Research On Water Flooding Characteristics Of Horizontal Well In HQ Ultra-low Permeability Reservoirs Based On The Stream-tube Method

HQ block belongs to typical ultra-low permeability reservoirs in China,with poor reservoirs properties,high flowing resistance,and strong heterogeneity.It is developed by multi-stage fractured horizontal wells with water injection,and the situation of water flooding is complicated.The stream-tube method is a simple and rapid method for evaluating the plane sweep coefficient and is widely used in the water flooding sweep evaluation of conventional oilfields.However,the traditional stream-tube method is mostly established for vertical well patterns and is not suitable for water flooding development of fractured horizontal wells in ultra-low permeability reservoirs.Therefore,it is urgent to improve and deduce the water flooding stream-tube method.Firstly,by analyzing the geological characteristics of ultra-low permeability reservoirs in HQ block and the dynamic production characteristics of horizontal wells,in this thesis,the main contradiction of water flooding development of fractured horizontal wells in reservoirs is summarized and geological main controlling factors and development main controlling factors affecting water flooding sweep coefficient are clarified.Secondly,on the basis of considering the threshold pressure gradient and anisotropy of ultra-low permeability reservoirs,the calculation model of water flooding stream-tubes in multi-stage fractured horizontal wells is established by dividing the stream-tubes calculation units,and the calculation module of water flooding sweep efficiency is established by using Python software,which can describe the water flooding flow field of different fracture geometry of fractured horizontal wells.Finally,based on the stream-tubes calculation model of fractured horizontal wells,sensitivity analysis of reservoirs permeability,sand body connectivity,natural fracture,well network perfection,well line spacing and fracture network pattern is carried out,forming the evaluation charts of water flooding sweep coefficient suitable for HQ ultra-low permeability reservoirs,and the current situation of water flooding sweep in horizontal wells in HQ ultra-low permeability reservoirs is evaluated.The development strategies of horizontal well pattern of small injection and production unit in new areas and the development adjustment techniques of perfecting well pattern and optimizing refracturing networks in old areas are proposed.In this thesis,a set of rapid evaluation methods suitable for water flooding plane sweep for the development of multi-stage fractured horizontal wells in ultra-low permeability reservoirs are provided,which guides the development and adjustment of actual blocks and has reference significance for the development and adjustment of similar reservoirs.