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China Ocean Engineering 2018年第6期32卷 633-645页

作者： ZHU Hong-jun ZHAO Hong-lei GAO Yue state key Laboratory of oil and gas reservoir geology and exploitation Southwest Petroleum University

The vibration response of a free-hanging flexible riser induced by internal gas-liquid slug flow was studied experimentally in a small-diameter tube model based on Froude number criterion. The flow regime in a curved riser model and the response displacements of the riser were simultaneously recorded by high speed cameras. The gas superficial velocity ranges from 0.1 m/s to 0.6 m/s while the liquid superficial velocity from 0.06 m/s to 0.3 m/*** slugging type 3, unstable oscillation flow and relatively stable slug flow were observed in the considered flow rates. Severe slugging type 3 characterized by premature gas penetration occurs at relatively low flow rates. Both the cycle time and slug length become shorter as the gas flow rate increases. The pressure at the riser base undergoes a longer period and larger amplitude of fluctuation as compared with the other two flow regimes. Additionally, severe slugging leads to the most vigorous in-plane vibration. However, the responses in the vertical and horizontal directions are not synchronized. The vertical vibration is dominated by the second mode while the horizontal vibration is dominated by the first mode. Similar to the vortex-induced vibration, three branches are identified as initial branch, build-up branch and descending branch for the response versus the mixture velocity of gas-liquid flow.

关键词： gas-liquid two-phase flow severe slugging liquid slug flexible riser flow-induced vibration

The gas recovery of water-drive gas reservoirs

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Journal of Hydrodynamics 2015年第4期27卷 530-541页

作者：李闽李滔蒋琼杨海刘世常 state key Laboratory of oil and gas reservoir geology and exploitation Southwest Petroleum University

This paper proposes a method for determining the gas recovery of water-drive gas reservoirs. First, the water influx coefficient B in the theoretical formula Pr =（1-Rg）/（1-RgB） is used to determine the influence of the aquifer behavior. According to the theoretical formula, the relationship between the norrnalized pressure Pr and the degree of the reserve recovery Rg can be obtained with different values of B, which can be used to determine the activity level of the aquifer behavior. Second, according to Pra = （1-Rga）/（1-aEva）（where a = 1-Sgr/Sgi ）, the relationship between the normalized abandonment pressure Pra and the ultimate gas recovery Rga can be obtained, as the Agarwal end-point line. The intersection of the above two lines represents the value of the estimated ultimate gas recovery and the normalized abandonment pressure pra. Finally, an evaluation table and a set of demarcation charts are established, with different values of Sgr/Sgi and Eva as well as the water influx coefficient B, which can be used to determine the gas recovery of water-drive gas reservoirs with different activity levels of the aquifer behavior.

关键词： water-drive gas reservoirs degree of reserve recovery water influx coefficient evaluation table demarcation charts

An optimal fracture geometry design method of fractured horizontal wells in heterogeneous tight gas reservoirs

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Science China(Technological Sciences) 2016年第2期59卷 241-251页

作者： ZENG FanHui KE YuBiao GUO JianChun state key Laboratory of oil & gas reservoir geology and exploitation Southwest Petroleum University

In this work, the unified fracture design （UFD） is extended for the first time to the fractured horizontal wells in heterogeneous closed box-shaped tight gas reservoirs. Utilizing the direct boundary element method and influence function, the dimensionless fracture productivity index is obtained and expressed in the function of proppant volume and fracture geometry at the pseu- do-steady state. With the iterative method, the effectively propped permeability, kfe, is corrected using the i^-situ Reynolds number, NRe. The goal of this paper is to present a new UFD extension to design the proppant volume and the optimal fracture geometry. The results show that there exists an optimal proppant volume for a certain reservoir. The small aspect ratio （yJXe） and high permeability reservoirs need short and wide fractures to diminish the non-Darcy effect. On the contrary, long and narrow fractures are required for the large aspect ratio and low permeability reservoirs. A small proppant volame is prone to creating long fractures, while a relatively large proppant volume creates wide fractures. The new extension can be used to evaluate the previous fracture parameters and design the following fracture parameters of the fractured horizontal well in heterogeneous tight gas reservoirs, with the non-Darcy effect taken into account.

关键词： tight gas reservoir heterogeneity non-Darcy effect fractured horizontal well fracture geometry design

Transient flow model and pressure dynamic features of tree-shaped fractal reservoirs

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Journal of Hydrodynamics 2014年第4期26卷 654-663页

作者：谭晓华李晓平 state key Laboratory of oil and gas reservoir geology and exploitation Southwest Petroleum University

A transient flow model of tree-shaped fractal reservoirs is built by embedding a fracture network simulated by a tree-shaped fractal network into a matrix system. The model can be solved using the Laplace conversion method. The dimensionless bottom hole pressure can be obtained using the Stehfest numerical inversion method. The bi-logarithmic type curves for the trce-shaped fractal reservoirs are thus obtained. The pressure transient responses under different fractal factors are discussed. The factors with a primary effect on the inter-porosity flow regime include the initial branch number N, the length ratio α, and the branch angle θ. The diameter ratio β has a significant effect on the fracture radial flow, the inter-porosity and the total system radial flow regimes. The total branch level M of the network mainly influences the total system radial flow regime. The model presented in this paper provides a new methodology for analyzing and predicting the pressure dynamic characteristics of naturally fractured reservoirs.

关键词： tree-shaped fractal transient flow pressure dynamic characteristic naturally fractured reservoir type curve

Pressure transient behavior of a slanted well with an impermeable fault

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Journal of Hydrodynamics 2014年第6期26卷 980-985页

作者：冯国庆刘启国 state key Laboratory of oil and gas reservoir geology and exploitation Southwest Petroleum University

Analytical solution is obtained for the pressure response of a slanted well in a slab reservoir with an impermeable fault. Based on the basic point source solution in an infinite space, the basic point source solution is obtained by using the mirror image principle. Wellbore pressure response of a slanted well is obtained by integration of the basic point source solution along the trajectory of a slanted well and the type curves are computed. The dimensionless bottom hole pressure and type curves are obtained and the sensitivities of related parameters are discussed. The model presented in this paper could be used for the well test analysis of a slanted well in a reservoir bounded by an impermeable fault.

关键词： slanted well point source solution impermeable fault type curves

Critical parameters of horizontal well influenced by semi-permeable barrier in bottom water reservoir

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Journal of Central South University 2015年第4期22卷 1448-1455页

作者：乐平杜志敏陈小凡朱苏阳贾虎 state key Laboratory of oil & gas reservoir geology and exploitation Engineering (Southwest Petroleum University)

It is well-known that barriers have a significant impact on the production performance of horizontal wells developed in a bottom water drive reservoir. In most cases, reservoir barriers are semi-permeable. Based on previous research on impermeable reservoir barrier, a mathematical flow model was derived for a horizontal well of a bottom water drive reservoir with a semi-permeable barrier. Besides, analytical equations were also presented to calculate critical parameters, such as production rate,pressure and potential difference. The effects of barrier, well and reservoir parameters on our model results were further *** results show that the larger the barrier size is or the higher the barrier location is, the higher the critical production rate and potential difference of a horizontal well are. When the barrier permeability equals the formation permeability or the barrier width equals zero, the critical production rates converge to the values same to that of the case with no barrier. When the barrier permeability equals zero, the problem is regarded as a case of impermeable barrier. This model can be applied to predicting horizontal wells' critical production parameters in reservoirs with semi-permeable barriers.

关键词： horizontal well bottom water reservoir semi-permeable barrier critical rate cresting

The coupling of fluid flow and uplift since Late Cretaceous in Zoige area, western Sichuan

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Science China Earth Sciences 2011年第7期54卷 1043-1052页

作者： DENG Bin LIU ShuGen LI JuChu WANG GuoZhi LIU Shun LI ZhiWu LI XiangHui state key Laboratory of oil and gas reservoir geology and exploitation Chengdu 610059 China

The uplift indicated by five AFT (apatite fission track) samples is more than 3400 m by multi-episodic uplift since Late Cretaceous in Zoige area; especially the processes of fast uplift in Late Cretaceous and Neogene have important influences on the stress of paleo-fluid. Based on field geology, macroscopic features of fracture, and geochemistry of fluid inclusions, we decipher the paleo-fluid process of episodic migration. In early uplift stage, the temperature of inclusions increased with the constant salinity, whilst both of them proportionally decreased in the mid-late stage, indicating the different tendency of heat-fluid warming and freshwater contamination at different time. Of particular importance are the features of episodic fluid flow, such as ESR ages, and features of multi-episodic migration that correspond well with the process of multi-episodic uplift. Thus, concerning the rock stress-strain behavior responding to uplift, we further discuss the spatio-temporal coupling effect of episodic migration and decompression in multi-episodic uplift, thereby to better understand petroleum geology in the region.

关键词： multi-episodic uplift paleo-fluid decompression in the uplift episodic migration Zoige area

Research on fabric characteristics and borehole instability mechanisms of fractured igneous rocks

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Petroleum Science 2013年第2期10卷 212-218页

作者： Liu Xiangjun Zhu Honglin Liang Lixi state key Laboratory of oil and gas reservoir geology and exploitation Southwest Petroleum University

There are favorable exploration prospects in igneous rock reservoirs. However, problems of borehole instability occur frequently during drilling igneous formations, which is a serious impediment to oil and gas exploration and production. The lack of systematic understanding of the inherent instability mechanisms is an important problem. A series of experiments were conducted on several igneous rock samples taken from the sloughing formations in the Tuha area in an attempt to reveal the inherent mechanisms of wellbore instability when drilling in fractured igneous rocks. Research methods involved slurry chemistry, analysis of micro-geological features （Micro-CT imaging, SEM）, and rock mechanics testing. The experimental results indicated that clay minerals were widely distributed in the intergranular space of the diagenetic minerals, crystal defects, and microcracks. Drilling fluid filtrate would invade the rock along the microcracks. Tile invasion amount gradually increased over time, which constantly intensified the hydration and swelling of clay minerals, leading to changes in the microscopic structure of igneous rocks. Primary and secondary microcracks can propagate and merge into single cracks and thus reducing rock cohesion and the binding force along cleavage planes. Based on this result the authors propose that a key towards solving wellbore instability in igneous formations is that specific micro-geological characteristics of the igneous rocks should be taken into consideration in the design of antisloughing drilling muds.

关键词： Igneous rocks microcracks clay minerals hydration instability

The effects of sulfide stress cracking on the mechanical properties and intergranular cracking of P110 casing steel in sour environments

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Petroleum Science 2013年第3期10卷 385-394页

作者： Hou Duo Zeng Dezhi Shi Taihe Zhang Zhi Deng Wenliang state key Laboratory of oil and gas reservoir geology and exploitation Southwest Petroleum University

Variation and degradation of P-110 casing steel mechanical properties, due to sulfide stress cracking （SSC） in sour environments, was investigated using tensile and impact tests. These tests were carried out on specimens, which were pretreated under the following conditions for 168 hours： temperature, 60 ℃; pressure, 10 MPa; H2S partial pressure, 1 MPa and CO2 partial pressure, 1 MPa; preload stress, 80% of the yield strength （os）; medium, simulated formation water. The reduction in tensile and impact strengths for P-110 casing specimens in corrosive environments were 28% and 54%, respectively. The surface morphology analysis indicated that surface damage and uniform plastic deformation occurred as a result of strain aging. Impact toughness of the casing decreased significantly and intergranular cracking occurred when specimens were maintained at a high stress level of 85% %.

关键词： Acidic solutions high-temperature corrosion hydrogen embrittlement intergranular corrosion sulfide stress cracking

Synergistic effect of erosion and hydrogen on properties of passive film on 2205 duplex stainless steel

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Journal of Materials Science & Technology 2021年第8期67卷 1-10页

作者： Jiuyi Li Xiankang Zhong Tianguan Wang Tan Shang Junying Hu Zhi Zhang Dezhi Zeng Duo Hou Taihe Shi state key Laboratory of oil and gas reservoir geology and exploitation Southwest Petroleum UniversityChengdu 610500China

Stainless steels have shown great potential in the application of offshore oil and gas ***,the internal surface of stainless steel pipeline may simultaneously suffer erosion from the fluid media inside the pipeline and the damage of hydrogen that is generated from the external activities such as cathodic *** synergistic effect of erosion and hydrogen on the properties of passive film on 2205 duplex stainless steel was studied for the first time in a loop system coupled with a hydrogen-charging *** components,protective performance and semiconductive structure as well as properties of the passive film under different conditions were investigated using in-situ electrochemical techniques,surface characterization and computational fluid dynamics *** results show that the combination of erosion and hydrogen could greatly thin the passive film,furthermore,the Fe^(3+)/Fe^(2+)ratio and O_(2)^(-)/OH^(-)ratio in the passive film also decrease dramatically under such a ***,the hydration degree of the passive film greatly increases,resulting in an increase in active sites and a decrease in the stability of the passive *** could destroy the passive film through the impact of sand particles and accelerate the mass transfer process of electrochemical *** hydrogen can not only enhance the charge transfer process,but also make the passive film highly *** the combination of erosion and hydrogen condition,erosion could enhance the hydrogen damage and simultaneously hydrogen could also enhance ***,the synergistic effect of erosion and hydrogen could dramatically change the passive film component,decrease the protective performance,and increase the susceptibility of pitting corrosion of 2205 stainless steel in Cl-containing environment.

关键词： Corrosion Erosion Hydrogen Stainless steel