渗流流态分析在致密储层压裂诊断中的研究与应用

Research and application of the seepage flow pattern analysis in the fracturing diagnosis of tight reservoirs

准确分析压后压降曲线可以诊断裂缝特征,评价施工效果。目前常用的致密储层压后诊断方法存在对数据精度要求高,难以准确获取瞬时停泵裂缝压力及施工净压力,无法准确识别多裂缝特征,不能区分闭合后双线性流及线性流,对停泵压降观测时间要求过长等问题。为此,建立了基于储层压后渗流流态分析的压裂诊断方法。该方法降低了诊断对现场压力数据精度的要求,通过识别并拟合线性流数据点以准确得到瞬时停泵裂缝压力、裂缝净压力及多裂缝特征,避免了闭合后分析中对停泵时间过长的假设,通过辨识闭合后双线性流或线性流定性评价支撑裂缝导流能力、求取储层原始地层压力。通过应用实例,验证了该方法在致密储层压裂诊断中的适用性及可靠性。

The accurate analysis of pressure decline after fracturing can be used to diagnose fracture characteristics and evaluate fracturing effect.But some disadvantages of the usual diagnostic method are existed,such as high demand for pressure data precision,inaccuracy of instantaneous shut-in pressure(ISIP)and net pressure,unidentified multi-fracture characteristics,indistinguishability of the bilinear flow and linear flow after closure,and excessive requirement for observation time of pressure decline during shut-in.Therefore,a diagnostic method for fracturing is proposed on the basis of seepage flow pattern analysis.This method reduces the high demand of pressure data precision.ISIP,net pressure and multi-fracture characteristics can be acquired accurately by identifying and fitting the pressure data point of linear flow,and there is no assumptions about excessive time of pressure decline in this method.Conductivity of the propped fracture can be evaluated qualitatively and the initial reservoir pressure can be acquired by identifying the bilinear flow or linear flow after closure with this method.An application example is used to verify the applicability and reliability of this method in fracturing diagnosis of tight reservoir.