【作者】 张雁；

【导师】 吕延防；

【作者基本信息】 东北石油大学 ， 矿产普查与勘探， 2011， 博士

【摘要】 本论文以大庆油田杏南萨葡油组的砂岩储层为主要研究对象,综合大量的铸体薄片、荧光薄片、电镜、压汞等资料,利用室内驱替实验、分形数学和计算机模拟方法等对储层的孔隙结构特征、分类、影响因素及其与剩余油关系进行了系统的分析和探讨。在本文中,除采用常规孔隙结构描述参数外,引入数学的分形理论,采用分维数、分形孔隙度、分形孔隙度/总孔隙度等参数来研究微观孔隙结构分布。发现研究区大部分样品的孔喉分布在分形上属于二段式,即孔喉分布可分为大孔喉和小孔喉两个主要群体,大孔喉群体主要反映了沉积作用的特点,而小孔喉群体则反映了成岩作用的特点。在前人基础上推导了计算二段式分形孔隙度公式,计算了各样品的分形孔隙占总孔隙的比例,并认识到一般大孔道分维数相差不大,主要是小孔道的分布决定了分维数的大小,小孔道分布频率高,则分维数大,分形孔隙度高,分形孔隙占总孔隙的比例大。综合常规孔隙结构描述参数和分形特征参数,在考虑与孔渗性的相关程度基础上将研究区的所有样品共划分为一至五类孔隙结构,从一类至五类,孔喉半径逐渐减小,孔喉比逐渐增加；孔渗性逐渐变差,填隙物含量逐渐增加,分形孔隙比例逐渐增加,非均质性增加。对不同沉积微相进行研究发现,分流河道微相砂体内主要发育一、二、三类孔隙结构,一、二类孔隙结构多发育在河道中下部或河道优势通道位置,上部或边缘多为三、四类孔隙结构。主体席状砂、非主体席状砂孔隙结构类型以三、四类为主,三类孔隙结构多发育在砂体上部或核部,下部和边部多发育四类储层。表外薄层砂孔隙结构类型以四、五类为主。详细研究了成岩作用对孔隙结构的影响,机械压实可以使孔喉分布的分维数减小,孔隙结构变得更均匀；不同胶结物由于其形态产状的不同,可不同程度的增加小孔的发育数量。其中以片状胶结物对小孔的贡献率最大。溶蚀作用也使孔喉表面变粗糙,增加了小孔喉的比例,但对分形孔隙的贡献较胶结物少,且使孔喉分布均匀化。不同水洗时期对孔隙结构也有影响。随着水洗程度的加剧,孔喉半径增大,相对分选变好,连通性增强。利用实际岩心获得的数据建立孔喉网络模型,并分别进行了二维、三维水驱油网络数值模拟,结合各种镜下薄片,总结了不同水洗时期不同孔隙结构内微观剩余油的分布规律。一、二类孔隙结构强洗时期以簇状、孔表薄膜状等赋存方式为主；三、四、五类孔隙结构则以粒内、粒间及膜状等剩余油类型居多。讨论了孔隙结构和驱油效率的关系,发现不同沉积微相各微观参数与驱油效率之间的相关性较数据整体与驱油效率的相关性高,说明沉积过程对微观孔隙结构的控制作用。平均孔喉半径、孔隙度、渗透率、渗透率/孔隙度值均与驱油效率呈正相关,分形孔隙度/总孔隙度与驱油效率呈负相关。曲流型分流河道驱油效率最低,顺直型分流河道驱油效率最高,三种类型的席状砂驱油效率居中。不同沉积微相中驱油效率均随分形孔隙度/总孔隙度的增大而减小。由此可见,沉积、成岩作用共同作用形成不同的孔隙结构,孔隙结构非均质性是影响驱油效率的主要因素。在上述研究基础上提出了不同微相类型的剩余油挖潜方案。分流河道的挖潜重点在砂体上部或优势通道外侧,可采取调剖、注聚及周期注水等方式挖潜剩余油；主体席状砂、非主体席状砂现阶段主要为中水洗。砂体内还有较多的剩余油未被驱出,可通过提高注水倍数、周期注水改变液流方向等方式挖潜剩余油；表外薄层席状砂现阶段以未洗、弱洗为主,通过改变周期注水方向的方法可以动用少量的油,但大部分细孔喉内的剩余油则应通过压裂措施增加渗流通道来开采。更多还原

【Abstract】 In this study, the sandstone reservoir of Xingnan Sa and Pu oil groups in Daqing Oilfield is the main research object, Through the collection of a large amount of materials, such as casting body chip, fluorescence chip, electron microscope and mercury penetration, systematic analysis and discussions were conducted on characteristics, classification and influence factors of reservoir pore structure and its relation with remaining oil using laboratory displacement experiment, fractal mathematics and computer simulation method.Apart from the conventional pore structures for description of parameters, mathematical fractal theory was also introduced in this paper, and distribution of microscopic pore structure was studied using parameters including fractal dimensionality, fractal porosity, and fractal porosity/total porosity. It was found that the pore throat distribution of most samples in the studied area was binary fractal, i.e., pore throat distribution could be divided into two main groups, namely, big pore throat and small pore throat. The big pore throat group mainly reflected the characteristics of sedimentary process, while the small pore throat group reflected the characteristics of diagenesis. Binary fractal porosity formula was deduced on the basis of previous researches in this paper, and the ratio of the fractal pores of each sample to the total fractal pores was calculated. It was concluded in this paper that the fractal dimension of large pore path did not differ greatly in general, and it was the distribution of small pore path which decided the fractal dimension:the higher the distribution frequency of small pore path, the larger the fractal dimension, fractal porosity and the ratio of fractal porosity to total porosity was.With the consideration of correlative degree of porosity and permeability, all the samples were divided into five categories of pore structures by integrating conventional pore structure description parameters and parameters of fractal characteristic. From the first category to the fifth category, the radius of pore throat decreased gradually, and pore-to-throat ratio gradually increased; porosity and permeability became increasingly worse; the content of interstitial matter, fractal pore ratio and heterogeneity all increased.The study on different sedimentary microphases found that the first, second and third categories of pore structures mainly developed in microphase sand body of distributary channels, while the first and second categories of pore structures mainly developed in the mid-lower river channels or predominant pathways of the river channels; and the third and fourth categories of pore structures developed mainly at the upper or the edge of river channels. Types of pore structures of primary shelf blanket sands and secondary shelf blanket sands mainly belonged to the third and fourth categories of pore structures. The third category of pore structure developed mainly at the upper or kernel part of sand body, while the fourth category of reservoir developed mainly at the lower or the edge of sand body. The pore structures of external thin sand body primarily belonged to the fourth and fifth categories.A detailed study of the influence of diagenesis on pore structure was conducted. Mechanical compaction could decrease the fractal dimension of pore throat distribution, rendering pore structure more uniform different cementing agents increased the number of pores under development to different extent due to the difference in occurrence and shapes. Among them, flake cementing agent produced the largest number of fine pores. Corrosion also made pore throat surface rougher, and increased the ratio of small pore throat, but with less influence on fractal pores than that of cementing agent.Different water washing period had different influence on pore structure. As the water washing intensified, radius of pore throat increased, and relative fractal became better, with enhanced connectivity. Data of the actual core was used to establish the network model of pore throat, and the numerical simulation of two-dimensional and three-dimensional displacement of oil by water was conducted, respectively. The microscopic distribution pattern of remaining oil in pore structures during different water washing periods was summarized using microscopic chips. The first and second categories of pore structures mainly occurred in the form of drusy or pore surface thin film during the strong water washing period;the third, fourth and fifth categories of pore structures were primarily of types of remaining oil as intragranular pore, intergranular pore or film.Discussion of the relationship between pore structure and oil displacement efficiency revealed that the correlation between all microscopic parameters of different sedimentary microphases and oil displacement efficiency was higher than that between data and oil displacement efficiency. This founding indicated the control of sedimentary process on microscopin pore structure. Values of average radius of pore throat, porosity, permeability, and permeability/porosity were positively correlated with oil displacement efficiency, while fractal porosity/total porosity was negatively correlated with oil displacement efficiency. The oil displacement efficiency of meandering type of distributary channel was the lowest, while that of straight distributary channel was the highest, with that of the three categories of blanket sands at the middle. The oil displacement efficiency of different sedimentary microphases decreased with the increase in fractal porosity/total porosity. Thus, pore structure was formed under the coaction of sedimentation and diagenesis, with the heterogeneity of pore structure being the main factor affecting oil displacement efficiency.Extraction scheme for remaining oil of different microphases was proposed based on the above research. Oil extraction of distributary channels should be targeted at the upper part of sand bodies or external part of the predominant pathways, and profile control agents, polymer injection and cyclic waterflooding could be used to extract remaining oil;for primary shelf blanket sands and secondary shelf blanket sands, medium water washing was mainly adopted. The larger amount of remaining oil in sand body could be extracted by doubling the amount of water injection or changing fluid flow direction of cyclic waterflooding; blanket sands of the external thin layer could be extracted using unwashed or weak washing methods. A small amount of remaing oil might be extracted by changing the injection direction of cyclic waterflooding, but the majority of oil remaining in thin pore throat should be extracted by increasing seepage channel through fracturing measures.更多还原