各向异性油藏水平井渗流和产能分析

ANALYSIS ON SEEPAGE FLOW AND PRODUCTIVITY OF A HORIZONTAL WELL IN AN ANISOTROPIC RESERVOIR

用拟三维方法分析了各向异性油藏的渗透率主值、主方向和油藏边界对水平井渗流的影响 ,给出了各向异性油藏内水平井渗流的压力场、流场分布及产量的解析解。结果表明 ,水平井的控制储量和产能由水平井方位、各向异性渗透率主值及主方向共同决定。计算产能时不仅要考虑边界点到井位的距离 ,还必须考虑边界点所处的位置。水平井与最大渗透率方向之间夹角越大及各向异性越强 ,则水平井的控制储量和产能越大。水平井筒中的流量分布及水平井所在直线上的压力分布既不受水平井方位的影响 ,也不受渗透率各向异性的影响。当油藏的水平方向尺度远大于其厚度时 ,水平方向渗透率对产能的影响明显大于垂向渗透率。水平井偏离地层的垂向中心位置越远 ,且水平井长度 (相对于地层厚度 )越小 ,水平井的产能越小。

The effects of principal values and directions of permeability and boundaries of an anisotropic reservoir on seepage flow of a horizontal well were investigated by the pseudo three dimension method. The analytic solutions of pressure, velocity of seepage flow and capacity of a horizontal well were given, and the relative figures and tables were provided as well. The controlled reserves and productivity of a horizontal well were determined by the wellbore direction, the principal values of main direction and permeability of the anisotropic reservoir. Both the distance and the direction from the well to the boundary must be considered in the caluclation of flow capacity. While the angle between the wellbore and the maximum principal direction of the permeability is raised, and the anisotropy of the permeability is strongened, the controlled reserves and the flow capacity of a horizontal well will increase. The flow rate distribution on a horizontal wellbore and the pressure distribuion on the straight line of the wellbore are not affected by the horizontal well direction or the anisotropy of permeability. The effect of the permeability in the horizontal direction on the flow capacity of a horizontal well is much more than that of the vertical direction, when the horizontal scales of the reservoir are much bigger than the thickness of the reservoir. When the horizontal wellbore goes far from the vertical center of the well, or the length of the horizontal section of the well is shortened (relative to the formation thichness), the flow capacity of the horizontal well will go down. The equipressure lines are not orthogonal to the streamlines in a reservoir with an anisotropic permeability.