Maokou Formation is one of the major pay zones of Sichuan Basin, in which there are Yangxin Series and Silurian potential source rock. Cracks, pores, and caves are dominant reservoir space of the Formation. In particular, corrosion caves developed from surface Palaeokarst generated after Dongwu Movement are widely distributed in the Formation. Now 99 wells have been drilled in Luzhou Paleouplift area, with the ratio drilled being 9.94% and even reaching as high as 11.35% thanks to repeated borehole drilling.Without the limit of region and structure, venting thickness ranges from 0.1m to 1.0m, with the maximum reaching 3.95m. Venting also exists in synclines, of which the exploration area is more extensive than that of structural traps. Development shows that it is better to cumulatively produce gas in Palaeokarst reservoirs which are well connected with fractured gas reservoirs. Networks consisting of Palaeokarst pores and caves interweave with networks developed from the connection between Palaeokarst reservoirs and fractured gas reservoirs. The interweaving is the best. So research on seismic reflection data should be intensified to find out such types of network systems.

Es3 2+3 complex reservoir in Liuzan Oilfield of Nanpu Sag has been under rolling exploration and development for more than 20 years. However, the output of development of the reservoir has not increased for many years according to preliminary evaluation. Analysis shows that the main causes of low-efficiency development are the fractured structures and the complicated relationship between oil and water. New second-time 3d seismic exploration techniques and new geological theories of sequence stratigraphy, i.e., new technical methods of strata research were applied during the Tenth Five-Year Plan period, which led to some new understandings on reservoir geology. Firstly, dramatic change of thickness near oil layers was caused by the local unconformity of basin-margin fault. Secondly, there were no so many breakpoints as mentioned in interpretation of the first-time poor-quality 3d seismic data. It was shown that Es3 2+3 reservoir was a complete fault nose and bulk anticline. Electrical characteristics and distribution law of oil-water layers of the reservoir were recognized as well. Alot of leakage oil-water layers were newly discovered. New geological understandings lead to remarkable change of reserves and output. During the Tenth Five-Year Plan period, more than 22 million tons of reserves were discovered in Es3 2+3 reservoir. The reservoir was finely described and waterflooding development was conducted on mini-layer series with scientific approaches. Annual oil output of the reservoir increased by 2.7 times than before. Some old oilfields turned into main reservoirs for increasing oil reserves and output in the area.

Depression-uplift structure is a basic structural unit developed on crustal surface. It is secondary structure and is superposed upon larger plate tectonics. Depression-uplift structural movement is a kind of undulatory movement and can be manifested on three levels. Firstly, depressions and uplifts alternate with each other and develop mutually. Secondly, they alternate and transform to each other. Thirdly, they migrate to a certain direction. Asthenosphere movement leads to the movement of depression-uplift structure. Crustal surface shows undulatory movement due to the asthenosphere. Deformation and movement law of depression-uplift structure accordingly develops. According to the movement law, it is possible to determine the structural position where basins were located then. According to the law that depressions and uplifts transform to each other and migrate to a certain direction, relative position of depression-uplift of old structures can be determined based on the depression-uplift distribution of new superstructures. This shows a way to conduct exploration for oil and gas in old structures. It is feasible to analyze faults, folds, magma activity, and motion source on the basis of the law of geological effect associated with the movement of depression-uplift structure.

The southwest of Zhongguai 158 area is next to three major source sags including Mahu Sag, Pen1 WellWest Sag, and Shawan Sag. It is longterm in favorable directional zone of hydrocarbon migration and hence has a sound basis at resources. Reservoir-cap assemblages, passage systems, effective traps, and preservation conditions are favorable for forming gas reservoirs. So it is possible to develop medium and small sized gas fields in the area. Based on the analysis of the typical gas reservoirs in the area, Permian Jiamuhe Formation and UpperWuerhe Formation are taken as main targets for natural gas exploration. Unconformity surfaces, sedimentary facies belts, and faults are main factors that affect gas accumulation of Permian Formation. Favorable sedimentary facies belts near unconformity surfaces of Permian Formation are the main target for natural gas exploration.

Based on the analysis of regional geology, according to drilling and logging data, seismic facies, and seismic attribute analysis of amplitude, frequency, and wave impedance, the genetic type, macro-distribution, and inner component of turbidity sandbody of Paleogene Dongying Formation of Block JZ31-A in Liaodong Bay area are analyzed. Result shows that sandbody of the Formation belongs to slump turbidite fan in front of braided delta and can be subdivided into upper fan, middle fan and lower fan subfacies. It comes from ancient river system of Fuzhou and generates from multi stagesof turbidite superposition. It is mainly controlled by valley and sloe-break zone, with less effect from dirpiric structures of the east. Combined with analysis of drilling and seismic data acquired in and around the area, pool-forming conditions of gas reservoirs are described from the perspective of basic pool-forming factors. It is shown that gas reservoirs described belong to large-scale self-generation and self-storage biogenetic gas and have good pool-forming conditions. The research is of significant theoretical and practical value for extending exploration direction and searching for similar hydrocarbon reservoirs.

To further study potential petroleum resources in Lufeng13 fault structural belt, crude oil sources of all oilfields and oil-bearing structures of the belt are analyzed on the basis of biomarker assemblage and geological background of the area. Different levels of secondary migration pathways of oil are discussed based on effective pathway thickness and migration intensity. Biomarker compounds and migration tracer parameters are used by studying the hydrocarbon migration directions of the belt. Hydrocarbon charging history of the belt is discussed as well, according to the homogeneity temperature and burial history of fluid inclusion in the reservoir.

Taizhou Formation of Upper Cretaceous (K2t) in Hai'an Sag of Subei Basin is a set of clastic rocks developed in the early stage of sag formation, which vertically forms a normal sedimentary cycle from lower to upper. Comprehensive analysis of the mud log, log, and core data of more than 30 wells shows that types of depositional systems in the area mainly belong to braided delta depositional system in the early to middle period of the first member of Taizhou Formation, while normal delta depositional system in the late period of the member. It can be divided into five types of sedimentary subfacies and 11 types of sedimentary microfacies. The normal delta sedimentary system in the area typically belongs to retrogradation depositional system with clear multicyclicities with frequent movement up and down of the lake level. Comprehensive analysis of the distribution and evolution of depositional systems of the Formation shows that Liangduo-Anfeng-Haizhong region where sand bodies developed is favorable for forming petroleum reservoirs.

There are mainly tight sandstone fracture gas reservoirs in Xingchang area west of Sichuan. Although a vast gas reservoir is exploited in the deep-seated strata of 851-well location, original seismic data have many disadvantages in describing deep-seated gas reservoirs. For example, it is difficult to solve problems of fault distribution, reservoir heterogeneity, and fracture prediction based on the data. Therefore, research on wide azimuth 3D3C seismic exploration is conducted. Firstly, a field acquisition method is analyzed including wide 3D3C observation system, seismograph, method of improving resolution and signal-to-noise, and test on acquisition method. Secondly, seismic data acquired from the field including their folds of P and converted wave, shot quality, frequency scan, anisotropic feature, and profile quality are discussed, which indicates that the acquisition data offer basic data for research on fracture reservoirs and meet the requirements of research on fracture prediction, anisotropy, and AVO hydrocarbon examination. Lastly, some problems to be solved are raised in near future, such as orientation problem, noise problem, coupling problem, resolution, static correction of converted wave, and anisotropic problem.

Reservoirs in Badaowan Formation in Xia79 Well zone in northwestern margin of Junggar Basin feature in strong heterogeneity and poor permeability, which result in vague understanding of target reservoirs distribution and have a negative effect on integrated development of oil regions. Exploration using surface-borehole electric method is conducted, which shows that oil and gas distribution is controlled by both structural and lithologic factors. The region where oil bearing sand bodies well developed is high-value anomalous region (favorable for hydrocarbon accumulation) of such comprehensive parameters as apparent resistivity and double-frequency phase. The region where mudstone well developed is low-value anomalous region (unfavorable for hydrocarbon accumulation). Saddle shaped anomalous region where low-value anomalous region transits to high-value one is a connection part that oil and gas migrates from low sand bodies to high ones, which is relatively favorable for hydrocarbon accumulation. Based on comparing the drilling results of 15 wells, the results of 13 wells accord with oil and gas prediction while two do not. Prediction accuracy reaches 86.7%.

Conglomerate reservoirs feature in stronger heterogeneity and more complicated hydrocarbon accumulation conditions, as compared to sandstone reservoirs. Based on using such techniques as Jason pseudo-acoustic inversion, EPS inversion, StratiMagic dip, and curvature measurement, research on conglomerate in Caiyu area is conducted, which precisely shows the distribution of conglomerate, favorable sedimentary facies zones, and fracture development zones. Enrichment and high productivity of conglomerate is mainly controlled by fracture development degree. The systematic method and technique developed from research on conglomerate in Caiyu area is a successful case of research on conglomerate reservoirs, which is helpful to guide exploration of the conglomerate in downthrown side of the whole Daxing fault and the conglomerate hydrocarbon reservoirs of other regions.

Systematic analysis and study is conducted on the difficulties in the sedimentary system in the lower part of Es1, reservoir characteristics, and logging evaluation of main target formations in the west slope of Qikou Sag. This is helpful to determine the exploration direction and target of the area. Taking the geological characteristics of Liujianfang area as an example, based on analyzing the sedimentary source, sedimentary characteristics and reservoir characteristics, effective identification of reservoir lithology is proposed to be conducted on the basis of drilling core data and cross plot method to solve the difficulties in evaluating micritic calcite dolomite reservoirs and calcarenite reservoirs. A set of effective approaches to evaluating such kind of reservoirs are developed based on the effective identification of hydrocarbon zones by using the method integrating mud-log and gas-log, the method integrating mud-log, gas-log, and image-log, the MDT testing technique, and the reservoir comprehensive evaluation method. Remarkable results are obtained by applying the newly developed approach to conduct a new round of fine reservoir evaluation of new and old wells in micritic calcite dolomite reservoirs in the lower part of Es1 in the west slope of Qikou Sag, which further proves the feasibility of the approach

The basic method that American estimators use to evaluate oil and gas reserves based on reservoir engineering analysis can not be taken as SEC rule. SEC standard is objective, however, how estimators evaluate is objective. Only based on combining the background of professional knowledge, effective local experience, objective evaluation attitude, and reasonable application of evaluation rules, can we be successful to evaluate oil and gas reserves. Comparative analysis shows that the measured remaining commercial recoverable reserves that developed and measure remaining commercial recoverable reserves undeveloped in China are respectively corresponding to SPE/WPC/AAPG proved reserves developed and proved reserves undeveloped. However, there still exist remarkable differences in the thinking mode, standpoint, and phases in the establishment of reserves, the correspondence between geological reserves and recoverable reserves, the dependence of reserves of various grades, the economic connotation and its definition of reserves, and the center of management.

As Aleisi Oilfield features in complex structure, complicated oil-water relationship, and difficult development, research is conduct on fine reservoir description, based on reinterpretation of 3D seismic data. This helps to clearly show structure and sequence of formations and deepen understandings of faults, which enables structure of major reservoirs to be completely determined. Fluid distribution model is established. Low resistivity reservoirs are discovered on the basis of new understandings of structure, deposits, and reservoirs and it enables the geological reserves of the oilfield to be determined and offers a solid basis for development plans design and scientific and reasonable development. Meanwhile, distribution of reservoir sand bodies is predicted based on reservoir inversion, providing sound foundation for the optimization of well location and drilling design. Seven vertical wells and three horizontal wells are deployed in the whole year of 2007, which leads to remarkable results. Practice shows that it is significant to conduct fine reservoir description, which can provide necessary and reliable geological bases for reasonable development of hydrocarbon reservoirs and the establishment of development strategies and technical measures.

Block Adaiski is located southeast of North Caspian Basin, where salt rock of mega-thickness developed in the late stage of Early Permian. Devonian-Permian covered under the salt rock belongs to pre-salt oil and gas bearing series, which is a set of marine facies formations mainly composed of limestone and clastic rock. Having been located in the sedimentary setting of Nan'en Depression, the facies formation features in rich source rocks, well-developed reservoir rocks, and favorable cap rocks, providing favorable geological conditions for pre-salt hydrocarbon accumulation. Research shows that pre-salt hydrocarbon reservoirs are the main components of the reservoirs in the area. Large traps are mainly distributed in pre-salt series. According to sedimentary settings and lithofacies palaeogeography as well as source-reservoir-cap rock combinations of hydrocarbon reservoirs, geological conditions for forming pre-salt oil and gas reservoirs in Block Adaiski are analyzed in detail, laying the foundation for further pre-salt exploration.