The Research In Lithologic Stratigraphic Traps Identification

Because the detection of oil and gas fields becoming more and more difficult,the conventional exploration methods with structural traps as the core are facing more chanllenges.The lithologic stratigraphic reservoirs have become the direction of offshore oil and gas exploration.The following problems are existing in this field:(1)The resolution and amplitude preservation of the seismic data are difficult to describe the characterization of lithologic stratigraphic traps;(2)The seismic sequence division is not accurate;(3)The development model and distribution of the lithologic-stratigraphic traps are unclear.(4)The exploration technology of lithologic stratigraphic traps are inperfect.In this paper,with the Dongying Formation in the central and southern part of the Western Liaoxi uplift as the research target,the sequence stratigraphic description is based on well log and seismic data,and the stratigraphic trap types and lateral distribution rules are analyzed.Based on the seismic data,multiple attribute analysis and inversion are carried out to predict the distribution of reservoirs.To solve these problems,the main research results and understanding are as follows:1.Establish the high-resolution sequence stratigraphic framework with well logging and seismic data,and analyze the spatial distribution and variation characteristics of sequence stratigraphic.We transfer the sequence interface and sequence body information which divigng by well logging to seismic data through the effective coupling and linkage of well logging and seismic time-frequency analysis.The responses of different frequencies to different scales of geological bodies are used to identificate different levels of sequence interface and sequence interpretation and division,thus the high frequency sequence frameworks are established effectively.The combinations of these two methods are more conducive to reflect the sedimentary environment of the underground geological structures and it’s also the main technical development direction to improve the accuracy of seismic sequence stratigraphy.2.Through the forward modeling with different main frequency and different angle,the influence of frequency and angle on pinch-out point/overlap point is verified.According to the geological structure characteristics of the field,the forward models which accords with the characteristics of the central and southern part of the Liaoxi uplift are established.The seismic response characteristics and distribution rules of lithologic stratigraphic traps in the field are summarized.3.Based on the generalized S transform multi-order smoothing combined deconvolution technique,the existing seismic data are processed with high resolution.Combine with(1)Instantaneous phase seismic pinch-out interpretation technique based on VMD 、(2)Spectral decomposition seismic pinch-out interpretation technique 、(3)Seismic pinch-out identification technique based on Multichannel synchrosqueezing generalized S transform for isofrequency、(4)Seismic pinch-out identification based on reflection coefficient inversion 、(5)Seismic pinch-out identification technique based on wave crest number variation,we describe the lithologic stratigraphic pinchout in this field,and the method system of lithologic stratigraphic pinchout identification in the central and southern area of Western Liaoxi is established.4.Taking the Dongying formation as an example,the study was carried out under the control of fourth order sequences stratigraphy which based on the seismic data and well logging.Based on the calibration of well logging and seismic data,combine with peripheral investigation,this field may have various types of sandstone reservoirs,such as channel sand type,delta type,turbidite type,beach bar sand type,and stratigraphic overlap reservoir.5.The methods of wave impedance inversion,peak frequency attribute and frequency attenuation gradient were used to comprehensively predict the reservoir.The reservoir prediction is carried out in the lithologic stratigraphic traps to optimize the favorable exploration targets.In this paper,we summarize the key techniques for characterizing lithologic stratigraphic traps in the central and southern part of the Western Liaoxi uplift.And a system of geologic-geophysical comprehensive prediction and evaluation techniques suitable for lithologic stratigraphic traps in this field is formed.In addition,we provide some ideas and methods for the description of lithologic stratigraphic traps and reservoir prediction of similar geological conditions.