【作者】 宋广寿；

【导师】 孙卫；

【作者基本信息】 西北大学 ， 油气田地质与开发， 2009， 博士

【摘要】 鄂尔多斯盆地待开发区块和新发现区块主要是小于0.5×10-3μm2储层,如何实现该类储层经济开发对油田的长远发展至关重要。近几年围绕该类储层作了大量的攻关试验,取得了一定的成果,但是由于储层的复杂性,仍然需要开展更细致的工作。针对低渗透储层的特殊性质,论文提出并论证了主流喉道半径、可动流体饱和度、启动压力梯度作为储层评价参数的必要性,同时引入地下原油粘度和粘土含量,形成了低渗透储层评价参数体系。给出了低渗透储层单参数分类界限。建立了低渗透储层模糊综合评价模型。根据综合评价值,将低渗透储层分为四类,一、二类在目前的技术条件下能够实现有效的开发,三类是目前正在攻关的储层,四类是目前技术难以动用的储层。鄂尔多斯盆地0.3×10-3μm2类储层主要指综合值小于0.6的二类下限和三类储层,从而明确了长庆油田攻关储层的类型。鄂尔多斯盆地0.3×10-3μm2类储层主要分布在延长统东北沉积体系的安塞三角洲及西南沉积体系的西峰三角洲的前缘,与1×10-3μm2相比,该类储层碎屑颗粒更细、分选更差、胶结作用更强。孔道大小与一般低渗透率储层相差不大,但储层喉道小,主流喉道半径小于1μm,喉道的大小决定该类储层渗流能力更差。低渗透油藏渗流属于非线性渗流,油藏可分为三个渗流区即井筒周围的易流区、近井地带低速高阻区和远井不流动区三种流动区间。实验及理论分析表明,渗透率越低非线性越强,井筒周围易流区域越小,开发也就越困难。论文对0.3×10-3μm2类储层的产能、压力系统和井网进行了评价,探讨了压裂五点井网有效压力系统评价方法及建立对策。特低渗透油藏采用菱形反九点井网转矩形五点井网较为合理,针对不同的储层,给出了庄19等五个区块建立有效驱动的极限排距；0.3×10-3μm2类油藏实施超前注水,压力系数达到1.1-1.2,有助于有效补充能量,建立有效的驱动,提高开发效果。通过分析,初步形成了0.3×10-3μm2类油藏开发原则、层系划分、产能评价、井网井距、水平井、注水方式、压力保持水平等系列技术。更多还原

【Abstract】 The reservoirs’s permeability of being-developed and new-discovered regions in Ordos Basin are mainly less than 0.5×10-3μm2, so how to explore these oilfields effectively and economically is of utmost importance to the long-term development. There are some achievments bye lots of key tests, despite of that, it is still necessary to do more meticulous work because of the reservoirs’ complexity.Based on the characteristics of low-permeability reservoir, the thesis first proposes and analyzes the necessity of reservoirs evaluation parameters, such as main flow throat radius, movable fluid saturation, and threshold pressure gradient; the parameter system also includes viscosity of underground crude oil and clay contents. Fuzzy comprehensive evaluation for low permeability reservoirs is established. According to the comprehensive value, there are four kinds of low-permeability reservoirs:the first two kinds have been effectively developed under present technical qualification, the third is in research now and the forth is out of recent technology. The 0.3×10-3μm2 reservoirs in Ordos Basin mainly refer to the ones with comprehensive value under 0.6, which belongs to the lower limit of the second and the third. All above makes it known which category of reservoirs in Changqing oilfield belongs to.The 0.3×10-3μm2 reservoirs in Ordos Basin locate in Ansai Delta, Yanchang Series, Northeast Depositional System, and the front of Xifeng Delta, Southwest Depositional System. Compared with 1×10-3μm2 reservoirs, the 0.3×10-3μm2 reservoirs have thinner kernels, stronger cementation, and are more poorly sorted. The channel diameter is almost the same with common low-permeability reservoirs’, but its throat is smaller. Otherwise, the main flowable throat radius is less than 1μm, which means low seepage ability of that kind of reservoirs.It is more difficult to develop 0.3×10-3μm2 reservoirs because of the strong pressure sensitivity and non-linear flow effect. Because of the existence of non-linear flow, there are easy-flowing area, low-velocity and high-resistance area, and non-flow area around the well. The results of experiments and theoretical analysis demonstrate that the lower the permeability is, the stronger the non-linear effect is and the smaller the easy-flowing area is. Additionally, the pressure sensitivity effect, which is stronger than common low-permeability reservoirs’, decreases the seepage ability around the well and influences the development result.The thesis evaluates the 0.3×10-3μm2 reservoirs’ productivity, pressure system, and well pattern. There is a good linearity relationship between output in early stage and testing rate. The productivity is controlled by the thickness, size of permeability, well spacing, producing pressure drop, and scale of fracturing. In early stage, output is high and decreases quickly. Soon after water flooding response, water break through. The output and dimensionless oil productivity index fall down quickly, which means no ability to increase the output. So, the key points of effective development are the declining rate in early stage and lengthening the time of low-to-moderate water-cut stage. It is also very important to establish an effective displacement pressure system for effective development of 0.3×10-3μm2 reservoirs. Based on the fluid mechanics in porous medium, the thesis discusses how to evaluate the effective pressure system of fracturing effect in five-spot pattern and establishing strategy. The well pattern is controlled by the fracture development level. Generally, diamond shaped nine-spot pattern is fit for super low permeability reservoirs, and five-spot pattern is fit for natural fracture developed reservoirs. In addition, oil and water wells which are fractured at the same time, long axis which follows the direction of sand body lay and parallels the main direction of fracture development, all above mean the good development effect.0.3×10-3μm2 reservoirs should be fractured firstly, then advanced flooding. For the advanced flooding blocks, we should pay attention on the swept volume and advancing recovery efficiency. Finally, the thesis discusses the developing strategy from six aspects.更多还原