【作者】 吴诗勇；

【导师】 林舸； 李自安；

【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

【摘要】 本文以大庆喇嘛甸油田北北过渡带SI组砂岩以及其顶部泥岩做为研究对象。在开发区的地质演化、沉积、以及应力、流体研究的基础上，主要采用有限差分的方法，对开发区泥岩的流变特性以及最优注采平衡问题开展模拟研究，获得的认识及成果如下：油田在注水开发过程中，地应力大小及分布受注采条件变化的影响。由增高的流体压力产生的作用力影响地应力的分布状态，导致其数值大小和方位的变化(偏转)。现场实验表明，改变注水井的工作条件后，最大主应力值变化达到了3～5MPa，最大主压应力方向由N84°E变化为N80°W。实际上，应力的变化及方位直接取决于流体压差的大小。因此，当油层内的最大主压应力接近区块压差时，就有可能导致地层段发生蠕动滑移以及地层内部出现裂缝，顶起上覆岩层。对于具有一定埋深的油层来说，当油层厚度与油层分布尺寸相比很小时，孔隙压力的改变只引起地层垂向变形，在水平面内的变形几乎为零。通过对研究区泥岩蠕变的数值模拟，得到研究区的最大主应力为-25.87～-24.88MPa，最小主应力为-19.95～-18.44MPa，下部应力大于上部；应变的分布与应力一致，其变化主要表现在垂向上，且底部应交增量大，约为0.53，往上则逐渐减小；位移方向垂直向上，底面上的相对位移量最大，达到了3.4mm，而顶面则接近于0。无论泥岩浸水与否，其应力、应变及位移都是随着下伏油层压力的增加而增大，且应变和位移都是在短时间内很快过渡到稳定状态。但是，泥岩浸水后，其流变效应显著增加。与未浸水时相比，当下伏油层压力增加1MPa时，上覆泥岩层中主应力增加了0.2MPa，位移增加了0.73mm，而应变则增加了约0.1。随着下伏油层压力的增加，两种情况下的主应力以及应变的差值都相应增大，而位移之间的差距却越来越小。另外，随着泥岩内含水量的增加，其孔隙压力也由0慢慢增大。而当下伏油层压力增加到7MPa时，泥岩内的孔隙压力则增加到1.9MPa。在物质平衡和渗流力学理论基础上，采用动态分析方法，推导了油藏产液能力、吸水能力以及地层压力之间的关系。对于注水开发油田来说，稳产阶段的采油速度的自然对数与注水速度的倒数呈直线下降的关系。而地层压力的变化，主要取决于年注水速度和年地下采液速度的关系，当年注水速度大于年地下采液速度时，地层压力就会上升；反之地层压力就会下降；当两者相等时，地层压力就会保持恒定，此时即达到注采平衡状态。从技术界限研究成果来看，开发区SI组的最大允许地层压力为13.0MPa。如果考虑到地层压力与采收率的变化关系，则合理的地层压力应为10.7MPa。另外，从套损、断层复合以及油层破裂的角度，得到的最大允许注水压力为13.4MPa；而从地层压力与油井流动压力的关系，得到的开发区合理流压界限为6.8MPa。油层动态模拟结果显示，当前油田注采处于非平衡状态，如果继续保持现有注采条件，则油层压力最终将超过最大允许的地层压力。而当地层压力保持在10.7MPa时，在平衡条件下，水井的注入强度不变，而油井的采液强度可提高1.7m~3／(d．m)。开发区相应的可采储量测算结果为2111.4×10~4t，采收率为36.24％，比实际提高了1.79个百分点。更多还原

【Abstract】 Based on the research of basal geology, depositional evolution, stress and fluid of the development area, this thesis simulated the sandstone of SI and its cap mudstone which located at the Beibei Transition Strap of Lamadian in Daqing Oil field by limited difference method to learn mudstone rheological property and optimum balance of injection-productionin in high-fluid-pressure system. The following main results have been achieved:During the oil production, the procedures of water-injection can significantly change the distribution of principal stress both on its power and direction. Field experiments indicated that changing the methods of water-injection could change the main principal stress (MPS) up to 3～5MPa in power and from N84°E to N80°W in direction. The changes of MPS were actually controlled by the pressure difference in the fluid (i.e., water and oil). The strata would creep or break when the main stress in the oil layer increased to the pressure-difference threshold of the local strata. To deep layers, changes in pore pressure would only cause deformation of strata in vertical direction and nearly nothing in horizontal direction if the ratio between the thickness of vertical direction and plane is very small.Numerical simulation on study area indicated that the maximum principle stress in this area is between -25.87—24.88MPa, and the minimum principle stress is -19.95～-18.44MPa. The distribution of strain consistent with stress which mainly behaved at vertical direction. The maximum increment of strain (about 0.53) is at the bottom of the mudstone and to the top is gradually diminished. The displacement is upward with relative maximum shift (～3.4 mm) at the bottom and nearly zero at the top. Whether the mudstone was soaked or not, all of the stress, strain and displacemen increased with bracing pressure of underlying sandstone, and became being stabilized in short time. Once mudstone was soaked, its rheological effect is significantly enhanced. Compared with un-soaked mudstone, when uploading stress of the sandstone increased 1 MPa, the increments were separately as below: principle stress is 0.2MPa, displacement is 0.73mm, and strain is about 0.1. Moreover, with the continuous stress increasing of underlying sandstone, the gaps of principle stress and strain between soaked or un-soaked mudstones became larger while the gap of displacement became smaller. When mudstone became saturated in water, its pore pressure started increasing from zero. Experiments indicated that pore pressure of mudstone would increase about 1.9MPa when bracing pressure of sandstone increase 7MPa.Based on the theories of Mass-balance and Seepage Mechanics, the relationship among oil productivity, water-injection rate and fluid pressure was calculated and discussed by applying dynamic analyses methods. During stable production period, the natural logarithm value of oil productivity was negatively correlated with reciprocal of water-injection rate. And fluid pressure of oil layer was mainly determined by annual water-injection rate and annual oil productivity. When annual water-injection rate was higher than annual oil productivity, the pressure would rise, and vice versa. If both of them were in equal, the original pressure of oil-layer would be maintained. Then this time must be in balanced state.Stress thresholds for SI oil layer in studying area were also calculated in this study. Results showed that the maximum bearing pressure is 13.0MPa. If the relationship of the pressure and recovery efficiency was thought about, the optimal pressure for SI oil layer should be 10.7MPa. And if considering the factors of casing damages, default and oil-layer breaking, the maximum water-injection pressure should be 13.4MPa. Based on the relationship between fluid pressure and oil-well flowing pressure, the optimal flowing pressure for study area was 6.8MPa. Dynamic simulation of oil layer further demonstrated that pressures from water-injection and oil production are not balanceable at present. The bracing pressure from oil layer would be over the maximum bearing pressure of cap mudstone if keeping current water-injection rate. However, if keeping strata pressure at 10.7MPa, oil productivity would increase 1.7m~3/(d · m) with constant water-injection strength. Recoverable reserves of study area was also calculated in this thesis, which is 2111.4×10~4t with a theoretical recovery efficiency of 36.24% which enhanced 1.79%.更多还原