Simulation of fracture communication effect of fracturing horizontal wells in seam-hole carbonates
The ultra-deep oil and gas resources in Shunbei Oilfield are mainly stored in carbonate fractures and caves.During the fracturing development of horizontal wells,the wellbore orientation often does not align with the direction of minimum in-situ stress,leading to the diversion of fracturing fractures and unsatisfactory reservoir communication effect.In order to improve the communication effectiveness of fracturing fractures,we employ a numerical simulation method based on discrete lattice theory and synthetic rock mass technology to establish models for carbonate reservoirs,single caves and multi-fracture-cave systems.We systematically investigate the effects of wellbore azimuth,geological parameters(horizontal stress difference and cave pore pressure)and operational parameters(displacement and viscosity)on fracture propagation paths and cave communication effects.The results show that the deflection radius increases with the increase of wellbore azimuth,displacement and viscosity.When the displacement exceeds 2.88 m3/min,the fracture turning radius stabilizes.Lower pore pressure in the cave bodies results in a more obvious repulsive effect on hydraulic fracture propagation.The larger the horizontal geostress difference is,the less the effect of karst caverns on hydraulic fracture propagation.When the horizontal geostress difference reaches 30 MPa,the geostress difference completely dominates the fracture propagation.With the increase of wellbore azimuth,displacement and viscosity,the lateral communication distance of fractures increases in multi-fracture-cave reservoirs.When the wellbore azimuth is greater than 30° or the displacement exceeds 9 m3/min,the increase of the lateral communication distance slows down.As the amount of construction fluid increases,both the vertical extension distance of cracks and the maximum joint length increase;however,an increase in natural fracture density gradually reduces the vertical communication distance of cracks.The results can provide theoretical guidance for the design of acidizing fracturing scheme in carbonate reservoirs.
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