基于脉冲注入理论的页岩储层微破裂试井解释技术及应用

微破裂测试可以获取页岩储层大规模体积压裂之前的物性参数，为资源量计算以及地质、工程双“甜点”的评价提供关键信息。目前基于常规关井压力恢复试井理论的解释方法在处理微破裂测试这类“短暂注入、长期关井”的特殊问题时精度低，且常出现流态无法识别及参数难以诊断的问题。结合微破裂测试的特殊性，提出了一种基于脉冲注入理论的页岩储层微破裂试井解释方法，即将开井注入和关井压降过程看作整体，假设关井后的压力响应是注入期和关井期的总和，在渗流数学模型的内边界条件处考虑，从而建立微破裂试井解释模型。求解得到压力动态曲线，通过敏感性分析明确各参数对测试曲线的影响。之后通过渐进分析得到测试曲线关键段压力解，据此引入3条组合诊断线，用以获取测试曲线上的流态信息，并在不同流态下解释对应的参数，最终建立了主控流态识别+特种直线分析的微破裂试井解释方法和流程。利用该方法对涪陵页岩气田南川区块平桥背斜不同构造部位两口测试井进行了分析解释，验证了方法的实用性，解释结果为认识该区页岩含气性提供了依据，并正确预测了不同构造部位气井压裂效果将存在分区差异，为之后正确划定甜点区和优先部署区提供了指导，后续试气和试采动态进一步证明了结果可靠性。

Mini-frac test interpretation for shale reservoirs based on impulse injection theory and its application

Mini-frac tests can be used to evaluate the physical property of shale reservoirs prior to large-scale fracturing， and provide key parameters for resource quantity calculation and evaluation of sweet spots both in geology and engineering. As of now， the well testing interpretation based on conventional shut-in pressure recovery has a very low accuracy in dealing with special issues like mini-frac test， featuring “short-term injection and long-term shut-in”， often accompanied by difficulties in flow pattern identification and parameter diagnosis. In view of the particularity of mini-frac test， the study proposes a well testing interpretation method based on pulse injection theory， where the process of injection and shut-in pressure drop is regarded as a whole， the shut-in pressure response is assumed to be the result of both injection and shut-in periods as considered at the inner boundary of mathematical diffusion-filtration model， and then a mini-frac test interpretation model is established. A pressure dynamic curve is calculated， and the influence of the parameters on the test curve is determined through sensitivity analysis. Pressure of key sections of the test curve is obtained through asymptotic solution， and 3 combined diagnostic curves are introduced to obtain the flow regime information. Finally， an interpretation method and process by mini-frac tests is established with parameter interpretation made for different flow regimes， including dominant flow regime identification and special straight line analysis. This method is then applied to analyze two wells located at different structural positions of Pingqiao anticline in Nanchuan block， Fuling shale gas field， through which its practicality is verified. The interpretation results serve to provide basis for understanding the gas-bearing potential of shale in the area， and predict the regional differences of fracturing effect successfully， which is of guiding value to future delineation of sweet spot zone and development zone of priority. The subsequent production tests also verify the reliability of the results obtained.