双重介质油藏低速非达西渗流封闭外边界试井模型

WELL TEST MODEL ON CLOSED OUTER BOUNDARY OF DUAL MEDIA RESERVOIR WITH LOW RATE NON- DARCY FLOW

已有的研究表明低渗透油藏存在低速非达西渗流机理。针对低渗透双重介质油藏，在低速非达西渗流条件下建立了考虑启动压力梯度、表皮效应、井筒存储效应和封闭外边界的试井理论模型，应用Laplace变换方法求解得到了该模型在Laplace空间的解，采用Stehfest方法对该解进行了数值反演，绘制了封闭外边界条件下的井底压力理论图版，讨论了启动压力梯度、边界距离等参数对理论图版的影响规律。研究表明：由于启动压力梯度的存在，使得理论图版中的导数曲线在后期出现上翘现象，其上翘幅度随启动压力梯度的增大而增大。理论图版可用于低渗透双重介质油藏试井资料的分析和解释。

Available study shows that low rate non-Darcy flow mechanism exists in low permeability reservoir. Aiming at dual media reservoir of low permeability, theoretical model of well test considering start-up pressure gradient, skin effect, borehole storage effect and closed outer boundary, is established under the condition of low rate non-Darcy flow, and the solution of model in Laplace space is drawn with Laplace variation method, numerical value inversion is performed to the solution with Stehfest method, theoretical plate of bottom pressure under the condition of closed outer boundary is mapped out, influence law of start-up pressure gradient and boundary distance and other parameters on the theoretical plate is discussed. Study shows that because of existing of start-up pressure gradient, derivative curve in theoretical plate begins to upwarp at the late stage, amplitude of which increases with the raise of start-up pressure gradient. The theoretical plate in this paper can be used for analysis and interpretation of test data from low permeability dual media reservoirs.