Effect of Stress-Sensitive Permeability and Porosity on Production Performance in Water-Soluble Gas Reservoirs

2021 ◽  
Vol 143 (11) ◽  
Author(s):  
Xiaoliang Huang ◽  
Zhilin Qi ◽  
Hao Zhang ◽  
Wende Yan ◽  
Chang Yan ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Effective Stress ◽  
Stress Sensitivity ◽  
Water Soluble ◽  
Sensitivity Test ◽  
Formation Water ◽  
Gas Reservoirs ◽  
Water Breakthrough ◽  
Test Result

Abstract Water-soluble gas reservoirs have the characteristics of high temperature and high pressure (HTHP) and experience obvious pressure-sensitive effects during the production process. Therefore, the influences of formation water and dissolved natural gas in formation water on water-soluble gas reservoirs are different from conventional gas reservoirs. In view of this, this work first carried out a stress sensitivity test with irreducible water and variable internal pressure at high temperature for a water-soluble gas reservoir, showing that permeability loss ratio and effective stress have an exponential relationship, a result basically consistent with conventional tests. However, the stress sensitivity test result with irreducible water was greater than the stress sensitivity test result without irreducible water; porosity decreased slightly with increasing confining pressure, and the total decrease ratio was less than 5.2%, with an average of 3.01%. Second, a high-pressure, high-temperature, nuclear magnetic resonance (NMR) online detection system was introduced to detect the pore signal of core samples under different effective stress states, and pore compression and deformation characteristics were evaluated. Results show large pores to have been compressed slightly more than small pores, pores to be significantly compressed in the initial stage, and the greater the increase in effective stress, the more obvious the compression. Third, the occurrence and characteristic changes of irreducible water in the process of rock compression were detected by the NMR online system, indicating irreducible water to be difficult to migrate through compression in water-soluble gas reservoirs under slight compression of rock and pore structure and the occurrence and characteristics of irreducible water to have not changed significantly. Finally, by establishing a theoretical model of water-soluble gas reservoirs to simulate the water breakthrough of gas wells under stress sensitivity conditions, this work shows that when stress sensitivity exists, gas-well water breakthrough time is earlier and production is diminished.

Study on Prediction Model About Water Content in High-Temperature and High-Pressure Water-Soluble Gas Reservoirs

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Xiaoliang Huang ◽  
Zhilin Qi ◽  
Sainan Li ◽  
Qianhua Xiao ◽  
Fei Mo ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
High Pressure ◽  
Water Vapor ◽  
High Temperature ◽  
Natural Gas ◽  
Water Content ◽  
Water Soluble ◽  
Formation Water ◽  
Gas Reservoirs ◽  
Pressure Stage

Abstract Because of a large amount of natural gas dissolved in the formation water of high-temperature and high-pressure (HTHP) water-soluble gas reservoirs, the water vapor content in water-soluble gas reservoirs is generally maintained under a supersaturated state; meanwhile, natural gas has a high carbon dioxide fraction, which significantly affects the water vapor content. Application of the conventional method to calculate the water content of HTHP water-soluble gas reservoirs leads to errors. In this work, the water content of HTHP water-soluble gas reservoirs was studied through laboratory experiments and theoretical research, and the main factors affecting water content were studied. Results show that the water content of water-soluble gas reservoirs decreases as pressure increases. The water content decreases faster in the low-pressure stage, while the decease of water content in the high-pressure stage is relatively steady. The water content of gas reservoirs increases with increasing temperature. When the temperature is lower than 100 °C, the change is slow; when the temperature is higher than 100 °C, the change is fast. The water content of gas reservoirs is affected by temperature during the low-pressure stage. The water content in the high-temperature stage is obviously affected by pressure; the water content of the gas reservoir is also affected by the carbon dioxide content of the natural gas component and the salinity of the formation water. Higher carbon dioxide content and lower formation water salinity yield higher water content. Furthermore, error analysis of the conventional water content prediction method and the measurement shows inconsistency in measurement and calculation. The error between the two methods is large, with an average of 54.88%. Based on the experiment, a mathematical model for calculating the water content of HTHP water-soluble gas reservoirs was established considering pressure, temperature, salinity, and natural gas composition. The predicted water vapor content of natural gas is close to the experimental value with a high precision. The average relative error between the measured and model calculated value is about 8.72%.

scholarly journals Experimental study on stress sensitivity of high‐temperature and high‐pressure sandstone gas reservoirs in Yingqiong Basin

2020 ◽  
Vol 8 (11) ◽  
pp. 4116-4125
Author(s):  
Yi‐Long Li ◽  
Xiao‐Ping Li ◽  
Feng Wu ◽  
Hong‐Lin Lu ◽  
Xiao Lei ◽  
...  
Keyword(s):  
Experimental Study ◽  
High Pressure ◽  
High Temperature ◽  
Stress Sensitivity ◽  
Gas Reservoirs

scholarly journals Gas-water relative permeability measurement of high temperature and high pressure tight gas reservoirs

2015 ◽  
Vol 42 (1) ◽  
pp. 92-96 ◽  
Author(s):  
Jianlong FANG ◽  
Ping GUO ◽  
Xiangjiao XIAO ◽  
Jianfen DU ◽  
Chao DONG ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Relative Permeability ◽  
Tight Gas ◽  
Permeability Measurement ◽  
Gas Reservoirs ◽  
Tight Gas Reservoirs

Design Challenge of Rigid Riser-Spool Piece Against HTHP Induced Expansion in Pipe-in-Pipe Systems

2014 ◽  
Author(s):  
Facheng Wang ◽  
Ming Gao ◽  
Jun Wang ◽  
Yigong Zhang ◽  
Xu Jia ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Energy Demand ◽  
Bohai Sea ◽  
Oil And Gas ◽  
Mainland China ◽  
Structural Complexity ◽  
Calculation Model ◽  
Fluid Temperature ◽  
Gas Reservoirs

Developments of oil and gas reservoirs in Bohai Sea, South China Sea etc., are presently accelerated, to cope with the significant increase in energy demand from the mainland, China. In recent developments in Bohai Sea, fluid temperature and pressure have been found dramatically being increased up to 100 °C and 20 MPa respectively. The fact that High Temperature and High Pressure (HTHP) in Bohai area brings design challenges, especially to jacket risers and spool pieces. Pipe-in-Pipe (PIP) flowline systems have been widely employed in this region and are continuously being considered for further developments. This is due to its significant thermal insulation capacity to deal with the High Temperature and High Pressure (HTHP) issue. To cope with the challenges induced by HPHT and structural complexity of PIP, COTEC Offshore Engineering Solutions, together with its mother company, China Offshore Oil Engineering Company, have developed a approach by using ABAQUS and AutoPIPE. This paper describes the relevant experience obtained during one development in Bohai Sea, BZ34-2/4 project containing dozens of risers and spool pieces. Two main parts are presented. Firstly, a beam-element based expansion calculation model adopting ABAQUS has been developed to achieve accurate HPHT induced expansions. The structural behavior of PIP can be represented in the developed model, meanwhile with minimum increase in modeling complexity. Secondly, practical and extensive parametric studies have been carried on the riser and spool flexibility against HPHT induced expansions. Since Bohai Sea has been developed extensively, many risers are post-installed and the existing of restriction areas practically enlarges the difficulties of anchor clamp and spool arrangements. Key parameters of these arrangements, such as Z/L shape, the length between two bends, the combinations of bend angles, the length of protection pipe on the riser etc. have been comprehensively investigated. “Gold” rules for rigid riser accessories arrangements and spool piece layout have been suggested accordingly.

scholarly journals Evaluation of the Percolation Sensitivity of Loose Sandstone Using Digital Core Technology

2018 ◽  
Vol 11 (1) ◽  
pp. 84-97
Author(s):  
Jin Pang ◽  
Junnan Li ◽  
Jie Liang ◽  
XiaoLu Wang ◽  
Mingqing Kui
Keyword(s):  
Effective Stress ◽  
Three Dimensional ◽  
Reservoir Rock ◽  
Formation Water ◽  
Pore Throat ◽  
Gas Reservoirs ◽  
Gas Reservoir ◽  
The Core ◽  
Core Technology ◽  
Digital Core

Background:The integrity of the extracted core in loose sandstone gas reservoirs is poor, and because hydration and collapse easily occur, it is difficult to evaluate the sensitivity characteristics accurately by the traditional core flooding experiments.Objectives:We instead investigate the stress sensitivity and water sensitivity of the formation water soaking time using digital core technology.Methods:We take the core of a loose sandstone gas reservoir as a research object and begin by scanning the core samples with a CT scanner. A three-dimensional image of the core can be obtained, the digital information extracted, the pore structure of the porous media mapped directly to the network, and a digital core established using the principles of fractal geometry. The three-dimensional pore network model can also be extracted. Next, we can compare and correct the results calculated by the model based on the real core experimental results, and an objective and effective digital core model can be obtained.Results and Conclusion:Finally, we can calculate the different effective stress, pore throat parameters (pore throat radius, shape factor, coordination number, pore-throat ratio) and relative permeability of different formation water injury times. The research results demonstrate that in sandstone gas reservoir development, as the effective stress continuously increases, the rock pore-throat parameters continue to decrease, and the permeability of the reservoir rock ultimately declines by more than 43.2%. Clay minerals will expand after the edge and bottom water intrude into the reservoir and soak it for a long time: the pore throat is significantly narrowed within 30 days, while after 30 days more, the pore throat undergoes any only slight further changes, and the final permeability decline of the reservoir rock is up to 5.7%. The research results provide important basic petrophysical data for the development of loose sandstone gas reservoirs which, in turn, provide a scientific basis for formulating a reasonable gas production rate in a gas reservoir.

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