scholarly journals Numerical Calculation of the Horizontal Stress Difference of Viscous-Elastic Fluid Acting on the Residual Oil in Micro Pore

2014 ◽  
Vol 04 (02) ◽  
pp. 120-124
Author(s):  
Lili Liu ◽  
Shuren Yang ◽  
Lihui Wang ◽  
Di Xu ◽  
Liang Zhao ◽  
...  
Keyword(s):  
Numerical Calculation ◽  
Horizontal Stress ◽  
Stress Difference ◽  
Residual Oil ◽  
Elastic Fluid ◽  
Horizontal Stress Difference

scholarly journals Numerical Analysis of Multiple Factors Affecting Hydraulic Fracturing in Heterogeneous Reservoirs Using a Coupled Hydraulic-Mechanical-Damage Model

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Tao Xu ◽  
Mingyang Zhai ◽  
Bo Huang ◽  
Liaoyuan Zhang ◽  
Aishan Li ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Damage Model ◽  
Mechanical Damage ◽  
Horizontal Stress ◽  
Injection Rate ◽  
Stress Difference ◽  
Multiple Factors ◽  
Multifactor Analysis ◽  
Treatment Design ◽  
Horizontal Stress Difference

Hydraulic fracturing performance, affected by multiple factors, was essential to the economic exploitation of oil and gas in heterogeneous unconventional reservoirs. Multifactor analysis can gain insight into the fracturing response of reservoirs and in turn optimize the treatment design. Based on characterizations of the geological setting of a heterogeneous glutenite reservoir, the hydraulic fracture (HF) initiation and propagation process, as well as the stimulated reservoir volume (SRV), were simulated and analyzed using a coupled hydraulic-mechanical-damage model. The Weibull distribution was employed to describe rock heterogeneity. The numerical model was verified with microseism (MS) interpretation results of HF geometry. A multifactor analysis and optimization workflow integrating response surface methodology, central composite design (CCD), and numerical simulations was proposed to investigate the coupling effects of multiple geomechanical and hydrofracturing factors on SRV and identify the optimum design of fracturing treatment. The results showed that the horizontal stress difference and injection rate were the most significant factors to control the SRV. Increasing the injection rate and reducing fluid viscosity may contribute to improving the SRV. It is more difficult to increase the SRV at higher horizontal stress difference than at lower horizontal stress difference. The multifactor analysis and optimization workflow introduced in this work was a practical and effective method to control the HF geometry and improve the SRV. This study provided a deep understanding of the hydraulic fracturing mechanism and possessed theoretical significance for treatment design.

scholarly journals Numerical Calculation of Viscous-Elastic Fluid Flooding Residual Oil Film in the Complex Pore

2013 ◽  
Vol 03 (03) ◽  
pp. 147-151
Author(s):  
Lili Liu ◽  
Chao Yu ◽  
Lihui Wang ◽  
Lu Liu
Keyword(s):  
Numerical Calculation ◽  
Residual Oil ◽  
Oil Film ◽  
Elastic Fluid

Study on Fracture Initiation Mechanisms of Hydraulic Refracturing Guided by Directional Boreholes

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Tiankui Guo ◽  
Facheng Gong ◽  
Zhanqing Qu ◽  
Xuxin Tian ◽  
Binyan Liu
Keyword(s):  
Sudden Change ◽  
Fracture Initiation ◽  
Horizontal Stress ◽  
Maximum Principal Stress ◽  
In Situ Stress ◽  
Borehole Diameter ◽  
Stress Difference ◽  
Induced Stress ◽  
Horizontal Stress Difference

In order to generate a new fracture far away from the original fracture in refracturing and effectively enhancing productivity, the technology of hydraulic refracturing guided by directional boreholes was presented. The effects of induced stress generated by the original hydraulic fracture, fracturing fluid percolation effect, wellbore internal pressure, and in situ stress on stress field distribution around wellbore were considered to obtain a fracture initiation model of hydraulic refracturing guided by two directional boreholes. The variation of maximum principal stress (σmax) under different conditions was investigated. The researches show that the directional boreholes result in a “sudden change region” of maximum principal stress around wellbore, reflecting dual stresses effects from vertical wellbore and directional boreholes on the rock. The width of sudden change region decreases as the distance from wellbore increases. Due to sudden change region, the refracturing fracture tends to initiate around directional boreholes. Whether the new fracture initiates and propagates along directional boreholes depends on comprehensive effect of borehole azimuth, borehole diameter, borehole spacing, horizontal stress difference, height, and net pressure of original fracture. The specific initiation position can be calculated using the theoretical model proposed in this paper. Affected by induced stress of the original fracturing, the rock tends to be compressed during refracturing, i.e., increased fracturing pressure. Sensitivity analysis with “extended Fourier amplitude sensitivity test (EFAST)” method shows the initiation of new fracture is mainly controlled by directional boreholes parameters and has little relation with in situ stress and parameters of original fracture. The influence rank of each parameter is as follows: borehole diameter > borehole spacing > original fracture net stress > borehole azimuth > horizontal stress difference > original fracture height. During design of refracturing, in order to better play the role of directional boreholes, and create a new fracture far away from original fracture, the optimal design is conducted with measures of optimizing boreholes azimuth, increasing borehole diameter and reducing borehole spacing if conditions permit. The research provides the theoretical basis for hydraulic refracturing guided by directional boreholes, which is helpful for the design of fracturing construction programs.

scholarly journals Roof Stability of Rectangle Coal Roadway: In Light of Calculation of Compressive Bar Stability

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Ma Shou-Long ◽  
Gao Linsheng ◽  
Yang Yue ◽  
Peng Rui ◽  
Zhao Qifeng
Keyword(s):  
Numerical Calculation ◽  
Critical Pressure ◽  
Bending Moment ◽  
Friction Angle ◽  
Horizontal Stress ◽  
Coal Roadway ◽  
Roadway Stability ◽  
Cohesion Force ◽  
Rock Interface ◽  
Roof Stability

The roadway roof is a key factor to the roadway stability. The analysis of roof stability is mainly based on numerical calculation and on-site observation, while the basic theory of the bearing mechanism is relatively weak. We have founded a critical pressure calculation model, on the theory of compressive bar, for the rectangle coal roadway stability. The model has been tested and verified on accuracy and feasibility while applied on a roadway case. The critical pressure for roof stability and roof bending moment and deflection under combined axial and lateral load was deduced using the theory of compressive bar stability. The numerical calculation verified the feasibility of numerical modeling of stability of compressive bar using FLAC3D, and the influence of the background ambient horizontal stress and the parameters of the contact surface to the roof stability were further studied. The result turns out that some factors lead to a higher instability tendency, including higher horizontal stress, higher cohesion force, and larger internal friction angle on the coal-rock interface and lower cohesion force and smaller friction angle on the rock-rock interface. The results contribute to bearing mechanisms of roadway roof stability, ground pressure and strata control theory and application, and design of bolting support.

scholarly journals Mechanical Analysis of Viscous-Elastic Fluid Acting on Residual Oil in the Micro Pore

2013 ◽  
Vol 03 (04) ◽  
pp. 248-251
Author(s):  
Lili Liu ◽  
Chao Yu ◽  
Lihui Wang ◽  
Chengchuyue Fu ◽  
Peixiang Li
Keyword(s):  
Mechanical Analysis ◽  
Residual Oil ◽  
Elastic Fluid

scholarly journals Experimental Study of Hydraulic Fracture Propagation Behavior during Multistage Fracturing in a Directional Well

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yongtao Zhang ◽  
Hao Jin ◽  
Bumin Guo ◽  
Shoumei Qiu ◽  
Peng Yang ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Horizontal Plane ◽  
Fracture Propagation ◽  
Horizontal Wells ◽  
Horizontal Stress ◽  
Deviation Angle ◽  
Multiple Fractures ◽  
Multistage Hydraulic Fracturing ◽  
Initiation Pressure ◽  
Horizontal Stress Difference

Due to the limited space of offshore platform, it is unable to implement large-scale multistage hydraulic fracturing for the horizontal well in Lufeng offshore oilfield. Thus, multistage hydraulic fracturing technology in directional well was researched essentially to solve this problem. Modeling of fracture propagation during multistage fracturing in the directional and horizontal wells in artificial cores was carried out based on a true triaxial hydraulic fracturing simulation experiment system. The effects of horizontal stress difference, stage spacing, perforation depth, and well deviation angle on multifracture propagation were investigated in detail. Through the comparative analysis of the characteristics of postfrac rock and pressure curves, the following conclusions were obtained: (1) multistage fracturing in horizontal wells is conducive to create multiple transverse fractures. Under relatively high horizontal stress difference coefficient (1.0) and small stage spacing conditions, fractures tend to deflect and merge due to the strong stress interference among multiple stages. As a consequence, the initiation pressure for the subsequent stages increases by more than 8%, whereas in large stage spacing conditions, the interference is relatively lower, resulting in the relatively straight fractures. (2) Deepening perforation holes can reduce the initiation pressure and reduce the stress interference among stages. (3) When the projection trace of directional wellbore on horizontal plane is consistent with the direction of the minimum horizontal principal stress, fractures intersecting the wellbore obliquely are easily formed by multistage fracturing. With the decrease of well deviation angle, the angle between fracture surface and wellbore axis decreases, which is not conducive to the uniform distribution of multiple fractures. (4) When there is a certain angle between the projection trace of directional wellbore on horizontal plane and the direction of minimum horizontal principal stress, the growth of multiple fractures is extremely ununiform and the fracture paths are obviously tortuous.

Sign in / Sign up

Export Citation Format

Share Document