Summary For reservoirs containing oil with a high total acid number, the alkali-cosolvent-polymer (ACP) flood can promote the formation of microemulsion rather than viscous macroemulsion and achieve good mobility control. The enhanced oil recovery (EOR) performance of ACP flood has been studied at core and reservoir scale in detail; however, the effect of ACP flood on residual oil still lacks enough research. In this paper, a micromodel with a single channel is used to clarify the dynamic effects of alkali-cosolvent (AC) and ACP solutions on the residual oil after waterflood. Based on this, medical computed tomography (Medical-CT) scan and microcomputed tomography (Micro-CT) scan are used in combination to visualize microscale flow and reveal the mechanisms of residual oil reduction during ACP flood. The heterogeneous core plugs containing two layers of different permeabilities are used for coreflood experiments to clarify the EOR performance of ACP flood in heterogeneous reservoirs. The oil saturation is monitored by Medical-CT. Then, two core samples are drilled in each core plug that is used in the coreflood experiment. The decrease of residual oil saturation caused by ACP flood is further quantified by Micro-CT imaging. Results show that ACP flood is 14.5% oil recovery higher than AC flood (68.9%) in relative high permeability layers (HPLs) and 17.9% higher than AC flood (26.3%) in relative low permeability layers (LPLs). Compared with AC flood, ACP flood shows a more uniform displacement front, which implies that the injected polymer effectively weakened the viscosity fingering. This is similar to the experimental results demonstrated visually in the micromodel experiments. ACP solution first generates an oil bank by the mobility ratio improvement to mobilize residual oil and then dissolve and emulsify residual oil under ultralow interfacial tension (IFT) conditions. Moreover, a method that can calculate the ratio of oil/water distribution in each pore is developed to establish the relationship between the residual oil saturation of each pore and its pore size, and concluded that they follow the power-law correlation.

Horizontal drilling and hydraulic fracturing can effectively increase the contact area between fractures and reservoir, which are important method to realize the economic and efficient development of unconventional reservoirs. In the traditional fracturing scheme design, “sweet spots” guide the fracturing construction. However, due to lack of the interaction process of using engineering data to validate and correct the original data until the final convergence with reality, it cannot be dynamically optimized and matched in time. To overcome above shortcomings, this paper proposes a new network fracturing scheme design workflow based on the integrated geological-engineering integration (GEI) method. The tight carbonate reservoir X layer of oil field A in the Middle East is set as a case. A comprehensive sweet spot evaluation method is established using the partial correlation coefficient analysis method, considering the physical properties and fracturing performance of reservoir. The comprehensive sweet spot model is calibrated and optimized using experimental data, stimulation parameters, well tests, and production data. Based on the comprehensive sweet spot model, the quadrant chart is plotted and varied single well fracturing scheme designs are implemented for different quadrant areas. The numerical simulation results show that it can improve the development efficiency of unconventional reservoirs.