复杂致密储层裂缝特征研究

塔里木盆地奥陶系碳酸盐岩储层是一类典型的复杂致密油藏，奥陶系地层经过多期构造运动和古岩溶共同作用形成的岩溶缝洞型碳酸盐岩油藏，其中的一间房组和鹰山组储层以灰岩和白云岩为主，属于超低孔超低渗复杂致密储层。根据岩芯资料分析，一间房组岩芯分析孔隙度低于2% 的占90%，鹰山组岩芯孔隙度低于2% 的占67.3%，平均基质孔隙度约1.69%。露头、岩芯以及镜下薄片观察发现，在此类储层中，基质基本不具有储渗意义，绝大部分油气是储存在成岩后期产生的溶洞和裂缝中。储集空间是以构造变形产生的构造裂缝与岩溶作用形成的孔、洞、缝为主，其中洞穴是本区储层最主要的储集空间。裂缝具有双重作用，既是重要的储集空间，又是洞穴和裂缝连通的关键通道。裂缝和溶洞也是这类储层储集空间形态多样、大小悬殊、分布不均、具有很强的非均质性的根本原因。本文重点对一间房和鹰山组裂缝性进行了研究，分析裂缝测井响应特征，裂缝发育和分布规律，采用序贯高斯随机建模方法建立裂缝孔隙度、张开度和渗透率的三维分布模型，模拟结果表明，裂缝对渗透率的改造作用特别大，说明裂缝在储层储渗方面起着重要作用。

Study on the Fracture Characteristics of Complex Tight Formation

Ordovician reservoir is the most important exploration and production block of Tahe Oilfield of Tarim Basin,which has undergone multiple-period tectonicmovements and paleo-karstification effects and become karst-vuggy carbonate reservoir.The main lithologies of Yijianfang and Yingshan Formation group are calcite and dolomite.The reservoir is typical super-low porosity and low-permeability.Investigations of outcrops,cores and scanning electron microscope(SEM)images show that in this kind of reservoir,matrix is almost non-porous and non-permeable.The main reserving spaces,however,are fractures and vugs,which resulted from tectonic deformation movement and,pores,caves,which occurred through karstification effects.Among these,caves are most important spaces for hydrocarbon.Fracture is another key element for this reservoir,which has double effects,one is that the fracture provides reserving space by itself,and the other,it is tunnel for hydrocarbon migration.Because of the pore morphology,different size and uneven distribution of reserving spaces,this kind of reservoir has very distinguished heterogeneous properties.We studied the characteristics of the fractures,and analysis the reason of fractures occurring,the distribution law of fractures.By using geological simulation software,we adopted sequence Gaussian randomizing methods,to model the fracture parameters,such as porosity,permeability and open width.The three-dimensional images of fracture parameters model shows seriously heterogeneous of this reservoir.The simulation result shows that the fractures modify the permeability of the Ordovician reservoir evidently.