Static Correction Processing Technology and Its Application to Improve the Imaging Accuracy of Low-Amplitude Structures

This is a success story of survey design and refraction static correction processing of a large 3D seismic survey in the South Pass area of the Mississippi delta. In this transition zone, subaqueous mudflow gullies and lobes of the delta, in various states of consolidation and gas saturation, are strong absorbers of seismic energy. Seismic waves penetrating the mud are severely restricted in bandwidth and variously delayed by changes in mud velocity and thickness, Using a delay-time refraction static correction method, we find compensation for the various delays, i.e., static corrections, commonly vary 150 ms over a short distance. Application of the static corrections markedly improves the seismic stack volume. This paper shows that intelligent survey design and delay-time refraction static correction processing economically eliminate the historic ‘no data’ status of this area. Introduction Large river deltas present unique problems for seismic exploration. Of particular interest to Gulf Coast geophysicists are the effects of the modern Mississippi delta on seismic data. Variations in the gas content and consolidation of sediments, corresponding to the mud structures of the delta, impose extreme attenuation and traveltime variations on seismic waves. These properties are responsible for designation of the delta area as a ‘no seismic data zone.’ Compensation for these effects is an important part of seismic processing. Deconvolution and spectral balancing compensate for attenuation effects, and refraction and reflection static correction processing compensate variation. Beginning in 1993, Western Geophysical solicited and obtained the participation of several oi I companies in a large 3D survey to be conducted in the area of the delta (Figure 1). This paper highlights the design and refraction static correction processing of Phase 1 of the project. Phase 2 has been acquired and is being processed. From the beginning, we realized that refraction static corrections would be crucial in processing of the survey. Previously, in refraction static correction processing of 2D shallow streamer data, we had produced results similar to those presented by Schatz, et al.] But, although we had been successful in static correction processing of both 3D land and 3D marine-streamer data, we did not know what to expect in this extreme environment. The modern Mississippi river delta has been studied extensively. A particularly useful report on studies by LSU and USGS of the soil properties and structure of the delta was presented by Coleman, et al.z Marathon Oil studied the delta and presented three papers in 1988: Tinkle, et al.3, studied acoustics of the mud structures in the delta; May, et al.4 used acoustic measurements and sediment samples to predict and help correct problems encountered in seismic data; Meeder, et al.s, constructed a velocity and depth model along a 2D profile based on borings and acoustic measurements, and compared static corrections from this model to those generated from refraction and reflection seismic data.

This is a success story of survey design and refraction static correction processing of a large 3D seismic survey in the South Pass area of the Mississippi delta. In this transition zone, subaqueous mudflow gullies and lobes of the delta, in various states of consolidation and gas saturation, are strong absorbers of seismic energy. Seismic waves penetrating the mud are severely restricted in bandwidth and variously delayed by changes in mud velocity and thickness. Using a delay-time refraction static correction method, the authors find compensation for the various delays, i.e., static corrections, commonly vary 150 ms over a short distance. Application of the static corrections markedly improves the seismic stack volume. This paper shows that intelligent survey design and delay-time refraction static correction processing economically eliminate the historic no data status of this area.

The BWH (broadband excitation receiving, wide azimuth observation, high density acquisition) seismic data size deployed in the deep complex tectonic area of the northern Songliao Basin was 7.5T, and the surface elevation of the study area varies greatly. The single point receiving observing system with high density and small cells presents a new challenge to static processing. The pick-up precision of the first break wave directly determines whether the static correction is accurate or not. The conventional method can pick up the first break wave in the shot domain, and the precision of the pick-up quantity cannot be required by the static correction of tomography. In this paper, according to the characteristics of BHW mass data, a new method is proposed to separate the data into small pick-up units by using detection lines as picking units and dividing offset groups into small pick-up units. The trend line which controls the pick-up accuracy is adapted to the influence of the far and near offset at the same time, and the pick-up accuracy is greatly improved. The static correction effect is achieved by the method of model-constrained travel-time tomography static correction. This method is especially suitable for BWH seismic data and other big offset data, the first break wave pick-up of high-density 3D seismic data received by single detect point can improve the pick-up accuracy to the maximum extent, and has wide application and popularization space.

Rugged surface topography for land seismic data presents a challenge in imaging near-surface and subsurface complex geologic structures in foothills. Conventional static correction process that simply shifts the data to a flat or floating datum distorts the wavefield and thus produces the inaccurate image. Migration from topography without static correction is apparently an ideal solution to the imaging of complex structures with a rugged topographic surface. The image result obtained from the migration directly from topography is significantly improved for near-surface and subsurface structures on a synthetic overthrust dataset in the foothills of Canadian Rockies. A hybrid reverse-time migration also produces clearer image for near-surface structures around the topographic surface than the conventional reverse-time migration.

We analyze the characteristics of different floating datums for static corrections and discuss the methods for determining them. The effect of different floating datum corrections was studied using theoretical model experiments, resulting in the conclusion that the velocity obtained after the floating datum correction with the minimum static correction errors depends on the velocity of the layer below the low velocity layer (LVL) lower boundary and is not related to topographic relief and LVL structure. For the real data processing case, wave equation numerical model experiments were conducted which resulted in a new method for calculating objective functions based on the waveform and modifications to the calculation equation for minimum static correction errors to make the method suitable for real data static correction processing using inhomogeneous velocity models with lower velocity boundary relief. Real data processing results demonstrate the method’s superiority.

In this paper, the static correction processing workflow was set up to utilize the deep phreatic surface in the Yingxiong Mountains region. The case study is applied to the western Qaidam Basin, China. The phreatic surface is clearly observed as a strong reflection interface in seismic sections at a depth of ~400 meters within the Yingxiong Mountains. Because of the distinct characteristics of the range, velocity and horizontal form, the static correction techniques with the deep phreatic surface were analyzed. The workflow includes that: (1) Compute the datum static correction for the low frequencies using the phreatic surface as the bottom of the model of the near surface structure. (2) Compute the refraction residual static for the greater high frequencies using the refraction wave of the phreatic surface. (3) Improve the processing by computing the residual static for the smaller high frequencies using the reflection wave of the phreatic surface. In the case study, the static correction techniques with the phreatic surface improve the seismic imaging sections with high signal-to-noise (S/N) ratio.

Free gossypol is a toxic compound which naturally occurs in cottonseed and its derivates, affecting animal and possibly human health. Consequently, alternatives for gossypol destruction must be evaluated. This work evaluated the emerging technology of ozone processing for free gossypol destruction in cottonseed meal. Ozonation was carried out in the actual cottonseed meal and also a model system, designed to describe the involved mode of action. The model system consisted of glass pearls beads covered with free gossypol. Ozonation was performed in two ways: as a static process, i.e., without homogenising the sample after placing them in the reactor, and also homogenising it. Ozone degraded free gossypol in all the systems, but reaching different levels. Free gossypol reduction was higher in the model system than the cottonseed meal, and higher in the homogenised processing than the static one: cottonseed meal in homogenised (56%) and static (25%); model system homogenised (98%) and static (80%). The obtained differences suggest a problem of gas penetration in the solid particles, the effect of unexposed surfaces due to contact areas, and the reaction with other organic molecules further than the target. Ozonation is a promising technique for gossypol degradation in cottonseed meal, but additional strategies are needed to optimise the ozonation process and evaluate toxicological aspects.

Summary Multi component technology has been used in a number of oil exploration area in China. However, due to the propagation characteristics of the PS-wave, the first arrival wave of the PS-wave data collected is not easy to identify, so the PS-wave static correction processing is a difficult problem in multi component exploration. The traditional PS-wave static correction values calculation is to multiply the PP-wave static correction values by an empirical coefficient, but this method will produce the phenomenon of periodic jump , so it is not accurate. Generally, the P-wave records contain clear information of the first arrival wave and surface waves, and there is a very important relationship between surface wave and shear wave. Therefore a new calculation method of PS-wave static correction by combining first arrival wave and surface wave is presented to improve the accuracy of PS-wave static correction. Applications on real data show very high performance of the proposed method in this paper.

An important part of statics solution is determination of the velocity and depth of the near-surface<br>layer. This information can be obtained from an uphole survey, Refraction First break methods and<br>sometimes from shallow refraction reciprocal surveys. Uphole surveys provide the most reliable results<br>but the spatial coverage of this method is always limited. Shallow refraction reciprocal surveys are only<br>effective for a certain geological situations. Refraction First break method are recently attractive, but<br>the methods recently used are heavily depend on the refractor data quality.<br>By using of first breaks picks in a range of given CDPs for apparent velocity and intercept time, the<br>velocity and depth for weathering and near-surface layers can be well estimated based on a local<br>constant layer assumption. By repeating this process for all CDP ranges, a good refine of a 2D/3D<br>velocity model can be built. This method improves refraction statics solution.<br>This paper will present uses of a reasonable amount of direct arrival and refraction picks data from 2D<br>and 3D Surveys in Muglad Basin to extract the apparent velocity and intercept time from overall<br>behavior of the picks, Replicating this process on multiple locations across the survey, to build an initial<br>velocity depth model to be used in calculating the velocity and depth of weathering layers accurately as<br>an alternative way to solve one of the main challenges in static correction process.

Block SZG is located in the western China and the topography is undulated sharply. Complex terrain makes deep seismic data poor and interpretation difficult. It is the first time to carry out 3D MT survey in the area for the purpose of assisting seismic survey to study deep structure. Compared with traditional 2D MT survey, 3D MT has more advantages on static correction, processing and inversion algorithms, and gives a technical basis to the study of spatial distribution of underground resistivity in complex area. With the calibration of logging data, after mapping the burial depth to the top resistive basement based on 3D inversion resistivity, the structure of top basement can be interpreted. The case in the area shows that it is feasible to study deep structures in complex area by 3D MT data and the application effect is also described in the following paragraphs.

Merging 3D seismic surveys into a seamless single 3D volume, either post-stack stage or pre-stack stage, is a challenging task on seismic data processing. This study describes some tips from coastline Abu Dhabi where we successfully managed merging two partially overlapping surveys during post-stack stage, one from transition zone (land and shallow marine) while the other one from offshore 3D OBC seismic survey, in order to understand subtle geological structure relationship among two areas. Since spatial sampling between two surveys are greatly diverse due to different orientations and grid sizes, a conjugate grid which is identical to a main cube had been applied over the subordinate one that enable the whole dataset to interpolate and process as a same grid. Then we deployed pre-conditioning steps over the subordinate dataset to minimize their quality differences where we particularly focused on residual noise, multiples, frequency contents and event timings. Lastly, a matching filter was designed and applied to the subordinate side to compensate residual amplitude, frequency and phase and produce a final dataset for structure interpretation. A single consolidated seamlessly merged volume was produced throughout the steps as described above along with well-to-seismic calibrations. Seismic interpretation was conducted over the main reservoir between two datasets/fields with a good degree of confidence. The present day structure separation and structure growth history were analyzed as a part of the structure interpretation. Moreover, this case study illustrates the add values of the seismic 3D merge from the aspect of regional structure restoration, and revealing structure relationship between the overlapping surveys. The final merging result outcome of this case study has an amenable structure continuity and seamless horizon mapping of the common reservoir target level between the two surveys. Additionally, the merged seismic cube did showcase a lateral zero phase wavelet stability of the existing wells that verified the reliability of the conducted post-stack seismic merging processing workflow. This case study has successfully demonstrated and summarized key technical tips that are recommended for merging datasets on post-stack domain in the future. However, pre-stack merge is also and still strongly recommended since static corrections, velocity pickings and imaging processing can be applied throughout the two surveys in one go while these cannot be fixed on post-stack merge. From data acquisition perspectives; enough overlap to reaching the full-fold rim of the overlapping surveys is highly recommended.

For a low SNR and fracture region in the piedmont zone of north Tarim Basin, fine processing and interpretation and comprehensive evaluation of geological data were carried out, giving priority to favorable areas for oil-gas exploration. Through high-precision static correction processing, pre-stack time migration, reservoir prediction, gas bearing analysis and other technical means, it had further determined the tectonic characteristics, put the trap distributions into practice, predicted the favorable reservoirs, given favorable exploration areas, and put forward recommended well locations.

Summary In an area covered with thick piedmont alluvial fan, LVL is thicker than 250m generally, hence, a conventional near-surface structure investigation method, such as short-refraction survey or deep-uphole survey, can hardly get the high velocity. In this case, it is difficult to establish a precise near-surface structure model. It affects not only the static correction accuracy and structure confirmation but also the pre-stack depth migration (PSDM) imaging effect for lack of accurate shallow layer velocity model. This problem exists commonly in the petroleum exploration in West China. This paper proposes a new method to build the near-surface structure model in thick alluvial fan area based on acoustic logging data and high-density 2D shallow layer survey data. This method was applied in the Tuha Basin PTG high-density 3D survey project in West China, resulting in a good application result.

In recent years, the criminal digital image processing technology is becoming more and more important in the public security business, especially the static fuzzy license plate processing technology. It is particularly important to identify the vehicle used by the suspect after the hit-and-run, the vehicle used by the suspect before and after the crime in the theft case and the vehicle used to transport the drug in the drug case. Paper focuses on using MATLAB how to deal with fuzzy plates allow investigators to identify the license plate content of Chinese characters, Numbers and letters, allow investigators to identify the vehicle's license plate number, determine the relevant vehicle information, locking the vehicles, and then to carry out relevant investigation activities, use a combination of theory and the software for processing images, Finally achieve the desired results.

The data of Internet of things (IOT) has the characteristics of polymorphism, heterogeneous, large amount and processing real-time. The traditional structured and static batch processing method has not met the requirements of data processing of IOT. This paper studied a middleware that can integrate heterogeneous data of IOT, and integrated different data formats into a unified format. Designed a data processing model of IOT based on the Storm flow calculation architecture, integrated the existing Internet security technology to build the Internet security system of IOT data processing, which provided reference for the efficient transmission and processing of IOT data.