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[en] Radioisotope microball tracer which was produced by new process is applicable to injection profiling in low injection rate wells. Five-parameter combo logging tools were developed, which enhance accuracy and reliability of log by integrating interpreting flowrates inside tubing, shut-in and flowing well temperatures and tracing results. Reliable impulse oxygen-activation logging tools and a tracer logging method with correlation arithmetic were developed to meet the need of profiling polymer injectors. These new techniques are widely used in injection profile logging at Daqing oilfield. (authors)
[en] In this paper, a conductance probe-based well logging instrument was developed and the total flow rate is combined with the response of the conductance probe to estimate the water cut of the oil–water flow in a vertical well. The conductance probe records the time-varying electrical characteristics of the oil–water flow. Linear least squares regression (LSR) and nonlinear support vector regression (SVR) were used to establish models to map the total flow rate and features extracted from the probe response onto the water cut, respectively. Principal component analysis (PCA) and partial least squares analysis (PLSA) techniques were employed to reduce data redundancy within the extracted features. An experiment was carried out in a vertical pipe with an inner diameter of 125 mm and a height of 24 m in an experimental multi-phase flow setup, Daqing Oilfield, China. In the experiment, oil–water flow was used and the total flow rate varied from 10 to 200 m"3 per day and the water cut varied from 0% to 100%. As a direct comparison, the cases were also studied when the total flow rate was not used as an independent input to the models. The results obtained demonstrate that: (1) the addition of the total flow rate as an input to the regression models can greatly improve the accuracy of water cut prediction, (2) the nonlinear SVR model performs much better than the linear LSR model, and (3) for the SVR model with the total flow rate as an input, the adoption of PCA or PLSA not only decreases the dimensions of inputs, but also increases prediction accuracy. The SVR model with five PCA-treated features plus the total flow rate achieves the best performance in water cut prediction, with a coefficient of determination (R"2) as high as 0.9970. The corresponding root mean squared error (RMSE) and mean quoted error (MQE) are 0.0312% and 1.99%, respectively. (paper)
[en] In a horizontal well with low flow rate, oil-water two-phase flow is stratified due to gravity. For measuring water cut accurately in a low-production horizontal well, a novel cylindrical capacitance sensor is proposed in this paper. The structure of the sensor is cylindrical and hollow with multi-layer structure which is consisted of inside insulation layer, electrode layer, outside insulation layer and metal casing from inside to outside. And the measurement principle is analyzed in this paper. The mathematical model is established, which shows that theoretically, there is a good relationship between the sensor response and water holdup. The response curve is monotone and the sensor has a good resolution and a high sensitivity in the whole range of water holdup. The electric field of cylindrical capacitance sensor was simulated respectively by using ANSYS software when the sensor is filled with pure water, pure oil and oil-water mixture. The results of the simulation are consistent with the mathematical model. Static experiments with the sensor filled with oil-water mixture were conducted finally. The results have verified the theoretical analysis and show that the proposed sensor is a viable solution to measuring water cut in a low-production horizontal well. Cylindrical capacitance sensor provides a good reference for the water cut in low-production horizontal well and has a good application prospect.
[en] This paper has proposed a new structure of full-bore conductance sensor, which is designed for measuring water cut of the oil-water two-phase flow. The structure of the full-bore conductance sensor and the measurement principle are introduced in the paper. The mental ring-shaped electrode is mounted on the outside wall of the cylindrical insulation body. When the electrode is provided with constant current, according to the electrical theory, the electrode generates a voltage, the value of which is inversely proportional to the conductivity of fluid flowing between the sensor and the casing. The electrostatic field simulations of the sensor are accomplished by using ANSYS software. The results of the potential distribution simulation show that the potential decays quickly from the electrode along r direction (radial) and z direction (axial)to both sides, and the potential only distributes in a very narrow area near the electrode. A series of static experiments on the sensor are carried out in laboratory. The experiment results agree with the simulation results. In radial direction, the closer the rod is to the sensor, the more sensitive the sensor becomes and the greater the relative response becomes. In axial direction, the electrode only responds in a certain region on both sides of the electrode and decays rapidly from the electrode to both sides. And the salinity experiment is conducted in salt solution (3000 ppm), which shows that within the allowable range of experiment error, there is no effect of salinity on the sensor response. response.
[en] This paper presents a minimum root-mean-square error (RMSE)-based method for a dual-circle conductance probe array to measure the water holdup of an oil–water two-phase flow in a horizontal oil well. The dual-circle conductance probe array consisting of 24 conductance probes, half of which are equidistantly distributed on a 34 mm radius inner circle and the other half on a 48 mm radius outer circle, is used to estimate the oil–water interface and hence the water holdup in the horizontal oil well. For the same water holdup, the number of probes immersed in water may vary with varying the azimuth angle due to the limited number of probes. The limited number of probes and unknown azimuth angle of the probe array in the oil well limit the measurement accuracy of the water holdup. In order to obtain a better water holdup estimate, a water holdup measurement method based on the minimum RMSE was proposed to decrease the effects of the limited number of probes and unknown azimuth angle of the probe array. To verify the proposed method, numerical simulations were carried out and compared with the commonly used equi-weight estimate method; results showed that the RMSE of the water holdup estimates obtained using the proposed method is smaller than that when using the equi-weight estimate method. Experiments were implemented in a 16 m long and 125 mm inner diameter horizontal pipe on an industrial-scale experimental multiphase flow setup in the Daqing Oil Field, China. The RMSEs of water holdup estimates obtained using the proposed and equi-weight estimate methods are 0.0632 and 0.0690, respectively, showing that the proposed method is better than the equi-weight estimate method. (paper)
[en] As is known, quantum key distribution could achieve information-theoretical security under several basic requirements, one of which is reliable identity authentications between the participants. Compared with classical identity authentication, quantum identity authentication (QIA) is considered to be more secure and more efficient to combine with quantum key distribution (QKD), and therefore, more and more scholars are involved in the study of QIA. During the last 3 decades, various types of QKD protocols have been proposed utilizing different kinds of quantum technologies. One of the most special QKD protocols is the orthogonal-state-encoding QKD protocol proposed by Goldenberg and Vaidman (Phys Rev Lett 75:1239–1243, 1995), which is usually called GV95 protocol. Almost all of the QKD protocols employ nonorthogonal states to prevent and detect eavesdropping, and the most famous exception is GV95. In this paper, we present a QIA protocol based on the GV95 technology, which can be performed in a revised circuit of the GV95 protocol. And we also analyze the security of both Alice’s and Bob’s identities.