Effect of matching relation of multi-scale, randomly distributed pores on geometric distribution of induced cracks in hydraulic fracturing

Reservoir rock contains many multi-scale, unevenly distributed pores, and the pore structures of shale in different reservoirs and geological environments vary greatly. Because the seepage velocity and pressure field are related to the pore spatial variations, the inhomogeneity of the seepage is superimposed on the anisotropy of the rock’s physical properties, which will affect the distribution of the induced cracks. A method for calculating the pore size in the bonded particle model, based on Delaunay triangulation, is proposed. A modeling approach capable of simulating the multi-scale pore distribution of actual rock is presented based on the proposed method. To understand how microcracks connect micropores in the process of fracturing, several bonded particle model samples with different pore structures were established, and numerical experiments were conducted based on the coupling calculation of the discrete seepage algorithm and discrete element method. The focus of this study was on the interactions between the distribution characteristics of multi-scale pores, the specific physical properties of the fracturing fluid, and the distribution differences of the induced cracks caused by the special seepage characteristics when using different fracturing fluids. The numerical results showed that the advantages of supercritical CO2 fracturing are maximized in deep reservoirs (high in-situ stress) and that a suitable in-situ stress condition is required (i.e. a stress ratio close to 1).

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Effect of faults and rock physical properties on in situ stress within highly heterogeneous carbonate reservoirs

Journal of Petroleum Science and Engineering ◽

10.1016/j.petrol.2019.106601 ◽

2020 ◽

Vol 185 ◽

pp. 106601

Author(s):

Chuyen Pham ◽

Chandong Chang ◽

Youngho Jang ◽

Abdurahiman Kutty ◽

Jaehoon Jeong

Keyword(s):

Physical Properties ◽

In Situ Stress ◽

Carbonate Reservoirs

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Mechanical Determination of Re-Fracture Well Create New Fracture

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.29-32.1369 ◽

2010 ◽

Vol 29-32 ◽

pp. 1369-1373

Author(s):

Wan Chun Zhao ◽

Ting Ting Wang ◽

Guo Shuai Ju

Keyword(s):

In Situ Stress ◽

Evolution Model ◽

Reservoir Rock ◽

Oil Well ◽

Injection Wells ◽

Induced Stress ◽

Artificial Fracture ◽

Fractured Well ◽

The Impact

The mechanical distribution of refracturing rock around well is Considered, the induced stress of vertical fractured well changes in pore pressure is first to establish, taking into account the fluid compressibility, the introduction of the initial artificial fracture fluid factor, an evolution model of in-situ stress is built up for initial fracture. Consider the impact of temperature on the reservoir rock, an evolution model of the temperature induced stress model is built up, Combined with in-situ stress field, an evolution model of Mechanical determination conditions of re-fracture well create new fracture is built up. Calculation of a block of Jilin Oilfield injection wells by the three effects of stress around an oil well, the theoretical calculation results are consistent with the field.

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The basis for a procedure to specify soil physical properties of a seed bed for wheat

Australian Journal of Agricultural Research ◽

10.1071/ar9790831 ◽

1979 ◽

Vol 30 (5) ◽

pp. 831 ◽

Cited By ~ 13

Author(s):

N Collis-George ◽

JE Lloyd

Keyword(s):

Shear Strength ◽

Physical Properties ◽

Temperature Regime ◽

In Situ Stress ◽

Soil Physical Properties ◽

Soil Conditions ◽

Wide Range ◽

The Mean ◽

Small Increments

The rationale of characterizing seed beds prepared for wheat by describing the environment at a distance from the plant/soil interface by a selected number of measurements on a bulk basis in the horizontal plane at small increments of depth is discussed. A field procedure is described of in situ measurements to specify the soil conditions of biological consequence to germination and emergence. Measurements at small increments of depth are made to determine: (i) moisture status by moisture content and by moisture potential; (ii) aeration status by air-filled porosity; (iii) temperature regime by monitoring the soil temperature profile with depth; (iv) soil strength by the bulk shear strength of the soil under in situ stress conditions. Field results suggest that the described field procedure is suitable for the routine study of soils involving a wide range of moisture contents, of moisture potentials and of structure. The results show that, within the top 15 cm of a prepared seed bed, soil physical properties change markedly with depth. In particular, tenfold increases of bulk shear strength were measured. Results also showed that bulk shear strength could not be predicted from penetrometer readings and that the mean aerial temperature at 1.2 m is not sufficient to define the mean temperature regime of the developing seedling. The field procedure described is recommended for the characterization of seed beds.

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Geomechanical Implications of Reservoir Depletion vis-à-vis Post-Blowout Well Capping: A Gulf of Mexico Case Study

10.2118/205878-ms ◽

2021 ◽

Author(s):

Andreas Michael

Keyword(s):

Gulf Of Mexico ◽

Fracture Initiation ◽

In Situ Stress ◽

Single Step ◽

Reservoir Rock ◽

Tensile Fracture ◽

Well Control ◽

Wellbore Pressure

Abstract Reservoir depletion can impose major implications on wellbore integrity following blowouts. A loss-of-well-control event can lead to prolonged post-blowout discharge from the wellbore causing considerable reservoir depletion in a well's drainage area. Fractures initiated and propagated during well capping procedures following an offshore blowout can lead to reservoir hydrocarbons broaching the seafloor. In this paper, reservoir depletion is examined for a case study on actual deepwater Gulf of Mexico (GoM) parameters, evaluating analytically its impacts on in-situ reservoir conditions, hence assessing the likelihood of longitudinal or transverse fracture initiation during post-blowout well capping. The reservoir rock is modeled as a porous-permeable medium, considering fluid infiltration from the pressurized wellbore. A novel analytical workflow is presented, which encompasses the major effects of reservoir depletion on the (i) in-situ stress state, (ii) range of in-situ stress states stable against shear fault slippage, and (iii) limits of tensile fracture initiation. The geomechanical implications of each individual effect on post-blowout well capping is discussed with the individual results illustrated and analyzed altogether on dimensionless plots. These plots are useful for engineers when making contingency plans for dealing with loss-of-well-control situations. The workflow is demonstrated on a case study on parameters taken from the M56 reservoir, where the April 20, 2010 blowout took place at the MC 252-1 "Macondo" well. A smaller post-blowout discharge flowrate is shown to increase the shut-in wellbore pressure build-up at any given time-point following well capping, whereas an increased post-blowout discharge period leads to a lower shut-in wellbore pressure build-up, hence reducing the likelihood of a fracture initiation scenario and vice versa. Assuming a robust wellbore architecture, the most likely location of fracture initiation is the top of the M56 reservoir within the openhole section of the Macondo well. The critical discharge flowrate, an established indicator for fracture initiation during well capping using information from the post-blowout discharge stage is employed, pointing that fracture initiation is highly-unlikely for the assessed parameters. Nevertheless, fracture initation during post-blowout well capping remains a real possibility in the overpressurized, stacked sequences of the GoM. Finally, the model is extended to an "incremental"/multi-step capping stack shut-in imposed over a longer time-period (e.g. 1 day than abruptly over a single-step) to suppress the wellbore pressure build-up, if necessary to avoid fracture initiation.

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Study on Seepage Simulation of High Pressure Grouting in Microfractured Rock Mass

Geofluids ◽

10.1155/2021/6696882 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Kai Wang ◽

Lianguo Wang ◽

Bo Ren ◽

Hao Fan

Keyword(s):

Soft Rock ◽

In Situ Stress ◽

Surrounding Rock ◽

Grouting Pressure ◽

Fracture Opening ◽

Seepage Characteristics ◽

Support Methods ◽

Soft Rock Roadway ◽

Rock Roadway

In coal mines, under high in situ stress and strong mining activity, roadway surrounding rock commonly contains large amounts of larger fractures and microfractures. Along with the large deformation and continuous rheology of the soft rock roadway, the fractures in the surrounding rock are likely to be compressed and closed, forming undeveloped microfractures, which hinder conventional grouting support methods. Based on the fluid-solid coupling between slurry seepage and microfracture deformation, a theoretical model of microfracture grouting seepage is established. A program for the analysis and calculation of microfracture grouting is developed to quantitatively describe the variation in slurry seepage distance and fracture opening. Numerical experiments are carried out to study the grouting seepage of microfractures under different grouting pressures and fracture opening conditions, and the variation rules for the spatial distribution of fracture opening and slurry seepage distance during grouting pressure are obtained. Fluid-solid coupling has a significant influence on grout seepage characteristics. The grouting pressure and the fracture opening changes are nonlinearly attenuated along the grout seepage direction.

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