【作者】 万新德；

【导师】 林舸；

【作者基本信息】 中国科学院研究生院（广州地球化学研究所） ， 构造地质学， 2007， 博士

【副题名】以大庆萨尔图油田北部为例

【摘要】 北二西开发区位于大庆萨尔图油田北部背斜构造西部，构造较为平缓，地层倾角1°～3°。该区共发育大小断层18条，均属正断层，走向为北北西向，断层密封性较好。北二西油层属于河流-三角洲相沉积，油层埋深870-1200m左右，砂泥质交互分布。该区单砂层划分为10种沉积类型，共发育8个油层组、34个砂体组、114个沉积单元。本文通过对北二区油层地质特征、地应力分布及扰动特征、油层流-固耦合渗流机理模拟、剩余油分布与应力扰动关系、注采井网调整部署的研究，获得如下认识及成果：根据对注水条件下油层地应力分布及扰动特征的观测试验，及对油田注水开发中后期油层地应力与流体压力耦合效应研究，建立了油层岩石流-固耦合渗流数学模型，给出了流-固耦合渗流模型的数值方法，为探讨油层岩石微裂缝的形成与分布模拟的理论及方法提供了科学依据。流-固耦合应力场模拟结果显示，油层开发之前，萨Ⅱ_7-8油层主应力值变化较小（最大主应力值介于-21.0～20.0Mpa；最小主应力值介于-4～-5.0MPa），但在断层重叠处最小应力值变化急剧，且出现多个极大值或极小值；油层开发中后期，除在断层密集区外，主应力值扰动增大（最大主应力值介于-25.0～-24.0Mpa之间；最小主应力值介于-19.0～-18.0MPa）。在断层带内，最小主应力值有明显的增大，出现一些极大值，同样在断层密集区内，变化急剧。流-固耦合流体（油和水）运移势模拟结果显示，油田开发中后期，研究区萨Ⅱ_7-8油层流体（油和水）运移势高值区主要分布在B2-3-35、B2-D4-429、B2-D5-426、B1-D1-26井的以西地区；其低值区则主要分布在上B2-3-35、B2-D4-429、B2-D5-426、B2-D1-24井的以东地区，其它地区流体（油和水）运移势值变化不大。在高势能分布区的西北部，存在三个明显的势能低值区，而在低势能区也分布有局部高势能区，低势能区大都呈闭合状分布，剩余油富集区主要分布在势能低值闭合区。油层裂缝的模拟结果显示，油田开发中后期。研究区萨Ⅱ_7-8油层普遍发育有张裂缝，一般呈北东-南西向，产状稳定，只有局部发育着剪裂缝。研究区裂缝指数变化较大，在研究区东、西两侧分别存在着一个大范围的高裂缝指数（大于7.5）区。除东、西两侧的高裂缝指数区外，大面积分布的是中等裂缝指数（3.0～4.0）区，包括从南侧的边界到北侧边界的大面积区域。应力扰动与流体运移二者关系研究表明，应力对流体运动的影响主要表现在两个方面，一是应力直接作用于岩石孔隙中的流体上，一般情况是构造应力越大，流体运移的势能值越大。二是应力作用于油层岩石的骨架上，使其产生弹性变形、塑性流动和脆性破裂，这些构造变动现象，严重影响岩石的物性和导水能力，从而影响流体的运移，在高应力作用区，由于应力作用于油层岩石骨架上，使岩石受到压缩，从而导致岩石孔隙度变小，导水系数变低；而在低应力作用区，导水系数相对增大。根据精细地质研究结果，分析了油层剩余油潜力、成因类型及与不同沉积类型储层的关系。应力扰动与剩余油分布二者关系研究表明，应力低值区即为剩余油分布区。在萨北油田北二西区萨Ⅱ_7-8油层扰动应力比较低的B1-D1-21、B2-6-420、B2-5-14和B2-4-122井西部、B2-4-122井的东部以及B2-4-126井北部的槽型地区为受应力直接影响的剩余油分布区；此外，在裂缝指数分布较小地区，剩余油也相对富集。但也有个别异常地区，这些地区裂缝指数较小，但却是高含水区，这表明裂缝对剩余油分布的影响效应，不仅与裂缝的发育密度有关，而且也与裂缝发育的方位有关。根据萨北油田北二西区井网调整部署目标和原则以及剩余油、微裂缝和断层的分布特征，在对调整区聚驱井网部署的基楚上，进行了二次加密井网的优化部署，根据不同方案数值模拟研究结果，确定了以转注间注间采排的边井形成横行列注水方式，提出了断层及裂缝附近井网部署设计的原则及方法，试采结果显示，注采系统调整可提高采收率0.82％，全区最终采收率达到43.16％，增加可采储量53.38×10⁴t。更多还原

【Abstract】 This paper made an integrated study of fluid flow in oil-bearing beds in the North Second Block of the Shaertu oil field, Daqing. It dealt with aspects such as geology, natural fractures, stress perturbation, coupling of fluid flow and solid skeleton in beds, residual oil, and adjustment of well network. Major conclusions drawn from this study are listed as follows.18 NNE-trending normal faults are recognized in the slightly dipping North Second Block, and all have relatively good seal ability. Oil beds are buried at a depth of 70 to 1,200 meters. They consist of intercalated sandstone and mudstone, of fluvial and lacustrine facies. They are substantially heterogeneous in space in that a number of 10 sedimentary for independent sandstone beds are discriminated.Stress perturbation was observed by changing work scheme and water well row. The in-situ maximum principal stress may vary in a range of 3 to 5MPa, and shear stress reaches a value or 0.35MPa, after the work scheme for 9 water wells at row 6-3 is changed. The perturbation would drive underground fluid flow, and enhance the nucleation and growth of micro-cracks in sandstone, enlarging the porosity and permeability of it. On the other hand, it should compress the pore in sandstone, reducing the porosity and permeability.A mathematical model is established for coupled stress and fluid flow at the middle and late stages of water injection development. It is implemented by adopting a numerical algorithm. In this model, the nucleation and spatial distribution of micro cracks are addressed.Simulation of stress field through the development shows that principal stress in oil-bearing bed ShaII_7-8 varies slightly before the development, and greatly at the middle and late stages. The maximum principal stress is in a range of -21.0 to -20.0 MPa before the development, and of-25.0 to -24.0 MPa at the middle and late stages.According to the simulation of fluid （namely, oil and water） potential, it is high to the west of wells B2-3-35, B2-D4-429, B2-D5-426 and B1-D1-26, and low to the east of wells B2-3-35, B2-D4-429, B2-D5-426 and B2-D1-24. The variation of fluid potential is small between them. Residual oil tends to remain in areas of low fluid potential in a close configuration.Fracture predication reveals that, at the middle and late stages tensional fractures are widely distributed in oil-bearing bed Sha II_7-8, in contrast with the local distribution of shear fractures. These tensional fractures are trended along the NE to SW direction, and extended in a stable way with a great variation of fracture density. Dense fractures have fracture index of greater than 7.5 are predicted in the eastern and western sides, respectively.The relation between stress perturbation and fluid flow is modeled to examine the impact of perturbed stress on fluid flow. The impact is both positive and negative, as described above. The fluid potential generally increases with the stress of rock skeleton acting upon the fluid in pore. Elastic deformation or plastic flow or even brittle fracturing might have resulted from the increase of stress, thus changing the properties and transmissivity of the rock. Both porosity and transmissivity in rock tend to decrease in highly stressed areas, and to decrease in slightly stressed areas.The potentialability and origin of residual oil, as well as its relation with reservoir of variable sedimentary kind, is analyzed on the base of detailed geological study. The distribution of residual oil is related in some way to factors including a low value of stress perturbation, a small fracture index, fracture orientation, and so forth. In oil-bearing bed, west of the North Second Block, there is a large possibility of having residual oil to the west of B1-D1-2, B2-6-420, B2-5-14 and B2-4-122, to the east of B2-4-122, and to the north of B2-4-126, because of the low value of stress perturbation. Additionally, residual oil is comparatively enriched in areas having small fracture index.Based upon the above study of residual oil, fractures and faults, injection-production well pattern in the North Second Block is rearranged, and a second infilled well pattern are optimized. Reservoir simulation of variable schemes confirms the best water-injection program, and adjustment pattern of injection-production well in the vicinity of faults and large fractures is promoted. It is shown by pre-production that in the new network the productivity may increase 0.82%, giving an additional amount of 53.38×10⁴ tons active oil.更多还原