致密油藏多轮次注水吞吐应力场-渗流场迭代耦合模拟研究OA

It is difficult to establish an effective displacement system for the conventional water injection development of horizontal wells in tight oil reservoirs.The method of depletion development after refracturing faces the problems of insufficient energy in the later stage and excessive production decline.Multi-cycle water huff and puff technology is an effective means to supplement formation energy in the later stage of horizontal well development in tight oil reservoirs.After initial fracturing,the stress field,fracture morphology,and flow field need to be studied urgently in the whole process of water injection development,depletion development after refracturing,and multi-cycle water huff and puff.In this paper,an iterative coupling simulation method of stress field,fracture propagation,and flow field was established,which accurately captured the changes of the artificial fracture morphology during multi-cycle water huff and puff and reduced the complexity of data conversion between models.By taking the typical horizontal well group in Changqing Oilfield of Ordos Basin as an example,the variation law of stress field,fracture propagation law,and flow field characteristics at different stages were studied,and the improvement effect of multi-cycle water huff and puff on the flow field was clarified.The results show that the principal stress difference near the well increases in water injection development after the initial fracturing,and the horizontal principal stress is deflected by about 13° compared with the initial direction.The horizontal two-way stress difference of the formation decreases after water injection for replenishment of energy.The old fractures are more likely to expand,and new fractures are generated after refracturing.After one round of water huff and puff for replenishment of energy,the stress difference near the well decreases.The horizontal principal stress's deflection angle reaches approximately 38°,which promotes the formation of branch fractures and makes the fracture morphology more complex.Subsequently,the near-well stress difference gradually increases.Among them,after the third round of water huff and puff,the performance significantly deteriorates,while the horizontal principal stress difference increases,and the fracture morphology remains basically unchanged.After five rounds of water huff and puff,the recovery can be increased by 1.9 percentage points compared to the depletion development method.