厚油层注采模式对纵向波及特征影响研究

注采模式优选对缓解厚油层层内矛盾，提高纵向波及效率具有重要意义。目前尚未形成油水井同时部分打开的井间解析渗流模型，无法支撑厚油层波及特征的研究。为此，采用保角变换方法，将油水井同时部分打开剖面地层依次变换为圆形边界偏心裂缝井地层、单位圆形边界两分支裂缝井地层、注水井全部打开采油井部分打开剖面地层，之后重复上述变换，将注水井全部打开采油井部分打开剖面地层变换为油水井全部打开剖面地层，从而将原始二维渗流过程变换为一维渗流过程，实现了不同注采模式下厚油层层内压力及流线分布的解析计算。与精细数值模拟方法的对比表明，该方法对不同井距/厚度比的情形均可获得较高计算精度。利用该方法，开展了注采模式对纵向波及特征的研究。结果表明：对于底注高采模式，注水井顶部为主力注入层段，注水井顶部1/3的井段控制超过1/2的地层，使超过2/3的采油井段受效；注水对地层的波及主要作用于注水突破前的阶段。在相同的打开厚度下，底注高采的注水突破最晚、波及效率最高，底注中采、中注高采次之，高注高采、底注底采注水突破最早、波及效率最低。采油井的打开厚度越大，注水突破时间越短，但注水突破时的波及系数增大，应综合考虑注水突破时间...

Research on influence of injection-production modes on longitudinalsweep characteristics of thick reservoirs

The optimization of injection-production modes is of great significance in alleviating intra-layer contradiction and improving longitudinal sweep efficiency for thick reservoirs. The analytical flow model of both producer and injector partially penetrating the reservoir is absent currently，which fails to support the study of the sweep characteristics of thick reservoirs. Therefore，based on the conformal mapping method，this article transformed the section formation with partially penetrating producer and injector into a formation with a circular boundary and off-center fractured well， a formation with a unit circular boundary and two-branch fractured well，and a section formation with fully penetrating injector and partially penetrating producer，sequentially. The above transformations were repeated to transform the section formation with fully penetrating injector and partially penetrating producer into that with fully penetrating injector and producer. In consequence，the original two-dimensional flow process was transformedinto a one-dimensional one，achieving analytical calculations of pressure and streamline distribution in thick reservoirs under different injection-production modes. The comparison with refined numerical simulation methods shows that the proposed method has high computational accuracy for different well spacing-thickness ratios. The influence of injection-production modes on longitudinal sweep characteristics of thick reservoirs was researched using the method presented in this article. The results show that for the bottom-injection-high-production mode， the top section of the injector acts as the main injection layer，and the top 1/3 of the injector controls more than 1/2 of the formation， resulting in more than 2/3 of the producer being affected. The main impact of water injection on the formation lies in the stage before the water breakthrough. The water breakthrough of bottom-injection-high-production mode is the latest and has the highest sweep efficiency，followed by bottom-injection-medium-production mode and mediuminjection-high-production mode under the same penetrating thickness. The water breakthroughs of high-injection-high-production mode and bottom-injection-bottom-production mode are the earliest and have the lowest sweep efficiency. The larger penetrating thickness of the producer indicates a earlier water breakthrough. However，the sweep efficiency in water breakthrough increases.Therefore， the optimal penetrating thickness should be selected by comprehensively considering the factors of water breakthrough time and sweep efficiency.