【作者】 冯树义；

【导师】 孙彦彬；

【作者基本信息】 大庆石油学院 ， 油气田开发工程， 2010， 博士

【摘要】 由于低渗透油田存在启动压力梯度,注水方式、注采井距不仅影响水驱控制程度,而且影响有效驱动系数,当注采井距超过一定值时,驱动压力梯度小于启动压力梯度,这部分油层的原油将不能够有效动用。目前,人们对低渗透油田有效驱动系数与井网、井距关系之间只是进行了定性的分析,缺乏定量研究,本文采用低渗透油层非达西渗流数值模拟方法,定量研究注采井网、启动压力梯度与有效驱动系数、水驱采收率的关系,结合经济评价,进行井网优化。本文以大庆外围榆树林低渗透油田为研究对象,首先进行基础地质研究,分析储层岩性特征、物性特征、孔隙结构特征,评价储层敏感性,确定常规水驱油效率,研究发现扶杨油层主要渗流通道的有效半径为0.25～0.65μm,扶杨油层渗滤性能、储集能力较差,排驱压力较高,储层开采难度大。根据室内实验结果,岩心驱油效率较低,一般在16.48%～38.70%之间,平均为32.80%。通过室内实验,开展了低渗透岩心非达西渗流特征研究,测定启动压力梯度与渗透率关系,当渗透率小于3×10-3μm2时,随着渗透率的降低,启动压力梯度急剧增大。在分析低渗透岩心非达西渗流力学机理的基础上,建立了低渗透油层非达西渗流三维、三相数学模型,对该模型进行差分求解,分别考虑油井定压或定产,水井定压或定注入量条件,编写数值模拟软件,应用低渗透油层非达西渗流数值模拟方法,定量研究启动压力梯度、井距、注水方式对开发效果、有效驱动系数的影响。模拟结果表明:300m井距下,随着渗透率从1×10-3μm2增大到12×10-3μm2,启动压力梯度由0.4481MPa/m降低到0.0377MPa/m,波及系数从0.00%增大到76.53%,水驱采收率从0.00%增大到24.29%。渗透率为5×10-3μm2的油层,井距从350m缩小为150m,波及系数从33.60%增大到62.80%,水驱采收率从11.10%增大到21.95%;不同注水方式对开发效果有较大影响。在此基础上,应用油藏工程方法,考虑低渗透油田井网部署对水驱控制程度、有效驱动系数的影响,建立低渗透油田水驱采收率与井网密度的关系式,定量研究不同原油价格下最优的井网密度和井距,为井网优化调整提供技术指标;最后,以榆树林油田东16区块为例,开展井网优化数值模拟研究,在充分分析现井网开发条件下剩余油分布规律的基础上,根据井网优化技术界限,设计了4套加密调整方案,并对不同方案进行对比优选,对优选的方案进行了现场应用,收到了良好的开发效果,表明该研究方法对低渗透油田井网优化具有重要的理论价值和实际应用价值。更多还原

【Abstract】 As starting up pressure gradient exists in low permeability reservoirs, water injection mode and injector producer distance affect not only waterflood control extent but also effective driving index. Driving pressure gradient is less than starting up pressure gradient and the part of oil layers can’t be employed effectively when injector producer distance exceeds a fixed value. At present, qualitative analysises are carried out on relation between effective driving index, well pattern and well spacing, which are still lack of the quantitative analysises in deep level. This paper will launch quantitative studies on relation between flooding pattern, starting up pressure gradient and effective driving index, water drive recovery efficiency by the method of non-darcy flow numerical simulation and then proceed well pattern optimization coupled with economic evaluation.This work will take Daqing peripheral low permeability oilfield of Yushulin as an object of study, at first base geologic researches are carried out, including analyzing lithologic characteristic, physical property, pore structure feature, reservoir evaluation and fixing routine water displacement efficiency, it finds that effective radius of Fuyang oil layers flow matrix is between 0.25μm and 0.65μm, filtration and storage abilities are poor, expulsion pressure is high and the oil layers are hard to recover. For Fuyu oil layers, core samples displacement efficiency is between 16.48% and 38.70%, average value is 32.8% which is quite low. Later nondarcy flow laboratory investigations of low permeability cores are carried out by way of laboratory experiments to to survey and evaluate the relation between starting up pressure gradient and permeability, starting up pressure gradient will rise substantially with the decrease of permeability when permeability is below 3×10-3μm2. Analyze nondarcy flow mechanism of low permeability cores, establish a basic math model to describe nondarcy flow, then a three-dimensional and three phases nondarcy flow math model of low permeability is established, the finite difference method was used to solve the model, and a corresponding numerical simulation software is developed considering the conditions of rate-specified pumping, pressure-specified pumping, rate-specified injection, pressure-specified injection respectively. Quantitative research about influence exerted by starting up pressure gradient, well spacing, water injection mode on development effect and effective driving index is carried out by way of nondarcy flow numerical simulation of low permeability, simulation results show that as permeability rise from 1×10-3μm2 to 12×10-3μm2, starting up pressure gradient decreses from 0.4481MPa/m to 0.0377MPa/m and sweep efficiency rises from 0.00% to 76.53%, water displacement recovery rise from 0.00% to 24.29% when well spacing is 300m, sweep efficiency rises from 33.60% to 62.80% and water displacement recovery rise from 11.10% to 21.95% as well spacing shrink from 350m to 150m when permeability is 5×10-3μm2, different water injection modes have great impact on development effects. On this basis, the relation between low permeability oilfield water displacement recovery and well spacing density is established by way of reservoir engineering considering the influence exerted by well pattern disposition on waterflood control extent, effective driving index, analyze optimal well spacing density and well spacing quantificationally under conditions of different oil prices and different tendering practice to provide technical descriptions for well pattern optimization and adjustment. At last, this paper tales Dong 16 block of Yushulin oilfield as an example, well pattern optimization numerical simulation study is carried out, according to technology limit of well pattern optimization, four proposals are designed on the basis of the law of distribution of remaining oil under the condition of present well pattern, through comparing and selecting these proposals, the preferred proposal is applied to case study and good development results have been obtained. Obviously, the research method has theoretical and practical significance to well pattern optimization of low permeability oilfield.更多还原