The Studies Of Interwell Dynamic Connectivity In High Water Cut Oil Field

At present, after decades of waterflooding processes, the old oilfields in the world have already went into the stages of high water cut and high degree of recovery. In the process of oilfield development, the characteristics of high water cut, high degree of recovery, low injection water utilization rate and development benefit are all associated with macroporous channel. Reservoir is porous medium composed of various kinds of mineral deposits and the cementation of cement. In the middle and later periods of the oilfield development, because of the influence of the water flooding effect, mineral particles and cement in the reservoir began to dissolve, gap between particles become bigger. For those reservoir with better sorting characteristics, larger grain size, larger reservoir permeability, due to the difference of reservoir permeability between each series of strata, the oil-water phase separates due to the different density. After the long-term washing by injection water, for the difference of permeability, plus the gravitative stratification of oil and water, there will be easily formed a channel which has big porosity and high permeability. Subject to the above, injected water priority dash to production wells along the strip, gradually formed interconnected, ribbon distributed, high penetrative and heavily washed channels whose radius about30μm～5mm.Predecessor has done massive research on formation mechanism and identification methods on macroporous channel. Although obtained the certain research achievements, the results are far from to satisfied water flooding development needs. This paper widely investigates and studies the domestic and foreign literature, synthetizes predecessor’s research results on the reason of macroporous channel. The external factors include hydrodynamic shocks and fluid friction carrying agent, and the internal factors include the degree of consolidation in the rock, permeability, crude oil viscosity and sedimentary rhythm. The results showed as follow:The sand is easily separated for the degree of consolidation is so weak that only small scouring velocity is required. The macroporous channel will be formed very easily when the high permeability zone be washing heavily. If the fluid viscosity is greater but the degree of consolidation is weaker, the moving of sand grains will be more easily. In different sedimentary rhythm model, the advancing speed of injected water is different in every permeability layer, when permeability contrast increased, the higher the injection rate, the faster the frontal movement, and the earlier the water breakthrough, macroporous channel will be more easier formed in this condition. After the oilfield entering into the high water cut stage, we must take massive tapping potential measures to increase recovery efficiency. But the key to success is clearing the distribution characteristics of macroporous channel. Therefore, how to effectively identify and describe macroporous channel is a urgent task when oilfield enter into the high water cut stage. At present, the methods of identify macroporous channel mainly rely on the dynamic data, static data and various monitoring data to make comprehensive recognition. The main methods are:The first one is Tracer Testing, adds tracer slug into injection well and monitors the tracer output from production well, according to the tracer output curves to estimate the formation parameter. The second method is analyzes the feature of high permeability zone in well test data, uses methods such as interference well test, non-stabilized well test to identify the high permeability layer or well. The third method is bases on the data of injection profile logging, calculates the cumulative water injection multiple in well-group to research the existence of ineffective circulation layers. The fourth method is combines Math with Reservoir Engineering to establish fuzzy identification system. The fifth method is uses numerical simulation technique to study ineffective circulation. The last one is analyzes the changes of property parameter by seismic technology or logging technology to identify macroporous channels’ distribution in the reservoir. The author makes a complete analysis on the method of identifying macroporous channel, because each method has its own principle, technical characteristic, applicable condition and the key of problem solving, so we should according to actual condition to choose a suitable method.During the oil field development, reservoir connectivity isn’t only important content of reservoir evaluation, but also the basement of development and managenment program. In water injection projects, the knowledge of reservoir connectivity is particularly important to maximize oil recovery. As the developme nt of reservoir, reservoir characteristics have changed a lot and the static state connectivity can not reflect layer property correctly. Work of dynamical interwell connectivity present prominent theory value and practical sense. Through the study of the flow simulation and history matching of the test area, the injection-production relationship at different time phase can be obtained from injection wells and production, and then quantify the injection rate and production rate between the injection-production well. According to the injection-production relationship of the regional and local injection and production wells, we can find the more thick well pair in the flow tube during continuous period. The more d ense the streamline, or the more thick the flow tube, the greater the flow of the region; otherwise, the less the flow of the region.This article mainly studies from the two aspects of channel identification an d dynamic connectivity between wells. We can judge the development situation of large channel in the reservoir through the recognition software, then simulate the connectivity between wells through the Rdosv software. Then we can confir m the preferential flow trends between oil and water wells.