【作者】 崔宝文；

【导师】 徐学纯；

【作者基本信息】 吉林大学 ， 矿物学、岩石学、矿床学， 2010， 博士

【摘要】 大庆外围扶杨油层属于低、特低渗透油层,孔隙不均匀、喉道细小、渗流阻力大,驱油效率较低,产量递减快,有效开发难度大。为此,本文通过铸体薄片恒速压汞和核磁共振等手段,分析了扶杨油层的微观孔隙结构特征,喉道形状,岩石颗粒大小、以及这些因素对渗流规律的影响。采用野外露头、岩芯观察、测井等手段,结合开发实际研究了大庆外围扶杨油层的裂缝发育类型、规模、分布特点、以及裂缝对注水开发的影响。把室内渗流物理实验和矿场开发试验有机结合起来,深入研究扶杨油层非达西渗流机理和渗流规律,明确了单相渗流产生非达西的空气渗透率界限,油水两相共渗时拟启动压力梯度与含水饱和度的关系曲线。根据非达西渗流规律,建立了特低渗透基质—裂缝流体定常、非定常流动模型,基质—裂缝耦合系统的两相非定常流动数学模型,提高了特低渗透储层开发指标预测精度和开发方案的编制水平,拓展了油藏工程的研究方法。应用研究成果,从改变储层流体流动状态和建立有效驱动两个方面考虑,提出了井网优化和压裂措施相结合的有效开发对策,解决了部分难采储量的有效动用问题,在开发实践中取得了很好的应用效果。更多还原

【Abstract】 The low and ultra-low permeability Fuyang oil layers in Daqing marginal oilfields are mainly developed by waterflooding. The uneven porosity, tiny throat, strong molecular force and capillary pressure on solid-liquid interface of Fuyang oil layers have caused large filtrational resistance, low displacement efficiency, rapid production decline and big difficulty in effective development. Therefore, based on the effect of microscopic pore structure on filtering flow in reservoirs and the influence of reservoir fractures on waterflooding effect, this paper makes deep study on non-Darcy flow mechanism and law in combination of physical experiments and field tests. The effective development strategy for Fuyang oil layers in Daqing marginal oilfields is put forward in this paper, and pretty good application results have been obtained by taking this measure. The major study content and results are showed as following:1. The microscopic pore structure characteristics, throat figures, rock particles sizes and their effects on filtering flow in Fuyang oil layers are analyzed by means of cast iron slice, electron microscope scan, constant rate mercury penetration and nuclear magnetic resonance. Fuyang oil layers are featured by deep buried depth, tiny and closely arrayed rock particles and high clay content. Its porosity type and throat type is dominated by reduced intergranular pore as well as laminar, curved lamellar and bundled tubes, respectively. Secondary growth of quartz and feldspar, along with filling of epigenetic calcite and carbonate saline minerals, both cause the further reduction of porosity, more complex distribution of throat and poor connectivity, where the filtering flow in the reservoir does not follow the conventional Darcy law while is feature by non-Darcy flow. As result, the conventional parameters including reservoir porosity, permeability, grading factor and uniformity coefficient can not precisely describe the inherent features of ultra-low permeability reservoirs in Daqing marginal oilfields, also it could not meet the needs of development. The throat characteristics are the parameters that with critical effect on fluid flow law, in which the size of throat radius and its distribution are deciding factors, especially.2. The development type, growth scale, distribution characteristics of fissures and their effect on waterflooding development are studied by means of field outcrop, core observation and well logging. Natural fractures are generally developed in Fuyang oil layers, where tectoclase mainly developed in tectonic axis, near faults and on big curvature structures. Explicit fractures are dominant by high dip angle shear stitches. The eastern fractures are mainly in approximately latitudinal trending, and the western fractures in approximate EN trending, but differences exist in different oilfields and blocks. Some minerals and matrix are sliced in micro-fractures, most of which have been filled by calcites wholly or partially. The existence of micro-fractures has double influences on oilfield development. On one hand, it increases reservoir percolation capacity and reduces water intake threshold pressure; on the other hand, explicit fractures increase intrastratal heterogeneity and interlayer contradiction. The open of fractures has sharp directivity, and the open order is relevant to injection pressure. The fracture system belongs to high-speed non-Darcy flow. Therefore, much attention should be paid on fractures and ground stress during waterflooding and effective measurements should be adopted based on relevant study3. The fluid flow mechanism of low permeability reservoir is studied through seepage experiment. Single phase fluid flow experiment of oil and gas further determines the air permeability limit for formation of non-Darcy single phase fluid flow. The air permeability limit for non-Darcy aqueous phase fluid flow and oil phase fluid flow is 1×10-3μm2 and 5×10-3μm2, respectively. Single phase flow experiments with different fluid viscosities show fluid viscosity is an important factor for non-Darcy flow in addition to pore throat features. The higher fluid viscosity is, the larger quasi-threshold pressure gradient will be. Stable-state oil-water seepage tests for rock samples with different permeability show that quasi-threshold pressure gradient for two-phase simultaneous flow is much higher than that of single phase fluid flow. The connection between quasi-threshold pressure gradient and water saturation assumes a parabolic shape. Water flooding experiments show that producing indexes will continuously reduce along with the advance of water displacement front to the producers. The period with low or medium water cut is featured by high degree of reserve recovery and injection efficient as well, and it is the main production period of the oilfield. Once water breakthrough exists in oil wells, the water cut will be very high and the producing indexes may sharply reduce, hence increasing the difficulty of boosting flowing back so as to maintain a stable production.4. Based on non-Darcy filtering flow theories and reservoir engineering fundamentals, the stationary and non-stationary flow models for fluids in ultra-low permeability matrix-fissure and the non-stationary 2 phase flowing mathematic models for matrix-fissure coupled system are built. In the former research method, it is assumed that the fluids flow in the fissures is accordant with the Darcy flow, while according to the new model, it is assumed that the flow in the fissures is high velocity non-Darcy flow, which is more accordant with the actual flow state. Moreover, with the considerations of field application, the matrix-fissure coupled flow potential models under different development well patterns are established. Foi the first time, the model can systematically demonstrate the combination and coupling relations between the fracturing well pattern mode and fissure system, provides the development well pattern optimization, development fracturing design and flow potentia prediction with theoretical basis, increases the accuracy of development indexes prediction foi ultra-low permeability reservoirs and the establishment of development plans, and improves the research methods for oil reservoir engineering.5. According to the research on the filtering flow mechanisms of ultra-low permeability reservoirs and considering both form the change of the flow regime of the fluids in the reservoirs and the establishment of effective driving, the effective development strategy combining well pattern optimization with the fracturing for development, is proposed, namely enlarging the well spacing, reducing the well line distance, enlarging fracturing scale anc optimizing the fissures parameters for the development design of rectangular pattern, and this becomes the most important and effective development technique in the development o Fuyang oil layers in Daqing marginal oilfields. With the application of this technique, a new design method for well pattern optimization is set up, changing the invariable inverted 9-spo pattern water flooding mode existed for many years and effectively employing most part o reserves difficult to be produced before.更多还原