Liu Yuzhang

Physical modeling of in-depth fluid diversion by “gel dam” placed with a horizontal well

Abstract Ineffective cycling of injected water in high permeability zones during water flooding processes can be an issue in positive rhythm reservoirs. The “gel dam” in-depth fluid diversion technique is proposed to ameliorate this problem. The technique involves the injection of gel by horizontal wells drilled in the highly permeable and strongly swept zones of thick positive rhythm reservoirs. The injected water then will bypass the “gel dam” and be diverted into the upper, lower permeability zones. As a result, the sweep efficiency and oil recovery from the overlying low permeability zone can both be increased. A 2D visible sand-pack physical model was set up to test the process, and a video camera was used to visualize the “gel dam” fluid diversion effects. The results of the experiments indicated that, with one or two “gel dams”, both the sweep volume and ultimate oil recovery increased greatly, while the rate of water cut decreased. Compared with physical models with no “gel dam”, the ultimate oil recoveries of those with one or two “gel dams” increased by 17.6% and 27.3%, respectively. By applying the “gel dam” in-depth fluid diversion technique, difficulties in the in-depth placement of plugging agents can be resolved, and the sweep efficiency of positive rhythm reservoir can be increased significantly.

Laboratory researches on deep fluid diversion agent with high strength and retarding swelling characteristics

Abstract Macromolecule networks were introduced into the networks of normal sopping swelling materials by redesigning the materials molecule structure, and thus forming materials with the characteristics of retarding swelling, high strength and the structure of interpenetrating networks. The microscopic structure of the materials was analyzed by TEM and SEM, and the homogeneous structure of interpenetrating networks was observed from TEM and SEM images. Its static water absorption performance and mechanical performance after water absorption indicate that the total swelling time of the retarding swelling particles, which can be suspended and dispersed in water, is more than 20 days. After swelling, the modulus of elasticity (G′) of the sample is over 104 Pa, higher than that of the general swellable particle diversion agent. The excellent deep part injection and plugging performances were confirmed by physical simulation experiments. These performances overcome the shortcomings of quick swelling, low strength and less placement depth.

Mechanism research of in-depth fluid diversion by “gel dam” place with horizontal well using X-ray CT

Abstract According to the concept of in-depth fluid diversion by “gel dam” place with horizontal well, its EOR mechanism is studied by means of laboratory water flooding experiment combined with X-ray computer tomography (CT) technique. In the experiment, the artificial cementing heterogeneous model is casted with epoxy resin on surface, and the flooding processes before and after the “gel dam” formed are scanned dynamically by X-ray CT. Through observing the distribution feature of gel dam, tracking the oil and water distribution, water flooding streamline change, oil saturation distribution and its dynamic variation, it is indicated that “gel dam” can effectively shut off the deep channeling in higher permeability layer, and divert the injected water into upper low-permeability layer to displace the remaining oil therein. After “gel dam” is formed, the ultimate oil recovery by water flooding increased by 16.7%, and the water cut ascending velocity slowed down. With “gel dam” technique, gel can be placed in the in-depth reservoir zone to achieve in-depth fluid diversion, which increase the water flooding sweep efficiency and oil recovery. “gel dam” in-deep fluid diversion technique is a promising EOR method for positive rhythm thick reservoirs.