页岩凝析气藏物质平衡方程及储量计算方法

页岩气藏的特点是无机基质孔隙、有机基质孔隙、天然裂缝孔隙、水力裂缝孔隙和吸附相孔隙并存。实验室和数学研究表明页岩气藏可以由五种孔隙度模型和干酪根溶解气储集机制来描述。基于Orozco和Aguilera方程,考虑页岩吸附气量和溶解气量随地层压力的变化以及两者对游离气储集空间的影响,建立页岩凝析气藏物质平衡方程。以Orozco和Aguilera文中的页岩凝析气藏为例,首先进行储量回归得到基质和裂缝游离气储量,再计算吸附气和溶解气储量以及总储量,然后根据各个储量所占比例计算一系列G_(pt)值(总的累计产气量),作p/Z_2(压力/两相气体偏差因子)和G_(pt)的关系曲线,与生产历史数据拟合较好。与Orozco和Aguilera的结果相比,总储量相差3%,各个储量所占比例也不尽相同。

MATERIAL BALANCE EQUATION AND RESERVES CALCULATING METHOD FOR SHALE CONDENSATE GAS RESERVOIRS

Shale gas reservoirs are characterized by multiple pores such as the inorganic matrix pore,the organic matrix pores,micro-fracture pores,hydraulic fracturing pores and adsorbed phase pores.It has been demonstrated by the laboratory and mathematical studies that these reservoirs can be characterized and represented by the quintuple porosity model and enriching mechanism of the kerogen dissolved gas.Based on Orozco and Aguilera's equations considering the changes of the adsorbed and dissolved gases with the formation pressure and the effects of both of them on the accumulating space of the free gas,the material balance equation of the shale condensate gas reservoirs was established.Taking the examples of the shale condensate gas reservoirs mentioned in the papers of Orozco and Aguilera,the reserves of the free gases in the matrix and fractures were obtained with the help of the reserves regression,and then the adsorbed,dissolved and total gas reserves were calculated.And then according to the taken proportions of each reserve,a series of Gpt value （ total accumulated gas production) were calculated.The relation between p/Z2 (pressure/two-phase gas deviation factor) and Gpt provides a good fit to the data of the production history.Comparing with the results of the above two papers,the total reserves differ by 3％ and furthermore the proportions of each reserve are quite same.