Papers by Author: Xiang Zhen Yan

Abstract: Coal principal stresses with reservoir plane is analyzed, consequently coal seam crushed classification method is presented based on Hoek-Brown criterion. According to the coefficient of coal crushing, coal seam crushed coefficient size, four grades of A,B,C,D are divided for coal crushed degree along wellbore direction, and coal crushed classification standard is determined. Using the classification method and standard, the distribution regularity of coal crushing is studied for ZP-05 Well in QinShui basin. The research results show that coal crushing of ZP-05 is considered as grade B. The prediction results agree well with the measured values.

Abstract: The differential GPS navigation and positioning technique, multi-channel shallow seismic exploration and high resolution single channel seismic technique were used for the geophysical exploration of the shallow stratum in Jiangshidi nuclear power plant site and its surrounding areas. Based on seismic data post processing results, the seismic section interpretation was performed, combined with regional geological background, borehole data and shallow anatomy data. Five main seismic reflection surfaces were recognized by using seismic stratigraphic method, and eight breakpoints were found according to the active fault discrimination criteria. Then the distribution and activity characteristics of main faults were obtained. The results show that any fault and marked deformation in the quaternary sediments has not been observed in the range of 5 km away from Jiangshidi nuclear power plant site. So the stability analysis results of shallow stratum in target area can meet the requirement of nuclear power plant site selection code.

Abstract: In this paper, a creep test was carried out for simulating the creeping of the core of the mudstone under condition of deep formation subsurface conditions by MTS-810 test system, the creep rule and the characteristic parameters of the mudstone formation were obtained from the experiments. According to the test results, the finite element model for casings load calculation was established, and the calculation program was also written. With the program, the casing load of one western oil well was calculated in mudstone formation. The numerical simulation results show that the casing load has a relationship with phase angle θ and creep time, and the casing load is 10% greater than the stress in situ.

Abstract: According to Mohr-Coulomb criterion, the yield approach index (YAI) of Hoek-Brown criterion is derived. The rock-mass intact coefficient KV is introduced, and coal failure approach index is defined by combining failure degree. On the basis of logging data and stratified in-site stress model, the failure approach index and yield approach index are calculated in wellbore direction. Based on FAI values, coal fracture degree is divided four grades of A, B, C, D, and coal fracture classification method is proposed. Taking ZP-1 Well in QinShui basin as an example, the distribution regularity of coal fracture degree is predicted by the method. The results indicate that failure approach index of ZP-01 well is between 0.8-1.2; the section of 551-552.7m of coal seam is fractured (grade A), and the rest section of coal seam is regarded as grade B. Through electron microscope to scan coal sample structure, the results agree well with the prediction results, therefore the classification method is reliable. Depending on theory results, computer program is corresponding developed.

Abstract: Depending on the mechanical characteristics of casing located at the bending part of sidetrack horizontal well, the calculation model of casing collapsing strength under the effect of bending load is established, and corresponding theoretical formulae is derived. During the process of deducing formulas, the influence of bending load on the casing section out of roundness is ignored, which made the calculation formula benefits intuition and practicality comparing to the T.Tamano formula. The result of this paper is verified through the simulation value and laboratory test of casing used in the Jilin oilfield. It shows that the formula of this paper can meet the engineering commands; the axial load is significant to affect casing collapsing strength, and in the actual production process should be strictly controlled.

Abstract: Based on the orthotropic physical properties of coal cleats, the fluid-solid coupling model for stress sensibility coal seams is established. The equations of the coupling model are solved by using the finite element method. The history matching for JS-3 well in Ordos basin is carried on by using the coupling model. The comparison between calculated results based on the coupling model and the measured values indicates their good agreement, which verifies the accuracy and rationality of the model. The effect of the permeability orthotropic coefficient of coal cleats on the pressure distribution in coal seams is analyzed. The results show that the pressure along the butt cleats direction increases with permeability orthotropic coefficient increasing; The pressure along the face cleats decreases with permeability orthotropic coefficient increasing between 0m~30m and 170m~200m, whereas both increases from 30m to 170m.

Abstract: The mathematical model of Two-Phase flow of water and gas in aquifer is established based on the Darcy linear percolation law and law of conservation of mass of fluid mechanics. According to the fully implicit difference method, time and spatial discretization of the model lead to a set of nonlinear equations, which can be transferred into a group of linear equations. The linear equations can be solved using the Jacobi-iteration pretreatment because of its high stability and fast convergence speed of the solution positively. The distribution of the saturation and formation pressure with time in the process of gas injection is analyzed by using the mathematical model. The results show that the gas saturation increases with the gas injection rate, the permeability and reservoir thickness increasing whereas the formation pressure increases slowly under same cumulative gas injection rate. The formation pressure increases at first and then decreases to reach a steady value.

Abstract: In order to complete the numerical simulation on internal flow and operating characteristics of down hole multiphase pump compress unit, establishing perfect finite element model, the three-dimensional turbulent current fields inside the impellers of compression unit for down hole multiphase pumps were simulated by using ANSYS. The calculation of multiphase flow is based on the standard k-ε turbulent current model. Reference information for the improvement of the pump can be obtained by the analysis of the flow of gas-oil in the channel of pump. Based on the finite method, we analyzed several situations in a pumping period. The velocity and liquid pressure distributing of sucker rod pump is studied in this paper, which may offer some evidences for the engineering design of sucker rod pump.

Abstract: With the application of ANSYS finite element analysis software and environmental data in ChengDao oil field, a nonlinear finite element model of suspended submarine pipeline coupled with sea-floor soil is developed. Discarding the traditional and imprecise pipeline model with double clamped or simply supported ends, the model is founded on the theory of elastic foundation beam, in which the nonlinear effect between pipeline and sea-floor soil is considered. Base on the model we developed, the influences of span length and shear strength of soil at the ends of span on the span’s natural frequency are discussed. And the effects of span length, shear strength of soil and current velocity on the dynamic response of span are also analyzed in this paper. The model we developed in this paper fits the actual structure better, and the analysis is instructive for preventing and controlling the suspending of submarine pipeline.

Abstract: In the process of drilling well, the kinematics of drill string is quite complicated. The drill string not only vibrates in longitudinal, transverse and torsional direction, but also random impacts and contacts well wall. Considering the random load of drill bit and rock, contact impact of drill string and well wall, a model is proposed to simulate the contact-impact of drill string and formation. The results show that: in the condition of this article the first principal stress of the drill string can reach to 130 MPa, for the random impacts, the strength of drill collar will reduced under cyclic loading; contact-impact is the principal source of drill premature failure. In this paper, an explicit integration and nonlinear finite element was adopted to simulate the collision between the drill string and formation, the process of the collision between the drill string and formation can be revealed compressively and delicately. Through an example, we can obtain the foundation for nonlinear dynamic theory of drill string system collision in the actual work condition, and has important theory significance and academic value.