Assessment of causes of overpressure different from sub-compaction: Application in unconventional reservoir
The necessity for hydrocarbon-producing countries to increase their reserves has led to companies exploring the deposits available in source rocks that might be over-pressured and thus, strict rules are required for their development. Overpressure, which may result in wellbore stability problems, could result from several causes such as mechanical effects, dynamic transfer, chemical stress, thermal stress, among others, in which undercompaction is frequently the main cause, generated when the sediment deposition velocity exceeds the fluid ejection rate.
The expansion of fluids generated by thermal stresses and the reduction of porosity caused by chemical stresses may be among the other causes of overpressure in shales.
The new methodology presented in this paper makes it possible to determine the pressure due to thermal stresses caused by the cracking of kerogen and oil in shales. In addition, petrophysical and geochemical models are considered in order to precisely ascertain the increase in pore pressure due to temperature and
fluid expansion. An increase of 20% in pressure is seen when compared with undercompaction. As a result of this methodology, the mud window was optimized and the hydrocarbons, generated under subsurface the conditions (pressure, temperature) analyzed, were quantified.
Hottmann C. y Johnson, R. Estimation of Formation Pressures from Log-Derived Shale Properties, Journal of Petroleum Technology. 1965
Eaton B.,1975, The Equation for Geopressure Prediction from Well Logs, AIM
Zhang, J. Pore pressureprediction from well logs: Methods, modifications,and new approaches. Earth-science Reviews, 108(1-2), 50 – 63 (2011)
Bowers G.L. Pore Pressure Estimation From Velocity Data: Accounting for Overpressure Mechanisms Besides Undercompaction, SPE Drilling & Completion. 1995.
K. Terzaghi. Die Berechnung der Duerchl¨assigkeitsziffer des Tones im Verlauf der hydrodynamischen Spannungserscheinungen. Szber Akademie Wissenschaft Vienna, Math–naturwissenschaft Klasse IIa, (132):125–138, 1923.
D. Grauls Overpressures: Causal Mechanisms, Conventional y Hydromechanical Approaches Oil & Gas Science y Technology – Rev. IFP, Vol. 54 (1999), No. 6, pp. 667-678
X. Luo y G. Vasseur. Contributions of compaction y aquathermal pressuring to geopressure y the influence of environmental conditions. AAPG Bulletin, 76(10):1550–1559, 1992.
Tissot,B ., Espitalie, .: L'evolution thermique de la matiere organique des sediments: application d’une simulation mathematique Rev. Inst Fr. Petr.30, 743 777( 1975)
Tissot, B., y D. H. Welte, 1984, Petroleum formation y occurrence (2d ed.): Berlin, Springer-Verlag, 699 p.
T. Hantschel, A.I. Kauerauf, Fundamentals of Basin y Petroleum 31 Systems Modeling, DOI 10.1007/978-3-540-72318-9 2,© Springer-Verlag Berlin Heidelberg 2009
M. J. Osborne y R. E. Swarbrick. Mechanisms for generating overpressure in sedimentary basins: A re–evaluation. AAPG Bulletin, 81:1023–1041, 1997.
Barker C 1972 Aquatermal pressuring: role of temperature in development of abnormal pressure zone. AAPG Bulletin v. 56 p. 2068-2071
Hedberg, H.D. (1974) Relation of Methane Generation to Undercompacted Shales, Shale Diapirs, y Mud Volcanoes. Am. Assoc. Pet. Geol. Bull., 58, 668-673.
Spencer, C. W., 1987, Hydrocarbon generation as a mechanism for overpressuring in Rocky Mountain region: AAPG Bulletin,v. 71, p. 368–388.
Meissner, F. F. Petroleum geology of the Bakken Formation, Williston Basin, North Dakota y Montana. Montana Geological Society, Billings, p. 207 - 227, 1978. Proceedings of 1978 Williston Basin Symposium, September 24–27
Spencer, C.W. y Law, B.E., 1981. Overpressured, low-permeability gas reservoirs in Green River, Washakie, y Great Divide Basins, southwestern Wyoming. Bull., Am. Assoc. Pet. Geol., 65: 569.
Waples, D.W., 1980. Time y temperature in petroleum formation - application of Lopatin’s method to petroleum exploration. BulL, Am. Assoc. Pet. GeoL, 64: 916-926.
X. Luo y G. Vasseur. Geopressuring mechanism of organic matter cracking: Numerical modeling. AAPG Bulletin, 80(6):856–874, 1996
Terzaghi, K., 1925, Principles in soil mechanics, III. Determination of the permeability of clay: Engineering News Record, v. 95, p. 832–836.
Mercer, J. W., G. F. Pinder, y I. G. Donalson, 1975, A Galerkinfinite element analysis of the hydrothermal system at Wairakei, New Zealy: Journal of Geophysical Research, v. 80, p. 2608–2621.
L. F. Athy. Density, porosity y compaction of sedimentary rocks. American Association of Petroleum Geophysicists Bulletin, (14):1–24, 1930.
Hubbert M. K., and Rubey W.W. 1959 Mechanics of fluid filled porous solids and its application to averthrust faulting 1, role of fluid pressure in mechanics of overthrust: Geological society of American Bulletin v. 70 p115 - 166
Vargas, D. A., Calderón, Z. H., Mateus, D. C., Corzo, R., & Acevedo, O. J. (2014, November 24). Mathematical Model to Quantify the Contribution of Thermal Stresses in Pore Pressure, Additional to the Compaction Effect. International Society for Rock Mechanics.