A number of oil and gas structures were found in Keshen structural segmentation of Kelasu structural belt, such as KL2, KS2 and KS1. The structural model is under argument because this segmentation is located in the foreland thrust belt with complicated structural deformations. Based on the previous understanding and with the help of surface outcrop and drilling data, a T-Q full level interpretation was made on 3D data of Keshen segmentation. The structural interpretation model of this structural segmentation was re-established to study the petroleum geological characteristics of this segmentation. The research results indicated that deformation characteristic of Keshen structural segmentation is vertically layered and south-north division of belts. It is vertically divided into four structural layers - suprasalt layer, salt layer, subsalt layer and basement layer. There are three main structural patterns developed in this area, such as thrust fault with the related folds, salt contractive structure and strike-slip structure. Of those, the structural pattern of subsalt layer is gradually turned into cap decollement structural pattern from high-angle basement curled structural pattern from the north to the south. The present-day structure of Keshen segmentation was shaped mainly in the middle and late periods of Cenozoic era and experienced four development stages, such as Late Permian-Triassic foreland basin, Jurassic-Cretaceous sag basin, Paleocene-Miocene weak contractive flexure basin and Pliocene-Quaternary intra-continental foreland basin. The practice of exploration showed that this area, with favorable conditions of good cap-rock, thick reservoir, large structure, strong injection and late accumulations, was the important target for foothill natural gas exploration in Kuqa Depression.

Based on the study of the distribution law of basin peripheral stratigraphic reservoirs in Jiyang Depression and the analysis of main accumulations-controlling factors and with adoption for the mindset for combination of qualitative analysis and quantitative assessment, the method for multi-level assessment of main accumulations-controlling factors was established on the basis of four geological conditions of conducting, storage, trap and reservoir. Of those, the condition of the conducting system highlighted the controlling effect of sourcing faults on accumulations of basin peripheral stratigraphic targets. Assessment of direct cap-rock thickness and top basement condition was introduced into the storage condition. Meanwhile, the standards for integrated assessment of the basin peripheral stratigraphic trap was established on the basis of conventional assessment of exploration targets. Establishment of these standards is of certain guiding significance to assessment and selection of basin peripheral stratigraphic exploration targets in the rift basins in China's eastern part

Changling rift in Songliao Basin was transformed in a number of periods.As a result, the present-day remaining basin is significantly different from basin prototype, affecting further oil and gas exploration of Huoshiling formation. Based on the study of the remaining basin characteristics and the geological background and data of this region as well as taking into account the applicable scopes of various methods and influencing factors, the vitrinite reflectance method and the profile trend method are selected to calculate the denudation quantity of Huoshiling formation in the light of different wells and areas. Restoration of the basin prototype of that period in the research area indicated that it was obviously a half-graben and horst structure, clarifying the location and scale of the depression during the basin prototype period. Based on analysis of the geological conditions for accumulations, it is pointed out that the stratigraphic onlap zone of Huoshiling formation on the western slope and the high position (volcanic rock body) of structure in the remaining dustpan-like sag of the western and southern fault zone are the favorable targets for oil and gas exploration in this region

Cenozoic terrestrial sediment directly overlies on Mesozoic marine limestone of Triassic System in the central uplift region of South Yellow Sea. The difference in velocity is quite big between Cenozoic formations and Mesozoic-Paleozoic marine formations. The special geological characteristics enable sea surface, sea bottom and Cenozoic bottom sediment to form three strong wave impedance differential interfaces, leading to the strongest multi-reflection and screening energy propagation downward. Based on the geological conditions in this region and seismic acquisition experience in the past, this article analyzes the seismic reflection characteristics of Mesozoic-Paleozoic in South Yellow Sea and makes wave equation forward modeling. The design for seismic acquisition is made on the basis of the efforts to analyze the reasons why the imaging quality is poor. The double geophone tow-cable acquisition technique is used for seismic data acquisition at this time. Finally, comparison ismade between the results of acquisition at this time and the results achieved in 2002, coming up with the orientation for further efforts.

Adoption of pre-stack depth migration technology for depth cross-section in a region where the seismic data S/N ratio is high can satisfactorily reflects the pattern of actual structure. However, in a mountainous complicated structural region where the seismic S/N ratio is low, pre-stack depth migration processing is difficult to meet the requirements for geological study of structure and development of oil and gas exploration because of a long period and a poor imaging quality. Two-step seismic depth imaging is a rapid and precise imaging method. The first step is migration in time domain, adopting post-stack time migration or pre-stack time migration to migrate the lateral distortion phenomena on the stack cross-section (such as bow-tie, diffraction, fault plane reflection and dipping reflection). The second step is migration in depth domain, vertically eliminating false anticline or false structure high caused by velocity "pull-up effect" and finally acquiring the really-reflected depth profile of underground structure. This technology has been extensively used in exploration and development of complicated oil and gas fields with good application results achieved.

With seismic exploration technology improved, the high-density seismic exploration technology characterized in high space sampling rate has made a great progress. To explore offshore application of this high-density and high-resolution 3D seismic acquisition technology, transverse bird technology was used for the first time at home for seismic data acquisition in PL zone of Bohai Sea, reducing bin size of data and optimizing parameters of seismic source and cable. Meanwhile, based on high-resolution processing, the data results were significantly improved in terms of transverse and vertical resolution, reflecting more abundant geological information, helping understand the fault system and adding exploration targets for selection

To solve the problem that the filtering methods, such as f-k and τ -p, cannot effectively attenuate near offset multiple, this paper comes up with a method for reconstruction of amplitude fitting and signal matching to suppress residual multiple. Combined with the filtering method, this method can effectively attenuate multiple from different generation mechanisms with high calculation efficiency and is suitable for huge magnitude of 3D data. Application of the model and actual data shows that using this method for suppression of residual multiple can effectively improve imaging quality of profile and reduce the difficulty for interpretation. Meanwhile, it can also improve CRP gather transverse energy relation so as to provide good basic data for subsequent use of prestack gather for AVO analysis

This article elaborates the definition of Poisson Dampening Factor (PDF) in detail and analyzes some characteristics of PDF. Actual application indicated that PDF is very sensitive to the property of reservoir fluid, closely related to water saturation and suitable to be used to detect the property of reservoir fluid and predict water saturation. PDF correlates only to P-Impedance and S-Impedance without explicit density item so that it doesn?t need high angle prestack gather data. Therefore, we can get the relatively stable prestack inversion results under the conditions of common seismic data quality. Actual application in Pinghu area indicated that this technology is a new method for quantitative seismic interpretation with desirable results achieved.

Located in the southern part of Pre-Caspian Basin, Bikzhal Northwest Block oilfield is a recently-found Jurassic oil field in Adaiski region. The property of crude oil is good and the density 0.83g/cm3. The oilfield sees a high production and a stable reservoir pressure. The daily production has bee kept stable at 100 tons for three years. The reservoir rock is quartz sandstone of delta facies with desirable physical properties. The average porosity is 35.25% while the average permeability is 913.83mD. Mudstone with a thickness of 60 meters developed above Jurassic system and was matched with screen of inverted fault, forming an excellent top-sealing and laterally-blocked fault trap. The main factors controlling Jurassic accumulations in Bikzhal Northwest Block include suitable buried depth, reasonable reservoir-cap assemblage good lithological boundary rock on the upper disc of inverted fault, excellent hydrocarbon sources and salt window conditions.

A total of 15 oil and gas fields were found in the presalt sequences of Campos Basin in Brazil between 2002 and 2012, with the recoverable reserves reaching 7?á108t of oil equivalent. Of those discoveries, there are 11 large-scale oil and gas fields, highlighting the oil potential of Campos Basin and making the presalt sequences of this basin another hot spot for exploration after Santos Basin. Campos Basin experienced three structural development stages - rift period, transition period and drift period. The presalt sequences are the typical continental sedimentary system deposited during the rift period (from Late Jurassic to Early Aptian), including Hauterivian fracture-developed basement basalt andAptian to Barremian carbonate rock. The main source rock of the basin is black calcareous shale of Lagoa Feia group in Cretaceous Period, which has an excellent potential for sourcing. A number of reservoirs developed in the basin, where the presalt sequences are low in exploration degree. The current oil and gas proven rate is only about 50 percent, thus indicating a great potential for oil and gas exploration. Campos Basin has a very promising exploration prospect for the presalt sequences, which are supposed to be the field to see the quickest growth in reserves in the future. The focus area for exploration is the central uplift zone. The main reservoirs are Lago Feia group while the main traps are carbonate lithological-structural ones.

At China?s current exploration and development stage, assessment of tight oil resources can preferably adopt three convenient methods, namely analogous method for abundance of resources, EUR analogous method and volumetric method for small area. Two additional methods for more detailed assessment can be used in some areas where exploration degree is relatively high, namely, method for prediction of spatial distribution of resources and method for numerical simulation of hydrocarbon accumulations. This article briefs about the principles of former three methods, assessment process, key parameters and conditions for application and selects tight oil from Yanchang Formation of Ordos Basin as the case for study. The characteristics of those three methods are shown on the basis of application and comparison. The application results confirm one another, indicating a great potential of tight oil geological resources in Yanchang Formation. With the recoverable reserves estimated at (4~6)× 108t, Yanchang Formation is indicated as the most important tight oil exploration target in China at the present time.