Experimental investigation of fluid thermal effects on fracture brittleness

2019 ◽  
Vol 59 (1) ◽  
pp. 457
Author(s):  
Alireza RezaGholilou ◽  
Hossien Salemi ◽  
Nathan Tarom ◽  
Pouria Behnoudfar ◽  
Mohammad Sarmadivaleh
Keyword(s):  
Thermal Effects ◽  
Treatment Approach ◽  
Injection Rate ◽  
Fluid Temperature ◽  
True Triaxial ◽  
In Situ Stresses ◽  
Initiation And Propagation ◽  
True Triaxial Stress ◽  
Rock Mechanical Properties

Fracture extent and formation quality are the key parameters affecting hydraulic fracturing results. Fracture brittleness, initiation and propagation are dominantly ruled by in situ stresses and rock mechanical properties which cannot be manipulated. However, operation parameters such as injection rate, viscosity and temperature of fluid can be adjusted for fracturing treatments. This paper focuses on a thermal treatment approach that affects brittleness. We investigated fractures when fluid temperature is lower than formation. Experiments were conducted using synthetic 50-mm cubic samples in a newly built true triaxial stress cell. This cell was fitted with cooling and heating auxiliary apparatus which enabled injection of fluids of various temperatures in the presence of orthogonal stresses. The samples and test records are evaluated in details to develop and upscale the results for real applications such as tight shale gas formations. Findings indicate that brittleness of material increases when considerable temperature differences exist between rock and injection fluid.

Valuation of hydraulic fracturing potentials of organic-rich shales from the Anambra basin using rock mechanical properties from wireline logs

2021 ◽  
Vol 19 (3) ◽  
pp. 45-44
Author(s):  
Homa Viola Akaha-Tse ◽  
Michael Oti ◽  
Selegha Abrakasa ◽  
Charles Ugwu Ugwueze
Keyword(s):  
Mechanical Properties ◽  
Hydraulic Fracturing ◽  
Horizontal Stress ◽  
Shale Formations ◽  
In Situ Stresses ◽  
Anambra Basin ◽  
Wireline Logs ◽  
Rock Mechanical Properties ◽  
Minimum Horizontal Stress

This study was carried out to determine the rock mechanical properties relevant for hydrocarbon exploration and production by hydraulic  fracturing of organic rich shale formations in Anambra basin. Shale samples and wireline logs were analysed to determine the petrophysical, elastic, strength and in-situ properties necessary for the design of a hydraulic fracturing programme for the exploitation of the shales. The results obtained indicated shale failure in shear and barreling under triaxial test conditions. The average effective porosity of 0.06 and permeability of the order of 10-1 to 101 millidarcies showed the imperative for induced fracturing to assure fluid flow. Average Young’s modulus and Poisson’s ratio of about 2.06 and 0.20 respectively imply that the rocks are favourable for the formation and propagation of fractures during hydraulic fracking. The minimum horizontal stress, which determines the direction of formation and growth of artificially induced hydraulic fractures varies from wellto-well, averaging between 6802.62 to 32790.58 psi. The order of variation of the in-situ stresses is maximum horizontal stress>vertical stress>minimum horizontal stress which implies a reverse fault fracture regime. The study predicts that the sweet spots for the exploration and development of the shale-gas are those sections of the shale formations that exhibit high Young’s modulus, low Poisson’s ratio, and high brittleness. The in-situ stresses required for artificially induced fractures which provide pore space for shale gas accumulation and expulsion are adequate. The shales possess suitable mechanical properties to fracture during hydraulic fracturing. Application of these results will enhance the potentials of the onshore Anambra basin as a reliable component in increasing Nigeria’s gas reserves, for the improvement of the nation’s economy and energy security. Key Words: Hydraulic Fracturing, Organic-rich Shales, Rock Mechanical Properties, Petrophysical Properties, Anambra Basin

Simulation of hydraulic fracturing in tight formations

2010 ◽  
Vol 50 (1) ◽  
pp. 581 ◽  
Author(s):  
Mohammad Sarmadivaleh ◽  
Vamegh Rasouli
Keyword(s):  
Mechanical Properties ◽  
Hydraulic Fracturing ◽  
Analytical Models ◽  
Particle Flow Code ◽  
Gas Formation ◽  
In Situ Stresses ◽  
Initiation And Propagation ◽  
Tight Formations ◽  
Tight Gas Formation

Production from tight formations is becoming a main focus around the world and particularly in Australia. Hydraulic fracturing is one of the commonly used approaches to stimulate production from tight reservoirs. A good understanding of mechanical properties of formation and the in-situ stresses is essential for a hydraulic fracturing study. In this work, using the log based approach, the mechanical properties and in-situ stresses were estimated in a tight gas formation. This data is then used as input for 2D numerical simulation of hydraulic fracturing in particle flow code (PFC). The initiation and propagation of an induced fracture was studied by increasing the rock strength to simulate a tight formation response. Thereafter, the model was divided into two zones to investigate the fracture containment capacity to simulate a fracture intersecting an interbed with formation properties being different on the two sides. The formation bond strength was increased on one side of the interbed and fracture extension was monitored. The results of both simulations showed how, by increasing formation strength equivalent to a tighter formation, the fracture extension ability reduces and the interbed containment capacity increases. The results were compared with some of the analytical models and good agreement was observed.

Stress Response Investigations Related to In-Situ Gasification of Coal

1977 ◽  
Vol 99 (4) ◽  
pp. 627-633 ◽  
Author(s):  
S. H. Advani ◽  
L. Z. Shuck ◽  
K. Y. Lee
Keyword(s):  
Stress Intensity ◽  
Stress Response ◽  
Combustion Front ◽  
Thermal Effects ◽  
Temperature Profiles ◽  
Intensity Factors ◽  
Underground Gasification ◽  
In Situ Stresses ◽  
Front Stability

The influence of in-situ stresses and thermal effects on underground gasification of bituminous coals is studied. Evaluations of temperature profiles, stress magnitudes and stress intensity factors are given. The effects of stresses and temperature on coal fracture permeabilities are discussed. In addition, the influence of stress on combustion front stability in thin seams is discussed.

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