多分量地震全波形弹性反演预测砂岩油藏剩余油分布

Prediction of the remaining oil distribution using multi-component seismic full waveform elastic inversion

中国东部油田经过几十年的开采,主力油层先后进入高含水后期,但仍有相当一部分原油留存在地下。笔者依据中国东部油田原油及地层水的物性特征,分析并研究了流体黏滞性对饱和岩石剪切模量的影响以及黏滞流体剪切模量的变化规律,提出了基于Krief模型和广义Gassmann方程的剪切模量分解及油、水识别方法,并在此基础上进行油水分布预测。根据地震波场的矢量特性和东部油区陆相沉积地层特征,将全波形弹性波动方程反演方法应用于叠前多分量数据处理,获取深度域地层密度、拉梅常数和剪切模量。在大庆油田某油区2D3C地震数据的应用结果表明,利用多分量地震数据全波形弹性反演和流体剪切模量可以比较好地识别油和水,预测剩余油分布。

Although main reservoirs in old oilfields of eastern China have high water cut after decades of production,there is a considerable portion of remaining crude oils being left in the reservoirs.To identify the remaining oil distribution in these reservoirs is one of the keys problems for optimizing development programs and enhancing oil recovery.Based on previous studies on physical properties of crude oils and formation water from oilfields in eastern China,the influence of viscosity fluid on shear moduli of saturated rocks and their variation laws were discussed in detail.A method based on the Krief model and generalized Gassmann equation was proposed to extract the fluid shear modulus from shear moduli of saturated rocks（also known as the effective shear modulus） and then to identify oils and water.The effective modulus was obtained from multi-component seismic data by using full waveform inversion based on the elastic wave equation that naturally takes the complex behavior of propagating waves into account and can be used to make accurate estimates of formation elastic parameters.The method was applied to field data from the Daqing oilfield in eastern China.The verification drilling confirmed that the distribution of remaining oils can be predicted effectively on condition that the full waveform elastic inversion of multi-component seismic data is integrated with the fluid shear modulus when distinguishing crude oils from formation water.