Speaker
Description
Hydraulic fracturing is one of the key stimulation technologies of Gulong shale, Qingshakou Formation, China. Proppant has always been a vital part in the hydraulic fracturing operation, as it supports the fracture against the closure stress. A successful delivery of the proppant to the aiming fracture, as well as a long-term propping effect to a great extent determines the reservoir permeability and well productivity. This requires a well-projected selection and injection scheme of proppant, from which an optimised proppant distribution and thus fracture conductivity could be achieved.
Hence, the main aim of the current research is to perform a systematic investigation of proppant, from its injection to the facture network to the long-term fracture conductivity. To achieve this, we conduct both experimental and numerical studies to seek for an optimised proppant injection scheme as well as a critical packing ratio with which the fracture permeability reaches the maximum. The numerical study is accomplished by the implementation of the numerical framework consisting of the lattice Boltzmann method (LBM) and the modified partially saturated method (MPSM). As an extension to our previous study where Queensland coals were investigated, we apply the mechanical parameters of the Gulong shale to our model. The results indicate an optimised proppant packing ratio of 0.2 - 0.4. The fracture conductivity is experimentally evaluated using the shale cores and sand proppant at the reservoir pressure. The GCTS tri-axial testing system is utilised to conduct the experiments. By adjusting the proppant packing ratio, we find an optimised proppant concentration, under which the fracture permeability reaches the maximum. Besides, the final distribution of proppant using different injection schemes are experimentally studied. The long-term fracture conductivity of these distribution patterns is further evaluated using a core testing holder under overburden pressure, from which a long-term conductivity curve is obtained.
The outcome of the current research contributes to a better design of the proppant and the resultant fracture permeability especially for shale. It also provides a theoretical basis for an optimised proppant selection and injection scheme for future hydraulic fracturing operations, which benefits the exploitation of the continental shale oil worldwide.
| Country | China |
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