Abstract

ARMANDO, Vargas-Silva Diego; MAIKA, Gambús-Ordaz  and  ZULY, Calderón-Carrillo. ASSESSMENT OF CAUSES OF OVERPRESSURE DIFFERENT FROM SUB-COMPACTION: APPLICATION IN UNCONVENTIONAL RESERVOIRS. C.T.F Cienc. Tecnol. Futuro [online]. 2019, vol.9, n.2, pp.5-14. ISSN 0122-5383.  https://doi.org/10.29047/01225383.177.

The need of hydrocarbon producing countries to increase reserves has led energy companies to explore 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) analysed, were quantified.

Keywords : Pore pressure; Geochemical; Petrophysical; Geomechanics.

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