Characteristics of fault zones and their control on remaining oil distribution at the fault edge: a case study from the northern Xingshugang Anticline in the Daqing Oilfield, China

Most major oil zones in the Daqing Oilfield have reached a later,high water cut stage,but oil recovery is still only approximately 35%,and 50%of reserves remain to be recovered.The remaining oil is primarily distributed at the edge of faults,in poor sand bodies,and in insufficiently injected and produced areas.Therefore,the edge of faults is a major target for remaining oil enrichment and potential tapping.Based on the dynamic change of production from development wells determined by the injection-recovery relationship at the edge of faults,we analyzed the control of structural features of faults on remaining oil enrichment at the edge.Our results show that the macroscopic structural features and their geometric relationship with sand bodies controlled remaining oil enrichment zones like the edges of NNE-striking faults,the footwalls of antithetic faults,the hard linkage segments（two faults had linked together with each other to form a bigger through-going fault）,the tips of faults,and the oblique anticlines of soft linkages.Fault edges formed two types of forward microamplitude structures：（1） the tilted uplift of footwalls controlled by inverse fault sections and（2） the hanging-wall horizontal anticlines controlled by synthetic fault points.The remaining oil distribution was controlled by microamplitude structures.Consequently,such zones as the tilted uplift of the footwall of the NNW-striking antithetic faults with a fault throw larger than 40 m,the hard linkage segments,the tips of faults,and the oblique anticlines of soft linkage were favorable for tapping the remaining oil potential.Multi-target directional drilling was used for remaining oil development at fault edges.Reasonable fault spacing was determined on the basis of fault combinations and width of the shattered zone.Well core and log data revealed that the width of the shattered zone on the side of the fault core was less than 15 m in general;therefore,the distance from a fault to the development target should be larger than 15 m.Vertically segmented growth faults should take the separation of the lateral overlap of faults into account.Therefore,the safe distance of remaining oil well deployment at the fault edge should be larger than the sum of the width of shattered zone in faults and the separation of growth faults by vertical segmentation.

Development of new endovascular stent-graft system for type B thoracic aortic dissection with finite element analysis and experimental verification

Endovascular repair of the thoracic aorta with self-expanding stent-grafts has been emerging as a less invasive alternative treatment compared with conventional open surgeries.Despite the promising efficacy and safety of endovascular stent grafting,the stent-graft failure remains a major concern in terms of stent migration,device fatigue,and the risk of endoleaks.Challenges associated with the stent-grafts involve optimized geometrical structure,lifetime fatigue resistance,and adequate radial support.In this work,a novel endovascular stent-graft system is developed specially for the treatment of Stanford type B thoracic aortic dissections(TAD).Numerical study with finite element analysis(FEA)was utilized to evaluate the mechanical behaviors of the individual stent component.Results of the simulation were validated by experimental tests.Based on the systematic analysis of the parametric variations,a final stent-graft system was developed by the selection and arrangement of the individual stent components,targeting an optimal performance for treatment of TAD.The optimized solution of the stent-graft system was tested in clinical trials,showing advantageous therapeutic efficacy.