东营凹陷前古近系地层结构复杂,地层展布南北、东西方向差异较大,地层划分与对比难度较大.在宏观分析华北板块构造演化特征基础上,通过野外露头、录井岩性组合、测井电性和地震反射等特征分析,建立了各层组地层划分与对比标志,明确了东营凹陷地层区域展布差异性,解剖了典型地区地层发育特征,研究了上古生界两种构造反转样式,以及构造反转运动对油气成藏的控制作用,为后续勘探工作奠定了基础.

在高勘探程度阶段,牛庄洼陷沙三中亚段浊积岩油藏主要勘探对象是“个体小、薄互层、横变快、含灰质”的复杂隐蔽储层.针对薄互层砂体地震难分辨、灰质泥岩背景下砂岩难识别两大难题,开展了岩性敏感曲线重构和波形指示反演相结合的砂体预测研究.结果 表明:波形指示反演明显压制了灰质泥岩对砂体预测的干扰,利用波形横向变化代替传统变差函数进行高频成分模拟,提高了反演精度,5m以上储层预测结果与实钻井吻合度为88.5％,2～5 m储层预测吻合度达到80.5％.反演砂体分布符合研究区沉积演化规律及油藏流体分布认识.利用反演结果指导牛庄洼陷滚动探井和开发井部署,在5个开发区共部署滚动探井和开发井20口,其中8口井完钻投产后获得工业油流,预计新建产能4×104 t.

东营凹陷浊积岩油藏勘探开发进入高程度阶段后,研究对象转为"个体小(单砂体面积<1 km2)、厚度薄(单层厚度2～5 m,累加厚度5～15 m)、橫变快、含灰质(灰地比5％～45％)"的超隐蔽储层,该类储层常规方法描述难度大、精度低.因此,开展了超隐蔽储层描述技术综合研究:①应用谐波拓频技术、属性融合方法和波形指示反演技术刻画"个体小"和"厚度薄"储层;②形成了复杂岩性背景下横波估算方法,开展叠后、叠前综合去灰技术研究,刻画灰质发育区有利储层边界.取得了四点成果及认识:①谐波拓频技术提高了地震资料分辨率,且具有较高保真性,能够识别追踪厚度>10 m储层;②波形指示反演技术刻画薄互层储层精度较高,单层厚度>5 m砂体预测结果与实钻井吻合度为88.5％,厚度2～5 m储层预测吻合率80.2％;③复杂岩性环境下横波估算方法,较传统的Xu-White模型方法横波估算精度提高了10％;④叠后、叠前联合储层预测技术在东营凹陷去除灰质的精度为84％.综合应用储层描述成果,在四个开发区块共部署滚动探井20口,目前完钻10口,8口井钻遇较厚油层,其中6口井投产后均获商业油流,新建产能约4.0×104 t.

A method of computing cap rock's effective thickness is proposed based on that cap rock's heterogeneity may result in different capillary sealing ability within cap rock. Using data of thin section,SEM,breakthrough pressure,porosity,per-meability and other test data of argillaceous cap rock and sandstone reservoir, the boundary between cap rock and reservoir can be defined,which includes breakthrough pressure limit,critical lithology(grain size) and petrophysics limit.Subsequent-lythe evaluation criteria of cap rock's capillary sealing ability is established. With gamma ray curve, interval transit time curve and test data,a logging interpretation model is established to quantitatively recognize cap rock's lithology and to calcu-late porosity,permeability and breakthrough pressure.A comprehensive evaluation on capillary sealing ability of cap rock has been made to first remove the cap rock with no capillary sealing ability and then to obtain the effective thickness. Our results show that between cap rock and reservoir of X gas reservoir, the breakthrough pressure limit is 2 MPa;the critical lithology (grain size) is argillaceous coarse siltstone;the porosity limit is about 6%, and the permeability limit is about 0.02×10-3 μm2. Cap rock's capillary sealing ability has been divided into five grades fromⅠtoⅤ. By removing gradeⅣandⅤwhich correspond to no capillary sealing ability,the effective thickness of single cap rock is obtained between 4 and 10 m. Correla-tion between the height of gas column and the effective thickness suggests the robustness of the method. Based on the effec-tive thickness,a weighted average of breakthrough pressure has been taken to obtain equivalent breakthrough pressure, and the whole capillary sealing ability of cap rock has been evaluated as moderate effectively.

The development of expulsion fractures in organic-rich shale is closely related to hydrocarbon generation and expulsion from kerogen. Organic-rich shales from the upper part of the fourth member and the lower part of the third member of the Paleogene Shahejie Formation in the Jiyang Depression, Bohai Bay Basin, East China, are used as an example. Based on thin sections, SEM and thermal simulation experiments, the characteristics of hydrocarbon generation and the conditions supporting the development of expulsion fractures were explored. The key factors influencing these fractures include the presence of kerogens, their distribution along laminae and around particle boundaries, their exposure to heat and the build-up in pressure due to confinement by low permeability. The development of excess pore fluid pressures and intrinsic low rock fracture strength are the main influencing factors. Pressurization by rapid generation of hydrocarbon provides impetus for fracture initiation and cause bitumen to migrate quickly. The shale laminae results in distinctly lower fracture strength laminae-parallel than laminae-normal and this directs the formation of new fractures in the direction of weakness. When pore fluid pressure increases, maximum and minimum principal effective stresses decrease by different proportions with a larger reduction in the maximum principal effective stress. This increases the deviatoric stress and reduces the mean stress, thus driving the rock towards failure. Moreover, the tabular shape of the kerogen aids the generation of hydrocarbon and the initiation of expulsion fractures from the tip and edge. The resulting fractures extend along the laminae when the tensile strength is lower in the vertical direction than in the horizontal direction. Particle contact boundaries are weak and allow fractures to expand around particles and to curve as the stress/strength regime changes. When pore fluid pressure fields at different fracture tips overlap, fractures will propagate and interconnect, forming a network. This paper could provide us more detailed understanding of the forming processes of expulsion fractures and better comprehension about hydrocarbon expulsion (primary migration) in source rocks.

东营南坡东部地区沙四上亚段碳酸盐岩储层沉积特征的研究程度一直较低.本文在研究了白云岩和灰岩岩相特征的基础上,分析了东营南坡东部地区沙四上亚段碳酸盐岩储层沉积的主控因素:古碳酸盐岩物源、古地貌、古气候等,建立了两种碳酸盐岩沉积模式,刻画了沙四上亚段古地形控制的岩相平面分布特征.