Study On Controlling Effect Of Reservoir Architecture On Remaining Oil Distribution

The Orinoco heavy oil belt in Venezuela is the largest heavy oil enrichment zone in the world.Due to the complexity of the internal structure of reservoirs,the distribution of remaining oil in horizontal well development process is not clear,and the degree of oil and gas recovery is less than 10%.In this paper,the braided river reservoir with high porosity and permeability in Morichal section of Ofinica formation,and the main development stratum in M block of Venezuela,are fully studied.Based on the development and distribution characteristics of reservoir architecture and quantitative parameters of reservoir architecture,the control effect of reservoir architecture on remaining oil distribution is explored by means of physical simulation experiments.The results show that:(1)the six-level and five-level architecture interfaces of flooding origin are relatively stable in Block M,and can be used as seepage barriers for fluid flow,which is one of the important factors affecting the distribution of remaining oil;(2)Because of the wandering characteristics of braided river deposits,the contact relationship between structural units such as core beach bar and braided channel is relatively complicated.The physical properties of reservoirs are quite different,leading to the overlapping of core beach and core beach.Five types of reservoir architectures,i.e.,core beach-core beach cutting type,core beach-braided channel overlapping type,core beach-braided channel cutting type and core beach-core beach facies separation type,have intensified the heterogeneity of reservoir architecture s,resulting in complex distribution of remaining oil;(3)Breaking through the drawbacks of the homogeneous model in the traditional macrophysical simulation experiments of remaining oil,the study area is the most widely developed.Taking into account the current situation of vertical well development in most braided river sandstone reservoirs in China,the design of this experimental scheme considers horizontal well and vertical well development methods,which makes the research results more widely applicable.(4)The visual results of the experiment show that the five-stage architecture interface shows strong impermeability,and the fluid is easily blocked during water flooding.Under the condition of horizontal well development,the reservoir utilization degree is higher.Most oil and gas are exploited in the control area of horizontal well.The remaining oil is concentrated in the blocking area of architecture interface and the top of reservoir.Under the condition of vertical well development,water flooding is easy to form an advantage at the bottom of single channel.The remaining oil is enriched in the upper part of the channel and the relatively low permeability area near the interface.(5)The distribution of remaining oil will be affected by the difference of physical properties among the four-stage architecture units,and the matching relationship between architecture units and development wells also results in different enrichment degree of remaining oil.Under the condition of horizontal well development,the inner development degree of the core beach with better physical properties is higher.The oil saturation in the structure unit drilled by horizontal well is often lower than that of other similar units.When it comes to vertical well development,the same rule exists.The remaining oil is more distributed in braided channel units with relatively poor physical properties.