scholarly journals Heterogeneous Transport of Free CH4 and Free CO2 in Dual-Porosity Media Controlled by Anisotropic In Situ Stress during Shale Gas Production by CO2 Flooding: Implications for CO2 Geological Storage and Utilization

ACS Omega ◽  
2021 ◽  
Vol 6 (40) ◽  
pp. 26756-26765
Author(s):  
Lijun Cheng ◽  
Dahua Li ◽  
Wei Wang ◽  
Jun Liu
Keyword(s):  
Shale Gas ◽  
In Situ Stress ◽  
Gas Production ◽  
Dual Porosity ◽  
Co2 Flooding ◽  
Geological Storage ◽  
Co2 Geological Storage

scholarly journals Fracturing curve and its corresponding gas productivity of coalbed methane wells in the Zhengzhuang block, southern Qinshui Basin, North China

2020 ◽  
Vol 38 (5) ◽  
pp. 1387-1408
Author(s):  
Yang Chen ◽  
Dameng Liu ◽  
Yidong Cai ◽  
Jingjie Yao
Keyword(s):  
Hydraulic Fracturing ◽  
Coalbed Methane ◽  
Continuous Production ◽  
Fracture Morphology ◽  
Geological Structure ◽  
In Situ Stress ◽  
Gas Production ◽  
Type Curves ◽  
Stable Type

Hydraulic fracturing has been widely used in low permeability coalbed methane reservoirs to enhance gas production. To better evaluate the hydraulic fracturing curve and its effect on gas productivity, geological and engineering data of 265 development coalbed methane wells and 14 appraisal coalbed methane wells in the Zhengzhuang block were investigated. Based on the regional geologic research and statistical analysis, the microseismic monitoring results, in-situ stress parameters, and gas productivity were synthetically evaluated. The results show that hydraulic fracturing curves can be divided into four types (descending type, stable type, wavy type, and ascending type) according to the fracturing pressure and fracture morphology, and the distributions of different type curves have direct relationship with geological structure. The vertical in-situ stress is greater than the closure stress in the Zhengzhuang block, but there is anomaly in the aggregation areas of the wavy and ascending fracturing curves, which is the main reason for the development of multi-directional propagated fractures. The fracture azimuth is consistent with the regional maximum principle in-situ stress direction (NE–NEE direction). Furthermore, the 265 fracturing curves indicate that the coalbed methane wells owned descending, and stable-type fracturing curves possibly have better fracturing effect considering the propagation pressure gradient (FP) and instantaneous shut-in pressure (PISI). Two fracturing-productivity patterns are summarized according to 61 continuous production wells with different fracturing type and their plane distribution, which indicates that the fracturing effect of different fracturing curve follows the pattern: descending type > stable type > wavy type > ascending type.

scholarly journals Experimental Study of Volumetric Fracturing Properties for Shale under Different Stress States

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Hongjian Wang ◽  
Jin Li ◽  
Fei Zhao ◽  
Jinyu Dong ◽  
Yanzong Cui ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Shale Gas ◽  
Three Dimensional ◽  
In Situ Stress ◽  
Failure Strength ◽  
Constant Loading ◽  
One Dimensional ◽  
Shale Rock ◽  
Volumetric Fracturing

Shale gas can be commercially produced using the stimulated reservoir volume (SRV) with multistage fracturing or multiwell synchronous fracturing. These fracturing technologies can produce additional stress fields that significantly influence the crack initiation pressure and the formation of an effective fracture network. Therefore, this study primarily investigated the evolution of crack initiation and propagation in a hydraulic rock mass under various stress conditions. Combining the in situ stress characteristics of a shale reservoir and fracturing technology, three types of true triaxial volumetric fracturing simulation experiments were designed and performed on shale, including three-dimensional constant loading, one-dimensional pressurization disturbance, and one-dimensional depressurization disturbance. The results indicate that the critical failure strength of the shale rock increases as the three-dimensional constant loads are increased. The rupture surface is always parallel to the maximum principal stress plane in both the simulated vertical and horizontal wells. Under the same in situ stress conditions in the wellbore direction, if the lateral pressure becomes larger, the critical failure strength of shale rock would increase. Additionally, when the lateral in situ stress difference coefficient is smaller, the rock specimen has an evident trend to form more complex cracks. When the shale rock was subjected to lateral disturbance loads, the critical failure strength was approximately 10 MPa less than that in the state of constant loading, indicating that the specimen with disturbance loads is more likely to be fractured. Moreover, shale rock under the depressurization disturbance load is more easily fractured compared with the pressurization disturbance. These findings could provide a theoretical basis and technical support for multistage or multiwell synchronous fracturing in shale gas production.

scholarly journals Casing Collapse Strength Analysis under Nonuniform Loading Using Experimental and Numerical Approach

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Dongfeng Li ◽  
Fu Yu ◽  
Heng Fan ◽  
Rui Wang ◽  
Shangyu Yang ◽  
...  
Keyword(s):  
Shale Gas ◽  
In Situ Stress ◽  
Strength Analysis ◽  
Collapse Strength ◽  
Diameter Variation ◽  
Nonuniform Loading ◽  
Variation Rate ◽  
Casing Deformation ◽  
Casing Collapse

Multistage fracturing is the main means of shale gas development, and casing deformation frequently occurs during fracturing of shale gas horizontal wells. Fracturing fluid entering the formation will change in situ stress nearby the wellbore. The changes of in situ stress are mainly reflected in the following two aspects: one is the increase of in situ stress and the other is the nonuniformity of in situ stress along the wellbore. And it is for this reason that the production casing is more likely to collapse under the nonuniform in situ stress load. According to the service conditions of production casing in shale gas reservoir, this paper studied the casing deformation and the collapsing strength subjected to the nonuniform loading by the experimental and numerical simulation method. The results show that under the condition of nonuniform loading, (1) the diameter variation rate of the casing reduces with the increase in the ratio of sample to tooling length. When the ratio is less than 3, the casing collapse strength will be significantly reduced. And when the ratio is greater than 6, the impact of sample length on casing collapse strength can be ignored. (2) The increase in the applied loading angle will decrease the diameter variation rate. When the loading angle increases from 0° to 90°, the critical load value increases from 1600 kN to 4000 kN. (3) The increase in load unevenness coefficient will rapidly decrease the casing collapse strength. When the load unevenness coefficient n is 0.8, the casing collapse strength reduces to 60%, and when the load unevenness coefficient n is 0, the casing collapse strength reduces to 28%. The findings of this study can help for better understanding of casing damage mechanism in volume fracturing of shale gas horizontal well and guide the selection of multistage fracturing casing type and fracturing interval design.

scholarly journals Review of Well Logs and Petrophysical Approaches for Shale Gas in Sichuan Basin, China

2015 ◽  
Vol 8 (1) ◽  
pp. 316-324 ◽  
Author(s):  
Yuanzhong Zhang ◽  
Sicheng Jin ◽  
Hao Jiang ◽  
Yuwei Wang ◽  
Pengyu Jia
Keyword(s):  
Shale Gas ◽  
Sichuan Basin ◽  
Development Trend ◽  
Development Stage ◽  
In Situ Stress ◽  
Gas Production ◽  
Well Logs ◽  
Petroleum Engineering ◽  
Gas Content ◽  
Horizontal Drilling

China has vast reserves of shale gas. Currently, shale gas is one of the focuses of the unconventional reservoir. Well logs play an import role in shale gas production, and it is the bridge connecting geology, geophysics and petroleum engineering. In the exploration stage, well logs are used to identify lithology, evaluate the parameters of mineral types and compositions, total organic carbon (TOC), porosity, permeability, gas content, and the potential resources quantity. In the development stage, well logs offer various parameters of geological and engineering for horizontal drilling and production, evaluate the mechanical properties and calculate the magnitude and orientation of the in-situ stress for hydraulic fracturing stimulation. We reviewed current well logs for shale gas in China and discussed the development trend in the paper. A case history in Sichuan Basin presented to analyze the logs response characteristics and parameters calculation for a shale gas well. The difficulty and the future attention focus are also discussed.

scholarly journals Experimental Study on Feasibility of Enhanced Gas Recovery through CO2 Flooding in Tight Sandstone Gas Reservoirs

Processes ◽  
2018 ◽  
Vol 6 (11) ◽  
pp. 214 ◽  
Author(s):  
Fengjiao Wang ◽  
Yikun Liu ◽  
Chaoyang Hu ◽  
Yongping Wang ◽  
Anqi Shen ◽  
...  
Keyword(s):  
Injection Rate ◽  
Co2 Flooding ◽  
Geological Storage ◽  
Co2 Geological Storage ◽  
Gas Reservoirs ◽  
Tight Sandstone ◽  
Gas Reservoir ◽  
Enhanced Gas Recovery ◽  
Gas Recovery ◽  
Dip Angle

The development of natural gas in tight sandstone gas reservoirs via CH4-CO2 replacement is promising for its advantages in enhanced gas recovery (EGR) and CO2 geologic sequestration. However, the degree of recovery and the influencing factors of CO2 flooding for enhanced gas recovery as well as the CO2 geological rate are not yet clear. In this study, the tight sandstone gas reservoir characteristics and the fluid properties of the Sulige Gasfield were chosen as the research platform. Tight sandstone gas long-core displacement experiments were performed to investigate (1) the extent to which CO2 injection enhanced gas recovery (CO2-EGR) and (2) the ability to achieve CO2 geological storage. Through modification of the injection rate, the water content of the core, and the formation dip angle, comparative studies were also carried out. The experimental results demonstrated that the gas recovery from CO2 flooding increased by 18.36% when compared to the depletion development method. At a lower injection rate, the diffusion of CO2 was dominant and the main seepage resistance was the viscous force, which resulted in an earlier CO2 breakthrough. The dissolution of CO2 in water postponed the breakthrough of CO2 while it was also favorable for improving the gas recovery and CO2 geological storage. However, the effects of these two factors were insignificant. A greater influence was observed from the presence of a dip angle in tight sandstone gas reservoirs. The effect of CO2 gravity separation and its higher viscosity were more conducive to stable displacement. Therefore, an additional gas recovery of 5% to 8% was obtained. Furthermore, the CO2 geological storage exceeded 60%. As a consequence, CO2-EGR was found to be feasible for a tight sandstone gas reservoir while also achieving the purpose of effective CO2 geological storage especially for a reservoir with a dip angle.

scholarly journals Geomechanical Analysis for Deep Shale Gas Exploration Wells in the NDNR Blocks, Sichuan Basin, Southwest China

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1117 ◽  
Author(s):  
Majia Zheng ◽  
Hongming Tang ◽  
Hu Li ◽  
Jian Zheng ◽  
Cui Jing
Keyword(s):  
Pore Pressure ◽  
Shale Gas ◽  
Sichuan Basin ◽  
In Situ Stress ◽  
Wellbore Stability ◽  
Geomechanical Model ◽  
Stress Regime ◽  
Xujiahe Formation ◽  
Geomechanical Analysis

The abundant reserve of shale gas in Sichuan Basin has become a significant natural gas component in China. To achieve efficient development of shale gas, it is necessary to analyze the stress state, pore pressure, and reservoir mechanical properties such that an accurate geomechanical model can be established. In this paper, Six wells of Neijiang-Dazu and North Rongchang (NDNR) Block were thoroughly investigated to establish the geomechanical model for the study area. The well log analysis was performed to derive the in-situ stresses and pore pressure while the stress polygon was applied to constrain the value of the maximum horizontal principal stress. Image and caliper data, mini-frac test and laboratory rock mechanics test results were used to calibrate the geomechanical model. The model was further validated by comparing the model prediction against the actual wellbore failure observed in the field. It was found that it is associated with the strike-slip (SS) stress regime; the orientation of SHmax was inferred to be 106–130° N. The pore pressure appears to be approximately hydrostatic from the surface to 1000 m true vertical depth (TVD), but then becomes over-pressured from the Xujiahe formation. The geomechanical model can provide guidance for the subsequent drilling and completion in this area and be used to effectively avoid complex drilling events such as collapse, kick, and lost circulation (mud losses) along the entire well. Also, the in-situ stress and pore pressure database can be used to analyze wellbore stability issues as well as help design hydraulic fracturing operations.

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