Study On Saturation Distribution Of Horizontal Wells In Anisotropic Waterfiooding Oil Reservoirs

Horizontal well development is an effective method in oil and gas reservoirs.The efficiency of horizontal wells for production is better than that of vertical wells and slant wells.The anisotropy of the reservoir has a great influence on the flow of oil and gas through the reservoir.The traditional methods for homogeneous reservoirs has large errors in the description of anisotropic reservoirs.In addition,due to horizontal sections,wellbore pressure drop in horizontal wells has a significant impact on actual production.The research on horizontal wells with wellbore pressure drop in anisotropic reservoirs provides a theoretical basis for the design and adjustment of development schemes.The flow theory of horizontal wells is complicated.The streamline simulation can describe the flow process more simply and accurately.The vertical well-horizontal well model and the horizontal well-horizontal well model in anisotropic reservoir is established.By the use of streamline simulation programme,distribution of oil saturation is obtained.The analysis of effects of time,well spacing,location relationship,flow rate,anisotropy,horizontal well length and wellbore pressure drop on distribution of oil saturation is accomplished.The main results are as follows:(1)Based on the point source function and superposition theory,the plane anisotropy is processed by coordinate transformation to obtain the pressure distribution of the vertical well-horizontal well model and the horizontal well-horizontal well model.And by using Darcy's law,the velocity distribution is obtained.(2)A streamline simulation programme based on a discretized velocity distribution is developed.After obtaining the velocity field in the reservoir,the programme can be used to simulate the streamline.(3)For the streamline distribution,flow rate and well location relationship has a greater impact on the two models.The streamline is pulled in the direction of higher permeability.(4)For the oil saturation distribution,flow rate and development time have a greater impact on the two models.The oil saturation decreases fast in the direction of higher permeability.(5)When considering wellbore pressure drop,there is a significant " heel-toe effect" in the production of horizontal wells.For the vertical well-horizontal well model,when vertical well is at toe of horizontal well,the sweep effect is the best;for the horizontal well-horizontal well model,when two wells are placed in the same direction,the imbalance between heel and toe is magnified,and when the two wells are placed in the opposite direction,this imbalance can be relieved to some extent,which makes the sweep effect better.