In order to accurately measure off potential in buried pipelines and provide basis for an effective evaluation on their cathodic protection, one domestic gas pipeline was taken as an objective to measure the off potential based on synchronous on and off. In addition, some factors affecting measurement accuracy were analyzed, and several suggestions were made. Results show that (1) setting a typical on-off cycle has a little influence on the measurement accuracy of off potential; (2) at the synchronous on moment of potentiostat, the pipeline potential undergoes greater pulse fluctuation, which can be reduced by using the constant-current operation mode, but the effect is not good; and (3) at the synchronous off moment of potentiostat, the pipeline potential undergoes pulse fluctuation, and the reading time of off potential can influence on its accuracy very little. It's deem that this measurement is just a rapid method to select the typical on-off cycle; in the process of off-potential reading, a pulse voltage occurs at the power-off moment, so the pipeline potential can be monitored in real time by means of data recorder, and then the off potential can be calculated; in order to improve the measurement accuracy, an off-potential test instrument can be developed and tested on site; and in the process of off-potential reading, pipeline depolarization is gentle, so a multimeter can be used for true measurement, whose error is just be acceptable.

In order to effectively control the external corrosion of shale-gas gathering pipelines and ensure their safe operation, it is necessary to keep them under cathodic protection (CP). So, Taking CP unprotective and underprotective status, the different degree of interference produced by CP's anode bed, the failed CP's electric insulation, the unreasonable installation mode of anode bed as objectives, the overall electric insulation in the pipelines was improved, and the locally radial gathering pipelines were protected step by step. In addition, the anode bed in mountainous was arranged in the mode of shallow burial and horizontal installation, and its installation environment was improved as much as possible. At last, a unique system to protect these pipelines was established for smooth transmission. Results show that (1) not only strengthening the construction management and quality acceptance of anti-corrosive pipelines but also ensuring the integrity of external coating are the prerequisite to pipeline CP; (2) CP in each pipeline can realize an independent regulation for CP current to avoid mutual influence among different pipelines; and (3) when an anode bed is installed, its interference shall be considered, its location shall be away from the low-lying wet position of the pipelines in and out of the station as far as possible, and there shall be no other metals or related underground structures between anode bed and protective pipelines. In conclusion, the pipeline CP shall be demonstrated sufficiently during its design and the construction quality shall be strengthened in order to run CP system normally and effectively.

For test-production separators in Weiyuan block, southern Sichuan Basin, the process pipelines frequently suffer corrosion perforation and wall corrosion thinning since 2019. In order to find out the cause, make corresponding countermeasures, and ensure normal shale gas production, some test-production separators were taken as objectives to analyze the corrosion appearance and products, flowback media, environment features, and perforation distribution at the failure location of process pipelines. Results show that (1) sulfate reducing bacteria (SRB) in flowback media at wellbore is the main cause why the pipelines are corroded. Furthermore, non-uniform and irregular surface at the welding joint of pipelines may aggravate adhesive accumulation of SRB. And in the flowback media, the scouring of trace sand may speed up corrosion process locally; and (2) several washout control technologies and countermeasures suitable for the separators in Weiyuan shale gas block are prepared, including modifying the connection mode of pipelines, treating the pipeline inner coating, injecting the bactericidal agent and corrosion inhibitor, and strengthening the equipment maintenance and operation monitoring and detection. Thus, for the process pipelines, the corrosion may be under effective control, the service life is prolonged, and the normal test and production is guaranteed, which is of great significance to the safe and smooth shale gas production in Weiyuan block.

Featured by simple process, small land occupation, and low investment, some technologies of dry desulfurization have been widely applied to purification treatment for distant gas wells with low sulfur content in Sichuan Basin. However, as for traditional dry desulfurization, the management process is tedious, the expense settlement of desulfurization service is complicated, and the desulfurization quality can be hardly controlled. In addition, desulfurizer is replaced mostly by means of artificial taking out and feeding in desulfurization tower, resulting in great safety risk. In order to solve these management difficulties affecting desulfurization efficiency and safety, the “one-stop” mode was innovated. Results show that (1) via this innovation mode, the whole-process closed transportation of desulfurizer may be realized and the rich agent is returned to factory to perform harmless treatment, which may fundamentally avoid field personnel and environment from contacting the desulfurizer, leading to better environment protection effect; (2) field operation efficiency may be improved greatly. The average sulfur capacity utilization may rise from 13% in the traditional mode to 32%, which sets up a new record of dry desulfurization in China; and (3) the new mode may greatly reduce fixed capital and personnel input, and equipment maintenance expense. For example, the settled desulfurization service expense in 016-H1 well decreases from 0.0214 yuan/m3 in the traditional mode to 0.0164 yuan/m3. In general, this mode is of certain popularization value and reference significance to the safe and efficient development of other sour gas reservoirs and the operation of "oil company" mode.

In order to sufficiently understand the key links to remove and recover the abandoned oil and gas pipelines for testing and provide reference for similar removal engineering, this study analyzed the importance of abandoned pipeline removal during pipeline life-cycle by taking some abandoned pipe segment laid beneath southwestern mountains as an objective. Then, several technologies for removing the abandoned pipelines were researched after analyzing domestic and foreign technologies and standards of disposing abandoned and long-distance pipelines. Finally, a few technological requirements of removing abandoned pipelines for testing were determined by systematically studying the technologies requirements of pipeline cutting, the consideration in the process of transportation, and the anti-corrosion measures at the storage site. Results show that (1) before removing the pipe segment for testing, it is necessary to determine the segment type , the serial number of welded joint, and the cutting length; (2) it is recommended to adopt the mechanical cold cutting and strip the corrosion protective covering by means of cold stripping or under heating temperature below 200 ℃; (3) during transportation, the pipe segment shall be classified on the basis of type, length, and anti-corrosion grade; and (4) when the segment is stored on site, it shall not contact water source and soil to satisfy the anti-corrosion requirements. Abandonment is one important stage in the pipeline life, and the recovery and disposal for testing may have direct influence on the accuracy of following test data, so it is necessary to strictly perform quality control in the links of pipeline cutting, transportation, and storage.

In order to fully understand the desulfurization mechanism of triazine solution, accurately make clear the sulfur capacity, optimal reaction temperature, and available H₂S concentration range, and provide beneficial reference for domestic desulfurization technologies used for natural gas with low sulfur throughputs, this study took the triazine solution based on desulfurization test in well sites and stations of natural gas with low sulfur throughputs in Sulige gasfield as an objective to analyze the desulfurization effect via this triazine solution in three new types of fluid desulfurization devices respectively used in lab tests, well sites, and stations. Results show that (1) this desulfurization-based triazine solution has the advantages of high sulfur capacity, fast desulfurization, no regeneration required, nonioxic desulfurization product, and direct injection into strata. Moreover, its application to domestic desulfurization of natural gas with low sulfur throughputs is more promising; (2) some lab device is developed to test the sulfur capacity with eight formulas of triazine solution, and the solution based on desulfurization devices suitable for well sites and stations are developed. And their application effects are better; and (3) as a novel technology, this solution has been successfully applied to some remote Lower Paleozoic gas wells and gas-gathering stations in Sulige gasfield. And with an increase of application scale and an improvement of formula technologies, its cost and the sulfur capacity will individually decrease and increase step by step, so its application will get broader in the future.

In order to sort the maintenance period of surface metering equipments during well testing out and propose many methods to optimize this period, the workload individual managing preventive maintenance, on-condition maintenance, and after-failure maintenance was analyzed in 2017 by means of maintenance statistics for the year on all the surface metering equipments, which were self-owned by CNPC Chuanqing Drilling Engineering Company Limited. Then, a mathematical analysis was carried out based on these statistics. Finally, two methods for calculating reasonable maintenance period during well testing and some concerns in the maintenance were put forward from the viewpoint of cost control. Results show that (1) as for the preventive maintenance which shall comply with the national mandatory standard, it is necessary to adopt one comprehensive method to calculate the instrument's replacement cost, relevant engineering loss, maintenance cost, and idle loss and to further reduce the electronic precision instrument, e.g. sensor; and (2) as for the on-condition maintenance, another method to control cost based on statistical analysis technology shall be employed to gain the cost curve in different maintenance intervals so as to extend the maintenance period and achieve the optimal balance between safety input and cost control.

As an important base of gas production in Sinopec, one surface gathering system with capacity over 50×10⁸ m³/a was built up in Daniudi gasfield, Ordos Basin. In view that in its gathering process, only partial C₃⁺ composition was recovered but ethane was not recovered or treated when treating gas at dehydration and dehydrocarbon stations. So, it's necessary to investigate whether to invest ethane recovery engineering or not to increase production for many products with high added value (e.g. ethane), so as to enhance an overall utilization rate of oil and gas resources and improve economic benefits of field production. Results show that, in Daniudi gasfield, (1) its resource potential in term of ethane production is predicted by analyzing ethane content; (2) by demonstrating an engineering technological scheme of ethane recovery, it's determined to adopt one technology of partial dry-gas circulation for ethane recovery and several main facilities are selected; and (3) after software simulation and calculation based on the calculated engineering investment and operation cost, it's proved that the ethane recovery engineering can greatly increase the economic benefits. In conclusion, the ethane recovery engineering is technologically and economically feasible, but it's essential to discuss and demonstrate some risks existing in sales links in advance.

So far, China is still a lack of study on monoethylene glycol (MEG) recovery devices used to develop deepwater oil and gasfields. In order to sufficiently recognize and accurately understand a role of MEG recovery system playing in deepwater gas exploitation, this study took some glycol recovery devices in eastern South China Sea, representative exploitation technology for deepwater gas in China, as objectives to analyze frequently internal leakage in reboilers and lean MEG coolers, and various phenomenon of serious wax deposit in filters. Results show that (1) one internal leakage within the reboiler of dehydration units is caused by a defect to select equipment type; (2) another internal leakage in the lean MEG cooler is caused by some technological defects; and (3) serious wax deposit is basically caused by no function of wax removal. In conclusion, for this MEG recovery system, its process transformation and innovative optimization can ensure a normal operation, improve stability and reliability, and guarantee safe operation in underwater production. In addition, much experience has been accumulated for future operation and technological research, and may provide a certain practical foundation for equipment & technology manufacturing and study.

In order to systematically verify the accuracy and credibility of in-line inspection data of metal loss defects, the in-line inspection data of metal loss defects in certain natural gas pipelines were analyzed deeply by means of data analysis and a method of excavation verification evaluation, based on multiple parameters comprehensively, such as defect depth, circumferential position, metal loss rate, and failure pressure level. Then, the defects that threaten pipeline operation safety the most were selected for excavation verification. Finally, the on-site defect measurement results were compared with the defect ones described in the in-line inspection report, and the accuracy performance of detector and the effectiveness of in-line inspection data were verified. Results show that (1) the depth information of metal loss defect in in-line inspection data is basically accordant with equipment's performance detection indicator, and the depth percentage is slightly lower than the actual defect depth; (2) there is a gap between the length and width information of metal loss defect and the performance detection indicators, and the inspection accuracy has a certain accidental deviation. It's indicated by conducting excavation verification and systematic comparison or analysis on the in-line inspection data of metal loss defect and mining the in-line inspection data deeply that there is a gap between the in-line inspection data of metal loss defects in gas pipelines and the on-site verification data. And these results are of guiding significance to eliminate defect measurement deviation later and perform whole-pipeline integrity evaluation.

In order to sufficiently analyze an effect of stray current interference on pipeline corrosion and reduce a few potential safety hazards, this study took one domestic natural-gas pipelines as an objective to analyze its in-line inspection data and position distribution data of pipelines and interference sources (e.g. high-voltage line and electrified railway). Then, various causes of pipeline defects were explored, and some prevention and control measures were made. Results show that (1) by virtue of in-line inspection, a lot of pipeline corrosion defects can be discovered in time. And external metal loss defects may be mainly found near the interference sources, such as high-voltage line and electrified railway; (2) even though protection potential may reach cathodic-protection standard, there are still risks of stray current interference; (3) a method to control source is the most effective one, and its adoption can control interference sources during planning; and (4) the effect of stray current interference on gas pipelines can be diminished by taking measures of segmental isolation, current drainage protection, and potential monitoring. In conclusion, pipeline enterprises should strengthen interference source control to avoid forming interference source, periodically carry out in-line inspection and AC/DC interference survey to find out corrosion situation or forming causes in real time, monitor some potential along pipelines and make corresponding measures to control stray current at interfered pipeline section effectively, so as to ensure safe and smooth operation.

So far, a complete set of surface testing technologies for super-high pressure oil and gas wells, which integrates super-high wellhead pressure control, multi-stage choking depressurization and separation, and multiple safety control, has been formed and already applied to Chuanyu oil and gasfield, and Tarim and Qinghai oilfields, which obtained a good effect. So, this study took Shixin 58 well in Qaidam Basin as an example to analyze these technologies. Results show that (1) this well with rich H₂S is featured by high temperature and pressure, and ice blockage and piercement tend to happen in the process of testing; (2) based on the surface testing technologies for super-high pressure oil and gas wells, some testing measures suitable for Shixin 58 well are made. And its choking depressurization during fluid displacement at wellbore, blowout flowing after perforation, production testing, and well testing are successfully performed; and (3) the testing methods consist of a series of advanced technologies, including high pressure control, choking depressurization, sulfur removal, and liquid-gas separation, so they can satisfy the needs of various working conditions during the testing. In addition, it's equipped with advanced safety control technology and optimized technological process resulting in higher operation safety. In conclusion, due to extensive adaptiveness, these surface testing technologies for super-high pressure oil and gas wells are not only applicable to the testing of three super-high gas wells in Sichuan-Chongqing area, but also can satisfy the needs of the testing operation for similar high-H₂S oil and gas wells in subnival regions.

In order to effectively reduce energy consumption in compressor stations along long-distance gas pipelines, this paper took not only single pipeline connected one by one but also compressor stations as examples. Furthermore, according to pipeline theory and dynamic programming methods, two pipeline models were developed on the basis of objective function of minimizing total energy consumption, including one steady-state simulation model and another steady-state operation optimization model. Then, two optimal aims of in-operation compressor quantity at each station and outlet pressure were determined. Finally, a case calculation was conducted on one certain pipeline at the given throughput by means of simulation and optimization. Results show that (1) as for the same throughput and start-up scheme, there is a smaller error between customized simulation result and TGNET one, indicating that this simulation program may meet the requirements of actual engineering in term of simulation precision and verify an accuracy of simulation calculation module. Therefore, it can be used as the basic calculation module to optimize programming run; (2) at the same throughput, to apply an optimized start-up scheme can effectively reduce total workload of all compressors along pipelines. It is verified that the newly established optimization model is of guiding significance to cost-effective pipeline operation; and (3) the newly established steady-state operation optimization model is also applicable to pre-design stage. It combines design and optimization together resulting in an increase of design conformity.

One natural-gas purification plant upgraded its super Claus process to euro Claus process in order to reduce total SO₂ emission of tail gas in super Claus sulfur recovery facilities. During this upgrading, some by-pass operation of super Claus reactors was optimized to decrease both SO₂ emission concentration and rate during shut-down sulfur removal of euro Claus process. Field tests prove that these sulfur-removal optimal measures are feasible, and data comparison before and after this optimization also indicates that the measures can improve sulfur removal effects. Results show that (1) upgrading the super Claus process to euro Claus process is an optimal method for improving super Claus process without tail processing system; (2) after shut-down sulfur removal mode of euro Claus process is modified, SO₂ emission rate can be reduced by 40% when these reactors are operated on line during shut-down sulfur removal of euro Clause process; (3) when on-line operation of reactors is carried out during shut-down sulfur removal of euro Claus process, the temperature and the H₂S content of process gas within reactors are controllable and meet technical requirements of sulfur removal time and effect; and (4) after the sulfur removal method is optimized, sulfur removal time is increased by 15-20 h while the reduction of total SO₂ emission is over 30%, which is of practical significance to environmental protection.

In order to make clear migration characteristics of edge water in Wen 96 gas storage during cyclic injection-production process and their effect on injection and production, the edge water was monitored and dynamically analyzed. Furthermore, a numerical model was established by means of one technology of numerical simulation and anther technology of grid upscaling. Then, this model was adopted to study the edge-water migration in Wen 96 gas storage. And combined with some liquid-level data measured in injection-production wells, the migration laws in the process of cyclic injection and production were figured out gradually. Finally, based on several performance characteristics, both activity degree and influencing range of edge water were evaluated preliminarily. Results show that, (1) in Wen 96 gas reservoirs, their water drive belongs to weak elastic one. Before these reservoirs were rebuilt into a gas storage, S_2X^{1-4 and 8} original gas/water interfaces were relatively consistent whereas S_3S^1-3 interface was more different; (2) according to some analysis on edge-water activity, the injection-production operation principles of "intense injection at high points, slow injection at low points, and rational control of production pressure difference" are adopted. The variation of cyclic liquid/gas ratio shows that, for Wen 96 gas storage, an effect of both gas injection and water displacement is better, and edge-water distribution is more reasonable; and (3) after adopting two technical measures of "intense injection and uniform production" and "pressure difference control" in the late stage of injection, the edge-water migration is under better control, the liquid drainage and storage capacity obtain a remarkable expansion effect, and the dynamic storage capacity approaches to the designed capacity gradually. The conclusion can provide not only further guidance for the injection-production operation and the capacity expansion to reach one production target, but also reference for this operation of other gas storages rebuilt from similar edge-water gas reservoirs.

With the energy restructuring and upgrading and the constant expansion of gas-applied domain, some stricter requirements on the fast construction and safe maintenance of matching gas supply facilities are put forward for gas enterprises. The most pressing challenges facing most enterprises are how to break through one bottleneck in the construction, repair, and maintenance process of gas supply facilities, and how to ensure facility safe and efficient construction and smooth repair and maintenance. So, many problems and defects of buried valve during its service were found out so as to ensure the safe and efficient operation of gas pipelines. In addition, several corresponding improvement measures were made, and their applicability was verified. Results show that (1) the reasons why buried valve cannot be released, replaced, detected, and locked are incomplete function design and unmatched support tools; (to) for these defects from gas pipelines or valve, the functions should be improved by designing the releasing short string and control valve, and manufacturing the sleeve-type support lock for valve locking; (3) by means of perfecting valve functions, not only gas in pipelines can be released, but also the replacement can be conducted, and its result can be detected by injecting inert gas into pipelines through some releasing control valve; and (4) when risk operations are carried out on gas pipelines, it's necessary to adopt sleeve-type lock to isolate and block square-head operation position of valve so as to prevent the outsiders from turning on the valve accidentally, and avoid some accidental personal injury. It's deemed that to adopt these improvement measures may reduce user number influenced by discontinuous gas supply during pipeline maintenance and repair, shorten time affecting users due to discontinuous gas supply, cut down labor cost and gas-releasing loss because of maintenance and repair, and increase both economical and social benefit for gas enterprises.

The technology of automatic welding is an optimally selected welding way for long-distance oil and gas pipelines. For X80M pipeline steel used in the Sino-Russian Eastern Route Gas Pipeline, the welding property, the parent and welding material, and the welding facilities were analyzed. Furthermore, a kind of X80M pipeline steel with 1422 mm of pipe diameter might be served as the welding facility of automatic welding technology. And the break form and welding material were selected. Results show that to choose welding parameters should focus on weld joint shape and internal quality, and it’s necessary to implement a lot of welding experiments on predetermining technical parameters.

In many LNG receiving terminals, screw air compressors often appear abnormal temperature due to various complexities. So, it is necessary to implement a further analysis on temperature parameters. In this paper, the basic structure and exhaust theory of air compressors are illustrated; and then, the factors affecting three abnormalities are analyzed, containing abnormal increase of exhaust temperature, exhaust temperature increase due to hot weather, and exhaust temperature less than interlock value owing to cold weather; in addition, some improvement and maintenance measures are made to solve temperature abnormality.

For most LNG plants, the effect of recirculating cooling water is important in a proper operation. However, as a common water quality trouble, corrosion may severely affect a normal equipment running. After cleaning and prefilming or during cold running, some indexes of both total iron and turbidity of recirculating water often exceed the allowed figures. So, taking the recirculating water system in one LNG plant as an example, we summed up the basic function of system and the situation at the onset of facility running, and analyzed existing problems. After our study, a scheme of cooling running has been developed to adjust the water quality of recirculating water and the effective component of water treatment agent. In addition, the scale and corrosion inhibitors of GX-102 and the antirust agent of GX-301 have also been developed for low-hardness and low-alkalinity recirculating water. For this adjusted recirculating water, the water quality meets the controllable demand and the sewage discharge decreases a lot.

As the main process in most LNG terminals, discharging not only ensures safe receiving and unloading, but also meets the demand of LNG ship’s demurrage time. Taking the Qingdao LNG Terminal as an example, we found out some common problems during discharging, including operation time over planned time, uneven pre-cooling speed for discharging leg, rapid increase of tank pressure, and unstable operation of BOG recondenser. And then, their reasons were analyzed. Finally, some countermeasure were made, including（1）to optimize the condensate discharge,（2）to keep the ship pressure at 0.3 MPa during precooling process, and（3）to accelerate the controllable discharge speed. After adopting these measures, discharge time might be shortened by over 2 hours, and some facilities such as recondenser and storage tank also became more stable and flexible.

For the wastewater pretreatment system of Daniudi gasfield, scaling in wastewater pipelines is a big problem severely affecting a normal operation. So, we first analyzed the component of both water and scale, and pointed out that the scale is dominantly by calcium carbonates. Furthermore, we analyzed the scaling tendency and its influencing factors by means of two methods of saturation index and stability index. Results show that the main reasons why scaling may occur in pretreatment pipelines contain pH value and temperature increase. Finally, through some technical optimization, the temperature and pH value after pretreatment decreased to 5 ℃~10 ℃ and 7, respectively. In result, the scaling might be evidently inhibited and period of acid cleaning postponed from 2 months to 4 months.

The technology of mixed refrigerant cycle to LNG may not only reduce power consumption but also improve exergy efficiency. So, three models of liquefaction process were developed, including mixed refrigerant cycle without pre-cooling, and single-stage and three-stage propane-precooled mixed refrigerants cycle. Under the condition of certain constraints, these models were used to simulate and calculate the unit power consumption, exergy loss, and refrigerant flow of the air compressor. Furthermore, unit power consumption and exergy loss were analyzed. Results show that（1）for the mixed refrigerant cycle without pre-cooling, its unit power consumption and exergy loss are the biggest ones among these of single-stage and three-stage propane-precooled mixed refrigerants cycle 7.28 times and 10.74 times of three-stage one, and 7.23 times and 10.62 times of one-stage one, individually; and（2）single-stage one is superior to three-stage one owing to simpler process and more easy maintenance. In general, the single-stage propane-precooled mixed refrigerant cycle should be optimally selected.

So far, ERP has been widely applied to SCADA system established for natural gas pipelines. In this study, we present values or benefits which ERP brings to oil and gas companies, and explore the process of applying ERP to PetroChina and the business-driven principles. In addition, taking PetroChina Oil & Gas Pipeline Control Center as an example, we analyze the deepening application of ERP to operation maintenance of SCADA system, and make some suggestions on one project implementing now called ERP System Application Integration and Establishment, containing fully considering special system integration program to meet different business demand from various PetroChina units, evaluating the availability of current function module and adjusting the unmatched module before implementing the project, and making an overall plan in advance then to proceed step by step.

For Lower Palaeozoic gas reservoirs in Daniudi gasfield, the corrosion environment is coexistence of both CO₂ and H₂S. And its corrosion mechanism has not been made clear yet. In order to enhance corrosion protection and further carry out an effective development, the corrosion mechanism of acid environment to both P110 and N80 pipes was studied by adopting some approaches including corrosion test one with cyclic flow and HPHT, and SEM. In addition, a chart of corrosion ratio was finished for these pipes based on a lot of experimental data. Results show that with partial-pressure increase of CO₂ and partial-pressure decrease of H₂S, the corrosion rate at first increases and then decreases; the same corrosion rate obtains along with an increase of temperature; and an increase of overall pressure may destroy membrane of corrosion product even falloff , further to expand this rate without interruption. In addition, experimental results show that the property of P110 steel pipe used for Daniudi gasfield is better than that of N80 pipe.

In winter, hydrate easily forms within gas pipelines, especially at the elbow, affecting seriously a normal running. There is a big difference between results from calculation methods and from actual operation. So, many natural-gas companies often use an inhibition of methanol to implement an injection. However, it brings about cost waste. So, this study firstly analyzes the forming conditions of gas hydrate, and then simulates and predicts the forming temperature and location through a software called PIPEPHASE, thirdly determines the difficulties in calculation on injection amount of methanol, such as mass concentration of methanol and total water at the end of pipeline, finally suggests the critical situation of methanol injection and more reasonable injection amount of methanol.

In recent years, there are lot of gas-imported pipelines which have been built, such as the Central Asia-China Gas Pipeline (the A, B, and C phases), and the Myanmar-China Gas Pipeline. Additionally, the Sino-Russian Eastern Route Gas Pipeline is building now. And there are other gas-imported pipelines which are planning to be constructed, including the Central Asia-China Gas Pipeline (the D phase) and the Sino-Russian Western Route Gas Pipeline. Before construction, it’s necessary to carry out a lot of business and technological negotiation. In this paper, some aspects about preliminary technical negotiation for the Sino-Russian Eastern Route Gas Pipeline are presented, including position of entry point, gas delivery pressure and temperature, design and usage factors. Moreover, many gas-quality parameters containing gas heat value, water and hydrocarbon dewpoint, component, and dust impurities are analyzed.

Generally, there are more complex environments around natural-gas pipelines. And long running time may result in gas leakage, even some accidents of fire or explosion. In order to keep a safe and normal running, the government and gas enterprises require that the safety protection distance of natural-gas pipelines should be in accordance with correlative standards. However, it's shown from two cases that even through the distance is in agreement to these standards, the accidents of gas leakage, fire, and explosion may also occur. So, two suggestions are made, including (1) to install PVC pipe just above gas pipelines if no hard surface forms above and around pipelines, (2) to built retaining wall just around one- or two-side of gas pipelines if hard surface forms in order to prevent gas leakage or diffusion from pipelines.

Gas gathering pipelines in western Sichuan gasfield pass through some areas with dense population and active economy, which may result in high cost to detect pipelines and long test period. Taking three gas pipelines from this field as examples, this study carried out a risk assessment by means of a method called Muhlbauer risk analysis. In addition, for this method, the basic principles and its evaluation were illustrated. Through the risk assessment on these pipelines, their running status was presented, risk weight of destructive factors was adjusted, relative risk value was analyzed. Results show they have a certain risk but at an acceptable value. Some suggestions are also made, including, to strengthen management, to perfect protective measures, and to increase relative risk value under cost control, all making pipeline safety increased by 7.1% or so.

Ethylene glycol regeneration and desalination system is one of key units in the development of deepwater gas. For salt in ethylene glycol solution, its crystallization rate may directly influence the desalting efficiency of the system. So, it’s necessary to analyze the crystallization process of sodium chloride. In this study, intermittent dynamic method and a software called 1stOpt were used to study the crystallization laws. And a model of crystallization kinetics of sodium chloride was developed. Results show that (1) the generation of sodium chloride crystal is in accord with a model of size-impendent growth, (2) an increase in temperature, and enlargement of both supersaturation and suspension distribution may enhance the nucleation and growth rate; and (3) the enlargement of nucleation rate is more obvious which affects the crystallization very evidently.

At present, the regional export of global LNG market is different from that in former years. The export volume in the Atlantic and Middle East Regions declines, export volume in the Pacific Region grows at a quick speed and Australia becomes a main growth force. The LNG market demand in Asia slows down and Emerging market maintains the growth rate of global import volume. Global LNG trade flow changes obviously and the export center of Qatar changes to Europe. In Asia, LNG short-term contract has low price and space for premium is narrowed. LNG trade modes become flexible and non-long term trade contract are favored. Under this change trend, based on analysis on Chinese LNG market development, the paper suggests China to grasp the opportunities in the downward stage of LNG market to optimize energy supply structure, rationalize the price in domestic natural gas market and appropriately speed up the reform of natural gas price, have negotiation and reconsideration on signed unreasonable long-term trade contracts at high prices, enhance the cooperation with countries in Northeast Asia and seek for mutual benefit and win-win.

The third-party access system of LNG terminal is of great importance for the fair competition in LNG market. China is trying to introduce the third-party access system to domestic LNG terminal market. To ensure the fair and reasonable formulation of third-party access system of LNG terminal market, experiences of typical countries in Europe can be used for reference. The paper analyzes the distribution rules of primary market and secondary market of LNG terminal in Belgium, describes the long-term and short-term capacity allocation of primary market and the service transfer procedures of secondary market in details and lists certain rules for opening and access, providing some ideas for the formulation of third-party access system of LNG terminal in China.

The profit and loss of natural gas is very critical for LNG terminals to increase economic benefits and ensure an effective and smooth operation. To make clear the natural-gas metering error likely calculated by different technologies may offer corresponding tips on economic and smooth operation. The effect of metering error on the profit and loss is analyzed by the error transfer formula according to a method of profit and loss account. And then, not only some corresponding metering error can be obtained, but also some factors causing error may be gained, which are conducive to a quantitative comparison of overall error. In this study, some actual data from a LNG terminal was analyzed. Results show that there is a little error between pipeline inventory of gas and metered LNG, and the metering error in gas storage tank is dominantly caused by no calculating the quality of gas phase space. In addition, it is deemed that the factors deeply influencing the profit and loss are marketing and unloading areas, and the most important ones are ultrasonic gas flowmeter and gas chromatograph, which need maintenance and inspection to reduce some man-made error as far as possible and to further ensure the profit-loss accuracy.

In recent years, with the wider and wider application of natural gas in urban power generation, heat supply and industrial and commercial sectors, LNG, as the supplement of urban gas, develops at a quick speed. The paper studies the gas supply process and cost accounting of two supply ways of LNG, “direct supply + agent transportation” and tank car transportation, and analyzes the effects of transportation distance and gas supply scale to economical efficiency of gas supply, providing reference to gas consumers and gas suppliers on gas consumption and gas marketing. Study and analysis results show that the reduction of gas transportation cost is beneficial for both gas consumers and gas suppliers and tank car transportation is superior to “direct supply + agent transportation” within a distance of 500 km. Shorter the transportation distance is, more obvious the advantages will be. Through analysis on a specific gas consumption project in Tianjin, it is acknowledged that the profit margin of gas suppliers is squeezed under current price conditions in Tianjin. Relatively speaking, the tank car transportation is of high economical efficiency.

The paper summarizes the classification of Chinese biomass gas projects, calculates the natural gas pricing level of non straw type and straw type biomass gas projects under the condition that the project full investment IRR (internal rate of return) is 10 % and the profit and loss of project are balanced, analyzes the cost and economy of project, analyzes the factors related to the investment of oil and gas enterprises to biomass gas projects at present based on Chinese natural gas development and summarizes the perspectives of oil and gas enterprises on biomass gas development.

On the basis of an analysis on some problems existing in Wen23 TEG dehydration devices, some improving measures are put forward, such as: installing flash drum, adopting efficient plate heat exchanger of glycol rich and lean solution, replacing diaphragm glycol cyclic metering pump with energy conversion pump, adjustable outer circulation of regenerating column top, and optimizing technical parameters. Results show that these measures can enhance their adjustability and operability, and reduce the operating cost and energy consumption as well as TEG loss. Thus, they have popularization value for the design and technical innovation of dehydration devices.

Shale gas produced from reservoirs often contains large amount of acid gas which may corrode pipelines and equipments during gathering and transportation. Thus, it should be purified to remove the acid gas. In this study, HYSYS 8.4 is applied to shale Block 1 for simulated calculation of DEA acid-gas removal technical process; the plate number of absorption and generation towers is fixed; and the acid-gas load in DEA solution and the variation rule of total energy consumption are observed through changing the circulation rate of DEA solution and the DEA mass fraction. Results show that reducing the circulation rate and mass fraction can increase the acid-gas load, and significantly lower the total energy consumption. Moreover, by parameter optimization of acid-gas removal technical process, the operation costs have been reduced with a 5.9% increase in acid-gas load and a 10.6% decrease in total energy consumption.

Integrated some tests of chemical immersion corrosion with a method of surface observation, we studied the effects of Cl and deoxidant concentration on the pitting behavior of 2205 duplex stainless steel in O2-saturated ethylene glycol saline solution. Results show that the maximum pitting depth and average weight loss of the steel may increase with the Cl concentration. When the solution temperature and Cl concentration reach 90℃ and 48276 mg/L, serious pitting appears at the sample surface with the maximum pitting depth of 0.305 mm. Furthermore, the higher the NaCl concentration is, the larger the maximum pitting depth and average weight loss of the 2205 samples are.

So far, gas pipeline systems with more and more large-sized peak-shaving and gas-boosting facilities become more complex. In this study, TGBET software was applied to operational scheduling for gas pipelines in western Sichuan Basin. At first, a model of gas pipelines was established for this area to implement an analogue simulation; and then, one technology of steady-state simulation was used to optimize an operational scheduling plan of booster set; at the same time, another technology of dynamic-state simulation was used to formulate an emergency scheduling. Results show, if working condition varies with time, the dynamic simulation can provide technological evidence for accurately making decision of emergency scheduling whereas the steady-state simulation makes this scheduling more simple and convenient.

Leakage occurring in LNG storage tanks easily brings about plenty of safety accidents. So, a model of leakage accidents is developed by means of the risk assessment software called Safer Trace. In this model, four accidents of leakage, flash fire, vapor cloud explosion, and pool fire are simulated. The scope of affecting thermal radiation and explosive overpressure wave from fire disasters after LNG leakage is analyzed. Furthermore, the ability of affecting accidents under different wind speed is analyzed. Finally, the minimum safe distance between storage tank and surrounding environment is defined.

Some current mathematic models are not suitable for annular gas network. So, we developed a non-tube element mathematic model with junction tee based on mathematic model of non-isothermal steady state, and analyzed the equation closure of non-isothermal steady state model, and finally got many examples and calculated. The obtained results are compared with those obtained from the Pipeline software, showing the maximum relative error of 0.29 % only. Therefore, the junction tee model is applicable and operable.