scholarly journals Introduction to this special section: Geomechanics

2021 ◽  
Vol 40 (11) ◽  
pp. 792-792
Author(s):  
Thomas Finkbeiner ◽  
Arpita P. Bathija
Keyword(s):  
Mechanical Behavior ◽  
Pore Pressure ◽  
Human Activity ◽  
Special Section ◽  
Petroleum Industry ◽  
In Situ Stress ◽  
Cap Rock ◽  
Broad Consensus ◽  
Rock Mechanical Behavior

The term “geomechanics” means different things to different people. We assert that in the petroleum industry the broad consensus for a definition would probably be something like this: Geomechanics is the discipline that investigates rock mechanical behavior in the subsurface (i.e., at the wellbore wall, the overburden, cap rock, and/or the reservoir) under present-day in-situ stress and pore pressure conditions or those changed through human activity/intervention (e.g., production, injection, stimulation) during the life of a well.

scholarly journals Laboratory Investigation on the -Effect of In-Situ Stresses on Hydraulic Fracture Containment

1982 ◽  
Vol 22 (03) ◽  
pp. 333-340 ◽  
Author(s):  
Norman R. Warpinski ◽  
James A. Clark ◽  
Richard A. Schmidt ◽  
Clarence W. Huddle
Keyword(s):  
Pore Pressure ◽  
Hydraulic Fracture ◽  
Laboratory Experiments ◽  
In Situ Stress ◽  
Enhanced Production ◽  
In Situ Stresses ◽  
Extensive Growth ◽  
Stress Variations ◽  
Fracture Growth

Abstract Laboratory experiments have been conducted to determine the effect of in-situ stress variations on hydraulic fracture containment. Fractures were initiated in layered rock samples with prescribed stress variations, and fracture growth characteristics were determined as a function of stress levels. Stress contrasts of 300 to 400 psi (2 to 3 MPa) were found sufficient to restrict fracture growth in laboratory samples of Nevada tuff and Tennessee and Nugget sandstones. The required stress level was found not to depend on mechanical rock properties. However, permeability and the resultant pore pressure effects were important. Tests conducted at biomaterial interfaces between Nugget and Tennessee sandstones show that the resultant stresses set up near the interface because of the applied overburden stress affect the fracture behavior in the same way as the applied confining stresses. These results provide a guideline for determining the in-situ stress contrast necessary to contain a fracture in a field treatment. Introduction An under-standing of the factors that influence and control hydraulic fracture containment is important for the successful use of hydraulic fracturing technology in the enhanced production of natural gas from tight reservoirs. Optimally, this understanding would provide improved fracture design criteria to maximize fracture surface area in contact with the reservoir with respect to volume injected and other treatment parameters. In formations with a positive containment condition (i.e., where fracturing out of zone is not anticipated), long penetrating fractures could be used effectively to develop the resource. For the opposite case, the options would beto use a small treatment so that large volumes are not wasted in out-of-zone fracturing and to accept a lower productivity improvement, orto reject the zone as uneconomical. These decisions cannot be made satisfactorily unless criteria for vertical fracture propagation are developed and techniques for readily measuring the important parameters are available. Currently, both theoretical and experimental efforts are being pursued to determine the important parameters and their relative effects on fracture growth. Two modes of fracture containment are possible. One is the situation where fracture growth is terminated at a discrete interface. Examples of this include laboratory experiments showing fracture termination at weak or unbonded interfaces and theoretical models that predict that fracture growth will terminate at a material property interface. The other mode may occur when the fracture propagates into the bounding layer, but extensive growth does not take place and the fracture thus is restricted. An example is the propagation of the fracture into a region with an adverse stress gradient so that continued propagation results in higher stresses on the fracture, which limits growth, as suggested by Simonson et al. and as seen in mineback experiments. Another example is the possible restriction caused by propagation into a higher modulus region where the decreased width results in increased pressure drop in the fracture, which might inhibit extensive growth into that region relative to the lower modulus region. Other parameters, such as natural fractures, treatment parameters, pore pressure, etc., may affect either of these modes. Laboratory and mineback experiments have shown that weak interfaces and in-situ stress differences are the most likely factors to contain the fracture, and weak interfaces are probably effective only at shallow depths. Thus, our experiments are being performed to determine the effect of in-situ stresses on fracture containment, both in a uniform rock sample and at material properly interfaces. SPEJ P. 333^

scholarly journals In situ stress and pore pressure in the Kumano Forearc Basin, offshore SW Honshu from downhole measurements during riser drilling

2013 ◽  
Vol 14 (5) ◽  
pp. 1454-1470 ◽  
Author(s):  
D. M. Saffer ◽  
P. B. Flemings ◽  
D. Boutt ◽  
M.-L. Doan ◽  
T. Ito ◽  
...  
Keyword(s):  
Pore Pressure ◽  
In Situ Stress ◽  
Forearc Basin ◽  
Downhole Measurements

scholarly journals In Situ Stress and Stress Regime in the Onshore Part of the Northeast Java Basin

2021 ◽  
Vol 44 (2) ◽  
pp. 95-105
Author(s):  
Agus M. Ramdhan
Keyword(s):  
Petroleum Industry ◽  
Horizontal Stress ◽  
In Situ Stress ◽  
Vertical Stress ◽  
Stress Regime ◽  
Severe Erosion ◽  
Tectonically Active ◽  
Minimum Horizontal Stress ◽  
Maximum Horizontal Stress

In situ stress is importance in the petroleum industry because it will significantly enhance our understanding of present-day deformation in a sedimentary basin. The Northeast Java Basin is an example of a tectonically active basin in Indonesia. However, the in situ stress in this basin is still little known. This study attempts to analyze the regional in situ stress (i.e., vertical stress, minimum and maximum horizontal stresses) magnitude and orientation, and stress regime in the onshore part of the Northeast Java Basin based on twelve wells data, consist of density log, direct/indirect pressure test, and leak-off test (LOT) data. The magnitude of vertical (  and minimum horizontal (  stresses were determined using density log and LOT data, respectively. Meanwhile, the orientation of maximum horizontal stress  (  was determined using image log data, while its magnitude was determined based on pore pressure, mudweight, and the vertical and minimum horizontal stresses. The stress regime was simply analyzed based on the magnitude of in situ stress using Anderson’s faulting theory. The results show that the vertical stress ( ) in wells that experienced less erosion can be determined using the following equation: , where  is in psi, and z is in ft. However, wells that experienced severe erosion have vertical stress gradients higher than one psi/ft ( . The minimum horizontal stress ( ) in the hydrostatic zone can be estimated as, while in the overpressured zone, . The maximum horizontal stress ( ) in the shallow and deep hydrostatic zones can be estimated using equations: and , respectively. While in the overpressured zone, . The orientation of  is ~NE-SW, with a strike-slip faulting stress regime.

In-Situ stress in some deep structures and their cap-rock quadrant 25, offshore Norway

1993 ◽  
Author(s):  
G. Caillet ◽  
R. Deboaisne ◽  
B. Mathis ◽  
C. Roux
Keyword(s):  
In Situ Stress ◽  
Cap Rock

Comprehensive Analysis of Borehole Stability with Temperature, Swelling, and Pore Pressure Change for Layered and Orthotropic Formations

2021 ◽  
Author(s):  
Takuma Kaneshima ◽  
Fuqiao Bai ◽  
Nobuo Morita
Keyword(s):  
Pore Pressure ◽  
Numerical Models ◽  
Pressure Change ◽  
In Situ Stress ◽  
Borehole Stability ◽  
Bedding Planes ◽  
Layered Formation ◽  
Side Track ◽  
Failure Theories

Abstract Borehole stability depends on various parameters such as rock strength, rock deformations, in-situ stress, borehole trajectory, shale swelling, pore pressure change due to osmosis, overbalance mud weight and temperature. The objective of this work is to construct analytical and numerical equations to predict borehole failure including all these parameters, and to comprehensively propose a methodology to improve the borehole stability. Analytical solutions are developed for inclined wells with respect to in-situ stress, shale swelling, pore pressure change due to osmosis, overbalance mud weight and temperature. A numerical model is developed for 3D inclined wells with orthotropic formation and layered formation. Using the analytical and the numerical models, stress state around inclined wells are evaluated. The breakout angle is predicted based on Mohr-Coulomb, Mogi, Lade and Drucker-Prager failure theories. Polar diagrams of mud weights are compared to judge the effect of each parameter and the magnitude predicted by the different failure theories. Shale swelling and pore pressure change due to osmosis are the most difficult to estimate among above-mentioned parameters. The laboratory measured swelling of cores obtained from various formations showed that the magnitude to induce breakouts caused by swelling was the largest comparing with other parameters. Therefore, when shale stability problems occur, we need to estimate the magnitude of shale swelling and osmosis due to water potential difference. Then, to overcome the shale stability problem, we evaluated the sensitivity of human controllable parameters on borehole stability. The parameters which can be controlled by drilling engineers are overbalance, type of mud, borehole temperature and borehole trajectory. If the shale swelling is small, the borehole stability is improved by the mud weight. However, from the swelling tests from the cores of Nankai-Trough, we estimated unless we used a swelling inhibitor to reduce the swelling less than 0.1%, the well was not possible to drill through. Actually, the well was abandoned due to instability after trying side track several times. Unlike previous works, this paper uses all important parameters (swelling, temperature, pore pressure, orthotropic formation, layered formation) to estimate the stresses around inclined wells with the same formation conditions for quantitative analysis. Failure analysis include Mohr, Mogi, Lade and Drucker-Prager. Finally, the polar diagrams of critical mud weight are used to judge whether we can choose well trajectory, orientation with respect to bedding planes, mud weight, shale inhibitor, and temperature to stabilize the borehole.

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