【作者】 杨钊；

【导师】 宋考平；

【作者基本信息】 东北石油大学 ， 油气田开发工程， 2010， 博士

【摘要】 随着大庆外围油田开发的不断深入,生产中的许多矛盾也逐渐显现出来,概括起来有3个方面:一是已开发油气田含水快速上升,产量递减加快,开发效果变差;二是开发储量品位越来越低,主要集中在特低丰度和特低渗透储层中,注水开发的技术难度越来越大;三是开发潜力和有效措施逐渐减少,成本上升,投入与产出的矛盾日益加大。在这种形势下,原有的评价方法、优选技术,开采方式和方法难以满足低渗透油田持续发展的需要,针对这一情况,本文从低渗透油藏微观结构特征入手,对低渗透油藏进行了分类,在此基础上提出了开发对策,从而促进外围低渗透低品位油藏的有效动用和商业性开发。为了研究低渗透油层孔隙结构的特征,本文利用恒速压汞实验、金相电镜实验,结合现场的已有实验数据,研究了不同渗透率天然岩心中渗透率、平均孔道半径、平均喉道半径、孔喉比、迂曲度、配位数、形状因子、分形维数等参数的的分布规律,取得以下认识:不同低渗透岩石孔道半径分布规律较为接近,喉道半径分布差异明显,孔道半径与渗透率相关性较差,喉道半径与渗透率具有明显规律性,二者呈正相关关系;总体上看,低渗透储层的渗透率主要受喉道半径控制;相同渗透率条件下,其喉道分形维数与孔道分形维数无明显大小关系,说明喉道与孔道在复杂程度上差异较小。低渗透储层水驱效果除了受孔隙结构影响外,还与低渗透岩石的渗流规律有关。本文应用核磁共振方法对可动流体饱和度进行了分析,结果表明:可动流体饱和度与驱油效率间存在很好的对应关系,可动流体饱和度比渗透率参数更能反映储层开发潜力;通过启动压力实验分析,渗透率小于1×10-3μm2时,随着渗透率的降低启动压力梯度急剧增加,说明渗透率低于1×10-3μm2时,常规水驱方法已经不适用,需要探索其它驱替方法;对比水驱启动压力梯度与气驱启动压力梯度变化曲线,可知水驱与气驱启动压力梯度变化规律近似,水驱启动压力梯度大于CO2驱启动压力梯度,岩芯渗透率大于0.5×10-3μm2时,气体启动压力梯度数值较小,随渗透率增大启动压力梯度下降趋势变缓;相对渗透率曲线研究表明:低渗透储层的渗透率与采收率有较强的相关性,随着渗透率的降低,驱油效率降低,当渗透率低于10×10^-3μm²时,采收率降低幅度增大,最低可降至16.5%,这说明渗透率低于10×10^-3μm²时水驱效果较差;孔喉比对残余油饱和度有较大影响,随着孔喉比增大,残余油饱和度增大,两相流跨度变小,水驱采收率降低。在系统研究低渗透岩石孔隙结构和渗流特征的基础上,选取了渗透率、孔喉比、喉道半径和启动压力梯度4个参数,利用聚类分析法把大庆外围储层分为4类;分析统计了大庆外围区块的特征,结果如下:外围区块总体上埋藏深度较浅,1500m以下的区块有52个,地质储量占65%;外围油田有49个区块发育潜裂缝、微裂缝和显裂缝,地质储量占78.3%,26个区块裂缝不发育,朝阳沟、榆树林、头台油田的裂缝以东西向为主,其它方向发育裂缝较少;外围已开发区块储量丰度21×10⁰4t/km²～92×10⁴t/km²,其中储量丰度小于50×10⁴t/km²的低丰度区块有25个,地质储量占44.8%,,丰度大于50×10⁴t/km²的特低丰度区块有54个,地质储量占扶杨油层总量的87.7%,平均储量丰度为58.9×10⁴t/km²,总体上属于较低丰度。针对以开发区块选含水率、注采比、水驱控制程度和采油速度对开发水平分级,为开发对策的制定提供了依据。根据大庆外围油田已开发区块的生产数据,研究了加密调整措施的作用,分析了大庆外围不同渗透率油田加密调整效果,确定不同类型油藏的加密调整方法;开展了低渗透储层的压敏效应实验,结果表明:无裂缝存在时,随着喉道半径减小,压敏效应变的显著,喉道半径是影响压敏效应的关键因素,渗透率相同时,裂缝对压敏现象影响较小;重点对超前注水、二氧化碳驱的机理进行了研究,给出了不同渗透率储层的超前注水和二氧化碳驱油效果;针对空气驱进行了可行性研究,当渗透率大于0.2×10-3μm²时,能够形成稳定的燃烧前缘,随渗透率降低,燃烧前缘的推进速度有所降低,但降低幅度较小;不同孔喉比,在相同的轴向比例位置上,温度的上升速度不同,当孔喉比较小的时候,温度上升的速度快,说明孔喉比对燃烧效率有一定影响。分析了径向水平钻孔技术的应用效果,该技术具有可定向和可定深的特性,可以对受效差的井进行改造,缩短注采排距,完善注采关系,能够调整层间或平面矛盾。在低渗透油藏分类的基础上,结合文中给出的开发水平分级情况,针对不同类型油藏提出了开发对策,为大庆外围区块的合理开发提供了理论依据。更多还原

【Abstract】 With the further development of the outskirt area surrounding Daqing oil field, many problems related to production appear gradually.Firstly, the production in the development process of the oil field is becoming less effective, the increase of the water cut and the decline of the production are both much faster than before; Secondly, the less grade of the production formation is, the more difficult in water flooding development technique is. The reservoir is mainly located in the area with much lower abundance and permeability.Thirdly, the develop -pment potential and effective methods decrease gradually, while the cost and the contradiction-n between input and output are increased day by day. In this condition, the requirement of continuous development of the low permeable oil field cannot be satisfied by the original evaluation method, optimum technologies, production modes and methods. According to this condition, the permeable reservoirs are classified by the study of micro characteristics of low permeable reservoirs in this paper. Based on this, production strategies are promoted to improve the effective production and commercial development of the outskirt low permeable and grade reservoirs.In order to study the characteristic of the pore configuration in the low permeable formation, the constant flowing rate mercury-injection and Kim Sang-electron microscope experiments are adopted to study the parameters pattern of the natural cores with different permeabilities such as: permeability, average porous channel radium, average throat channel radium, pore throat ratio, tortuosity, coordinate number, form factor and fractal dimensionality. Some recognition can be obtained by followings: the distribution pattern of the pore channel radium is similar with different low permeable rock; however, the difference in distribution of the throat channel radium is apparent. The correlation between the throat channel radium and permeability is less, on the contrary, there is apparent pattern of the correlation between the throat radium and permeability. In a word, the permeability of low permeable reservoir is controlled by the throat radium. At the condition of the same permeability rock, there is no apparent relationship between the throat channel fractal dimensionality and the pore channel fractal dimensionality which can be concluded that the difference in complexity between throat channel and pore channel is small. The water flooding effect in low permeable reservoirs is not only affected by pore structure but also by the pattern of fluids flowing in porous media in low permeable rock. The mobile fluid saturation analysis is made by the nuclear magnetic resonance method, as the results indicate that: There is a favorable correlation between the mobile fluid saturation and the sweepefficiency，the production potential of the reservoir can be better revealed by the mobile fluidsaturation rather than the parameters of the permeability.Based on the experimental analysis of the actuating pressure test，when the actuatingpressure gradient permeability is less than 1×10^-3μm²，the actuating pressure will increasesharply with the decreased permeability，which indicate that when the permeability is lowerthan 1×10^-3μm²，the other displacing methods should be explored because of the unfavorableuse of water flooding.Based on the comparison between the cure of actuating pressuregradient of water flooding and that of gas flooding，it indicates that the alternation pattern ofactuating pressure gradient is similar between the water flooding and gas flooding. When theactuating pressure of water flooding is higher than that of CO₂ flooding，and the permeabilityis higher than 0.5×10-3μm2，the value of the gas actuating pressure gradient is lower，andthe trend of the decrease in actuating pressure gradient will be flatten out with the increase ofthe permeability.According to the relative permeability curves，there is a more strongcorrelation between the permeability and recovery in the low permeable reservoirs，and thesweep efficiency will decrease with the decrease of the permeability. When the permeability islower than 10×10^-3μm²，the decrease amplitude of the recovery is the most，the lowestvalue can be to 16.5%，which can indicate that when the permeability is lower than10×10^-3μm²，the water flooding effect will be worse; the pore throat ratio has a greatinfluence in the residual oil saturation，with the increase of the pore throat ration，theresidual oil saturation will be increased，if the stretch of two phase flowing fluids is less，the recovery of water flooding will be decreased.Based on the research on the low permeable rock pore structure and the characteristic offluid flowing in porous media，four parameters such as permeability，pore throat ratio，throat channel radium and actuating pressure gradient are adopted. Cluster analysis is adoptedto classify the outskirt reservoir of Daqing oil field into four categories: The characteristics ofoutskirt reservoirs in Daqing oil field are analyzed，following results can be obtained: Thedepth for the whole outskirt areas is lower，and there are 52 reservoirs which is less than1500m，the reserve ratio is 65%. There are 49 reservoirs in outskirt with shallow fracture，micro fracture and apparent fracture，the formation reserve is 78.3%. There are 26 reservoirwithout fractures，the fractures are mainly in east-west direction in Chao Yanggou，YuShulin and Tou Tai oil fields. There are less fractures in other directions. The reservesabundance of developed outskirt reservoirs is 21×10⁴t/km²～92×10⁴t/km²，and there are 25reservoirs with the reserves abundance less than 50t/km2，which is 44.8% of the geologicreserve. There are 54 reservoirs with the much lower reserves abundance more than 50 t/km2， where the geologic reserve is the 87.7% of the Fu Yang formations, the average reserves abundance is 58.9×10⁴t/km², which belongs to lower reserves abundance.The water cut, injection production ratio, control degree of water flooding and production rate are chosen to classify the developed reservoirs, which provide the foundation for the development strategy.According to the production data of outskirt developed reservoirs in Daqing oil field, the effect of the infill adjustment is studied. The adjustment infill effect of the reservoirs with different permeability in Daqing oil field is analyzed, plans of infill adjustment are determined for different types of reservoirs. The experiments on pressure sensitive effect of low permeable reservoirs are operated. The results indicate that when there is no fracture, the pressure sensitive effect will be apparent with the decrease of the throat radium. The main factors that affect the pressure sensitive effect can be due to the throat radium. When the permeability is the same, the fracture will affect a little on the pressure sensitive , the degree of pressure sensitive effect will be higher with the increase of the fracture density.The research is mainly focused on the theory of advancing water injection and CO2 flooding, the displacement effects of different type reservoirs with advancing water injection and CO2 flooding are provided; The air displacement possibility is studied, when the permeability is higher than 0.2×10-3μm2, the stale burning front can be formed. With the decease of the permeability, the displacing rate of the burning front will decrease, but which is less. At the same position of axial ratio, the increasing rate of temperature will be different with different pore throat ratio. When the pore throat ratio is less, the increase of the temperature will be larger which can indicate that the burning efficiency could be influenced by the pore throat ratio. The effect of horizontal drilling process in radial direction is analyzed, this technique with the characteristic of direction determination and depth determination. It can also improve the less effective layers or wells condition, short the space between the injection and production wells, improve the relationship between the injection and production, which can also adjust the contradiction of the layer space or the plane.Based on the classify of the low permeable reservoirs, combined with the development grading methods, according to the different kinds of reservoirs, the production development strategies are promoted, also, the theoretical foundation of the reasonable development of the outskirt reservoirs in Daqing oil field is provided.更多还原