裂缝性油气藏采收率:100个裂缝性油气实例的经验总结

摘要

One hundred fractured reservoirs from around the world were evaluated to determine how ultimate recovery wasaffected by inherent reservoir and fluid properties, such as porosity, permeability, viscosity, mobility ratio, Sw, wetability, fracture distribution, and drive mechanism vs. The choice of reservoir management strategy, e. G. , optimization ofproduction rate and type of EOR technique. Fractured oil reservoirs were divided into four groups. Type Ⅰ reservoirs havelittle matrix porosity and permeability. Fractures provide both storage capacity and fluid-flow pathways. Type Ⅱ reservoirshave low matrix porosity and permeability. Matrix provides some storage capacity and fractures provide the fluid-flowpathways. Type Ⅲ (microporous) reservoirs have high matrix porosity and low matrix permeability. Matrix provides thestorage capacity and fractures provide the fluid-flow pathways. Type Ⅳ (macroporous) reservoirs have high matrixporosity and permeability. Matrix provides both storage capacity and fluid-flow pathways, while fractures merely enhancepermeability. Results of studying 26 Type Ⅱ and 20 Type Ⅲ reservoirs demonstrate that recovery factor is controlled bydifferent factors in these two reservoir types. Recovery factor in Type Ⅱ reservoirs is sensitive to aquifer-drive strength andoptimization of flow rate. Type Ⅱ reservoirs are easily damaged by excessive production rates, but when managedproperly, some achieve good recovery without the need for secondary or enhanced recovery programs. Recovery factor inType Ⅲ reservoirs is affected by inherent rock and fluid properties, particularly matrix permeability, API gravity, wetability, and fracture intensity. The choice of proper FOR technique is essential for optimum exploitation. No Type Ⅲreservoir is produced to final depletion without the aid of some type of secondary or EOR technique. Recognition of thedifferences between Type Ⅱ and Type Ⅲ fractured reservoirs should lead to better choices of exploitation strategy.%通过对世界上100个裂缝性油气藏的综合评价,研究储集层及流体本身的性质(包括孔隙度、渗透率、黏度、可动油比例、含水饱和度、润湿性及裂缝分布特征等)和驱动机制及油藏管理战略(优化日产量和采用不同类型的提高采收率技术)对其最终采收率的影响.将裂缝性油气藏分为4类:Ⅰ类的基质几乎没有孔隙度和渗透率,裂缝是储存空间和流体流动的通道;Ⅱ类的基质有较低的孔隙度和渗透率,基质提供储存空间,裂缝提供流动通道;Ⅲ类(微孔隙)的基质具有高孔隙度和低渗透率,基质提供储存空间,裂缝提供流动通道;Ⅳ类(大孔隙)的基质具有高的孔隙度和渗透率,基质提供储存空间和流动通道,裂缝仅增加渗透率.对26个Ⅱ类油气藏和20个Ⅲ类油气藏的开采历史的研究表明:Ⅱ类油气藏的采收率受水驱强度和最优日产量控制,日产量过高会很容易破坏Ⅱ类油气藏,一些Ⅱ类油气藏如果管理得当,采收率可以很高,不需要二次或三次采油;Ⅲ类油气藏的采收率主要受岩石和流体本身性质的影响,特别是基质渗透率、流体重度、润湿性以及裂缝强度等,不进行二次或三次采油不可能完全开采,往往需要采用一些提高采收率的专门技术.以往将Ⅱ类和Ⅲ类裂缝性油气藏归为一类,认识它们的区别将有助于选择更好的开发策略.