Application of fluid modulus inversion to complex lithology reservoirs in deep-water areas

It has been a challenge to distinguish between seismic anomalies caused by complex lithology and hydrocarbon reservoirs using conventional fluid identification techniques,leading to difficulties in accurately predicting hydrocarbon-bearing properties and determining oil-water contacts in reservoirs.In this study,we built a petrophysical model tailored to the deep-water area of the Baiyun Sag in the eastern South China Sea based on seismic data and explored the feasibility of the tri-parameter direct inversion method in the fluid identification of complex lithology reservoirs,offering a more precise alternative to conventional techniques.Our research found that the fluid modulus can successfully eliminate seismic amplitude anomalies caused by lithological variations.Furthermore,the seismic databased direct inversion for fluid modulus can remove the cumulative errors caused by indirect inversion and the influence of porosity.We discovered that traditional methods using seismic amplitude anomalies were ineffective in detecting fluids,determining gas-water contacts,or delineating high-quality reservoirs.However,the fluid factor Kf,derived from solid-liquid decoupling,proved to be sensitive to the identification of hydrocarbon-bearing properties,distinguishing between high-quality and poor-quality gas zones.Our findings confirm the value of the fluid modulus in fluid identification and demonstrate that the tri-parameter direct inversion method can significantly enhance hydrocarbon exploration in deep-water areas,reducing associated risks.

Fluid discrimination incorporating viscoelasticity and frequency-dependent amplitude variation with offsets inversion

Frequency-dependent amplitude versus offset(FAVO)inversion is a popular method to estimate the frequency-dependent elastic parameters by using amplitude and frequency information of pre-stack seismic data to guide fluid identification.Current frequency-dependent AVO inversion methods are mainly based on elastic theory without the consideration of the viscoelasticity of oil/gas.A fluid discrimination approach is proposed in this study by incorporating the viscoelasticity and relevant FAVO inversion.Based on viscoelastic and rock physics theories,a frequency-dependent viscoelastic solid-liquid decoupling fluid factor is initially constructed,and its sensitivity in fluid discrimination is compared with other conventional fluid factors.Furthermore,a novel reflectivity equation is derived in terms of the viscoelastic solid-liquid decoupling fluid factor.Due to the introduction of viscoelastic theory,the proposed reflectivity is related to frequency,which is more widely applicable than the traditional elastic reflectivity equation directly derived from the elastic reflectivity equation on frequency.Finally,a pragmatic frequency-dependent inversion method is introduced to verify the feasibility of the equation for frequency-dependent viscoelastic solid-liquid decoupling fluid factor prediction.Synthetic and field data examples demonstrate the feasibility and stability of the proposed approach in fluid discrimination.

惠西南地区储层含油气性叠前地震固液解耦识别

惠西南地区位于珠江口盆地珠一坳陷惠西半地堑南侧,主要以构造-岩性复式圈闭勘探为主,主力油气层为K08—K22,其砂体纵向变化大,常规的流体识别方法难以排除因孔隙度造成的假"亮点"。本文对Xu-White模型进行改进,建立了变孔隙纵横比的砂泥岩地震岩石物理模型,发展了基于测井约束反演修正的横波预测技术。基于地震岩石物理模型,进行地震岩石物理分析,优选弹性阻抗和固液解耦等效流体体积模量为敏感参数,为储层描述和流体识别工作提供有力支撑。利用贝叶斯弹性阻抗反演方法获取部分角度叠加的弹性阻抗数据体,推导了相应的弹性阻抗方程,对固液解耦等效流体体积模量进行直接提取。该方法综合利用了地质信息、测井数据以及叠前地震AVO信息,既保证了常规弹性阻抗反演的抗噪性,又避免了间接反演的误差累积和孔隙度等物性的影响。实际资料处理结果与测井解释结果和地质认识吻合较好,证明了方法的可行性和实用性。

利用五维数据直接提取裂缝型储层参数

现有裂缝型储层流体识别方法在构建流体敏感参数过程中没有考虑岩石骨架、裂缝、孔隙及油气水耦合影响,对五维数据中丰富的方位信息蕴含的流体信息挖掘不够,并且针对裂缝型储层油气识别以间接计算参数为主。宽方位地震五维数据反演本身存在“病态解”及“不确定性”等问题,多裂缝参数同时反演更易导致储层参数反演精度下降。因此,基于间接代数组合的流体因子在计算过程中不可避免地累积计算误差,影响油气识别效果。为此,结合各向异性Gassmann孔隙弹性理论和线性滑动理论,以“固液缝”解耦流体因子为基础,推导了由“固液缝”解耦流体因子直接表征的新的纵波反射系数方程,分析、讨论了新纵波反射系数方程的适用条件及敏感性;在此基础上,构建贝叶斯框架的地震反演目标函数,并基于时频资料研究五维数据流体识别方法,可直接获得裂缝型储层“固液缝”解耦流体因子,消除了累计误差的影响,提高了预测精度。模型试算及实际资料处理表明,所提方法可以合理、可靠地预测裂缝型储层油气分布。

东沙隆起区灰岩强振幅影响下储层识别与流体检测研究及应用

H1S地区位于珠江口盆地珠一坳陷东沙隆起边缘,发育两套呈条带状展布的岩性砂体K08和K22,由于邻近生烃洼陷,成藏条件极佳。该砂体超覆于东沙隆起台地碳酸盐地层之上,且横向变化大,因受到灰岩强反射界面的干扰,该区域储层识别和流体预测一直未得到较好解决。这里首先利用匹配追踪算法理论,对强反射进行压制,恢复原有储层应有的反射特征,通过对工区内典型探井进行分析,建立高精度的岩石物理模型,优选弹性阻抗和固液解耦等效流体体积模量为敏感参数,为储层描述和流体识别工作提供有力支撑。利用贝叶斯弹性阻抗反演方法获取部分角度叠加的弹性阻抗数据体,对固液解耦等效流体体积模量进行直接提取,获取含气性分布。实际反演结果与实测测井解释结果吻合率达到83.4%,证明了反演精度较高,明确了H1S地区的含油气的潜在目的层系的展布范围和储层情况。