串珠状缝洞型碳酸盐岩储层压力变化特征研究

目前的缝洞型碳酸盐岩储层模型建立主要以多重介质、渗流、管流或渗-管流结合等理论为基础，但是当储层内具有大尺度溶洞时，多重介质、渗流理论不能准确表征宏观缝洞储集体。当储层内具有大开度裂缝时，其内部流体流动特征与平板流特征更为接近。因此，需要建立以裂缝平板流与宏观非均质性理论为基础的储层模型。根据气体物质守恒方程与流体力学方程，推导了更接近于真实大型裂缝中气体流动特征的平板流动模型，建立了串珠状缝洞型碳酸盐岩气藏储层的宏观非均质数学模型，并通过数值方法求解出该模型定产量生产时井底压力与各溶洞压力数据。绘制出了溶洞压力导数半对数曲线和井底压力双对数曲线。压力导数双对数曲线可以分为4段：井筒储集反应段、裂缝反应阶段、溶洞反应阶段和边界反应阶段。随后，分别研究了各类缝洞参数对压力导数双对数曲线形态特征的影响。研究表明，不同的缝洞参数会影响压力导数双对数曲线上相应阶段的形态特征。

Pressure Variation Characteristics in Bead-shaped Fractured Vuggy Carbonate Gas Reservoirs

This paper establishes a mathematical model for gas flow through bead-shaped fractured vuggy carbonate gas reservoirs based on material balance and fracture flow equations. This model could calculate the pressure variation in each vug during the gas production stage. A series of numerical calculations were conducted on the mathematical model, and then a double logarithmic curve of the bottom hole pressure(BHP) and a semi-logarithmic curve of pressure derivative were plotted. According to the semi-logarithmic curve, pressure derivative curves of vugs initially increase and then decrease; meanwhile, the derivative curves of the nearest vug from the well increases and decreases most rapidly, and its turning point presents earlier than other vugs. The double logarithmic curve could be divided into four stages-wellbore storage effect reaction stage, fracture reaction stage, vug reaction stage, and boundary reaction stage. Finally, we studied the characteristics of the double logarithmic curve from a series of models with different number/volume/arrangement of vugs and different apertures/arrangements of fractures, and it was found that the characteristics of double logarithmic curves change with the different above-mentioned parameters.