injection and oil production combination quite different from the main layer. Commingled injection in the class II oil layer can not well solve the problem of interlayer production because thin and poor layers could be hardly recovered and water fingering in thick layers occurs frequently, so the effect of polymer flooding is still not highly satisfactory. It is important to define the optimal adjustment moment of polymer flooding for different injection-production types of the class II oil layer in Daqing oilfield. There are four types of the injection-production combination for the class II oil layer in Daqing oilfield, i.e. thick-layer injection with thick-layer production, thick-layer injection with thin-layer production, thin-layer injection with thin-layer production, and thin-layer injection with thick-layer production. Through isobaric polymer flooding experiments on parallel models of the four types, we obtained the optimal adjustment moment for these four different types, namely the polymer volume at the optimal adjustment moment is 740 PV·mg/L, 780 PV·mg/L, 810 PV·mg/L and 860 PV·mg/L respectively. Ceasing polymer injection at the optimal moment for each injection-production well type could make the oil increment per ton polymer maximum and reservoir recovery the most effective. Therefore, ceasing polymer injection at the optimal adjustment moment and taking further measures in time to enhance oil recovery can make the injection amount of each well type efficient and economical. By comparing displacement effects between the thick-layer injection with thin-layer production and the thin-layer injection with thick-layer production, we concluded that the pattern of injection in a high-permeable zone and production in a low-permeable zone was the most favorable and effective way of the horizontal heterogeneous reservoir development. Source

During the early stage of the build-up pressure to shut-in well, the pressure sampling density generally set at surface is difficult to capture the down-hole data point of early buildup pressure timely at the instantaneous state from the flow stage to shut-in well. It is tested by examples of the fitting contrast effect to reservoir model before and after sampling point encryption of pressure recovery data of the early close well, and from early stages of shut in well to every stages of reservoir, influence on reservoir model of the general homogeneous, heterogeneous and fractured of early sampling density of close well, and diagnosis and analysis of identifying well testing data of fractured reservoir characteristics. Source

Wei F.,Shihezi University | Xiong C.,Huazhong University of Science and Technology | Gou K.,Great Wall Drilling Company
Advanced Materials Research

La0.7Ca0.2Sr0.1MnO3/xIrO 2 (LCSMO/xIrO2) compounds were fabricated by solid state reaction method. X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and Dc four probed method were used to investigate the structure, magnetic and magnetotransport properties. The results show that at low doping level (x≤0.15) IrO2 goes into the perovskite lattice substituting Mn in LCSMO, but at high doping level (x≥0.20) some part of the IrO2 substituted for Mn4+ in LCSMO lattice and the remainder resided in the grain boundaries in the form of IrO2. LCSMO/xIrO2 composites are influenced remarkabled by the IrO2 doping. With increasing IrO2 addition, the magnetic moment (σs) decreases and Curie temperature (TC) decreases first, and then rises slowly of the compounds; In the doping range of 0∼0.35, the resistivity rises first, and then decreases slowly, furthermore, the resistivity versus appears double peaks with increasing IrO2 addition. At room temperature, the magnetoresistance (MR) of the composites have been improved remarkably. © (2011) Trans Tech Publications. Source

Recently, Chinese Geographic Name Database was published, based on which the author has located as many as 5825 coalmines. “Replayed” by natural order, it has been found that 48.7% of coalmine disasters did not occur randomly, but tended to occur continuously within certain scopes, presenting cluster feature, some accompanied with earthquakes (with magnitude>3), in which all the disaster types are involved. In further research, with micro earthquakes introduced, quite a few coalmine disasters are found to be accompanied with micro earthquakes, in which earthquakes tended to occur earlier than coalmine disasters. Of all the causative factors, stress disturbance is the only one that can cause all kinds of disasters at one time. The earthquakes accompanied with disasters may be the vital geophysical evidence of the tectonic stress fluctuation around mining area(causing coalmine disasters). This paper made a quantitative research, by which the ratio of disasters involved in cluster series and the number of earthquakes accompanied with disasters are achieved. For example, under threshold of 100 miles, of all the 7368 disasters, at least 38.5% are involved in cluster series, in which 372 disasters are accompanied with earthquakes. Of all the cluster series, the proportion of the durations sorted by descending order is 2 days, 1 day, 3 days, 4 days, …, 11 days. Potentially, the duration of cluster series reflects the duration of stress disturbance. The majority of the durations are composed of short ones, such as 1 and 2 days, which correspond well earthquakes (with magnitude<5) and are speculated to be more likely related to local stress disturbance. While the minority long durations correspond well with fatal earthquakes, which are speculated to be related to regional stress disturbance. In addition, all the cluster series under every threshold have been picked out successfully and a full open access is provided. As to the mechanism, the author makes the most common speculations on a given geological model, in which five affecting cases are analyzed. The phenomena remain unknown to human, which, to earthquake research and coalmine disaster prevention, widely scientific significance is suggested. © 2016, Editorial Office of Earth Science Frontiers. All right reserved. Source

Shang Y.-B.,Xian Changqing Technology Engineering Co. | Shang Y.-B.,China University of Petroleum - East China | Li C.-X.,China University of Petroleum - East China | Shang X.-F.,Great Wall Drilling Company | And 2 more authors.
Oilfield Chemistry

The simulated produced fluid (10%-50% water ratio) for polymer-surfactant flooding of north third region in Changqing oilfield was prepared, containing 1000 mg/L polyacrylamide and 1667 mg/L betaine surfactant. The demulsification experiment of simulated produced fluid (30% water ratio) was carried out under the condition of 55°C dehydration temperature, 100 mg/L demulsifier and 40 min dehydration time. The water-soluble sulfonate demulsifier KL-9, KL-10 and KL-14 were screened from 28 kinds of demulsifier, showing better demulsification effect. When the dosage of demulsifier was 50 mg/L, the dewatering rate of KL-14 was 92.6%, 97.8% and 99.9% under dehydration temperature 40°C, 45°C and 50°C, respectively, greater than that of KL-9, KL-10. The demulsification effect of KL-14 was the best. The similar results were obtained from simulated produced fluid with 10% and 50% water ratio. Therefore, it was concluded that KL-14 was the best demulsifier for the simulated produced fluid with 10%-50% water ratio. The dehydration rate increased under same demulsifier dosage, with increasing demulsification temperature. The dehydration rate of KL-14 increased under same dehydration temperature, with increasing demulsifier dosage. With extending dehydration time, the dehydration rate increased and turned to be stable gradually. The optimum demulsification condition was obtained as follows: 50-55°C dehydration temperature, 100 mg/L demulsifier, 30 min dehydration time. Source

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