The Combination Technology Of Deep Reservoir Water Shutoff-Huff And Puff Production In Tight Reservoirs

Due to the ultra-low permeability matrix and strong formation heterogeneity in the tight reservoirs,the water cut of production wells increases rapidly and the oil production decreases rapidly,leading to a low reservoir recovery.With the aid of physical simulation,the main mechanism,dominate factors and related laws of deep reservoir water shutoff-huff and puff production technology in tight reservoirs are studied.A combination technology of deep reservoir water shutoff-huff and puff production based on a single production well is developed.In view of the special requirements of the complex tight reservoir conditions on the performance of huff and puff fluid and water shutoff fluid,based on the evaluation index of emulsifying ability and supplemented by interface performance,a kind of composite surfactants system named TIECC agent with high-efficient"oil displacement"and"assist plugging"function is developed,and its emulsified oil rate can be as high as 75%.In order to solve the contradiction between the injectability of water shutoff fluid and the plugging ability in deep reservoir,a kind of colloidal particles with automatic aggregation function(CSA colloidal particles)is developed.The test results show that the CSA colloidal particles have both good dispersibility and injectability.They are able to maintain their stable properties under the Calcium&Magnesium ions up to 2×10~4 mg/L within the formation water.No matter using as the reservoir conformance control fluid or the production well water shutoff fluid,the plugging rate of the CSA colloidal particles in the channeling-path can both exceed 90%.In addition,the size of the CSA colloidal particles can be precise synthesized within the scope of 50 nm～100μm.Due to the scale limitations of the conventional small core models and the structure defects of the conventional huff and puff production experimental devices,the energy(pressure)dynamics in each huff and puff production stage cannot be high accurately simulated with a practical reservoir,resulting in a great error between the laboratory experimental results and the field practical production characteristics.In order to solve above technical problem,a novel"deep reservoir water shutoff-huff and puff production simulation experimental setup"is invented.With the aid of the invented setup,the accurately simulation of the energy storage dynamics in the fluid injection process and the energy release dynamics in the production process to the practical reservoir can be achieved.In addition,the pressure fluctuation stabilizer in the setup can effectively reduce the distortion of experimental results caused by human operation.The test results show that the production performance of the oil well Xi-233 in Changqing Oilfield is successfully simulated by this invented experimental setup.The reservoir pressure,liquid production,oil production and water cut performance in the laboratory simulation experiment are all highly consistent with that of the oil well Xi-233.With the aid of the invented simulation experimental setup,the dominant mechanism and related laws of deep reservoir water shutoff-huff and puff production in tight reservoir are studied.The results show that the reservoir recovery of deep reservoir water shutoff-huff and puff production and the injection amount of the CSA colloidal particles show a non-monotonic relation.Taking 0.3～0.6 PV of the channeling-path as a boundary,too high or too low injection amount of CSA colloidal particles will lead to a reduction of the recovery;The reservoir pressure decline rate is verified to be the dominate factor affecting the production performance of a tight reservoir,and the recovery is monotonically decreasing with the reservoir pressure decline rate.The implementation of deep reservoir water shutoff using the CSA colloidal particles can effectively reduce the reservoir pressure decline rate,so as to significantly improve the reservoir recovery.In addition,it is confirmed that the advantage superposition synergistic effect of the CSA colloidal particles-TIECC agent slug is the dominate mechanism of significantly enhancing the oil recovery under the combination technology“deep reservoir water shutoff-huff and puff production”.The relationship between deep reservoir water shutoff-huff and puff production performance and the main technical parameters is investigated.The results show that the reservoir recovery of the deep reservoir water shutoff-huff and puff production technology by decomposing the CSA colloidal particles and TIECC agent into several small slugs is significantly higher than that of with one large slug under the same injection amount;The production performance under the CSA colloidal particles-TIECC agent multiple rounds of deep reservoir water shutoff-huff and puff production mode is better than that of single round by continuously injected with the same slugs combination.The experimental results show that taking 0.1 PV_c(PV_c represents the pore volume of the channeling-path)TIECC agent and 0.1 PV_c CSA colloidal particles as a slug group,couple with three rounds of deep reservoir water shutoff-huff and puff from far well to near well mode contributes to obtain the best production behavior,and its recovery can reach 43.51%.The research results show that the multi-round deep reservoir water shutoff-huff and puff production combination technology is also suitable for medium and high permeability reservoirs,and its laboratory recovery is more than 50%.This research achievements would provide a promising technology for improving the production benefit of such tight reservoirs and some others with bad geological structure.