Forward Analysis Of The Discontinuity Boundary Of Fluvial Facies Reservoirs

In fluvial facies reservoir,many discontinuity boundaries,such as lithologic pinchout,interbeded sandstones,physical property change,fault line,are formed by the sedimentation,diagenesis modification and tectonic movement and other reasons.These discontinuous boundaries can be both a conduit for oil and gas migration and a barrier to reservoir connectivity.In the exploration and development of oil and gas from fluvial facies reservoir,accurate identification of discontinuity boundary,not only can enhance the accuracy in development well deployment,but also help to water injection of oil and gas exploration and analysis of the development of residual oil distribution.In the literature research of discontinuity boundary of the fluvial facies reservoir,scholars at home and abroad made a lot of work about reservoir architecture of fluvial facies,and summarized the different types of interbeded sandstones,they also studied connectivity and discontinuity boundary of fluvial facies reservoir from logging,well-log and seismic data,seismic wavefonn classification and the conventional seismic attributes,etc.Summarizes these techniques can be seen that,based on logging,well-log and seismic data,conventional seismic attributes,seismic waveform classification techniques in identification of fluvial facies reservoir discontinuity boundary,each method has its own advantages but also has many disadvantages.The author found that these methods have a common characteristic,whether based on logging curves of logging facies model,or in the preset waveform when the seismic waveform classification,or a well combination of seismic forward modeling analysis,they all involve analysis of waveform characteristics.However,because of the thickness of single channel sandstone is thin,interbeded sandstones is widespread due to frequent migration and accretion of the channel,the resolution is limited by seismic data,discontinuity boundary of sandstone is still not easy to identify rapidly and accurately.In this paper,on the basis of predecessors' research,first of all,based on domestic and foreign scholars' classification of reservoir architecture,establishing different interbeded range of 2D and 3D interbeded sandstones models according to geological and logging data of central and southern of BoHai Sea,and forwarding synthetic seismic records.Secondly,a detailed discussion of two-dimensional interbeded sandstones,in a horizontal superimposed distance and the vertical elevation difference of different cases,by changing the frequency and random noise to analysis the waveform features,then introduced the seismic waveform structure attributes that can depict seismic waveform structure properties,and is divided into three categories:integral class(waveform area,waveform length),statistics class(variation coefficient,skewness,kurtosis of peak,kurtosis of trough,kurtosis of peak and trough),difference class(complex envelope difference,half-time bending difference).And then,introduced a period time window which is verified by comparison of time window to extract the seismic waveform structure attributes that is more advantageous to depict discontinuity boundary of interbeded sandstones of fluvial facies.Then,analyzing the 2D and 3D interbeded sandstones model by seismic waveform structure attributes,integral class attributes mainly depict the thickness of sandstone,statistics class attributes are better characterized interbeded area of sandstones,difference class attributes mainly depict discontinuity boundary of interbeded sandstones.Then,the influence of different dominant frequency and random noise to three kinds of seismic waveform structure attributes is analyzed.And,the technical method and processes that identification discontinuity boundary of fluvial facies reservoir based on three kinds of seismic waveform structure attributes in three steps is proposed;Finally,the validity of the method is verified through geological and logging data in BoHai Bay BZ34 1 oil field.