考虑渗吸和驱替的致密油藏体积改造实验及多尺度模拟

矿场试验表明，压裂后不立即放喷，依靠焖井过程的驱替和渗吸可置换小孔隙内的原油，提高原油采出程度。为探索该过程机理，进行了实验和模拟研究。首先，带压渗吸实验，模拟裂缝壁面在驱替压差和毛管力共同作用下的渗吸行为，无因次时间中加入驱替项（Δp），对实验结果进行归一化处理；其次，建立基于CT 扫描的孔隙尺度模型，通过致密岩心采收率拟合， 获得驱替、渗吸的相渗和毛管压力；最后，在油藏尺度，分别赋予基质和裂缝不同的相渗和毛管压力，模拟矿场实际油水流动。结果表明:带压渗吸采收率明显高于自发渗吸采收率，提高幅度10%~15%；无因次时间中加入驱替项，可对实验结果进行较好的归一化；调整微观孔隙结构如孔道/ 喉道半径、孔喉比、配位数等参数可以实现渗吸采收率的拟合；油藏尺度对基质/ 裂缝以及渗吸/ 驱替的划分，可准确反映开采初期含水率变化。

Volumetric reconstruction experiments and multi-scale simulation of tight oil reservoir with considerations of imbibition and displacement

TField experiences show, before prompt blowout after fracturing, soaking process can proceed to sweep the crude oil in minor pores through displacement and imbibition to enhance oil recovery. Tests and simulation have been conducted to analyze the mechanism in these processes: First of all, pressurized imbibition tests were conducted to simulate imbibition of fracture sidewalls under joint effects of differential displacement pressures and capillary force by adding displacement (Δp) in the dimensionless time. Relevant test results were processed through normalization; Secondly, models on pore scale were constructed based on CT scanning. By fitting with oil recovery in tight cores, relative permeability and capillary pressure of displacement and imbibition can be determined; In the final step, matrix and fractures were given different relative permeability and capillary pressures on field scale to simulate actual oil/ water flows in formation. Test results show: oil recovery of pressurized imbibition is significantly higher than that of spontaneous imbibition approximately by 10%~15%; By adding the displacement term in dimensionless time, better normalization of test results can be obtained; By adjusting microscopic pore structures, such as pore/pore throat radius, pore throat ratio, coordination number and other parameters, satisfactory matching between imbibition and oil recovery can be performed; Partition of matrix/fracture and imbibition/ displacement on field scale may accurately reflect changes in watercut in early development stages.