摘要
大庆和长庆低渗透油藏开发结果表明,气测渗透率相近的油藏开发难度和效果迥异,这种现象对开发决策和产能建设规划带来了很大的不确定性。目前低渗透储层的分类评价工作主要以渗透率进行展开,所以有必要深入研究低渗透储层分类评价方法。
论文首先论证了主流喉道半径、可动流体饱和度和启动压力梯度作为低渗透储层特性评价参数的必要性,同时引入粘土含量及类型和地下原油粘度,组成了低渗透储层评价参数体系。
给出了单参数分类界限,对大庆和长庆低渗透区块进行了单参数评价,各参数并不总是处在同一类别,因此应用模糊数学理论建立了低渗透储层模糊综合评价方法。首先对比分析了常用隶属度函数和常用权重确定方法的优缺点,应用层次分析法对五个参数的权重进行了计算,采用变权理论解决评价区块缺少评价参数的问题。根据综合评价值,将低渗透储层分为四类,一、二类在目前的技术条件下能够实现有效的开发,三类是目前正在攻关的储层,四类是目前技术难以动用的储层。
应用建立起来的模糊综合评价方法对大庆和长庆油区的低渗透区块进行了评价和对比分析,评价结果显示同一类储层,大庆和长庆低渗透储层渗透率相差很大,大庆低渗透储层渗透率远大于长庆低渗透储层。长庆低渗透区块和单井的评价结果和实际开发效果表明,综合评价值越大单井的生产能力越强。利用该方法对长庆特低渗透储层进行了综合评价,长庆0.3毫达西储层主要指综合值小于0.6的二类下限和三类储层,这为长庆油田指明了攻关储层类型。
基于神经网络方法建立了低渗透储层智能化评价方法,并编制了软件。以长庆7个区块为学习样本进行了智能化培训,建立起了评价参数与单采指数之间的关系。应用神经网络方法对长庆低渗透区块的产能进行了预测,预测趋势与单井采油强度趋势基本一致。对长庆9区块的单采能力进行了预测,为油田下一步开发投资提供了参考。
The exploitation of low permeability reservoirs in Daqing and Changqing tells that there is a great disparity in exploitation difficulty and effect, although the lateral permeability is similar. The active reservoir classification and standard system focus on the key factors of permeability, which adds uncertainty to the developing policy and construction programming. So, it is necessary to do more research on how to classify the reservoirs.
Firstly, the paper demonstrates the necessity of the low permeability reservoirs' analysis factors that include main throat radius, movable fluid saturation, and starting pressure gradient, then the contents and types of clay and the viscosity of underground crude oil added in. All above build up the system of low permeability reservoirs' analysis factors.
Following the single kind of factor range, the analysis for certain factor gotten from low permeability reservoirs in Daqing and Changqing shows that the factor is unsteady. In this condition, fuzzy mathematical comprehensive evaluation on low permeability reservoirs, which is based on fuzzy mathematics, is in use. First of all, with the comparison between advantages and disadvantages of both membership function and conventional method of deciding weight, the analysis hierarchy process(AHP) calculates various percentages of five factors, then the variable weight theory solves the lack of sector analysis factors. According to the integrative analysis value, the low permeability reservoirs are separated into four kinds: the first and the second can be effectively developed under the actual technology; the third is the reservoir that scientists do research on; the forth is undiscovered.
With fuzzy integrative analysis system mentioned above, all analysis and comparison results gotten from low permeability reservoirs in Daqing and Changqing show that the permeability of low permeability reservoir in Daqing is much higher than the ones in Changqing, when the reservoirs are of the same kind. The analysis and actual developing results of single well and the whole section in Changqing prove that the high integrative analysis value means high single well production. The same method works in the super-low permeability reservoir in Changqing. The reservoirs with 0.3md in Changqing is the floor level of the second kind mentioned above or the third ones whose integrative value is lower than 0.6. It is significant for making clear the target reservoir in Changqing oil field.
The intellective analysis system for low permeability reservoir, which is based on nerve cell network, has been made into software. The software takes the 7 sections in Changqing as examples for intellective training, and establishes the relationship between analysis factor and single production index. The production prediction under the nerve cell network is almost equal to the oil extraction strength of a single well. The prediction of single production ability for the 9 sections in Changqing offers valuable references for the future development and investment.
引文
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