四川盆地北部震旦系下寒武统是继安岳气田发现和绵阳—长宁裂陷提出之后备受关注的另一重点勘探领域,但对其沉积-构造格局的认识存在严重分歧.文中基于露头剖面、地震、钻井和地球化学分析资料并结合前人研究成果,提出四川盆地北缘震旦纪—早寒武世期间存在隆-坳并存的格局.四川盆地北缘震旦系—下寒武统厚度、岩相、地震反射和地球化学等指标的详细分析表明:(1)沉积-构造格局表现为隆-坳相间的特点,即自西向东依次为绵阳—长宁裂陷→汉南—米仓山隆起→万源—通江裂-坳陷→达州—开江隆起→城口—开县裂-坳陷→东安—巫溪隆起→巴东—恩施裂陷→神农架—黄陵隆起;(2)发育台地、斜坡和盆地三种沉积环境,其中斜坡环境以发育大量风暴、重力流、滑塌角砾沉积及同沉积滑移变形等为主要识别标志;(3)经历了三个“隆-坳”旋回,即陡二段末期—灯二段早期、灯二段晚期—灯四段早期、灯四段晚期—筇竹寺组晚期.四川盆地北缘震旦纪—早寒武世隆-坳格局的形成受控于震旦纪基底构造薄弱带、南秦岭地幔上隆底侵和原特提斯洋壳板片拖拽三者的联合作用,与罗迪尼亚大陆裂解和冈瓦纳大陆聚合的全球构造背景密切相关.四川盆地北缘震旦纪—早寒武世隆-坳并存格局的提出不仅有助于进一步认识该时期扬子克拉通区域沉积-构造格局和演化,也为川东北地区下一步油气勘探决策提供了参考依据.川东北地区震旦纪—早寒武世隆-坳格局控制了烃源岩和储集层的发育及源储配置关系,建议首先将裂-坳陷边缘带作为下一步勘探的重点.

Compared with the conventional migration method, least-squares reverse time migration (LSRTM) has a lot of advantages, such as higher imaging resolution, amplitude preservation and amplitude balance and so on. But, the L2 norm based LSRTM algorithm is very sensitive to noise, especially when the data contains outliers. Compared to L2 norm, Student’s t distribution has better robustness. We extend the Student's t distribution to the LSRTM algorithm. In addition, multi-sources inversion is an effective way to reduce the computational cost. However, it often generates crosstalk noise. In this paper, we use L1 norm sparse regularization constraints with K-SVD dictionary learning to suppress the crosstalk noise caused by phase encoding. Theoretical models and field data processing verify the effectiveness of the algorithm and suitability for complex models. Presentation Date: Tuesday, September 17, 2019 Session Start Time: 1:50 PM Presentation Start Time: 3:30 PM Location: Poster Station 10 Presentation Type: Poster

以普光地区长兴组和雷口坡组为例,展示了地震资料岩性标定在碳酸盐岩储层预测中的应用流程和思路。首先在井点处系统分析储层岩性组合的地震响应和横向变化特征;再根据实际地质情况对地震相变进行合理解译,获取相应的地震地质认识;最终结合认识将各井点处的标定结果拓展到横向上。在实际应用中,通过岩性标定识别出了能准确代表长兴组厚储层的地震响应及横向上的变化规律,为储层预测提供了依据;将90°相位转换更好的应用到岩性标定中,解决了雷口坡组薄储层的精细识别问题。应用实例表明,精细的岩性标定能够简化解释工作,并有效提高储层预测的精确度和可信度。此外,碳酸盐岩地层岩性变化缓慢,经常出现一定范围内岩性和物性相对稳定的地层,合理的利用这类地层能够有效提高岩性标定和储层预测结果的准确性。

In order to solve complicated faults imaging problem of the Dongpu oilfield,the authors utilized multi?step reverse time mi?gration method and realized GPU accelerate parallel algorithm for overcoming the low compute efficiency disadvantage of RTM.The GPU accelerated multi?step reverse time migration method was successfully applied to complicated faults imaging processing. The RTM ima?ging result of Qianliyuan 3D data proved the technological advantage of RTM for complicated small faults imaging and Lanliao dip?angle faults imaging.Migration efficiency analyses demonstrate that RTM based on GPU accelerate algorithm can effectively improve the com?putational efficiency by 75 times.

现今逆时偏移的应用面临海量数据存储及计算量巨大的问题.本文应用震源重构方法解决了逆时偏移互相关成像条件需要的海量存储问题,引入GPU Kernel解决逆时偏移计算效率低的问题.在此基础上,本文建立了一套基于GPU加速的叠前逆时偏移成像方法,并成功地应用于四川盆地A复杂区块.

There are many difficulties in reverse time migration applications for nowadays seismic exploration, storage and computations of the mass data may be the top ones. In this paper we use source reconstruction method to reduce mass storage brought by cross-correlation imaging condition, and introduce GPU kernel to improve computation efficiency. And based on these, we build a GPU accelerated reverse time migration method, which successfully applied in Block A, a complex area in Sichuan Basin.

By taking the drilling core samples from Dongpu Depression for examples,the acoustic characteristics of dried rock samples and rocks filled with porous fluid were measured at the conditions of simulated well temperature and pressure in the laboratory.Eight acoustic and elastic parameters such as the pressure and shear wave velocity,density,Poission's ratio,Yang's modulus,elastic modulus,shear modulus as well as bulk modulus of the sandstone were measured at the interval of 20% water saturation.The relationship of the pressure with P and S wave velocity,the Vp/Vs ratio,Poission's ratio as well as the elastic parameter is fitted for No.1 sample.The relationship of the P and S wave velocity,the Vp/Vs ratio,Poission's ratio and elastic parameters of rocks under different conditions of pressure and temperature changing with water saturation are fitted for No.2 sample during water-oil displacement.The result provides fundamental data for the pre-stack seismic inversion,lithology identification and fluid detection for Dongpu Depression.The results also provide petrophysical evidence for the future geological and geophysical research in the area.

Based on the seismic reflection,features of palaeogeomorphology and distribution of valley as well asthe combination types of light-heavy mineral in rock fragment,the direction and pattern of multi-provenance ofthe lower Cretaceous in the western gentle slope belt,Baiyinchagan Depression have been studied. The researchshows that seismic facies of lower Cretaceous in Xilinhaolai area,gentle slope belt of Baiyinchagan depression canbe divided into three types. The west east is dominated by the oblique crossing propagational reflections,whilereflection amplitude in the middle region is weaker comparatively. Provenance in the west is abundant and thus thefan scale is larger relatively. Both the heavy mineral combinations and debris components of sandstone in differentarea are different. Sandstone in the south is dominated by lithic sandstone,while the west and the east are dominatedby feldspar lithic sandstone;lithic of the western sandstone is mainly granite gneiss,while the eastern one is mainlymetamorphic lithic such as schist,yet the southern one contains intracoastal such as ooid,carbonate and so on. It isbelieved that there are three provenances in the western gentle slope belt including the western one along the longaxis,the southern one along the short axis and the eastern one. The short axis provenance prevails in the early timeof the basin evolution,yet it changes to be the long axis provenance in the middle and late time.

Pre-stack elastic impedance inversion involves the calculation of elastic impedance curve,while the conventional calculations are based on the assumption that K is a constant,but the assumption does not match with the actual situation,which results in the deviation in calculating elastic impedance curve and extracting the lithology parameters.Therefore,we introduced K scan method to optimize the selection of K.The method includes three steps.Firstly, different K was selected to compute elastic impedance.Then,the elastic impedance was transformed into reflectivity.Finally,the difference of the reflectivity obtained from the second step and accurate Zeoppritz equation was calculated,and the minimum difference was the optimal K.application on theoretical model and actual logging curve show that the method can be used to select best K and has good applicability.

Seismic exploration accuracy meets higher and higher requirements since the exploration targets in Dongpu Sag tend to be more subtle and complicated.For this,this paper puts forward a new method for acquiring horizon velocity based on joint inversion of stack velocity and migration velocity,improving the accuracy of velocity calculation.Through study on methods for establishing velocity field,the technology of establishing velocity field on the basis of combining such information as seismic velocity,logging,drilling and structural horizon is developed,and the velocity field reflecting the macroscopic law of velocity distribution is obtained,which is in good agreement with the well.Integrating the concept and application of seismic velocity,this paper defines the correlation of various types of velocity and its applicability,providing a complete velocity field solution for different phases of seismic exploration.Based on coordinate positioning and unified format transformation of seismic velocity data,the velocity base of all over Dongpu Sag is established,supporting seismic imaging,variable velocity mapping,and prediction of regional formation pressure technically,and yielding good results.

The conventional 3D seismic geometry designing is based on the horizontally stratified medium presumption, its main objective is to obtain regularly sampled stacking dataset, which can be used to image the geological target through post-stack migration. Different from post-stack migration in which the regular post-stack data volume is used, the pre-stack migration uses irregular offset datasets. The irregular spatial sampling of the 3D geometry could probably result in severe migration noise, which then may partially decrease the effect of the pre-stack migration. Designing the 3D geometry which meets the requirement of pre-stack migration has great significance by fully making use of the advantages of the pre-stack migration and raising the imaging accuracy. The new geometry designing method was introduced in this paper, based on the evenly sampling and bin attribute consistence principle the geometry template was designed, good spatial samples were acquired, the designed geometry were gradually optimized by using focus beam, pre-stack migration response, forward modeling, wave field illumination and other techniques, at last the geometry which could meet the requirement of pre-stack migration and could resolve geological problem was obtained. The new method was applied in QK survey in Dongpu Depression and the excellent results were achieved in the survey.

The main objective of conventional 3D seismic geometry design is to obtain regularly sampled stacking dataset, which can be used to achieve good images through post-stack migration.However, pre-stack migration has strict requirements on seismic geometries.In order to exert the technical advantages of pre-stack migration and improve the accuracy of seismic images, it is very important to design seismic geometries based on pre-stack imaging. This article puts forward an approach of seismic geometry design based on pre-stack imaging.The first step is to design the basic spatial sampling of seismic geometry based on the anti-aliasing criteria of pre-stack migration.The second is to design the layout of seismic geometry according to the rule of regular sampling and uniform bin attributes. Then, it optimizes step by step and finalizes seismic geometry by using techniques such as focal beams, pre-stack migration response of scatter point, forward modeling, and wavefield illumination.This method has been applied to high accuracy seismic exploration of the Zhongyuan Oilfield in recent years and it has obtained very good results.

Aiming at different targets during developing period,Zhongyuan Oilfield has acquired 3D seismic data of small-scale for 10 disperse batches in Baiyinchagan depression since 1993,it was unfavorable for local research and depression exploration,stamp patterned data was not content with depression exploration development.In order to meet the requirement of exploration in the sag,Geophysical Research Institute of Zhongyuan Oilfield Company adopts the 3D data merged processing technique using 9 batches,which eliminates field data difference and lays solid foundation for exploration breakthrough.

In 2005,Zhongyuan Oilfield Company carried out high-precision 3D seismic exploration in Machang area of Dongpu sag,in which the design and demonstration of geometry scheme is a key step.The main geometries utilized in the sag in the past are first analyzed by using forward modeling techniques.By comparison of simulated data,the knowledge that imaging effects can be improved with increasing spatial sampling density is cognized.The acquisition geometry is determined by analyzing the two geometries with higher spatial sampling during the survey design of high-precision seismic exploration in the area.Focal analysis shows that the designed geometry has good property in amplitude accuracy and in horizontal illumination,which is favorable for lithology recognition in final seismic data.With the practice of high-precision seismic exploration in the area,imaging quality is significantly improved and very good results are achieved,which also proves the correctness of the geometry design.

When velocity anisotropy exists in subsurface rocks,the conventional isotropic migration methods may lead to not only wrong imaging position but also inaccurate image quality.This paper presents a method of anisotropic pre-stack time migration with real 3D seismic data in Dongpu sag.First,velocity and anisotropy parameters are obtained by using bi-spectral velocity analysis,and then the pre-stack data is migrated with an anisotropic method.Good imaging results are fulfilled in real 3D data.

When velocity anisotropy exists in subsurface rocks,the conventional isotropic migration methods may lead to not only wrong imaging position but also inaccurate image quality.This paper presents a method of anisotropic pre-stack time migration with real 3D seismic data in Dongpu sag.First,velocity and anisotropy parameters are obtained by using bi-spectral velocity analysis,and then the pre-stack data is migrated with an anisotropic method.Good imaging results are fulfilled in real 3D data.

Through the discussion of the current state of lithologic & stratigraphic reservoir of Dongpu sag and the contrastive analysis of some typical basins in China,the geological conditions favorable for the formation of lithologic & stratigraphic reservoir in the sag are illustrated.The main area to explore lithologic & stratigraphic reservoir is within the area of hydrocarbon generation where structural trap is not developed.The countermeasures for exploring the lithologic & stratigraphic reservoir in the sag are analyzed and summarized.More attention should be paid to high-precision 3D information and reservoir characterization in order to effectively explore the lithologic & stratigraphic reservoir.

Dongpu sag is a sophisticated oilfield which has been explored and developed for 30 years.At present,complex fault-block reservoirs are the major target for exploration and development,of which the fault blocks are small and cracked,the fault plane is steep,and oil column thickness is small.All the features require more accurate seismic exploration.To meet the requirements of exploration and exploitation,combined with the trends of geophysical technology,we shall learn from the relevant advanced techniques both at home and abroad and focus on high precision 3D seismic techniques to tackle the imaging problems in complex fault-block reservoirs.Finally,a series of techniques are developed to implement high precision 3D seismic exploration.The application of the techniques in the areas such as Machang and Qiaokou shows that they are effective in solving the exploration and development problems in complex fault-block areas,and are valuable to be more widely applied in the same problematic area.

A pressure predicting model is established by synthetically using the data of seism, well logging and well drilling in combination with statistical matching method and nonlinear inversion. A pressure predicting model for the whole working area is obtained through spatial interpolation after single-well is analyzed for multi-wells, and then seismic inversion is used to obtain precision velocity data. The stated pressure predicting model is used to detect pressure in the area with better effect.

有限差分法是求波动方程数值解的一种常用方法,但常规的有限差分法难以克服数值频散的干扰.在总结、分析前人工作的基础上,本文对有关技术做了整合和扩展,形成了有限差分的优化算法,主要内容包括高阶有限差分、优化差分参数和通量校正传输(FCT)技术.与常规方法相比,本文方法既提高了波动方程正演的精度又减少了计算量,可广泛用于起伏地形和复杂地下地质构造的波场模拟和分析.通过对煤层模型和BM工区进行正演模拟,验证了本文方法的有效性.