含砂岩薄互层陆相页岩气藏生产预测模型研究

Study on production model prediction of continental shale gas reservoir with thin interbedded sandstone

为了进一步加快对延安地区陆相页岩气的开发,针对鄂尔多斯盆地中页岩气储层普遍发育砂岩薄互层的情况,运用基于改进的电容电阻法推导出定产条件下考虑或不考虑层间窜流的生产预测模型。针对3种典型储层岩性组合(砂岩-页岩组合,页岩-砂岩-页岩组合及砂岩-页岩-砂岩组合)构建数值模型进行对比验证以及敏感性分析,结果表明:1)存在层间窜流时,砂岩薄互层与页岩气层相互沟通,气井初始产量提升约5~10倍;2)不存在层间窜流时,多层储层的开采过程表现出高渗层(砂岩薄互层)的早期递减特征,气井初始产量高,稳产时间较短;低渗层(页岩层)的后期递减类似于低渗基质中油气衰减的特征,气井以较低产量持续生产较长时间。该研究成果为陆相页岩气实际开发方案的制定提供理论支撑。

In order to further accelerate the exploitation of continental shale gas in Yan’an Area.In view of the situation that thin interbedding sandstones are commonly developed in continental shale gas reservoirs in Ordos Basin,a production prediction model with or without crossflow is derived based on the improved capacitance resistance method.Aiming at three typical reservoir lithology assemblages(sandstone-shale,shale-sandstone-shale and sandstone-shale-sandstone combination),the comparative analysis and sensitivity analysis are adopted.The result show that:1)When crossflow exists,thin interbedded sandstone layers communicate shale gas layers,the initial production of gas wells increases about 5~10 times;2)When there is no crossflow,the multi-layer reservoir can show the early decline characteristics of high permeability layer(thin interbedded sandstone),which mean the initial production of gas well is high and the stable production time is short.The later decline characteristics of low permeability layer(shale)is similar to the decline characteristics of oil and gas in low permeability matrix,which show that gas wells produce at lower rates for longer periods of time.It also provides theoretical support for the formulation of continental shale gas development plan.