Study On Development Effect Evaluation And Potential Tapping Measures For Water Flooding In C Reservoirs

The reservoir C is a high porosity and high permeability sandstone reservoir. After 40 years of development, It's water cut as high as 89.04% and it has already entered the ultra-high water cut stage. C reservoir experienced five development stages:natural depletion phase, early stage water flooding, subdivision of reservoir stage, perfect the pattern and stabilizing oil water control oil comprehensive stage. At present, because of the casing damage wells are shut down and stopped injecting and the high water-cut wells are stopped producing and so on, the original well pattern form is destroyed and bigger reserves is out of control. With the vague understanding of residual oil distribution, the control of residual oil in reservoir and the realization of the goal of stabilizing oil production and water control in the later stage has been effected. Therefore, there are several key factors that load to the enhance of the reservoir oil recovery as follows:the evaluation of reservoir water-flooding development effectiveness should be based on a fresh recognition of the geologic feature, the analysis of residual oil distribution feature, optimal research of development scheme for small oil sand bodies, explore reasonable method of tapping potential.In this paper, reservoir engineering method is used to calculate and evaluate the control degree of water drive reservoir, series of strata adaptability, well network adaptability, energy status, water-cut escalating rate, water storage rate and water drive index of C reservoir. The ultimate recovery of reservoir which is method by five kinds of methods is 47.54%.Compared with the present 40.53% of recovery degree, it still have space to increase the production. It also used 4 kinds of functions which are deduced by the water drive curve in narrow sense to forecast the reservoir's ultimate water flooding volumetric sweep efficiency. At the same time, a new formula based on generalized water drive curve (Yu Qitai) is proposed to predict the water flooding volumetric sweep efficiency.According to the analysis, the reservoir layer division is reasonable currently, rational formation pressure maintenance level are more than 80%, a good energy maintain level, and water cut rises rate consistent with type A water drive curve theory of water increased by the rate of curve, the implementation of the comprehensive adjustment measures achieved the objection of stabilizing oil production and controlling water cut, but it still has the problems such as the corresponding injection and production rate of the existing layers is low, the production wells are seriously one way effective, well improve the degree of difference, a bad well net perfect degree, well network of reserves control degree is low, actual number of injection wells is less than the theoretical number of wells, water rate and water flooding index declined and so on.It indicates that during the later stage of the reservoir the existing well net should be complicated and should increase the control degree of the residual oil.According to the technology of numerical simulation, It analyzed and summarized the residual oil distribution feature and It is considered that the residual oil is mainly distributed in the main oil layer of small fault and block region, injection production well pattern is not perfect position and the high position of the structure, and non-main oil layer of well pattern is not perfect sand body and unused small sand body. And it also has a classification and optimal selection on the reservoir well net type of type one and type two of sand bodies and it proposes a conclusion that the type one should adopt the line shape well net pattern which the vertical injection well array Parallels to the structural trend and the type two should adopt the vertical well net pattern that a injection well with two production wells.According to the result of water flooding development effectiveness evaluation, residual oil distribution feature and the result of different sand bodies well net and well type optimization, It designs the next step of development measures.The result of forecast by numerical simulation indicates that the daily oil production increases from 29.6t to 87.0t after the regulation and also the annual water cut decreases from 96.9% to 94.5%, and the recovery has increases 3.8 then it doesn't use the development measures. It indicates that the design of the measure is reasonable and it has a better production increasing effect.