Zhang Hengrong, Tan Wei, Hu Desheng, Hu Xiangyang, Sun Jianmeng, Yang Dong
CNOOC Limited, Zhanjiang 524057, China.
China University of Petroleum (East China), Qingdao 266580, China.
ACS Omega. 2024 Aug 23;9(36):37678-37686. doi: 10.1021/acsomega.4c02279. eCollection 2024 Sep 10.
When the gas reservoir contains CO, the logging response tends to be complex. When calculating porosity with neutron and density curves, the accuracy of porosity calculation is reduced due to the uncertainty of fluid parameters, which in turn affects the evaluation of CO content. It increases the uncertainty of reserve evaluation. In this paper, a forward modeling model of density logging is established based on the equivalent volume model, and the method of neutron logging is formed by putting forward the nonlinear formula of the reciprocal of the comprehensive deceleration length. The key parameters and their variation rules of neutron logging and density logging forward modeling under different temperature and pressure conditions are obtained by experimental means and Monte Carlo method, respectively. The variation law of the influence of different CO content on neutron logging and density logging curves is simulated. The research shows that with the increase of CO content, the neutron logging value of gas reservoir decreases, while the density logging value increases, and the greater the porosity of gas reservoir, the more obvious this change trend is. Compared with CH, CO has a more significant impact on the excavation effect of neutron logging. On this basis, combined with the conductivity model of the study area, the porosity and CO content of CO bearing gas reservoir are solved by the least-square method. The practice shows that the relative error of porosity calculation is within ±4% and the error of CO content calculation is within ±10%, which proves the reliability of this method.
当气藏含有一氧化碳时，测井响应往往较为复杂。利用中子和密度曲线计算孔隙度时，由于流体参数的不确定性，会降低孔隙度计算的准确性，进而影响一氧化碳含量的评价，增加储量评价的不确定性。本文基于等效体积模型建立了密度测井正演模型，并通过提出综合减速长度倒数的非线性公式形成了中子测井方法。分别通过实验手段和蒙特卡罗方法获得了不同温度和压力条件下中子测井和密度测井正演的关键参数及其变化规律，模拟了不同一氧化碳含量对中子测井和密度测井曲线影响的变化规律。研究表明，随着一氧化碳含量的增加，气藏的中子测井值减小，而密度测井值增大，气藏孔隙度越大，这种变化趋势越明显。与甲烷相比，一氧化碳对中子测井的挖掘效应影响更显著。在此基础上，结合研究区的电导率模型，采用最小二乘法求解含一氧化碳气藏的孔隙度和一氧化碳含量。实践表明，孔隙度计算的相对误差在±4%以内，一氧化碳含量计算误差在±10%以内，证明了该方法的可靠性。
