Evaluation of initial rock stress state by hydraulic fracturing test in Korea

Using elastic mechanics and fracture mechanics, analyzing the coal seam hydraulic fracturing breakdown pressure, given its theoretical formula. According to hydraulic fracturing stress status, given the form of two typical hydraulic fracture morphology. Analyzing hydraulic fracturing highly elliptical shape. The displacement field in plane stress state is given, and the theoretical formula of fracturing radius of hydraulic fracturing is deduced. The fracturing technology of underground fracturing is presented, and the fracturing location and fracturing parameters are determined. In Sihe Coal Mine conducted fracturing test, the test results showed that: the average of drainage volume of fracturing hole improved 4.4 times compared with non-pressed-hole. The extraction compliance time is reduced by 38%. Roadway tunneling speed was improved by 15%. It can solve the problem of gas overrun in roadway excavation well, and has a good application and popularization value.

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The Bolmen project: Rock stress measurements using hydraulic fracturing and overcoring techniques

Tunnelling and Underground Space Technology ◽

10.1016/0886-7798(87)90177-5 ◽

1987 ◽

Vol 2 (1) ◽

pp. 100

Keyword(s):

Hydraulic Fracturing ◽

Rock Stress ◽

Stress Measurements

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BP Neural Network with Genetic Algorithm Optimization for Prediction of Geo-Stress State from Wellbore Pressures

International Journal of Computational Intelligence and Applications ◽

10.1142/s1469026816500139 ◽

2016 ◽

Vol 15 (03) ◽

pp. 1650013 ◽

Cited By ~ 4

Author(s):

Shike Zhang ◽

Jincheng Lv ◽

Xinsheng Yuan ◽

Shunde Yin

Keyword(s):

Neural Network ◽

Genetic Algorithm ◽

Tensile Strength ◽

Stress State ◽

Hydraulic Fracturing ◽

Pore Pressure ◽

Poisson's Ratio ◽

Algorithm Optimization ◽

Genetic Algorithm Optimization ◽

Bpnn Model

Although lots of ways can be used to estimate geo-stress state, estimation of geo-stress state without knowing geomechanical parameters such as pore pressure, tensile strength and Poisson’s ratio, etc., still remains one of the most challenging tasks in geotechnical engineering. The main contribution of this paper is to present a back-propagation neural network (BPNN) with genetic algorithm (GA) optimization to predict the geo-stresses based on wellbore pressures of hydraulic fracturing tests during drilling. In the suggested hybrid model, the BPNN is used establish a mapping between the recording pressures and the geo-stress state. Also the GA is used to carry out the optimization of the weights and thresholds of BPNN model for improving accuracy of prediction. Finally, based on the record pressures in hydraulic fracturing (HF) tests, the BPNN model with genetic algorithm optimization successfully predicts the geo-stresses at the corresponding formation in the event that these parameters such as pore pressure, tensile strength and Poisson’s ratio are unavailable. In the meantime, the geo-stress state has been calculated using the theoretical formula by assuming pore pressure and tensile strength of rock mass are known. Then results from theoretical equation, BPNN and BPNN with GA optimization are compared, which shows that the degree accuracy of geo-stresses predicted by using GA-BPNN model is more obviously improvement than the predicted results by the basic BPNN model.

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Calculation and Analysis of Rock Stress State near the Bit

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.594-597.65 ◽

2012 ◽

Vol 594-597 ◽

pp. 65-69

Author(s):

Wei Li ◽

Tie Yan ◽

Si Qi Li ◽

Ling Zhang ◽

Xing Hua Xu

Keyword(s):

Stress State ◽

Pore Pressure ◽

Penetration Rate ◽

Oil Field ◽

Rock Stress ◽

Concentrated Force ◽

Underbalanced Drilling ◽

Permeable Rock ◽

Mechanics Characteristic ◽

Column Pressure

Underbalance drilling has been applied to each oil field at home and abroad, due to the advantage of increasing the penetration rate substantially, protecting the reservoir effectively and reducing the drilling costs. But in respect of rock stress state characteristics near the bottom, relatively speaking, the study was rarely.Take the borehole near the bottom in underbalance drilling as the research object, analyze the influence of terrestrial stress, pore pressure and fluid column pressure on mechanics characteristic of rock in the bottom, to study the rock crushing efficiency, well deviation and hole stability of non-permeable wellbore and permeable wellbore in underbalanced drilling. The result shows that the mechanical properties of rocks near the bottom are subject to terrestrial stress, pore pressure and fluid column pressure. In non-permeable rock, the rock crushing efficiency, the penetration rate and the concentrated force of well trend to increase, the well trends to inclination. In permeable wellbore, with the permeability increasing, the rock crushing efficiency, the penetration rate and the concentrated force of well trend to decrease, the tendency of inclination becomes lower.

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Three Dimensional Stress Measurement by Hydraulic Fracturing forDetermination of Initial Rock Stresses and Stress Variation Induced by Excavation

Journal of the Mining and Metallurgical Institute of Japan ◽

10.2473/shigentosozai1953.103.1188_75 ◽

1987 ◽

Vol 103 (1188) ◽

pp. 75-85

Author(s):

Yoshiaki MIZUTA ◽

Osamu SANO ◽

Shoji OGINO ◽

Masanori OCHIISHI ◽

Harumi KATO

Keyword(s):

Hydraulic Fracturing ◽

Stress Measurement ◽

Three Dimensional ◽

Stress Variation ◽

Initial Rock

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MULTISTAGE HYDRAULIC FRACTURING WITH PRODUCTION INTERVALS—A PROMISING TECHNOLOGY FOR RESERVOIRS SUBJECT TO REVERSE FAULTING STRESS REGIMES

The APPEA Journal ◽

10.1071/aj05006 ◽

2006 ◽

Vol 46 (1) ◽

pp. 89

Author(s):

M.K. Rahman

Keyword(s):

Stress State ◽

Hydraulic Fracturing ◽

Basic Mechanism ◽

Deformation Analysis ◽

Small Scale ◽

Stress Regime ◽

Induced Stress ◽

Stress Changes ◽

Reverse Faulting ◽

Reservoir Conditions

The performance of hydraulic fracturing technology has not been so promising for some Australian tight-gas reservoirs. The existence of reverse faulting stress regimes (i.e. the vertical stress is the minimum one) in these reservoirs is found to be one reason among many others. Previous studies have established that the vertical hydraulic fracture initiated from a vertical well in a reverse faulting stress regime severely turns and twists to become horizontal while fracturing fluid is injected for further propagation of the fracture. This severely turned and twisted fracture impedes the fluid and proppant (engineered sand grains) injection and thus the fracturing job results in a short and constricted fracture. This is considered to be one of the major reasons for premature screen-outs that occur at extremely high-pressure on many occasions in the field, and the subsequent disappointingly low production rates. The aim of this paper is to present the results of an investigation with a model-scale gas reservoir to avoid this problem by carrying out the fracture treatments in a number of stages with production intervals. The basic mechanism that would allow the growth of a long, planar, productive fracture in such a manner is the production-induced stress change around the fracture tip. A simplified propped fracture configuration is modelled in a hypothetical small-scale reservoir with idealistic material properties. Production is simulated in time by varying different parameters and the production-induced stress changes are characterised by coupled fluid flow and deformation analysis. It is found from parametric results that the non-uniform reservoir pressure depletion induces a suitable stress state at the fracture tip for further planar propagation. The duration of production to induce the suitable stress state is found to be dependent on a number of parameters. The paper also highlights the implications and limitations of the concept for hydraulic fracturing in the mentioned reservoir conditions, and discussed further research directions.

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