Stress-sensitive permeability of matrix cores and artificially fractured cores with non-proppant-filled fractures under high-pressure conditions

Geophysics ◽  
2021 ◽  
pp. 1-102
Author(s):  
Ren-Shi Nie ◽  
Zheng Wang ◽  
Zhangxin Chen ◽  
An-Cheng Wang ◽  
Chang-Hong Zhou ◽  
...  
Keyword(s):  
High Pressure ◽  
Internal Pressure ◽  
Confining Pressure ◽  
Stress Sensitivity ◽  
Curve Analysis ◽  
Test Method ◽  
Gas Reservoirs ◽  
Gas Reservoir ◽  
Permeability Damage ◽  
Fractured Sandstone

Stress-sensitive permeability (SSP) influences gas well productivity and is a crucial element influencing gas reservoir development. SSP for high-pressure fractured gas reservoirs with an initial reservoir pressure of more than 20 MPa has never been comprehensively evaluated to the best of our knowledge. SSP experiments with special procedures were designed by adopting the variable confining pressure (VCP) and variable internal pressure (VIP) methods. VCP is a test method in which confining pressure is altered and a constant internal pressure is maintained for the experimental core holder. VIP is a test method in which internal pressure is changed and a constant confining pressure is maintained. A four-stage curve analysis method was developed to perform regressions on semi-logarithmic curves and exponential curves of experimental data. A method to evaluate the SSP was presented using stress sensitivity coefficients obtained via regressions. A calculation approach for determining the degrees of permeability damage and permeability recovery was also proposed. Six matrix cores and six cores with artificial fractures from a high-pressure fractured sandstone gas reservoir were tested using the two methods. The SSP curves for high-pressure reservoirs were characterized by four-stage variation trends, which differentiated with low-pressure reservoirs with an initial reservoir pressure less than 20 MPa. The stress sensitivity of the VCP method was stronger than that of the VIP method. The core samples mainly showed a “Medium” / “Medium-Strong” stress sensitivity under low/high effective stress conditions. Compared with matrix cores, fractured cores showed stronger stress sensitivity owing to its strong plasticity and weak elasticity. The maximum permeability damage degree reached 99.67% and the minimum permeability recovery was only 6.9%. The presented method of experimental design, four-stage curve analysis, stress sensitivity evaluation and the summarized findings in this paper can provide references for future studies on SSP in high-pressure fractured sandstone gas reservoirs.

Application Analysis and Stress Sensitivity Experiment for a Gas Reservoir in Daqing Oil Field

2013 ◽  
Vol 634-638 ◽  
pp. 3577-3581
Author(s):  
Li Li ◽  
Gao Ning Zhou
Keyword(s):  
Confining Pressure ◽  
Stress Sensitivity ◽  
Oil Field ◽  
Gas Reservoirs ◽  
Gas Reservoir ◽  
Sensitivity Experiment ◽  
Rock Hardness ◽  
Application Analysis ◽  
Daqing Oil Field ◽  
The Impact

By measuring the change of confining pressure penetration on sandstone samples of a gas reservoir in Daqing Oil Field, it has been proven that stress sensitivity existed in this gas reservoirs. The measuring results also show that the stress sensitivity levels of mafic is from weak to medium weak due to the better glutinosity and the greater rock hardness. However, some sandstone samples generally do not have stress sensitivity. The impact of stress sensitivity should be thoroughly considered during the development of natural gas, because the existence of cracks which often result in stronger stress sensitivity.

Stress Sensitivity of Low Permeable and Water-Bearing Gas Reservoir without Gas Slippage Effect

2014 ◽  
Vol 962-965 ◽  
pp. 570-573
Author(s):  
Jian Yan ◽  
Xiao Bing Liang ◽  
Qian Wu ◽  
Qing Guo
Keyword(s):  
Water Saturation ◽  
Stress Sensitivity ◽  
Testing Methods ◽  
Gas Reservoirs ◽  
Gas Reservoir ◽  
Gas Well ◽  
Well Production ◽  
Gas Slippage ◽  
Slippage Effect ◽  
Function Relationship

Because of the gas slippage, the testing methods of stress sensitivity for gas reservoir should be different from that for oil reservoir. This text adopts the method that imposing back pressure on the outlet of testing core to weaken the gas slippage effect and tests the stress sensitivity of low permeability gas reservoirs, then analyzes the influence of permeability and water saturation on stress sensitivity. The results show that: low permeable and water-bearing gas reservoirs have strong stress sensitivity; the testing permeability has the power function relationship with net stress, compared to the exponential function, the fitting correlation coefficient is larger and more suited to the actual; the lower the permeability is and the higher water saturation is, the stronger the stress sensitivity is. The production of gas well is affected when considering the stress sensitivity, so the pressure dropping rate should be reasonable when low permeable gas reservoirs are developed. The results provide theoretical references for analyzing the well production and numerical simulation.

scholarly journals Dynamic Material Balance Method for Estimating Gas in Place of Abnormally High-Pressure Gas Reservoirs

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 1) ◽  
Author(s):  
Lixia Zhang ◽  
Yingxu He ◽  
Chunqiu Guo ◽  
Yang Yu
Keyword(s):  
High Pressure ◽  
Material Balance ◽  
Balance Method ◽  
Production Data ◽  
Reservoir Pressure ◽  
Material Balance Equation ◽  
Gas Reservoirs ◽  
Gas Reservoir ◽  
Material Balance Method ◽  
The Relationship

Abstract Determination of gas in place (GIP) is among the hotspot issues in the field of oil/gas reservoir engineering. The conventional material balance method and other relevant approaches have found widespread application in estimating GIP of a gas reservoir or well-controlled gas reserves, but they are normally not cost-effective. To calculate GIP of abnormally pressured gas reservoirs economically and accurately, this paper deduces an iteration method for GIP estimation from production data, taking into consideration the pore shrinkage of reservoir rock and the volume expansion of irreducible water, and presents a strategy for selecting an initial iteration value of GIP. The approach, termed DMBM-APGR (dynamic material balance method for abnormally pressured gas reservoirs) here, is based on two equations: dynamic material balance equation and static material balance equation for overpressured gas reservoirs. The former delineates the relationship between the quasipressure at bottomhole pressure and the one at average reservoir pressure, and the latter reflects the relationship between average reservoir pressure and cumulative gas production, both of which are rigidly demonstrated in the paper using the basic theory of gas flow through porous media and material balance principle. The method proves effective with several numerical cases under various production schedules and a field case under a variable rate/variable pressure schedule, and the calculation error of GIP does not go beyond 5% provided that the production data are credible. DMBM-APGR goes for gas reservoirs with abnormally high pressure as well as those with normal pressure in virtue of its strict theoretical foundation, which not only considers the compressibilities of rock and bound water, but also reckons with the changes in production rate and variations of gas properties as functions of pressure. The method may serve as a valuable and reliable tool in determining gas reserves.

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.

Effect of Test Mode on Stress Sensitivity Evaluation of Full-Diameter Volcanic Rock

2013 ◽  
Vol 718-720 ◽  
pp. 525-531
Author(s):  
Juan Wang ◽  
Ping Guo ◽  
Cai Zhen Peng ◽  
Fang Wang
Keyword(s):  
Internal Pressure ◽  
Volcanic Rock ◽  
Confining Pressure ◽  
Stress Sensitivity ◽  
The Other ◽  
High Permeability ◽  
Pore Connectivity ◽  
Test Mode ◽  
Sensitivity Evaluation ◽  
Study Results

some reservoir property change which occurs during reservoir development has been studied, however, the study about the effect of test mode on stress sensitivity evaluation of full-diameter volcanic rock is few since the volcanic gas reservoir in Da-qing is buried deeply and the properties and flow mechanics are extremely complex. Therefore, there are two different test modes for stress sensitivity to study the effect of test mode on stress sensitivity evaluation. One of the test modes is to keep the internal pressure constant and change the confining pressure and the other is to change the internal pressure and keep the confining pressure constant. The study results are as follows: (a) the permeabilitys variation law at different test mode is similar when the net stress varies. There are two type, one is sensitive with high permeability since for well development of micro-fracture and pore connectivity, the other is not sensitive with high permeability since for the weak pore connectivity and micro-fracture; (b) the permeability could decrease with times of pressure cycling , so, the times of flow/shut in operation should be decreased as few as possible; (c) the relative variation of permeability in the mode of changing confining pressure is smaller than it in changing internal pressure, which means the stress sensitivity of changing confining pressure is weaker; (d) the results of changing internal pressure should be used since the test mode is more similar with the actual operation. The results are significant for gas-water RPs accurate determination and efficient development of volcanic reservoirs.

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 Stress sensitivity evaluation of ultra-low permeability sandstone reservoir and its influence on oilfield development

2021 ◽  
Vol 292 ◽  
pp. 01027
Author(s):  
Xin Bai ◽  
Chunfen Guo ◽  
Xingli Yang ◽  
Xi Liu
Keyword(s):  
Water Injection ◽  
Confining Pressure ◽  
Stress Sensitivity ◽  
Low Permeability ◽  
Oil Well ◽  
Pressure Stage ◽  
Bottom Hole ◽  
Sensitivity Evaluation ◽  
Permeability Damage ◽  
Sandstone Reservoir

Luohe ultra-low permeability sandstone reservoir is a hot block in Yanchang oilfield, which is a potential point for increasing production and reservoir. In view of the current situation that there is no unified stress sensitivity evaluation standard for ultra-low permeability sandstone in the study area, taking the ultra-low permeability sandstone in Luohe district as the research object, the stress sensitivity evaluation of ultra-low permeability sandstone is carried out by using experimental analysis as the main means. The results show that it is more accurate to evaluate porosity by using pore stress sensitivity coefficient instead of pore compressibility coefficient. With the increase of net overburden pressure, the porosity stress sensitivity decreases gradually; the permeability stress sensitivity is evaluated by variable confining pressure. With the increase of confining pressure, the permeability damage decreases. With the decrease of confining pressure, the permeability damage increases, but it can not recover to the original value, so the permeability damage is irreversible; in the low bottom hole pressure stage, stress sensitivity has a greater impact on oil well productivity, while in the high bottom hole pressure stage, stress sensitivity has a smaller impact on oil well productivity; advanced water injection can reduce the adverse effect of stress sensitivity on the development of ultra-low permeability sandstone and maximize the economic benefits. The research results clarify the method of stress sensitivity evaluation, and provide guidance for efficient water injection in the next step.

The deliverability evaluation of abnormal high pressure gas reservoir with stress sensitivity model

2014 ◽  
Vol 50 (3/4) ◽  
pp. 270
Author(s):  
Hansen Sun ◽  
Yu Yang ◽  
Xiaodong Peng ◽  
Xindong Lv ◽  
Luyi Tong
Keyword(s):  
High Pressure ◽  
Stress Sensitivity ◽  
Gas Reservoir

scholarly journals An Experimental Study on Percolation Characteristics of a Single-Phase Gas in a Low-Permeability Volcanic Reservoir Under High Pressure

2015 ◽  
Vol 8 (1) ◽  
pp. 186-192
Author(s):  
Tang Xiaoyan
Keyword(s):  
High Pressure ◽  
Pore Pressure ◽  
Gas Flow ◽  
Single Phase ◽  
Stress Sensitivity ◽  
Gas Production ◽  
Low Permeability ◽  
Gas Reservoir ◽  
The Core ◽  
Slippage Effect

In this paper, we find that with the decrease in the average pore pressure in the process of gas production, both the slippage effect and the stress sensitivity effect will gradually increase; the increase in the slippage effect is significant, while the increase in the stress sensitivity effect is not. In this paper, the Kalamay volcanic gas reservoir of the Junggar Basin in China was selected as the object of our research. The gas reservoir has typical fractured volcanic reservoirs, and the long-term percolation feature remains unclear. To study the percolation characteristics of singlephase gas under high pressure, the experimental method was designed to simulate these characteristics in the process of gas production by measuring the gas flow in the core and the input and the output pressure at both ends. We carried out simulation experiments of single-phase gas flow percolation characteristics under high pressure using 11 pieces of volcanic rock samples in three wells of the study area. The results show that as the core pore pressure increased, the permeability of low-permeability cores of the volcanic rock decreased significantly at room temperature. However, this decrease became more gradual, which means that the higher the core pore pressure is, the smaller the permeability variation caused by gas slippage is; when the pore pressure is above 10 MPa, the permeability is nearly constant, slippage effect significantly reduces in the process of gas percolation, so it can be completely ignored under these formation conditions. As the pore pressure decreases, the slippage effect and stress sensitivity effect will gradually increase; when the pore pressure is less than 10 MPa, the permeability appears to increase significantly, and this is especially true for a pressure of 5 MPa. The main cause of this result is the slippage effect of gas seepage during the depletion of the gas reservoir, when the pore pressure is lower than a certain value. The valid stress changes of the core are not large, and the stress sensitivity is not strong, so the slippage effect plays a major role, which leads to an increase in the gas permeability during the late period of certain flow gas production.

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