Globally, the research on risk quantification of natural-gas production is still in its infancy, mainly due to certain uncertainty to select and quantify some sensitive factors as well as the lack of gas reservoirs with a complete development cycle as samples for verification. To fully understand the main factors affecting production risk in the developed gas reservoirs and provide theoretical basis for technical adjustment and EOR, taking 25 Carboniferous gas reservoirs in eastern Sichuan Basin as examples, a production risk quantification model for the Carboniferous gas reservoirs in eastern basin was innovatively established by using the Monte Carlo method. After compared with some existing quantification methods, the Monte Carlo method was recommended. Four decision-making risk factors were defined by analytic hierarchy process, including gas production rate in stable production period, stable production period, recovery efficiency at the end of stable production period, and average productivity of kilometer-deep wells, and the probability distribution curve of each factor and production was constructed by the multi-cycle Gauss probability distribution density function to clarify the main factors affecting the production risk. The formula for calculating the production in the stable production period was established as the objective function for Monte Carlo simulation. The maximum probability of production in these 25 gas reservoirs ranges from 43.43×10~8 m~3 to 126.35×10~8 m~3, and the cumulative probability from 14.59% to 92.88%. The study result represents a breakthrough in risk assessment from the qualitative to the quantitative.

科学预测油气产量变化趋势对制定能源开采计划及调整发展战略具有重要意义.四川盆地中部古隆起震旦系气藏勘探开发潜力巨大,目前已成为四川盆地继磨溪地区下寒武统龙王庙组气藏后又一重要上产领域,成为盆地常规天然气产量增长的主体和天然气上游业务效益贡献的关键,合理的产量规模预测对实现其高质量开发意义重大.因此,从四川盆地中部古隆起震旦系气藏天然气资源地质与开发特点出发,将最终可采储量作为影响产量增长趋势的边界条件,引入到峰值预测产量增长趋势理论的Hubbert与Gauss两种非线性时间序列峰值预测模型中,开展不同探明率条件下的四川盆地中部古隆起震旦系气藏产量预测研究,进一步明确未来勘探开发潜力.模型预测结果表明:①2种预测模型对四川盆地中部古隆起震旦系气藏产量发展趋势都有着较乐观的预测结果,预测结果较为接近;②产量预测结果表明,Gauss模型的预测结果相关性更高;③四川盆地中部古隆起震旦系气藏将在未来20年继续保持产量快速增长趋势,将于2036年达到(140～285)×108 m3/a峰值产量,并在2032—2040年处于相对稳产期,稳产阶段结束时最终可采储量采出程度将超过60％.

针对传统的翁氏和Weibull产量预测模型受指数预测误差的影响而易出现指数倍级别的偏差,不能有效拟合四川盆地油气产量发展趋势的问题.提出了一种基于倍数和指数修正系数的模型修正方法——基于原始数据和一次计算结果计算指数与倍数修正系数,指数修正系数通过调整对模型影响较大的e指数消除数量级上的计算误差,倍数修正系数修正整体计算误差,再利用原产量函数中的t子函数指数多值求解,选取最优解减少预测曲线与原始数据变化规律的差异性,构建符合四川盆地产量发展特点的峰值预测模型.研究结果表明:①基于上述方法改进的翁氏模型和Weibull模型能够有效模拟四川盆地油气产量变化趋势并预测其全生命周期的产量变化趋势;②该盆地天然气产量峰值时间将出现在2050年左右,峰值产量为1453.28×108～1750.38×108 m3;③改进模型具有较高的预测精准度,在油气发展预测工作中具有一定的决策参考价值.

安岳震旦系-寒武系特大型整装气田下寒武统海相烃源岩具有热演化程度高、有机碳含量丰富、生烃潜力巨大等特点,是震旦系-下古生界油气成藏的重要物质基础.目前尚未建立下寒武统烃源岩有机碳测井评价方法,优质烃源岩的分布情况不确定.根据研究区测井、岩心分析、地化等资料,通过分析岩心总有机碳含量与对应测井响应参数之间的关系,建立总有机碳含量的预测模型.通过研究区30余口单井烃源岩有机碳含量计算,完成研究区优质烃源岩分布情况预测.研究认为,德阳安岳裂陷槽内发育麦地坪组与笻竹寺组2套泥质烃源岩,烃源岩有机碳含量大于2.0％ 的优质烃源岩的累计厚度达到200 m以上,是四川盆地震旦系-下古生界主要生烃中心;磨溪构造北斜坡存在一个下寒武统的烃源灶,其内优质烃源岩的厚度超过了20 m,是研究区下一步的勘探方向.