热采水平井变质量流与油藏渗流的耦合数值模拟

为真实反映水平井及近井地带的流体流动情况，需要将水平井井筒内的流动与在油藏中的渗流耦合进行油藏数值模拟。假设“微元段”，引用“交错网格”和“等效渗透率”概念，建立了热采水平井井筒变质量流的等效渗流模型；在此基础上提出耦合井筒变质量流与油藏渗流的水平井产量公式，建立了井筒变质量流与油藏渗流耦合的数学模型。利用该模型进行热采水平井开采机理研究，认为：水平井井筒内的压降影响水平井生产动态，忽略压降将使计算的产油量和油汽比偏高；水平井所产油主要来自水平井筒的始端，在一定的油藏条件、水平井参数等情况下，每口水平井都有最优水平段长度。图2表1参5

Thermal recovery numerical simulation coupling flow in reservoir with various-mass-rate flow in horizontal well-bore

In order to describe the actual flow of fluid in and nearby the horizontal well, it is necessary to study the coupling of the flow in the reservoir with various-mass-rate flow in the horizontal well-bore. An assumption is given that the horizontal well-bore is divided into several micro-elements and the fluid flows into the horizontal well-bore only at the interface of the two nearby micro-elements, which results in constant-mass-rate flow in any micro-elements. An equivalent seepage flow model is built for the various-mass-rate flow in the horizontal well-bore by using the staggered grid and equivalent permeability. A thermal recovery numerical simulation model coupling the flow in the reservoir with various-mass-rate flow in the horizontal well-bore is constructed. A recovery mechanism study of horizontal wells is carried out with the coupling model built and several important results are obtained. The pressure drop within the horizontal well-bore has influence on the production performance of the well. If neglecting the pressure drop along the well-bore, the calculated production parameters such as oil production and oil-steam ratio will be higher than the true values. The most oil production is derived from the production end (the first end) of the well-bore. Under a certain condition (certain reservoir condition, horizontal well parameters and so on), there exists an optimum horizontal well-bore length.