低渗透油田油水两相低速非达西渗流规律研究

【作者】 石京平；

【导师】 向阳；

【作者基本信息】 成都理工大学 ， 油气田开发， 2006， 博士

【摘要】 本文从流体、多孔介质和流动状况三个基本因素出发，通过大量的实验研究和理论分析，探究了大庆外围低渗透油田油水单相及两相渗流的规律，并且利用非达西渗流理论提出了减小或消除启动压力负面影响的改善措施。本文所做的研究工作有：1、通过粘土矿物分析、压汞分析、电镜扫描、铸体薄片等分析方法，研究了大庆外围低渗透油田扶杨油层孔隙结构类型，指出储层的主要渗流孔喉半径为0.25～1.6μm，这种细微孔道增加了油水流动阻力，是低渗透储层产生非达西渗流的主要原因。2、通过不同温度下原油流变性的分析，指出大庆外围低渗透油田原油具有胶凝—触变性，而且在一特定温度下为非牛顿流体，温度偏低时为屈服值塑性流体，这也是低渗透油田产生非达西渗流的一个原因。3、通过调节温度改变流体粘度，研究了粘度对流体渗流曲线的影响，阐明粘度也会对非达西渗流产生影响。4、根据实验的需要，本文设计了“非稳态驱替-毛细管计量法”测定低渗透岩心的最小启动压力梯度，采用常规的“流量—压差”法测定拟启动压力梯度。5、通过一系列油、水单相和两相渗流实验研究了非达西渗流曲线的特征及其影响因素，指出油水两相渗流的拟启动压力梯度是含水饱和度的函数，它即大于残余油状态下的水单相渗流的拟启动压力梯度，也大于束缚水状态下油单相渗流的拟启动压力梯度，同时低渗透油层主要有两相存在，即使是束缚水状态下或者残余油状态下的单相渗流，其启动压力梯度大于油单相和水单相的拟启动压力梯度，单相水流动产生非达西渗流的渗透率界限为1×10^-3μm²；单相油流动产生非达西渗流的渗透率界限为5×10^-3μm²，这个结论在油水两相实验中也得到了验证。6、在两相渗流理论的基础上，建立了一套描述特低渗透储层的油水两相渗流公式，该公式不仅考虑了油水非达西渗流的影响，而且还考虑了毛管压力的影响。通过实验验证该公式可以应用到低渗透岩心低速渗流时的油水相对渗透率曲线测定。7、通过对大庆外围低渗透油田非达西渗流理论的分析和应用，提出了一些适合低渗透油田开发的改善措施，如井网加密措施；确定合理注水压力；注活性水降低注水压力等，都取得了一定实践效果和认识。更多还原

【Abstract】 Basted on three fundamental factors of fluid, porous medium and fluid condition, by plentiful experimental studies and theoretical analysis, the single-phase and oil-water two-phase flow seepage rules have been researched in Daqing periphery low permeability oil field. And using the non- Darcy seepage theory, some improving measurements that reduce and eliminate the negative influence of starting pressure have been proposed. The research work of this article includes:Based on the methods of clay mineral analysis, pressure mercury analysis, scanning electronmicroscope （SEM）, thin section analysis and so on, the type of pore result on Fuyang oil layer in Daqing periphery low permeability oil field has been studied. It is pointed out that the main flow throat radius of the reservoir was 0 .25 - 1.6um . Th i s kind of slight passageway increased the oil and water flow resistance, and this was the main reason of non- Darcy seepage in the low permeability reservoirs.Through the analysis of rheological property to crude oil under the different temperature, the study pointed out that the crude oil of low permeability oil field in Daqing periphery has the ge11ing-thixotropy, and it is anon - Newtonian flow at a specific temperature, it is a yield value plastic fluid when the temperature is lower than the specific temperature. This is also a reason that the low permeability oil field has a non- Darcy seepage.By adjusting temperature to change fluid viscosity, the impacts of viscosity on fluid transfusion curve were examined and also the impacts of viscosity on non-Darcy seepage were clarified.According to the need of test, a method was designed that "unsteady displacement-capillary measurement" determines the minimum starting pressure gradient of low-permeability core and the average starting pressure gradient using the conventional "flow-differential pressure" measurement.According to a series of single-phase or two-phase flooding of oil and water, the characteristics of non- Darcy flow curve and its influence factors have been studied. It pointed out the initial pressure gradient of oil-water two-phase flow are functions of the water saturation, it namely is bigger than the initial pressure gradient of water single-phase flow on residual oil condition, is also bigger than the initial pressure gradient of oil single-phase flow on inreducible water condition. At the same time, the oil layer with low permeability mainly existed two phase, even if it is the single-phase flow in the condition of inreducible water or the residual oil, the initial pressure gradient is bigger than the oil single-phase or the water single- phase initial pressure gradient. The oil single-phase flow has the non-Darcy flow with the permeability limit of 5×10^-3um², and water with1×10^-3um². This conclusion was confirmed by the oil-water two-phase flow experimental.Based on two-phase flow theory, a set of two-phase seepage formula describing especially ultra-low permeability reservoir has been established. This formula has considered not only the influence of oil- water non-Darcy seepage, but also the influence of capillary pressure. By testifying, this formula can be applied to the determination of oil-water relative permeability curve when low seepage core is low speed seepage.Through the theory analysis and application of non- Darcy seepage in Daqing periphery low permeability oil field, some improving measurement for the development of low permeability oil field——the infill of well pattern, the determination of reasonable water injection pressure, reducing water injection pressure by injection of surfactant water and so on has been proposed and has obtained certain practice effect and understanding.更多还原