高CO2含量气藏物质平衡方程及其动储量评价

针对高CO₂含量天然气在气藏衰竭式开发过程中存在的溶解气释放效应导致动储量无法得到有效评价的问题，建立了考虑水侵、应力敏感效应、水蒸气含量以及溶解气释放效应的物质平衡方程。采用PVT实验研究了CO₂含量分别为3.18%~53.90%的天然气混合物在压力由53.01 MPa降低至3.01 MPa的溶解度变化情况，回归得到了溶解度的预测模型。为了研究高CO₂含量对气藏的动储量评价方面的影响，分别利用压降法、考虑应力敏感储量计算模型、考虑应力敏感、水蒸气含量及水蒸气膨胀量的储量计算模型，以及针对高CO₂含量提出的计算模型对A气藏动储量进行计算。研究结果表明，不考虑高CO₂含量天然气的释放效应计算得到的动储量结果普遍偏高，误差范围在（0.69~2.55）×10⁸ m³，因此，高CO₂含量天然气的释放效应在气藏的动储量评价过程中不能被忽略。

Material Balance Equation and Dynamic Reserve Calculation of CO2-rich Gas Reservoir

For an accurate calculation of dynamic reserve during the depletion-drive development of CO2-rich gas reservoir,which is a consequence of release of dissolved gas,a material balance equation is established considering water encroachment,reservoir stress sensitivity,water vapor concentration,and release of dissolved gas.PVT experiments were performed to investigate changes in the solubility of natural gas mixtures with a CO2 concentration of 3.18%～53.90%when the pressure dropped from 53.01 MPa to 3.01 MPa.Based on the experimental results,a prediction model for solubility analysis was developed based on regression.To investigate the effect of high CO2 concentration on the dynamic reserve calculation of gas reservoirs,the latter(denoted by A)was calculated utilizing the pressure drop method,the reserve computation model only considering stress sensitivity,the reserve computation model considering stress sensitivity,water vapor concentration and water vapor expansion,as well as the proposed computation model that also considered high CO2 concentration.The results showed that when the effect of the release of CO2-rich natural gas was not considered,the calculated dynamic reserves were considerably high,with errors ranging from 0.69×10^8 m^3 to 2.55×10^8 m^3.Therefore,its effect cannot be ignored in the evaluation of the dynamic reserve of gas reservoirs.