GEOPHYSICAL RESEARCH, 2017, vol. 18, no. 2, pp. 5-26. DOI: 10.21455/gr2017.2-1
UDC 539.219.2
Abstract References Full text (in Russian)
IN-SITU HORIZONTAL STRESS ESTIMATION BASED ON THE GEOMETRICAL PROPERTIES OF FRACTURES IN WELL VICINITY
N.V. Dubinya(1), K.A. Ezhov(2)
(1) Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
(2) Naftna Industrija Srbije Science and Technology Center, Novi Sad, Serbia
Abstract. A great amount of information regarding the in-situ stresses acting in the upper layers of the Earth’s crust is provided by the geophysical well surveys. Presently, the methods for determination of the mechanical properties of rocks surrounding the wells and estimation of in-situ stress state are well developed. Nevertheless numerical evaluation of maximum horizontal stresses causes significant problems. The study is devoted to the problem of decreasing the uncertainty appearing in the inverse problem of horizontal stresses reconstruction. The additional data on the inner structure of surrounding rocks obtained with borehole microimagers are used for solving the problem.
The microimagers provide information on the structural heterogeneities in rocks and to distinguish natural and drilling-induced fractures. The approach described in the study makes it possible to group the fractures according to their filtration properties. The model connecting the geometry of fractures, their spatial orientations, and in-situ horizontal stresses is proposed, conceptualized, and formalized in the paper. As a result, a novel approach to microimager data interpretation for horizontal stress estimation is developed.
The approach was verified using synthetic data. The uncertainty analysis revealed that the approach proves its usefulness as the uncertainty in horizontal stress estimation decreases drastically.
The study carried out makes it possible to introduce the new parameter into solution of the stress estimation problem. This parameter characterizes the features of fracture orientations and is connected with the in-situ stresses. Its application leads to a significant increase in accuracy of estimation of maximum horizontal stresses.
Keywords: geomechanics, in-situ stress, well logging.
References
Afanasyev I.S., Nikitin A.N., Latypov I.D., Haidar A.M., and Borisov G.A. Hydrofracturing crack geometry prediction, Oil Industry, 2009, no. 11, pp. 62-66.
Barton C.A., Zoback M.D., and Moos D. Fluid flow along potentially active faults in crystalline rocks, Geology, 1995, vol. 23, no. 8, pp. 683-686.
Gantmacher F.R. Teoriya matrits (The theory of matrices), Moscow: Nauka, 1967.
Ito T., Nayuki T., Kato K., Funato A., Satoh T., Kitagawa Y., and Kato H. Development of the deep rock stress tester, 7th International Symposium on In-Situ Rock Stress Proceedings. 2016, pp. 376-384.
Prats M. Effect of burial history on the subsurface horizontal stresses of formations having different material properties, SPE 9017-PA, 1981, vol. 21.
Silva I., Domingos F., Marinho P., Laronga R., and Khan S. Advanced borehole image applications in turbidite reservoirs drilled with oil based mud. A Case Study From Deep Offshore Angola, 2003-AA SPWLA Conference Paper, 2003.
Townend J. and Zoback M.D. How faulting keeps the crust strong, Geology, 2000, vol. 28, no. 5, pp. 399-402.
Zoback M.D., Barton C.A., Brudy M., Castillo D.A., Finkeiner T., Grollimund B.R., Moos D.B., Peska P., Ward C.D., and Wiprut D.J. Determination of stress orientation and magnitude in deep wells, International Journal of Rock Mechanics and Mining Sciences, 2003, vol. 40, pp. 1049-1076.
Zoback M.D. Reservoir geomechanics, Cambridge University Press, 2007.