多级压裂水平井分段测试压力分析方法

多级压裂水平井缝间渗流规律及相互干扰程度对于确定生产过程中缝间干扰程度、诊断产水缝及来水方向具有重要意义。基于Cinco-Ley有限导流裂缝模型,采用点源法,将压裂缝离散为若干裂缝微元,联立内外边界条件构建矩阵求取每个裂缝微元的流量,通过各测试段裂缝微元流量之和进行约束,建立了多级压裂水平井分段测压的试井模型。如果分段测试各测试段流量呈现规则的U型分布,则导数曲线与全井段测试曲线重合;无量纲流量比合段测试流量偏高的压力导数曲线在井储和线性流阶段相对全井段测试曲线上移,反之相对全井段测试曲线下移。各测试段裂缝半长减小,压力导数曲线线性流段向上移动;裂缝间距增大,线性流阶段持续时间延长;裂缝导流能力增大,早期压力导数下降但趋势减缓;缝间干扰出现在第2过渡流阶段,水平井中部测试段压力导数出现上翘。提出的半解析模型在简化条件下与商业试井软件数值试井结果吻合度极高,证明离散求解方法准确、可靠。水平井分段测压实例解释拟合效果好,得到的参数为诊断水平井缝间产液情况、制定开发调整措施提供了依据。

An analysis method for the segmental pressure measurement in multi-stage fractured horizontal well

Inter-fracture flow laws and fracture interaction degrees of multi-stage fractured horizontal well are of great significance to determine fracture interaction degree in the process of production and diagnose water producing fractures and water directions. Based on the Cinco-Ley finite conductivity fracture model, a hydraulic fracture was divided into several fracture micro-elements by means of the point source method. A matrix was constructed by combining internal and external boundary conditions together to calculate the flow rate of each fracture micro-element. The well testing model for the segmental pressure measurement of multi-stage fractured horizontal well was established under the constraint of the sum of the flow rates of fracture micro-elements in each testing segment. If the flow rate in each testing segment is distributed in the shape of regular U, the derivative curve is coincident with testing curve of the full hole. Compared with the testing curve of the full hole, the pressure derivative curve whose dimensionless flow rate is higher than the regular flow rate moves upward in the stages of well storage and linear flow. And otherwise, it moves downward. With the decrease of the fracture semi-length in each testing segment, the pressure derivative curve moves upward in the stage of linear flow. With the increase of the fracture interval, the stage of linear flow lasts longer. As the flow conductivity of the fracture increases, the early pressure derivative decreases, but the trend slows down. Fracture interaction occurs in the stage of second transition flow, when the pressure derivative of the testing segment in the middle of horizontal well upwarps. The coincidence between the result of the proposed semi-analytic model under the simplified conditions and the numerical well testing result of commercial well testing software is extremely high, indicating the discrete solution method is accurate and reliable. The interpretation on the segmental pressure measurement in the horizontal well case is well fitted, and the obtained parameters provide the basis for diagnosing the inter-fracture liquid producing situations of horizontal well and formulating development adjustment measures.