High-sulfur Gas Field Research Articles

Numerical simulation of welding residual stress in Incoloy 825/L360QS bimetal clad tube

With severe corrosion issues afflicting nearly half of all high sulfur gas fields, bimetal composite tubes have emerged as an optimal solution due to their superior corrosion resistance, mechanical properties, and cost-effectiveness. These tubes have gained widespread adoption in gas gathering applications. However, the evaluation of the corrosion performance of Incoloy 825 bimetal composite tubes within high sulfur gas field environments is yet to be adequately addressed. An investigation into the welding performance of both the base metal and weld is instrumental in ascertaining the safety and reliability of bimetal composite pipes. To this end, this paper presents a thermodynamically coupled finite element model of bimetal composite pipes, developed using SYSWELD software, and corroborates the model using the borehole method for empirical verification. The study further delineates the distribution of residual stress encountered during multi-layer and multi-pass welding of bimetal composite pipes.

Development of wellbore compound blockage removal technology to reduce production loss in the ultra-deep and high-sulfur Yuanba gas field

Wellbore compound blockage occurs in several wells of Yuanba gas field during production, which seriously affects the stable production. The prior treatment with inorganic acid injection does not show a good effect. Therefore, it is urgent to establish an effective blockage removal technology. In this work, the composition analysis of compound blockage samples is firstly carried out. Then, two types of acid solution and barite dissolvent for different types of wellbore blockage are developed. Finally, the corresponding crafts of wellbore blockage removal for different degrees of wellbore blockage are set up. Analysis results show that the inorganic components of blockages are mainly FeS2, CaCO3, BaSO4, and SiO2. The organic components of blockages are mainly the decomposition products of macromolecular materials and the asphaltene. There are differences in the components of blockages between different wells in Yuanba gas field. Some wells are the type of organic-based blockage, while others are the type of inorganic-based blockage. The field application shows that the developed wellbore compound blockage removal technology has successfully guided the in situ removal operation of eight wells in Yuanba gas field, ensuring the smooth completion of production task of this gas field. This effective blockage removal technology can be extended to similar ultra-deep and high-sulfur gas field.

Development dynamic monitoring technologies used in the Puguang high-sulfur gas field

There is lack of performance monitoring technologies and related standards and specifications in the Puguang gas field, which is ultra-deep with high sulfur content. In this paper, five key technologies of dynamic monitoring were developed and the related standards and specifications were formulated by investigating high-sulfur gas fields at home and abroad, combined with equipment development, laboratory experiments, theoretical research and field tests. The five key technologies include gas production profile logging, downhole sampling and fluid phase analysis, dynamic water invasion prediction and water producing horizon identification, gas well productivity testing and evaluation, and development monitoring and safety control of high-sulfur ultra-deep wells. Then, these key technologies were applied for verification in the Puguang gas field. And the following research results were obtained. First, the sulfur-resistant gas production profile logging tool has a temperature resistance of 175 °C and pressure resistance of 105 MPa. Forty-three well times gas production profile logging is carried out with a success ratio of 100%. Second, the high-sulfur downhole pressure sampler has a temperature resistance of 150 °C and pressure resistance of 70 MPa. Seven well times downhole pressure sampling is carried out with a success ratio of 100%. Third, elemental sulfur is precipitated in the formation when the formation pressure drops to 29.5 MPa. And no sulfur is deposited in the wellbore when the production rate of gas well is higher than 20 × 104 m3/d. Fourth, water producing horizons can be identified accurately and water breakthrough time of gas wells can be predicted by using water producing horizon identification technology and dynamic water invasion prediction model. Water influx rates can be controlled and water-free gas production period of gas wells can be extended by optimizing and adjusting the working systems of gas wells. And fifth, full coverage of gas well productivity testing is realized by using the testing technology of "downhole implanted gauge & cable delivery & wellhead flow-variable rate", pressure calculation model and well testing interpretation model, and the productivity evaluation results of gas wells are accurate. Sixth, the dynamic gas tight pressure of the cable multi-stage leakage control system of super-high pressure and gas tightness is 50 MPa, and the processing technology for waste gas of blowout hookup is applied to 143 well times testing operation with zero leakage and zero pollution. In conclusion, these performance monitoring technologies have been playing an important role in scientifically formulating the production and reserves increase measures and ensuring long-term stable production of the Puguang gas field.

Characteristics of the Changxing Fm biohermal gas reservoir in the Yuanba Gasfield, Sichuan Basin and development countermeasures

Located in the Sichuan Basin, the Yuanba Gasfield is the deepest high-sulfur carbonate gas field among those discovered in the world. Its biohermal gas reservoir of the Upper Permian Changxing Fm is characterized by ultra depth, multi-stage small and scattered reef, thin reservoir, poor physical properties, strong heterogeneity, complex fluid distribution, and low production of vertical wells. The development of the biohermal gas reservoir is subject to many difficulties. For example, it is necessary to deepen the studies on time–space distribution laws of reef dolomite reservoirs; it is difficult to characterize small reefs precisely and predict thin reservoirs quantitatively; the deployment and optimization design of horizontal wells are influenced by multiple factors; and the difficulty for horizontal wells with long horizontal sections to run through high-quality thin reservoirs is high. In order to develop the Yuanba Gasfield efficiently, therefore, it is necessary to carry out a series of technical researches on the distribution laws and development models of biohermal reservoirs, precise characterization of small reefs, quantitative prediction of thin reservoirs, optimization design of horizontal wells in banded small reef gas reservoirs, and real-time trajectory optimization and adjustment of horizontal wells in ultra-deep thin reservoirs. These research results provide a powerful support for the development and construction of the Yuanba Gasfield. Based on these technologies, China's first ultra-deep high-sulfur large biohermal gas field was built with a mixed gas annual production capacity of 40 × 108 m3. The successful commissioning of the Yuanba Gasfield lays a basis for the leading position of China in the field of high-sulfur gas field development. In addition, it is of great significance to the long-term stable gas supply in 70 cities of six provinces and two municipalities along the “Sichuan-to-East China Gas Transmission Pipeline”, as well as to the industrial structure adjustment in central–western China and the economic development along the Yangtze River.

An Approach and Case Study on Determination of the Sulfur Deposition Radius in High Sulfur Gas Reservoir

In the process of high sulfur gas field development, the sulfur will separate out from the mixed gas when the pressure near wellbore area drops to a critical pressure of H2S. This will reduce the reservoir porosity greatly and decrease the gas well productivity as well. This paper discusses the characteristics of pressure transient testing plots when sulfur deposition occurs based on the redial composite reservoir model. And introduce an approach to determine the sulfur deposition radius near the wellbore with pressure transient testing interpretation in high sulfur gas reservoir. The method has been applied in some high sulfur gas field in eastern Sichuan Basin. The result shows that the method is simple and practical.

Gaseous Mechanics and Effect Evaluation Method of Wellhead Deliverability Equation in Puguang Gas Field

Puguang gas field is the first deeply buried formation and high-sulfur natural gas field on developing. Due to the special composition of natural gas, the deliverability evaluation has a lot of problems. So it is very difficult to conduct a deliverability evaluation with the pressure of well bottom. In this study, an equation of wellhead deliverability is established by testing data. And it is evaluated through the wellhead open flow potential and absolutely open flow potential which is determined by another deliverability equation from well testing data. Results show that there exists a good linear correlation between wellhead open flow potential and absolutely open flow potential in each well of Puguang gas field. In addition, through applying this correlation, absolutely open flow potential can be calculated through wellhead deliverability equation, which provides a new method to study deliverability.

Ecological Restoration Programs for SO<sub>2</sub> Emission from an Operation High-Sulfur Gas Field

A high-sulfur gas field is at trial operation, and its H2S content is up to 14%~18%. If the high-sulfur gas field was operated properly and improperly, effects of SO2 emission on regional ecological environment were analyzed. Based on the investigation of ecological environment status, the sulfur-absorption capacity of regional ecosystem was estimated, and then the ecological restoration programs were put forward, including the vegetation restoration program, the spoil ground restoration program, the ecological landscape reconstruction program and soil protection measures. This may offer experience for development and management of other similar gas fields.

The Design and Realization of the Safety Emergency System for the Longgang High-surfer Gas Field Based on 3DGIS

Based on World Wind Java SDK,the authors have developed the 3DGIS applied in the emergency management of the high-sulfur field.Through temporal-spatial construction analysis and pre-creation clips,difficulties of data-transmission and visualization of numerical simulation model of H2S gas dispersion in 3D environments caused by massive data volume can be solved.Emergency management data and model database are achieved in the visualized 3D environment and the emergency application functions are developed in terms of business process,which include receiving alarm,emergency analysis and emergence disposal on the 3DGIS platform.This research not only attempts to construct the technology of 3DGIS but also offers a tool of 3DGIS to both research and practice for critical incident management in the high-sulfur gas field.

Simulation analysis of environmental risk accident and management of high-sulfur gas field development in complex terrain

Environmental risk of high sulfur gas field exploitation has become one of the hot spots of environmental management studies. Severe gas H2S blowout accidents in recent years have shown that poor understanding and estimates of the poisonous gas movement could lead to dangerous evacuation delays. It is important to evaluate the real concentration of H2S, especially in complex terrain. Traditional experiential models are not valid in the case of rough terrain, especially in low-lying areas where the gas accumulates. This study, using high sulfur content gas field of Sichuan “Pu Guang gas field” as study object and adopting objective diagnosis of wind field of land following coordinate three dimensions, applied Lagrangian Puff Model and breaking up technique of puffs to simulate the H2S diffusion condition of blowout accidents produced in the high sulfur content gas field of complex terrain area. The results showed that the H2S distribution did not occur mainly in low wind direction, and due to the obstruction of the mountain’s body, it accumulated in front of mountain on produced turn over, flowed around submitted jumping type distribution. The mountain waist near the hilltop and low hollow river valley site rapture points simulating contrast showed that the higher the rapture point, the better the diffusing condition of pollutant, the distribution of risk sensitive point decided piping rupture environmental risk size combining the H2S diffusion result and residential area dispersing in the study area, synthetic judge located in the high rapture point environmental risk was smaller than the low hollow point, thus it was suggested to carryout laying of lining build of equal high line of higher terrain. According to simulation results, the environmental risk management measures aimed at putting down adverse effects were worked out.