Experimental Study on Water and CO2 HnP With Tight Oil Reservoir Cores

Abstract Water injection is a conventional way to increase tight oil recovery, which faces challenges of high injection pressure, low injectivity, and water channeling. Therefore, further research is urgently required on how to efficiently recover oil from tight reservoirs. In this article, the Lucaogou Formation in Xinjiang Oilfield, China, is selected as the target area. The properties of tight rock samples are tested with a set of experiments. The average permeability and porosity are 0.044 × 10−3 μm2 and 0.170, showing a tight property. Combined scanning electron microscope (SEM) with pressure increase and decrease experiments, the stress sensitivity, and threshold pressure gradient (TPG) of the samples are identified. The wettability of samples with different fluid systems has been analyzed by X-ray diffraction (XRD) and the measurement of contact angle. CO2 HnP (huff-n-puff) can obtain the best oil recovery, followed by activated water HnP which can change the rock from oil-wet to water-wet.