岩石可压裂性的判定大多以脆性指数的方法来评价,但脆性指数概念混杂,地质依据不足,大多停留在半定量估算的水平,没有从岩石破裂机理出发定量评价其可压裂性大小,适用性及准确度均存在较大的局限性.基于低渗透油藏砂岩储层可压裂性缺乏可靠判据的实际,对大庆外围某油田压裂先导试验区块储层开展精细地质建模.采取有限元定量模拟手段,改善固有裂缝预测模式,将原先局限于垂直地层剖面的裂缝预测导向转变为“水平方向预测”.首次提出“平面逐层累积”压裂缝预测方法,对压裂目的层段每小层开展平面裂缝模拟,实现了在三维空间中开展压裂缝定量预测的目的.建立起“实际压裂指数(AFI)”、“潜在压裂指数(PFI)”、“总压裂指数(FI)”、“测井压裂指数(LFI)”4个新判据.结论与现场井下微地震检测结果吻合良好,这将为低渗透油藏提高采收率提供重要的科学依据.
Brittleness index method was mostly used to evaluate the distinction of rock fracturing though the concept and calculation process of brittleness index is complex and absence of geological basis,so the estimation of the fracturing capability was mostly staying in the level of semi-quantitative,which is not the quantitative evaluation of the fracturing capability based on the rock failure mechanism,so the applicability and accuracy have great limitations.Based on the reality of the lack of a reliable criterion for fracturing capability in low permeability sandstone reservoir,a geological modeling of the fracturing test area in Daqing oilfield was performed.By the approach of finite element simulation,the natural fracture prediction mode was improved,which changed the original "vertical profile fracture prediction" to "horizontal layer fracture prediction" and the method of "accumulation from each horizon" was firstly put forward.Fracture of each small layer was simulated,which realized the purpose of quantitative fracture prediction in the three-dimensional space.Four kinds of new criteria named "actual fracturing index (AFI)","potential fracturing index (PFI)","fracturing index (FI)","logging fracturing index (LFI)" were all firstly proposed.The conclusion was fit to the results of downhole micro-seismic technique.This will provide important scientific basis for enhancing the recovery efficiency in low permeability reservoir.