致密油气藏裂缝介质压力敏感分析与计算方法

致密油气藏裂缝介质的压力敏感性对油气藏开发效果具有显著影响。基于物质守恒理论,通过理论推导建立了基质和裂缝的压力敏感方程;同时,通过开展单条裂缝压力敏感渗流物理模拟实验,研究裂缝变形特征和介质渗透率变化特征,并利用实验结果验证了压力敏感裂缝性介质渗透率模型的合理性。研究表明:建立的基质和裂缝压力敏感方程是关于流体压力的函数,能够解决常规压力敏感方程中变形系数确定困难的问题,增强了压力敏感方程在实际致密油藏开发中的适应性。实验中发现流体压力下降,基质块发生膨胀使得基质块之间的裂缝闭合,开度变小,介质渗透率变小;流体压力升高时,基质块发生收缩,使得基质块之间裂缝开启,开度增大,介质渗透率变大。对比实验模拟结果与基于实验参数的渗透率模型的计算结果,验证了渗透率模型的合理性。通过研究,揭示了致密油藏裂缝介质的压力敏感变形机理,又为裂缝介质的渗透率表征奠定了基础。

PRESSURE SENSITIVITY ANALYSIS AND CALCULATING METHOD FOR THE FRACTURE MEDIUM OF THE TIGHT OIL RESERVOIR

The pressure sensitivity of the fracture medium in the tight oil and gas reservoir possesses a significant impact on the development effects of the petroleum reservoir.Based on the theory of material conservation,the pressure sensitivity equations of the matrix and fracture were established with the help of the theoretical deduction;as the same time,by means of the physical simulation experiment of the pressure sensitivity percolation for the individual fracture,the fracture deformation and medium permeability change characteristics were studied,and moreover the rationality of the flow model of the pressure-sensitive fracture medium was verified by the experimental results stated above.The researches show that the established pressure sensitivity equation for the matrix and fracture is the function of the liquid pressures,this understanding can solve the problem that the deformed coefficient in the conventional pressure sensitivity equation is difficult to determine,and thus the adaptability of the equation is enhanced in the actual development of the tight oil reservoir.The experiment found that the liquid pressures were dropped,the fractures among the swollen matrix blocks were closed,the fracture aperture was decreased and the medium permeability was increased;when the liquid pressure rising,the contracted blocks made the fractures among the blocks open,both the aperture and medium permeability were enlarged.The contrast between the results of the experimental simulation and permeability model based on the experimental data has verified the rationality of the permeability model.All the achievements have exposed the pressure-sensitive deforming mechanism of the fracture medium in the tight oil reservoir,thus the basement of the permeability characterization has been laid for the fracture medium.