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Aiming at the problems of early water appearance, rapid increasing in water-cut and difficulty in development of bottom-water reservoirs, in this paper, we have used a conceptual numerical model to quantitatively analyze major influence factors on the coning rule and finally analyzed the remaining oil formation mechanism of these types of reservoirs. The results showed that the heterogeneity mainly causes the uneven advancement of the bottom-water and leads to local remaining oil. The higher the oil viscosity, the faster the non-uniform coning of bottom-water, which accelerates the well flooded and the enrichment of remaining oil. The positive rhythm reservoir is more likely to form water cones than the anti-rhythm reservoir, further exacerbating the accumulation of residual oil at the top of the reservoir. Differences in the seepage field are caused by different well patterns, which leads to different distributions of remaining oil during development. The lower the oil column height results in the non-uniform coning rate of bottom-water accelerating, which intensifies the flooding of oil wells and the enrichment of remaining oil. The water coning rules and remaining oil distribution rules studied above provide a solid foundation for the reasonable and effective development of bottom-water heavy oil reservoirs and has a broad field application prospects in the future. [ABSTRACT FROM AUTHOR]

Aim at solving the problem on the time-variant of reservoir parameters such as permeability and porosity during the water flooding process of sandstone reservoirs and the lack of microscopic mechanism studies, which has an important impact on reservoir development. In this paper, based on the a network model typical unconsolidated sandstone reservoirs and a comprehensive consideration of the microscopic mechanisms of loss, trapping, and migration of micro-particles in the pore throat, a three-dimensional network simulation method of layer parameter variation was used to simulate and study the change law of physical parameters such as porosity and permeability under different conditions. Simulation results showed that: In the process of long-term water flooding, particles in the pore throat will fall off, and some particles will flow out of the reservoir with the injected fluid, resulting in a distribution of pore throat radius. There was a small change in the circumference, and the pore throat radius showed an overall increasing trend, and the reservoir connectivity was enhanced. The permeability and porosity gradually increased, and the increased amplitude gradually decreased. The strength of water injection and the degree of clay cementation affect the extent of changes in reservoir permeability and porosity by affecting the exfoliation rate of the particles. The study further reveals the time-varying microscopic mechanism of sandstone reservoir parameters, and provides a theoretical basis for the numerical simulation of time-varying reservoir parameters. [ABSTRACT FROM AUTHOR]

The ratio of injection-production control area is an important aspect in evaluating the development effect and calculating oilfield development index. Conventional approaches to determine the ratio of injection-production control area neglect the heterogeneity of the reservoir and require long time simulating and a lot of complex iterations. This paper establishes a prediction formula to quickly determine the ratio of injection-production control area in triangle well pattern. A total of 410 sets of streamline models are built to acquire the database. Permeability, oil saturation, injection-production pressure drop and injector-producer spacing are selected as independent variables to establish the prediction formula by multivariate parametric regression. Based on error analysis and application, the accuracy of this prediction formula is approved. Results indicate that the prediction formula has a correlation coefficient R2 of 0.96, representing a satisfactory performance. Normality and homoscedasticity tests and standardized residual diagnostics demonstrate the statistical significance of the results. The application of this prediction formula shows an excellent match between the predicted and actual injection-production area, which further confirms the accuracy of this prediction formula. The established prediction formula can effectively and accurately decide the ratio of injection-production control area for waterflooding reservoir. [ABSTRACT FROM AUTHOR]