An integrated workflow for fracture propagation and reservoir simulation in tight oil

摘要

Various fracture-propagation models have been used to capture complex hydraulic fracture (HF) geometry. However, they cannot obtain the production performance. Besides, many researchers developed reservoir simulators to obtain production performance with given fracture geometry. However, these geometries are easy to deviate from the reality of a certain reservoir. To fill this gap, there is an urgent demand to integrate the simulation of fracturing and production processes. In this work, we present an integrated workflow for fracture-propagation and reservoir simulation for tight oil. First, we employ cohesive zone model (CZM) to simulate fracture propagation. In comparison with previous studies, our CZM can simulate complex fractures. Then, we apply the complex fracture geometry to embedded discrete fracture model (EDFM). In this reservoir simulator, nonlinear flow in the tight matrix, complex HF geometry, and pressure-dependent fracture permeability (stress sensitivity effect) are considered simultaneously. Finally, we obtain production performance of this fractured well. To verify the reliability of our models, we compare the results of laboratory experiment and commercial simulator with CZM and EDFM, respectively. Using this workflow, we studied the effect of geological factor (i.e. natural fracture distribution) and fracturing schedule (i.e. injection rate) on production performance. Results reveal that the cumulative oil production in the case with regular natural fracture (NF) is 1.67% higher than that with staggered NF, and 14.6% higher than that without NF. There is an optimal injection rate to maximum production performance. In this case, medium injection rate increases cumulative oil production by 2.42% than higher injection rate, and 1.1% than lower injection. Most importantly, the continuous simulation of fracturing and production processes is implemented in our proposed simulation workflow. In this way, this workflow can be used to optimize both fracturing and production schedule to maximize production performance and/or economic benefit for tight oil in our future work. Furthermore, our method can be further extended to the simulation of multi-stage fractured horizontal well (MFHW) in tight oil or other unconventional oil and gas resources.