Research on Stress Sensitivity of Low Permeability Sand Stone Reservoir

2011 ◽  
Vol 317-319 ◽  
pp. 2432-2435
Author(s):  
Yu Xue Sun ◽  
Fei Yao ◽  
Jing Yuan Zhao
Keyword(s):  
Plastic Deformation ◽  
In Situ Stress ◽  
Stress Sensitivity ◽  
Oil Field ◽  
Low Permeability ◽  
High Permeability ◽  
Permeability Changes ◽  
Loading And Unloading ◽  
Sandstone Reservoir

In the process of low-permeability sandstone reservoir exploitation, stress sensitivity takes place with the effective stress rises gradually, which will cause permeability decline. Allowing to the condition of in-situ stress, the study and experiment on the rock core in Jilin oil field Fuxin326 oil layer are presented. The experimental results show that the stress sensitivity of this oil layer is small; the regularity of permeability changes is in accordance with exponential function. The stress sensitivity of high permeability core is larger than that of low permeability core. Moreover, experimental and theoretical analysis shows that low permeability core has a larger permeability loss than high permeability core in loading and unloading process where elastic plastic deformation of rock will happen, which is the major reason that permeability loss can not return completely.

Stress Sensitivity of Low-Permeability Sandstone Reservoir

2013 ◽  
Vol 753-755 ◽  
pp. 686-689 ◽  
Author(s):  
Shi Ji Li ◽  
Ze Hua Wang ◽  
Yu Xue Sun ◽  
Jian Bo Xie
Keyword(s):  
Plastic Deformation ◽  
Theoretical Analysis ◽  
Exponential Function ◽  
Effective Stress ◽  
Stress Sensitivity ◽  
Low Permeability ◽  
High Permeability ◽  
Permeability Changes ◽  
Loading And Unloading ◽  
Sandstone Reservoir

In the time of low-permeability sandstone reservoir explored, effective stress rise gradually, stress sensitivity has happened, which cause permeability decline. Allowing to initial geostress, the study on Jilin oilfield Fuxin326 oil layer and made the rock core experiment are presented. The experimental results show that the stress sensitivity of this oil layer is small the regularity of permeability changes is in accordance with exponential function. The stress sensitivity of high permeability core is larger than low permeability. Moreover, experiments and theoretical analysis shows that low permeability core has a smaller permeability loss than high permeability core in load and unload process. Loading and unloading process leads to elastic plastic deformation of rocks, and it is the major reason which permeability can not return completely.

Experiment on Mechanical Properties and Seepage Capability of Deep Tight Sandstone Under True-Triaxial Stresses Environment

2021 ◽  
Author(s):  
Jiaying Li ◽  
Chunyan Qi ◽  
Ye Gu ◽  
Yu Ye ◽  
Jie Zhao
Keyword(s):  
Mechanical Properties ◽  
In Situ Stress ◽  
Stress Sensitivity ◽  
Stress Conditions ◽  
Tight Sandstone ◽  
Gas Reservoir ◽  
True Triaxial ◽  
Strain Behavior ◽  
Triaxial Stresses

Abstract The characteristics of seepage capability and rock strain during reservoir depletion are important for reservoir recovery, which would significantly influence production strategy optimization. The Cretaceous deep natural gas reservoirs in Keshen Gasfield in Tarim Basin are mainly buried over 5000 m, featuring with ultra-low permeability, developed natural fractures and complex in-situ stress states. However, there is no comprehensive study on the variation of mechanical properties and seepage capability of this gas reservoir under in-situ stress conditions and most studies on stress-sensitivity are conducted under conventional triaxial or uniaxial stress conditions, which cannot truly represent in-situ stress environment. In this work, Cretaceous tight sandstone in Keshen Gasfield was tested under true-triaxial stresses conditions by an advanced geophysical imaging true-triaxial testing system to study the stress-sensitivity and anisotropy of rock stress-strain behavior, porosity and permeability. Four groups of sandstone samples are prepared as the size of 80mm×80mm×80mm, three of which are artificially fractured with different angle (0°,15°，30°) to simulate hydraulic fracturing. The test results corresponding to different samples are compared to further reveal the influence of the fracture angle on rock mechanical properties and seepage capability. The samples are in elastic strain during reservoir depletion, showing an apparent correlation with fracture angles. The porosity decreases linearly with stress loading, where the decrease rate of effective porosity of fracture samples is significantly higher than that of intact samples. The permeabilities decrease exponentially and show significant anisotropy in different principal stress directions, especially in σH direction. The mechanical properties and seepage capability of deep tight sandstone are successfully tested under true-triaxial stresses conditions in this work, which reveals the stress-sensitivity of anisotropic permeability, porosity and stress-strain behavior during gas production. The testing results proposed in this paper provides an innovative method to analyse rock mechanical and petrophysical properties and has profound significance on exploration and development of tight gas reservoir.

Modeling of Wormhole Propagation in Carbonate Rocks by Use of In-Situ-Gelled Acids

SPE Journal ◽  
2017 ◽  
Vol 22 (06) ◽  
pp. 2032-2048 ◽  
Author(s):  
Behzad Hosseinzadeh ◽  
Mohammad Bazargan ◽  
Behzad Rostami ◽  
Shahab Ayatollahi
Keyword(s):  
Shear Rate ◽  
Mechanistic Model ◽  
Injection Rate ◽  
Two Dimensions ◽  
Low Permeability ◽  
Clear Understanding ◽  
High Permeability ◽  
Influential Parameters ◽  
Dual Core

Summary Diversion in heterogeneous carbonate reservoirs plays the most important role to the success of acidizing. Without the use of diversion, more acid preferentially flows into the high-permeability region and leaves the low-permeability region underreacted. But a clear understanding of diverting agents, such as polymer-based in-situ-gelled acids, can help uniformly stimulate the near-wellbore region. In this paper, we correct the rheological model that was developed by Ratnakar et al. (2013) according to experimental data from Gomaa and Nasr-El-Din (2010b) by considering shear-rate effect in a two-scale continuum model. It is found that the rheology parameters and shear rate are influential parameters in diversion. In addition, the amount of acid required for the breakthrough is found to be strongly dependent on rheology parameters and permeability in single-coreflood simulation. In our study, the viscosity of the spent acid is found to be the key parameter for diversion efficiency. We have constructed a mechanistic model similar to that in Panga et al. (2005) that simulates the acid injection in two dimensions. Then, we extended our simulation to dual-core systems with different permeability contrasts. The results show that there exists an intermediate injection rate that develops a wormhole in low-permeability core. This intermediate injection rate increases with increasing the permeability contrast. The results suggest that the dissolution pattern in the high-permeability core is dependent on the permeability contrast. It changes from wormhole to uniform shape when the permeability contrast increases.

Analytic and Numerical Solutions of Load and Stress of Casing and Cement in Cementing Section

2012 ◽  
Vol 268-270 ◽  
pp. 721-724
Author(s):  
Zhan Qu ◽  
Xiao Zeng Wang ◽  
Yi Hua Dou
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Analytical Solutions ◽  
Numerical Solutions ◽  
Element Model ◽  
In Situ Stress ◽  
Oil Field ◽  
Oil Well ◽  
Production Term

With the prolonged production term and the stimulation of the oil well in oil-field, the load which results from the in-situ stress is one of the main reasons to the casing damage. Taking the casing in Cementing section, the cement and the rock surrounding the cement into consideration, a mechanical model is established, while analytical solutions of displacement and stress distribution is obtained. The finite element method is adopted to obtain the numerical solutions of the mechanics model. The result shows that analytical solutions and finite element solutions are approximate. Finite element model of casing/cement/formation which is established in the paper can be used to analyze the load and stress distribution of worn casing with non-uniform in-situ stress.

scholarly journals Study on the Coalbed Methane Development under High In Situ Stress, Large Buried Depth, and Low Permeability Reservoir in the Libi Block, Qinshui Basin, China

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Jinkuang Huang ◽  
Shenggui Liu ◽  
Songlei Tang ◽  
Shixiong Shi ◽  
Chao Wang
Keyword(s):  
Coalbed Methane ◽  
Horizontal Wells ◽  
In Situ Stress ◽  
Low Permeability ◽  
Qinshui Basin ◽  
Hole Pressure ◽  
Bottom Hole ◽  
Single Well ◽  
Coal Reservoir

Coalbed methane (CBM) has been exploited in the deep area of the coal reservoir (>1000 m). The production of CBM vertical wells is low because of the high in situ stress, large buried depth, and low permeability of the coal reservoir. In this paper, efficient and advanced CBM development technology has been applied in the Libi Block of the Qinshui Basin. According to the characteristics of the coal reservoir in the Libi Block, the coiled tubing fracturing technology has been implemented in four cluster horizontal wells. Staged fracturing of horizontal wells can link more natural fracture networks. It could also expand the pressure drop range and control area of the single well. This fracturing technology has achieved good economic results in the Libi Block, with the maximum production of a single horizontal well being 25313 m3/d and the average single well production having increased by more than 60% from 5000 m3/d to 8000 m3/d. Based on the data regarding the bottom hole pressure, water production, and gas production, the production curves of four wells, namely, Z5P-01L, Z5P-02L, Z5P-03L, and Z5P-04L, were investigated. Furthermore, a production system with slow and stable depressurization was obtained. The bottom hole pressure drops too fast, which results in decreasing permeability and productivity. In this work, a special jet pump and an intelligent remote production control system for the CBM wells were developed; hence, a CBM production technology suitable for the Libi Block was established. The maximum release for the CBM well productivity was obtained, thus providing theoretical and technical support for CBM development with geological and engineering challenges.

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