Crack system development in a heated rock with kerogen-filled pores

This paper deals with modelling of crack system formation in an initially impermeable rock with pores filled by solid kerogen upon its thermal treatment. Heating of the rock matrix results in the transformation of the kerogen particles into oil and gas, thus the pores become subject to internal pressure, which can initiate the development of cracks and formation of crack systems. Conditions at which the development of crack system becomes possible are analysed, and mechanical interaction of certain number of cracks and their coalescence is modelled, in order to estimate the portion of oil-containing pores that can be involved in filtration. Two-dimensional modelling is based on the method of complex singular integral equations that takes into account full mutual interaction of cracks emerging from arbitrarily placed kerogen-containing pores. It is assumed that the cracks grow in quasistatic manner step -by -step, provided that the mode I stress intensity factors at all crack ends are positive. The crack trajectories are determined by the criterion of the maximum tensile stress in the vicinity of the crack ends. Calculations of fracture characteristics are performed for different number of nodes (and collocation points) in order to maintain the accuracy of calculations when the neighbouring cracks become close to each other. Results are presented for different initial placement of pores, including periodical, regular lattice, and randomly placed.