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Li W.,China Central Depository & Clearing Co., Ltd. | Zhang J.,China National Petroleum Corporation | Zhang M.,China National Petroleum Corporation | Zhang S.,Southwest Branch of China Petroleum Engineering Co. | Duan Y.,Chongqing University of Science and Technology
Natural Gas Industry | Year: 2015

Oil and gas drilling engineering practices show that high pressure jet assisted rock breaking is an effective way to enhance the deep-well ROP, and the downhole supercharging technology is one way to generate a high pressure jet. Stability and reliability of the downhole supercharging system is the key to the industrial application of this technology. For this reason, research and experiments were carried out concerning the key tools of the downhole supercharging system: (1) The optimized screw supercharger can convert the rotary motion of the positive displacement motor into an axial reciprocating motion to supercharge part of the drilling fluid; (2) A UHP double-channel drill bit was developed to adapt to the screw supercharger based on rock erosion data of high pressure fluid obtained in the laboratory test at different spray distances and jet angles; (3) Clear water was used in the ground test of the system. With the downhole screw supercharger with a high-pressure nozzle of 1.5 mm in diameter, pump pressure of 4 MPa and displacement of 18 L/s, a significant high-pressure pulse jet from the high-pressure nozzle in the ground test was created and it ran steadily. This system has been adopted in the drilling of 5 wells with a total footage of 1015 m and actual drilling time of 206 h, the average rate of penetration increased by 51.4% compared with that in adjacent wells. Field test results show that this downhole supercharging system is good in design and reliable in performance, and can significantly increase ROP. ©, 2015, Natural Gas Industry Journal Agency. All right reserved.

Zhang L.,China National Petroleum Corporation | Su X.,China National Petroleum Corporation | He Y.,Southwest Branch of China Petroleum Engineering Co. | Huang J.,Southwest Branch of China Petroleum Engineering Co. | Zhang W.,Petrochina
Natural Gas Industry | Year: 2013

A complete series of piping class ratings is of great significance to pipeline-associated projects including engineering design, material procurement, pipe installation and operation. First, this paper compares the foreign and domestic piping class ratings and the differences were found out in the aspects of their compiling concept, modes and content. The following shortcomings were concluded for domestic piping class ratings. a. The important role of the piping class ratings has long been ignored by many domestic engineering companies so that their full play could not ever been given to engineering construction and pipeline operation. b. The domestic piping class ratings aim only to engineering design so they do not meet the procurement need. c. Different piping class ratings with distinctive formats and contents can be seen from various departments or different projects even in the same company, which results in the waste of resources. Accordingly, some positive proposals were presented for domestic piping class ratings. a. Their importance and seriousness should be strengthened and their compiling aims should also meet the procurement need. b. Their compiling format and content should be unified and material requirements, valve description, etc. should be completed. c. Their compilation should be done by special tubular goods departments, coordinated and supported by the other disciplines like those of storage and transmission, processing, and so on.

Li P.,Southwest Branch Company of China Petroleum Engineering Co. | Tao Y.,Zhejiang University | Zhou J.,Zhejiang University
Natural Gas Industry | Year: 2013

The stress-based criteria have long been adopted as the major guideline in the design of line pipes, but for those under the displacement control, such as pipelines in seismic regions, landslide areas and subsea environment, the stress-based criteria tend to be relatively conservative, instead the strain-based criteria will be more economic and reasonable to use in the pipe design. Hence, the strain-based design methods in different international standards were summarized and compared, as well as their applicable conditions. In view of the different formulas of the ultimate compressive strain of local buckling in the standards of Norway, Canada, etc., calculations of the ultimate compressive strain were conducted under different radius-thickness ratios and design pressures. It is revealed that the Canadian standard expression and Japanese SUZUKI formula are more conservative. To meet the demand of real engineering application, it was suggested that 0.3 t/D (t refers to the pipe wall thickness; D refers to the external diameter of pipes) be adopted as a conservative estimation of the ultimate compressive strain in the absence of design pressure, and that the Canada standard expression be employed while the design pressure can not be ignored. Because the strain-based design process has not been proposed in the Chinese pipeline codes, the work of this paper can serve as a reference for the research in the relevant areas in present China.

Zhang G.A.,Hubei Key Laboratory Of Materials Chemistry And Service Failure | Zeng Y.,Hubei Key Laboratory Of Materials Chemistry And Service Failure | Guo X.P.,Hubei Key Laboratory Of Materials Chemistry And Service Failure | Jiang F.,Southwest Branch of China Petroleum Engineering Co. | And 2 more authors.
Corrosion Science | Year: 2012

Through the design of experimental setup, the electrochemical corrosion behavior of carbon steel under dynamic high pressure of H 2S/CO 2 environment was studied by in situ electrochemical measurements and weight loss measurements. Computational fluid dynamics (CFD) was also performed to simulate the flow velocity and shear stress on specimen surface. The results show that both the anodic and cathodic processes are activation controlled. The impedance spectra are characterized by double capacitive semicircles. The in situ electrochemical measurements are in accordance with the CFD simulation of flow velocity and shear stress on the specimen surface. © 2012 Elsevier Ltd.

Ren C.,Southwest Petroleum University | Zhu M.,Southwest Petroleum University | Du L.,Southwest Branch of China Petroleum Engineering Co. | Chen J.,Southwest Petroleum University | And 3 more authors.
International Journal of Electrochemical Science | Year: 2014

An investigation on the galvanic corrosion of dissimilar metals in CO2/H2S environments to simulate annulus pressure between casing and tubing string in sour gas well was conducted by methods of electrochemical measurement technique, high-pressure and high-temperature corrosion test and corrosion scale analysis. When C110 steel is coupled with 17-4 stainless steel or 718 nickel-base alloy, the galvanic effect is obviously found due to looser scale. The galvanic corrosion strongly depends on coupled material, environmental temperature, medium phase and annulus protection fluid. To mitigate galvanic corrosion, the two-metal casing joint should be placed in vapor or immersed in annulus protection fluid. © 2015 The Authors.

Zhu Z.,Carnegie Mellon University | Zhao X.,Southwest Branch of China Petroleum Engineering Co.
Natural Gas Industry | Year: 2013

When a pure carbohydrate compound is developed as a novel combustion fuel, its physical properties of each component will be first necessarily predicted and screened. However, the experimental determination of these properties for a huge amount of molecules can be very time-consuming and costly. In view of this, the artificial neural network - quantitative structure-property relationships (ANN-QSPR) algorithm was applied to build the desired models. Molecular descriptors were calculated based on a large number of pure components with evaluated values in DIPPR 801 database and the software package DragonX. The models developed were combinations of QSPR and two-layer feed-forward ANN. Thus the relatively comprehensive and reliable models were developed for predicting physical properties, including normal boiling point, flash point, enthalpy of combustion, enthalpy of vaporization, liquid density, surface tension, liquid viscosity, melting point, etc. For improving the consistency, principal component analysis (PCA) was introduced to further eliminate the dimensions of molecular descriptor values. Finally, the idea of cross-validation for consensus modeling is further utilized to improve the predictive quality of obtained models.

Wu X.,Southwest Petroleum University | Shu H.,Southwest Petroleum University | Zan L.,Southwest Branch of China Petroleum Engineering Co. | Jiang X.,Southwest Branch of China Petroleum Engineering Co. | And 2 more authors.
Natural Gas Industry | Year: 2013

Stress analysis has rarely been conducted of gas pipelines through shield tunnels especially under pressure testing conditions. In general, the testing pressure is higher than the operating pressure so it is quite necessary for the operators to analyze the distribution of pressure on the gas pipeline through shield tunnels under such conditions. In view of this, the integraph CAESAR II software was adopted to build a stress analysis model for a case study of XX silo shield tunnel. On this basis, the stress distribution was clearly shown; the stress key points were determined; the strength of the pipe was checked; and the maximum value of stress was found on the gas pipe elbows. Moreover, the primary stress, the secondary stress, and the self-weight stress were comparatively analyzed to demonstrate that under higher testing pressure, the internal pressure is the main factor inducing the pipe stress while both temperature and the self weight of the pipe have little impact on the pipe stress. In the end, this paper suggests that stress analysis especially under pressure testing conditions should be done in the design of tunnel-through pipelines; in this way, the stress concentration position will be so easily found out that corresponding engineering measures should be taken to ensure safe operation of tunnel-through pipelines.

Wu X.,Southwest Petroleum University | Lu H.,Southwest Petroleum University | Huang K.,Southwest Petroleum University | Tang X.,Southwest Branch of China Petroleum Engineering Co. | And 3 more authors.
Natural Gas Industry | Year: 2014

Crossing through seismic belts, gas pipelines are under the condition of soil rupture resulted from a strong crustal movement, which would easily cause pipe bending deformation. At present, both domestic and abroad oil and gas pipeline stress analysis is limited to static analysis, while dynamic stress analysis has not yet been touched upon. In view of this, based on the principle of seismic spectrum analysis, a pipeline dynamic stress analysis was performed by inputting spectral parameters of the pipelines crossing through the XX seismic zone into the seismic analysis module of CAESAR II. The results indicated whether or not the pipeline displacement and stress under a violent earthquake action would conform to ASME B31.8 specification. The following findings were made. First, the radial, transverse, longitudinal and combined seismic actions has the biggest impact on the lateral displacement of gas pipelines; and the maximum lateral displacement is obviously higher than the maximum radial or transverse displacement. Second, under the seismic action, both the maximum transverse and longitudinal displacement occur on the top of slopes, which should be highly focused on in the design. Third, the displacement and stress caused by the combined seismic actions are higher than those by any single direction seismic action and the combined seismic load has the worst damage to the pipelines. Accordingly, we put forward the following proposals. The ultimate design method should be adopted to strengthen pipelines against earthquakes; the pipe lateral displacement should be highly monitored; and such measures as changing pipeline routes or reducing soil compaction degree should be taken to minimize the earthquake impact, thereby to control the displacement of gas pipelines.

Cen K.,Southwest Petroleum University | Jiang X.,Southwest Petroleum University | Zhu Y.,Southwest Petroleum University | Yang J.,Southwest Branch of China Petroleum Engineering Co. | Zan L.,Southwest Branch of China Petroleum Engineering Co.
Natural Gas Industry | Year: 2014

The current research is insufficient on the transient flow characteristics of the pigging process of high sulfur gas-liquid mixed transmission pipelines, which leads to the inconveniency of determining the pipeline design pressure and the size of a slug catcher. Taking some high sulfur gas-liquid mixed transmission pipelines in service as instances, the variation rule of their running parameters including a pig's running position and velocity, the start-point pressure as well as terminal drainage volume of pipelines during the pigging process were studied by the numerical simulation method. The influences of the gas-phase velocity and gas-liquid ratio on the pigging process of high sulfur gas-liquid mixed transmission pipelines were also discussed by numerical simulation. In addition, an optimal method was put forward to determine the pipeline design pressure and the size of a slug catcher. The results showed that (1) because the over-pressure phenomenon at the starting point of a pipeline is not striking when the gas-phase superficial velocity in the pipeline is 2 - 6 m/s, the gas-phase velocity in the pipeline should be controlled within this scope; (2) the start-point pressure peak and terminal drainage volume of pipelines would increase with the decrease of gas-phase superficial velocity or gas-liquid ratio, while the increasing degree in different pipelines is not consistent, i.e. the longer a pipeline or the bigger the elevation difference between the starting and terminal point of a pipeline, the greater the increasing degree will be; and (3) the pipeline design pressure and the size of a slug catcher should be determined based on the low gas-phase velocity and low gas-liquid ratio which may be encountered at the later stage of pipeline operation. The achieved conclusions and recommendations provide effective guidance for the optimal design and pigging operation of high sulfur gas-liquid mixed transmission pipelines in the future.

Cen K.,Southwest Petroleum University | Jiang X.,Southwest Petroleum University | Yang J.,Southwest Branch of China Petroleum Engineering Co. | Zhu Y.,Southwest Petroleum University
Xinan Shiyou Daxue Xuebao/Journal of Southwest Petroleum University | Year: 2016

The hydrate freeze-plugging phenomenon is easy to occur in pipelines during the open period of natural gas wells especially for wells with high pressure. The dynamic characteristics and optimal hydrate control schemes during well opening period, however, have not been studied systematically. So the specific dynamic models have been established to analyze the dynamic characteristics during well opening period by Dynsim package. The influences of the fluid flowrate, installation modes of pipelines, thickness of thermal insulation layer as well as throttling regulation schemes on throttling temperature and pressure during well opening period have been discussed by using the dynamic models. The dynamic characteristics of heat transfer between fluid in pipelines and ambient environment during well opening period have also been analyzed. In addition, the optimal control schemes for hydrate inhibition during well opening period and optimization design for pipelines have also been put forward in the paper. The results demonstrate that the fluid flowrate during well opening period has dramatical influence on the risk of hydrate formation in pipelines. And no matter how to regulate the fluid flowrate during well opening period, hydrate formation risk in pipelines exists all the time, especially when the flowrate remains small. In order to avoid hydrate formation in pipelines, the fluid flowrate during well opening period should be increased as large as possible by regulating different throttle valves simultaneously or regulating the secondary and tertiary throttle valves mainly. Meanwhile, necessary measures like alcohol injection or heating should be done to mitigate the risk of hydrate formation. Furthermore, it is suggested that the pipelines between wellhead and heating furnace should be buried underground without thermal insulation layer, whereas other overhead pipelines should be covered by thermal insulation layer. © 2016, Science Press. All right reserved.

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