页岩油气产能预测新思路及方法流程

New ideas and workflow to predict shale-oil and shale-gas productivity

产能预测是页岩油气资产评估、开发方案设计等工作的重要前提,但由于页岩储层特低孔低渗及多级压裂的特点,常规油气产能预测方法在页岩油气中的适应性不强。为此,深入分析了页岩油气产能预测中存在的问题,提出了页岩油气产能预测新思路,推荐了产能预测方法流程。研究结果表明:①常规方法不适合页岩油气产能预测主要在于页岩渗透率极低不具备产能试井需达到拟稳态流动的条件,产量递减规律认识不清尤其是后期产量递减规律认识不够,多套产能预测模型选择困难,流动机理无定论致数值模拟不确定性大等;②页岩油气产能预测中应转变思路,重点关注4个方面:重视生产数据的挖掘并找寻产量与地质、油藏工程参数的关系,采用多种方法综合评价并互为补充验证,注重不确定性产能预测方法以降低评估风险,加强生产动态分析并开展储层及裂缝参数反演加深参数认识;③针对有无生产数据、生产数据多少等不同情况建立产能预测推荐流程,有选择地开展多方法综合评价,以实现页岩油气产能预测目标。

For shale oil and shale gas,to predict their productivity is an important prerequisite for asset assessment and development scheme design.Due to extra-low porosity,low permeability,and multi-stage fracturing of shale reser voirs,however,those methods available for predicting conventional oil and gas productivity are not better suitable for them.In this study,many problems involved predicting shale-oil and shale-gas productivity were analyzed thoroughly,new ideas on this prediction were proposed,and prediction process was recommended.Results show that(1)the main reasons why conventional prediction methods are unsuitable for shale oil and shale gas include that,shale permeability is extremely low and cannot meet productivity test,i.e.,pseudo steady state flow;decline laws particularly in the late stage are not made clear;to select a model among multiple prediction ones is difficult;no final conclusion on flow mechanism is made,all leading to great uncertainty in numerical simulation.(2)It's necessary to convert the ideas to predict shale-oil and shale-gas productivity from four aspects,i.e.,mining production data and finding out relationships among production rate,and geological and engineering parameters,adopting many methods for comprehen sive evaluation and complementary verification,paying attention to uncertainty productivity prediction methods to reduce assessment risk,strengthening production performance analysis,and carrying out reservoir and fracture parameter inver sion.And(3)it's essential to establish a workflow to predict productivity for certain situations without production data or with various production data,and to carry out multiple-method comprehensive evaluation selectively so as to achieve one target to predict shale-oil and shale-gas productivity.