三维数字岩心覆压矫正方法

微米CT通常在常压环境下开展,导致地下实际覆压情况下的孔喉特征与岩心CT得到的并不相同。为了使微米CT构建数字岩心的孔喉结构更符合地下实际情况,以松辽盆地龙虎泡地区青山口组二段、三段致密砂岩覆压孔渗资料为基础,开展上覆压力对孔隙度、渗透率影响的研究。并结合微米CT资料以及膨胀算法,模拟数字岩心在覆压情况下孔渗变化,最终建立了基于覆压指数函数和膨胀算法进行覆压矫正的数字岩心。结果显示,数字岩心覆压矫正后孔隙空间明显减小,且矫正后模型模拟所得渗透率与实验计算值较为一致,符合率达到90%以上。该方法矫正后的数字岩心与直接利用微米CT构建的数字岩心相比更能反映地下覆压情况下的孔喉特征,对油气开发更具指导意义。

An Overburden Pressure Correction Method of 3D Digital Cores

Micro CT is usually used at atmospheric pressure,leading to the pore throat characteristics obtained under the actual overburden pressure different from those obtained from CT scanning.In order to make the CDRM’s pore throat structure more similar to the actual one,taking the porosity and permeability data under overburden pressure from tight sandstones of the second and third member of Qingshankou formation in Longhupao area,Songliao basin as examples,the paper studies the influences of the overburden pressure on porosity and permeability.Combined with Micro CT scanning images and dilation algorithm,the variations of porosity and permeability of a digital core under the overburden pressure are simulated and a digital core model corrected with overburden pressure is established on the basis of overburden pressure exponential function and dilation algorithm.The results show that the pore space in the digital core is reduced obviously,and the simulated permeability obtained from the corrected digital core model is consistent with the calculated value of overburden permeability test with the coincidence rate over 90%.Compared with the traditional CDRM,this model can reflect the characteristics of pore throats under the condition of overburden pressure and provide guidance for oil and gas development.